Kleiber's law and its possible implications for obesity

Kleiber's law () is one of those “laws” of nature that is both derived from, and seems to fit quite well with, empirical data. It applies to most animals, including humans. The law is roughly summarized through the equation below, where E = energy expenditure at rest per day, and M = body weight in kilograms.

Because of various assumptions made in the original formulation of the law, the values of E do not translate very well to calories as measured today. What is important is the exponent, and what it means in terms of relative increases in weight. Since the exponent in the equation is 3/4, which is lower than 1, the law essentially states that as body weight increases animals become more efficient from an energy expenditure perspective. For example, the energy expenditure at rest of an elephant, per unit of body weight, is significantly lower than that of a mouse.

The difference in weight does not have to be as large as that between an elephant and a mouse for a clear difference in energy expenditure to be noticed. Moreover, the increase in energy efficiency predicted by the law is independent of what makes up the weight; whether it is more or less lean body mass, for example. And the law is very generic, also applying to different animals of the same species, and even the same animal at different developmental stages.

Extrapolating the law to humans is quite interesting. Let us consider a person weighing 68 kg (about 150 lbs). According to Kleiber's law, and using a constant multiplied to M to make it consistent with current calorie measurement assumptions (see Notes at the end of this post), this person’s energy expenditure at rest per day would be about 1,847 calories.

A person weighing 95 kg (about 210 lbs) would spend 2,374 calories at rest per day according to Kleiber's law. However, if we were to assume a linear increase based on the daily calorie expenditure at a weight of 68 kg, this person weighing 95 kg would spend 2,508 calories per day at rest. The difference of approximately 206 calories per day is a reflection of Kleiber's law.

This difference of 206 calories per day would translate into about 23 g of extra body fat being stored per day. Per month this would be about 688 g, a little more than 1.5 lbs. Not a negligible amount. So, as you become obese, your body becomes even more efficient on a weight-adjusted basis, from an energy expenditure perspective.

One more roadblock to go from obese to lean.

Now, here is the interesting part. It is unreasonable to assume that the extra mass itself has a significantly lower metabolic rate, with this fully accounting for the relative increase in efficiency. It makes more sense to think that the extra mass leads to systemic adaptations, which in turn lead to whole-body economies of scale (). In existing bodies, these adaptations should happen over time, as long-term compensatory adaptations ().

The implications are fascinating. One implication is that, if the compensatory adaptations that lead to a lower metabolic rate are long term, they should also take some time to undo. This is what some call having a “broken metabolism”; which may turn out not to be “broken”, but having some inertia to overcome before it comes back to a former state. Thus, lower metabolic rates should generally be observed in the formerly obese, with reductions compatible with Kleiber's law. Those reductions themselves should be positively correlated with the ratio of time spent in the obese and lean states.

Someone who was obese at 95 kg should have a metabolic rate approximately 5.6 percent lower than a never obese person, soon after reaching a weight of 68 kg (5.6 percent = [2,508 – 2,374] / 2,374). If the compensatory adaptation can be reversed, as I believe it can, we should see slightly lower percentage reductions in studies including formerly obese participants who had been lean for a while. This expectation is consistent with empirical evidence. For example, a study by Astrup and colleagues () concluded that: “Formerly obese subjects had a 3–5% lower mean relative RMR than control subjects”.

Another implication, which is related to the one above, is that someone who becomes obese and goes right back to lean should not see that kind of inertia. That is, that person should go right back to his or her lean resting metabolic rate. Perhaps Drew Manning’s Fit-2-Fat-2-Fit experiment () will shed some light on this possible implication.

A person becoming obese and going right back to lean is not a very common occurrence. Sometimes this is done on purpose, for professional reasons, such as before and after photos for diet products. Believed it or not, there is a market for this!

Notes

- Calorie expenditure estimation varies a lot depending on the equation used. The multiplier used here was 78,  based on Cunningham’s equation, and assuming 10 percent body fat. The calorie expenditure for the same 68 kg person using Katch-McArdle’s equation, also assuming 10 percent body fat, would be about 1,692 calories. That would lead to a different multiplier.

- The really important thing to keep in mind, for the purposes of the discussion presented here, is the relative decrease in energy expenditure at rest, per unit of weight, as weight goes up. So we stuck with the 78 multiplier for illustration purposes.

- There is a lot of variation across individuals in energy expenditure at rest due to other factors such as nonexercise activity thermogenesis ().

All diets succeed at first, and eventually fail

It is not very hard to find studies supporting one diet or another. Gardner and colleagues, for example, conducted a study in which the Atkins diet came out on top when compared with the Zone, Ornish, and LEARN diets (). In Dansinger and colleagues’ study (), on the other hand, following the Atkins diet led to relatively poor results compared with the Ornish, Weight Watchers, and Zone diets.

Often the diets compared have different macronutrient ratios, which end up becoming the focus of the comparison. Many consider Sacks and colleagues’ conclusion, based on yet another diet comparison study (), to be the most consistent with the body of evidence as a whole: “Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize”.

I think there is a different conclusion that is even more consistent with the body of evidence out there. This conclusion is highlighted by the findings of almost all diet studies where participants were followed for more than 1 year. But the relevant findings are typically buried in the papers that summarize the studies, and are almost never mentioned in the abstracts. Take for example the study by Toubro and Astrup (); Figure 3 below is used by the authors to highlight the study’s main reported finding: “Ad lib, low fat, high carbohydrate diet was superior to fixed energy intake for maintaining weight after a major weight loss”.

But what does the figure above really tell us? It tells us, quite simply, that both diets succeeded at first, and then eventually failed. One failed slightly less miserably than the other, in this study. The percentage of subjects that maintained a weight loss above 25 kg (about 55 lbs) approached zero after 12 months, in both diets. This leads us to the conclusion below, which is always missing in diet studies even when the evidence is staring back at us. This is arguably the conclusion that is the most consistent with the body of evidence out there.

All diets succeed at first, and eventually fail.

In using the terms “succeed” and “fail” I am referring to the diets’ effects on the majority of the participants. This is in fact better demonstrated by the figure below, from the same study by Toubro and Astrup; it is labeled as Figure 2 there. Most of the participants at a certain weight, lose a lot of weight within a period of 1 year or so, and after 2 years (see the two points at the far right) are at the same original weight again. What is the average time to regain back the weight? From what I’ve seen in the literature, all the weight and some tends to be regained after 2-3 years.

The regained weight is not at all lean body mass. It is primarily, if not entirely, body fat. In fact, many studies suggest that those who diet tend to have a higher percentage of body fat when they regain their original weight; proportionally to how fast they regain the weight lost. Since the extra body fat tends to cause additional problems, which are compounded by the dieting process’ toll on the body, those dieters would have been slightly better off not having dieted in the first place.

Guyenet and Schwartz have recently authored an article that summarizes quite nicely what tends to happen with both obese and lean dieters (). Take a look at Figure 2 of the article below. The obese need to lose body fat to improve health markers, and avoid a number of downstream complications, such as type 2 diabetes and cancer (). Yet, with very few exceptions, the obese (and even the overweight) remain obese (or overweight) after dieting; regardless of the diet.

So what about those exceptions, what do they do to lose significant amounts of body fat and keep it off? Well, I rarely use myself as an example for anything in this blog, but this is something with which I unfortunately/fortunately have personal experience. I was obese, lost about 60 lbs of weight, and kept it off for quite a while already (). Like most of the formerly obese, I can very easily gain body fat back.

But I don’t seem to be gaining back the formerly lost body fat, and the reason is consistent with some of the studies based on data from the National Weight Control Registry, which stores information about adults who lost 30 lbs or more of weight and kept it off for at least 1 year (). I systematically measure my weight, body fat percentage, and a number of other variables; probably even more than the average National Weight Control Registry member. Based on those measurements, I try to understand how my body responds in the short and long term to stimuli such as different exercise, types of food, calorie restriction, sleep patterns etc.

And I act accordingly to keep any body fat gain from happening; by, for example, varying calorie intake, increasing exercise intensity, varying the types of food I eat etc. With a few exceptions (e.g., avoiding industrial seed oils), there is no generic formula. Customization based on individual responses and cyclical patterns seems to be a must.

Looking back, it was relatively easy for me to lose all that fat. This is consistent with the studies summarized in this post; all diets that rely on caloric reduction work marvelously at first for most people. The really difficult part is to keep the body fat off. I believe that this is especially true as the initial years go by, and becomes easier after that. This has something to do with initial inertia, which I will discuss soon in a post on metabolic rates and their relationship with overall body mass.

For people living in the wild, I can see one thing working in their favor. And that is not regular starvation; sapiens is too smart for that. It is laziness. Hunger has to reach a certain threshold for people to want to do some work to get their food; this acts as a natural body composition regulator, something that I intend to discuss in one of my next posts. It seems that people almost never become obese in the wild, without access to industrial foods.

As for living in the wild, in spite of the romantic portrayals of it, the experience is not as appealing after you really try it. The book Yanomamo: The Fierce People () is a solid, if not somewhat shocking, reminder of that. I had the opportunity to meet and talk at length with its author, the great anthropologist Nap Chagnon, at one of the Human Behavior and Evolution Society conferences. The man is a real-life Indiana Jones ().

In the formerly obese, the body seems to resort to “guerrilla warfare”, employing all kinds of physiological and psychological mechanisms, some more subtle than others, to make sure that the lost fat is recovered. Why? I have some ideas, which I have discussed indirectly in posts throughout this blog, but I still need to understand the whole process a bit better. My ideas build on the notion of compensatory adaptation ().

You might have heard some very smart people say that you do not need to measure anything to lose body fat and keep it off. Many of those people have never been obese. Those who have been obese often had not cleared the 2-3 year “danger zone” by the time they made those statements.

There are many obese or overweight public figures (TV show hosts, actors, even health bloggers) who embark on a diet and lose a dramatic amount of body fat. They talk and/or write for a year or so about their success, and then either “disappear” or start complaining about health issues. Those health issues are often part of the “guerrilla warfare” I mentioned above.

A few persistent public figures will gain the fat back, in part or fully, and do the process all over again. It makes for interesting drama, and at least keeps those folks in the limelight.

The Barefoot Kilimanjaro Challenge

The Barefoot Kilimanjaro Challenge

Only 3 days to go before I jet off to Kilimanjaro to tackle Africa's highest summit, and the world's highest free-standing mountain...barefoot...

 
Let me start off by pointing out that doing this climb has NOTHING to do with advocacy for barefoot running (or living) and nor is it even related to the whole barefoot running debate, which I've covered quite a lot lately here on The Science of Sport (you can read the most recent posts here and here if you're interested in my position!)

No, this trip is all about a) the challenge, b) the charity and c) the quite fascinating problem-solving approach required to combat the terrain, the altitude and the cold, and how these three "foes" interact with one another.  Basically, it's an exploratory trip, which I think is possible, but I readily accept may not be! (It has been done before, reportedly - local guides report that an Italian man did it, and a woman from Colorado has done it, but wearing cycling booties to cover the top of the feet, apparently).  We can only control every variable possible and then hope for best on the day!  My mission is to help get ONE person to the top barefoot, and to do it safely.  I'd obviously love to be that person, or one of many to do it barefoot, but I accept that given the time-frames, it may not be possible for me.  Only time will tell, but as I say, the goal is to get one person, minimum, to the top of Africa.

The bottom line is that people's first response is "Impossible" or "Outrageous".  And maybe that's the truth, but it's also the best reason to try, because just maybe, if you think about the challenges, then you start to see potential solutions.  And if you can overcome then, then you do the impossible, and that's what I'm looking forward to exploring!

But before I get into that, this trip is also aimed at raising money for a great cause - the Red Cross Children's Hospital in South Africa.  It's a world class facility, with some great doctors doing among the best medical work you'll find anywhere.  They are the beneficiaries of this trip, and I'd love to help raise them money through your donations.  Visit the expedition homepage for more information and to donate!

The start of the journey

To take you back to the very beginning of this particular story (for me, anyway), I met a group of guys last year in September who asked me for some assistance in their preparation for an attempt to become the first people to reach the summit of Kilimanjaro without shoes.  They'd been doing pretty much everything barefoot since July 2011 and wanted to know more about altitude and the cold. 

I gave them some advice, stayed in touch, until in about November, the expedition organizer, Matt Botha floated a proposal that was simply too good to ignore: "Come with us, help us on the mountain and not just before".  I took about 5 seconds to say yes, and another 5 minutes to decide that I didn't want to merely think about the challenges facing these "nutters", to rationalize and intellectualize the effects of cold, altitude and sharp rocks on the team's chance of success - I wanted to feel it.  And so I decided in November that I would also try to do this barefoot.  I'm willing to accept that in the 6 weeks since that I decision, I may not have had the time to get my feet ready.  Much will depend on the surface and on the speed at which we walk (try run on gravel and then walk slowly to see what I mean).  So I am, as I type this, a mixture of confident, hopeful, and anxious.  But therein lies the challenge...

A set of problems: Terrain, altitude and cold - which one gets you first?

Hiking to 5,895m brings with it a quite fascinating set of problems to solve.  Some are obvious, some less so.  The obvious ones are the altitude (not unique to being barefoot of course), the cold (a particular problem for us) and the terrain.  Kilimanjaro is known for it's sharp, jagged shale and the prospect of many hours on that surface is an anxiety-inducing one!

The terrain and nature's outsole

Getting the feet tough enough is just a matter of being habitually barefoot.  It means walking on tar, gravel, off-road at every possible opportunity until "nature's outsole" becomes so thick that those small stones feel like pressure, and not pain.  There's not too much to say about this, other than that everyone (barring me) has done it for six months and should be ready in this regard.  We've sent an experienced guide up our planed route (the Rongai route from the north-east) armed with a camera to film the various stages.  We've scouted it through a collection of photographs, testimonials and videos, and we've walked on surfaces that simulate what we'll encounter, but of course, we will only truly know when we feel it for ourselves.  And that's about as well prepared as we can be for now!

Altitude

The altitude is equally difficult to predict.  It's impossible to know who will thrive at altitude, and who will suffer.  The physiological response to arrival at altitude (even the lower slopes of Kili are high enough to be classified as altitude) is to hyperventilate.  We breathe more deeply and more often, and the result is that we breathe of carbon dioxide.  Carbon dioxide is known as a volatile acid, because it combines with water to produce carbonic acid. As a result, breathing off CO2 causes our blood pH to rise - we develop what is called respiratory alkalosis.  That's not necessarily good news, because as our pH rises, it actually blunts the ventilatory response.  So in the very situation where we would want to breathe more, this physiological response kind of dampens it - we breathe with "the handbrake" on.

The next step is that the kidneys kick in, and help to correct this alkalosis by excreting more bicarbonate.  The result is a corrected alkalosis, which bascially removes the "handbrake" and allows hyperventilation to help us keep our pO2 and oxygen delivery to the tissues normal.  The problem is that this takes time, particularly the metabolic correction, and so when the altitude continues to increase without this adaptation, we are unable to adapt and can, in severe cases, develop acute mountain sickness, the worst symptoms of which are pulmonary and cerebral oedema.  If you get those, you're having a bad day out. 

Predicting who this will be is a difficult, if not impossible task.  Individuals with the highest alveolar ventilation and highest oxygen saturation levels tend to do better at altitude, but there is little correlation to fitness or to training, and so the fact that the team is fit and well-trained has only limited relevance in this case.  We'll only really know about the altitude once we're up above 4,000m. 

We have a set of plans in place to minimize the effect, and they are not limited to medication.  The trip has been designed to take one day longer to ascend, which gives us a day of adaptation at 4000m.  We also have a day where the change in altitude is minimal (from 4300 to 4700m, so only 400 m ascent) and so these are two "buffer days" that we are optimistic will allow us to get above 5,000m feeling strong for that final push. 

And this will be vital.  One of the "combination problem" we face is that the cold is going to force us to stop often in order to warm our feet up (see below).  Therefore, we'll be losing time, and for every 10 minutes, we'll only be walking about 7 minutes.  The ability to walk faster than normal in order to get this lost time back is going to be crucial.  That means that we need to not only adapt, but do well at altitude, and this a crucial success factor.

The cold - not an endurance test, but physiology

And finally, we have the cold.  This is probably the biggest concern, and has been the main source of worry for me (there have been sleepless nights in the last month!)

The temperature at the summit has remained relatively constant over the last month, at around -5 to -6 degrees celsius (23F).  At night, it drops to around -8 (18F).  The wind chill factor is worth another 4 to 5 degrees, so we are looking at a temperature of around -9 to -10 degrees at the summit when we go up (we will not go up at night).  That's cold enough to keep you up at night with worry, I'm sure you'd agree!

I won't bore you with discussions of frostbite, other than to say that it's not fun, and equals a very bad day out.  I say this from experience... I hope, and will spend every ounce of my energy on the climb to make sure of this, that I will not see a case of frostbite in either my feet of those of the other 6 teams members.  This is all about prevention, and not treatment. If anyone develops symptoms, their expedition is over, for safety's sake, and I've worked hard at emphasizing this - there cannot be any "macho" toughing it out, or pushing through the pain.  As I said, I'll do everything I can to ensure that we stay well below the limits of freezing our tissues.  It's a big challenge.

To prepare, we have been testing the limits of tolerance to various cold temperatures.  That is, I've been taking some of the team into a cold room, at temperatures ranging from -6 C to - 18 C and testing how long we can walk for, and how long it to rewarm the feet to allow us to continue.  It has been a fascinating experience, but not without peril.  I guess the only way to truly know what the "limit" is is to exceed it, which I did on myself.  Just over a week ago, I developed mild frostbite in both feet as a result of staying at -10 C for too long without rewarming.

It was a valuable lesson, for me, and for the team, because it drummed home how cautious we will have to be (you can read more about the experience and my thoughts on the cold at this article which I wrote for the Barefoot Impi website).  It also finally confirmed for me what the schedule will be on the mountain.  The plan at this stage (and it is a flexible plan, that's for sure) is to walk for 7 minutes, then stop for 3 minutes to actively warm our feet.  That will be repeated for an hour, followed by a 20 minute stop to properly re-warm.  Seven "repeats" of this hour equals the summit.  No one said it would be easy...but the idea is that by stopping every 7 minutes, we never allow the tissue to freeze, and then return to baseline every hour with a long heating stop.

There is more to it than this, but I'll share the details with you from the mountain, as the expedition evolves.  The other thing that we have in our favour is that we ascend gradually, and the temperature drops along with our ascent. Therefore, on our third day when we are an Mawenzi Tarn (4300m), we expect the temperature to be around + 5 C (41 F).  That is cold, but safe, and so we'll have a good idea of what the mountain is throwing at us BEFORE we hit those sub-zero temperatures. On our rest day at 4,700m, we plan to hike up to the rim (partly for altitude adaptation) and return to camp later, and during this day-hike, we'll wear shoes, but check the terrain and temperatures to get an idea of what waits the next day.   Learning and adapting on the go will be the name of the game.

Ground temperature - a key factor

And finally, the key factor, the one that is probably going to make or break the expedition, will be the ground temperature.  It's one thing for the air temperature to be -5 C, but it's another thing to be walking on a solid surface at -5 C.  The cold room we have trained in has a steel floor that is probably -10 C, and that was a huge factor in my own case of frost-bite last week.  Walking on freezing ground would be a very, very difficult ask. Probably impossible.  However, having viewed countless videos on Kilimanjaro at this time of the year (Jan and Feb are the warmest monthson the mountain, by the way), I am confident that there is no ice on the path.  That means the ground temperature is above zero for a good portion of the day, even if the air is -5 C, and that's cause for optimism.  If the ground, heated by the sun, reaches anything in the range of positive temperatures, our task will be made exponentially easier.  In fact, based on the cold room tests, I'd say that air temperatures of -10 with a ground temperature of +2 C is easier than air temps of -5 and ground temps of -5. 

To capitalize on this ppssibility, we will not hike at night.  The normal procedure is to start for the summit from the Kibo camp at midnight, so that you get to the top for the sunrise (they allocate 7 hours for these 4.6 km, so steep is the climb and so inhibiting is the effect of the altitude).  We have modified this plan - we will start a few hours after sunrise, summit just before sunset, and then put shoes on and head down at night.  We are hoping that the addition of radiant heating of the ground does us a big favour.  Let's hope for the Africa sun to work its magic.!

Finally, other reasons for confidence... when you are walking 4.6 km in 7 hours, you are taking 9 minutes per 100m.  Try walking that slowly.  Now, the good thing about this is that if you walk as slowly as that, you can get away with walking on quite sharp, rough ground.  Try it.  Find some gravel and walk your normal speed (about 1 to 1.5 min per 100m), and then repeat at 5 min per 100m pace.  Feel that difference.  We are optimistic that this will be in our favour on the shale slopes of Kilimanjaro.

Impossible?  Possibly, but delve deeper

Having said this, I remain anxious. Optimistically anxious, I guess you could call it. There is a lot that we cannot predict.  We don't know how altitude, or cold (air and ground), or the ground will affect us independently, let alone how they may interact with one another. I am also worried about the time on my feet - 6 to 8 hours, five days, that's a tough ask to repeat barefoot.

Then there are other, more subtle issues to worry about as well.  Sore feet mean adapted walking, and so we may end up with overuse injuries as a result of compensating how we walk. Cuts are a factor. Broken toes. So certainly, I'm nervous. We will take no risks - at the first sign of problems like frostbite or acute mountain sickness, we will act decisively to prevent long-term problems. But we are still committed, and I still believe that it is possible. Only time will tell.
Finally, I realise that the first response to this is often "impossible".  And perhaps we will return on Jan 31st saying "yes, it is".  But what I hope emerges, apart from achieving the first barefoot summit of the mountain, is the realization that when we dismiss something as impossible, we might be blinding ourselves to the fact that all it takes is some planning, preparation and deeper thought before potential solutions emerge.  For example, people have told me it's crazy because the temperatures at night are -18 degrees celsius when they did the summit.  Well, we're not doing it at night, and the temperatures don't drop that low in January.  It's actually quite disheartening how easily people dismiss things based purely on their experience.  It's almost as though they believe that if they got cold then it will be impossible for everyone else. 

The point is that there may be solutions to every possible problem you can think of.  Imagine if people stopped to think about them and solve them instead of labelling ideas outrageous and never making that second, third and fourth step.  Those steps may still fail, of course, but until you take them, you never know.

I've briefly discussed some of the steps we'll be taking in the post above.  Over the course of the next 8 days, I will be filming videos from the summit, talking you through what we are doing to combat the three issues mentioned above in more detail.  I don't know if I will be able to post these videos "live", but the worst case scenario is that when I return to South Africa on Jan 31st, I'll upload all the videos, and you can watch the trip evolve and hear me talk you through how difficult it is!

Also, I'll try to provide progress updates on Facebook and Twitter.  So if you haven't joined those communities, do so now!

And again, any donations to the Children's Hospital are greatly appreciated!

Ross

P.S.  As a final comment on Kilimanjaro, have a look at the video at this link (I tried to embed but there seems to be a blogger problem, so click through).  It shows Killian Jornet breaking the record for summitting Kilimanjaro - 7 hours 14 minutes return trip from the bottom.  Incredible performance.  But specifically, have a look at what he wears, on his hands and his head.  And yes, I realize that he is running up the climb and generating a lot more heat than we will, but anyone who has ever run at anything close to -10 C knows that your head and hands still get cold.  Jornet also doesn't wrap up at the summit when he stops for a break.  Look also at his team waiting for him on the summit, warmly dressed but without gloves.  There are many other videos of the summit where people are not in gloves at this time of the year.  This is basically to make the point that all the nay-sayers who point out that it's -20 at the summit are probably recalling the wrong time of year!  Let's hope so anyway!  And besides, it's the ground temperature that really matters!

The video also shows the terrain quite nicely - at 1:50, when Jornet gets onto the rim, there's a great close-up of what we'll be walking on.  It's a great video, educational and impressive!

The China Study II: Wheat’s total effect on mortality is significant, complex, and highlights the negative effects of low animal fat diets

The graph below shows the results of a multivariate nonlinear WarpPLS () analysis including the variables listed below. Each row in the dataset refers to a county in China, from the publicly available China Study II dataset (). As always, I thank Dr. Campbell and his collaborators for making the data publicly available. Other analyses based on the same dataset are also available ().
    - Wheat: wheat flour consumption in g/d.
    - Aprot: animal protein consumption in g/d.
    - PProt: plant protein consumption in g/d.
    - %FatCal: percentage of calories coming from fat.
    - Mor35_69: number of deaths per 1,000 people in the 35-69 age range.
    - Mor70_79: number of deaths per 1,000 people in the 70-79 age range.

Below are the total effects of wheat flour consumption, along with the number of paths used to calculate them, and the respective P values (i.e., probabilities that the effects are due to chance). Total effects are calculated by considering all of the paths connecting two variables. Identifying each path is a bit like solving a maze puzzle; you have to follow the arrows connecting the two variables. Version 3.0 of WarpPLS (soon to be released) does that automatically, and also calculates the corresponding P values.

To the best of my knowledge, this is the first time that total effects are calculated for this dataset. As you can see, the total effects of wheat flour consumption on mortality in the 35-69 and 70-79 age ranges are both significant, and fairly complex in this model, each relying on 7 paths. The P value for mortality in the 35-69 age range is 0.038; in other words, the probability that the effect is “real”, and thus not due to chance, is 96.2 percent (100-3.8=96.2). The P value for mortality in the 70-79 age range is 0.024; a 97.6 percent probability that the effect is “real”.

Note that in the model the effects of wheat flour consumption on mortality in both age ranges are hypothesized to be mediated by animal protein consumption, plant protein consumption, and fat consumption. These mediating effects have been suggested by previous analyses discussed on this blog (). The strongest individual paths are between wheat flour consumption and plant protein consumption, plant protein consumption and animal protein consumption, as well as animal protein consumption and fat consumption.

So wheat flour consumption contributes to plant protein consumption, probably by being a main source of plant protein (through gluten). Plant protein consumption in turn decreases animal protein consumption, which significantly decreases fat consumption. From this latter connection we can tell that most of the fat consumed likely came from animal sources.

How much fat and protein are we talking about? The graphs below tell us how much, and these graphs are quite interesting. They suggest that, in this dataset, daily protein consumption tended to be on average 60 g, whatever the source. If more protein came from plant foods, the proportion from animal foods went down, and vice-versa.

The more animal protein consumed, the more fat is also consumed in this dataset. And that is animal fat, which comes mostly in the form of saturated and monounsaturated fats, in roughly equal amounts. How do I know that it is animal fat? Because of the strong association with animal protein. By the way, with a few exceptions (e.g., some species of fatty fish) animal foods in general provide only small amounts of polyunsaturated fats – omega-3 and omega-6.

Individually, animal protein and wheat flour consumption have the strongest direct effects on mortality in both age ranges. Animal protein consumption is protective, and wheat flour consumption detrimental.

Does the connection between animal protein, animal fat, and longevity mean that a diet high in saturated and monounsaturated fats is healthy for most people? Not necessarily, at least without extrapolation, although the results do not suggest otherwise. Look at the amounts of fat consumed per day. They range from a little less than 20 g/d to a little over 90 g/d. By comparison, one steak of top sirloin (about 380 g of meat, cooked) trimmed to almost no visible fat gives you about 37 g of fat.

These results do suggest that consumption of animal fats, primarily saturated and monounsaturated fats, is likely to be particularly healthy in the context of a low fat diet. Or, said in a different way, these results suggest that longevity is decreased by diets that are low in animal fats.

How much fat should one eat? In this dataset, the more fat was consumed together with animal protein (i.e., the more animal fat was consumed), the better in terms of longevity. In other words, in this dataset the lowest levels of mortality were associated with the highest levels of animal fat consumption. The highest level of fat consumption in the dataset was a little over 90 g/d.

What about higher fat intake contexts? Well, we know that men on a high fat diet such as a variation of the Optimal Diet can consume on average a little over 170 g/d of animal fat (130 g/d for women), and their health markers remain generally good ().

One of the critical limiting factors, in terms of health, seems to be the amount of animal fat that one can eat and still remain relatively lean. Dietary saturated and monounsaturated fats are healthy. But when accumulated as excess body fat, beyond a certain level, they become pro-inflammatory.

Ground meat treats: Beef and bison meatza

At the time of this writing, there was no Wikipedia article for the term “meatza”, which surprised me a bit given the number of recipes on the web. In fact, I could not find anything concrete about the dish’s tradition or  history.

Another thing that surprised me about this dish is how much my family and I like it. It has become a regular weekend treat for us for quite some time now.

The recipe below is for a meal that feeds 4-8 people. Like in my previous recipe for a zucchini and onion meatloaf (), the ground beef used here has little fat, and thus a relatively low omega-6 content. Most of the fat comes from the ground bison, which has a higher omega-3 to omega-6 ratio.

- Prepare some dry seasoning powder by mixing sea salt, parsley flakes, garlic powder, chili powder, and a small amount of cayenne pepper.
- Mix 2 lb of very lean ground beef (96/4) with 1 lb of ground bison.
- Add the dry seasoning and a whole egg to the ground meat mix.
- Vigorously mix by hand until you get a homogeneous look.
- Place the mix into a sheet pan coated with olive oil. Richard’s suggestion of creating edges helps keep the sautéed vegetables on top, when they are added later ().
- Preheat oven to 375 degrees Fahrenheit.
- Bake the meatza for about 15 minutes.
- Grate 1 lb of aged cheese.
- Slice one tomato, half an onion, and one green bell pepper, and sauté them in olive oil.
- Drain the meatza after if comes out of the oven, and add the sautéed vegetables to the top, together with half a can of tomato sauce.
- Add the 1 lb of grated aged cheese on top of the vegetables and tomato sauce.
- Return meatza to the oven, still at 375 degrees Fahrenheit, and bake it for about 10 minutes.

The photo montage above shows a side dish of baked potatoes and zucchini. That is optional, as the meatza has vegetables added to it. I usually cut the meatza into 8 rectangular pieces. Each rectangle will have about 50 g of protein and 20 g of fat. The fat will be primarily saturated and monounsaturated (both healthy), with a good balance of omega-3 and omega-6 fats. Each piece of meatza will also be a good source of vitamins B12 and B6, niacin, calcium, zinc, selenium, and phosphorus.

HCE user experience: The anabolic range may be better measured in seconds than repetitions

It is not uncommon for those who do weight training to see no gains over long periods of time for certain weight training exercises (e.g., overhead press), even while they experience gains in other types of exercise (e.g., regular squats).

HealthCorrelator for Excel (HCE) and its main outputs, coefficients of association and graphs (), have been helping some creative users identify the reasons why they see no gains, and break out of the stagnation periods.

It may be a good idea to measure the number of seconds of effort per set; in addition to other variables such as numbers of sets and repetitions, and the amount of weight lifted. In some cases, an inverted J curve, full or partial (just the left side of it), shows up suggesting that the number of seconds of effort in a particular type of weight training exercise is a better predictor of muscle gain than the number of repetitions used.

The inverted J curve is similar to the one discussed in a previous post on HCE used for weight training improvement, where the supercompensation phenomenon is also discussed ().

Repetitions in the 6-12 range are generally believed to lead to peak anabolic response, and this is generally true for weight training exercises conducted in good form and to failure. It is also generally believed that muscular effort should be maintained for 20 to 120 seconds for peak anabolic response.

The problem is that in certain cases not even 12 repetitions lead to at least 20 seconds of effort. This is usually the case when the repetitions are performed very quickly. There are a couple of good reasons why this may happen: the person has above-average muscular power, or the range of motion used is limited.

What is muscular power, and why would someone want to limit the range of motion used in a weight training exercise?

Muscular power is different from muscular strength, and is normally distributed (bell curve) across the population, like most human traints (). Muscular power is related to the speed with which an individual can move a certain amount of weight. Muscular strength is related to the amount of weight moved. Frequently people who perform amazing feats of strength, like Dennis Rogers (), have above-average muscular power.

As for limiting the range of motion used in a weight training exercise, one of the advantages of doing so is that it reduces the risk of injury, as a wise commenter pointed out here some time ago (). It also has the advantage of increasing the number of variations of an exercise that can be used at different points in time; which is desirable, as variation is critical for sustained supercompensation ().

The picture below is from a YouTube video clip showing champion natural bodybuilder Doug Miller performing 27 repetitions of the deadlift with 405 lbs (). Doug is one of the co-authors of the book Biology for Bodybuilders, which has been reviewed here ().

The point of showing the video clip above is that the range of repetitions used would be perceived as quite high by many bodybuilders, but is nevertheless the one leading to a peak anabolic response for Doug. If you pay careful attention to the video, you will notice that Doug completes the 27 repetitions in 45 seconds, well within the anabolic range. If he had completed only 12 repetitions, at about the same pace, he would have done that a few seconds before hitting the 20-second mark.

Doug completes those 27 repetitions relatively quickly, because he has above-average muscular power, in addition to having above-average muscular strength.

Science of Sport awards: Teams of the year - Kenya & Barcelona

Team of the year - Kenyan athletics and Barcelona

Welcome to 2012!  It's an Olympic year, the undoubted highlight of the year for us, but there are Tours, Marathons, meets and matches to cover and we are looking forward to the analysis, debate and discussion.  We hit our three millionth visitor on New Year's Eve, and we're hoping for another million this year!  Dollars, that is...!

I'm still forging on with the recap of 2011 (better late than never), only three to go, and then we'll start looking ahead to 2012.  And today, it's Team of the Year, which is a shared award between Kenya (a pseudo-team, since athletics/running aren't exactly team sports) and Barcelona.

Kenya - total dominance

2011 was the year of the marathon, and it was completely owned by Kenya.  Not just dominated, but owned.  The year-end lists show that the Top 20 times in the marathon were run by Kenyans.  That's right - all 20 were from Kenya.  That list includes a new world record, and the winning performances from every major city marathon in 2011, and the World Championships marathon.  Not only were the majors won by Kenyans, but the course records at every major city marathon were broken too.  Not in that list are the incredible Boston marathon performances, where Mutai and Mosop ran 2:03:02 and 2:03:06 respectively, since those times are not eligible for official lists (the result of that, in case you are wondering, is that Ryan Hall's 2:04:58 also doesn't feature on that list - it's the fastest performance by a non-Kenyan in 2011, but not official).

The result of this Kenyan dominance was that the average of the Top 10 performances was a staggering 2:05:00.  That's almost 40 seconds faster than the world record only nine years ago, and more athletes broke 2:07 in 2011 than ever before (25 did it - 24 were Kenyan, only dos Santos of Brazil is in that company.  2:06 was broken by 11 men, incidentally).  In November, I analyzed the top performances and discussed the "seismic shift" that has occurred, along with some of the reasons behind it - worth a read for more detail.

Perhaps the most remarkable statistic was this one - 70 Kenyans ran faster over the marathon than the fastest European athlete. That was Oleksandr Sitkovskyy, a Ukranian who ran 2:09:26.  Ryan Hall's officially recognized performance from Chicago (2:08:04) is the second-fastest of the year by a non-African (dos Santos being first).

Kenya's dominance does not end with it's men marathon runners.  On the women's side, marathon running is not nearly as dominant, but they still have four women in the top 10, including the second fastest performance of 2011 with Keitany's London win.  Kenyan women swept the medals in the Daegu World Championships in August (Kiplagat, Jeptoo and Cherop), and they won two of the Majors (London and Berlin).  The battle between the Kenyans, particularly Keitany who really should have won New York but for her super fast early pace, and Liliya Shobulkhova, 2011's world number 1 will be one of the highlights of 2012, whether it comes in London in April or in August.

On the track, Kenya had one of their most successful campaigns ever.  At the Daegu World Championships, Kenya finished third on the medal table, winning 7 golds, 6 silvers and 4 bronzes.  The golds were won across the spectrum - Men's 800, men's 1500m, men's steeplechase, men's marathon, women's 5000m, women's 10000m and women's marathon.

Only one missing accolade

The only area where Kenya have yet to figure out a solution to the Ethiopian riddle is the long track events for men.  In the 10,000m in particular, Ethiopian men have shut Kenya out of gold since 1993.  In fact, with the exception of Charles Kamathi's gold in 2001, Ethiopian men have won every 10,000m gold since 1993 (admittedly, of the twelve golds won by Ethiopia in this stretch, 11 were shared between two men - Geb and Bekele!)

Unless Kenya can discover a 26:40 man with 52 second final lap closing speed in the next 6 months, that streak looks set to continue in London, though Mo Farah may have something to say about whether it's an Ethiopian streak or just a 'non-Kenyan' one!

Other than this, however, it's difficult to see Kenyan dominance being broken.  20 out of 20 in the marathon.  Their gold medallists looked peerless in Daegu.  And in Vivian Cheruiyot, they have the world's best female athlete, one of the stars of London 2012 if she maintains her 2011 form.  Kenya will therefore be the best performing African nation in London.

For the rest of the world, competing at the very highest level must feel futile. Hall flies the flag, as does Keflezighi, for the USA.  The promise of Galen Rupp stepping up to the marathon will be interesting, since he brings 26:40-credentials to the road.  That of course is one of the big reasons for the shift in marathon running - the entry of very fast, 26:40 men into the marathon before they have lost that speed.  Mo Farah is the other athlete who will be looked at to challenge Kenya over the marathon one day.

The genetic vs training debate

The scientifically fascinating debate is whether this dominance is genetic or environmental.  That's an unnecessarily polarized question.  To repeat a mantra I used a lot in 2011 - when someone wants to polarize an explanation into one of two things, they are always wrong.  The reality is that the kind of dominance that has been achieved by Kenya is too complex to the result of one or two factors.  If it was one, or even two-dimensional, then the world would imitate it very easily.  The fascinating thought experiment would be to apply the same environmental factors (training, diet, altitude, culture, socio-economic factors) to a few groups around the world, over three or four generations, and see how successful they are.  Of course, this experiment isn't going to happen, so we speculate.

There's no question that the pioneers of distance running in Kenya, the men who won Kenya's first global medals in the 1960s, were the catalyst for a generation of young athletes who could now simply imitate and aspire to follow in their footsteps.  Physical activity is a part of life in Kenya (not always running to and from school, I might add), and so is the desire to become a great runner.  The economic incentives are enormous, there are sufficient competition structures to identify the most talented athletes, and a culture of success that is demonstrated by the 2011 marathon results - "he did it, why not me?"

But none of these factors, as well-described as they are, disprove that some genetic factor is also in play.  The same ingredients applied elsewhere (because let's face it, there are many other regions around the world with similar isolated factors) may not produce the same results.  In a nation of 270 million people, for example, is there not a single athlete who has trained as hard as 100 Kenyans, with the same desire to succeed?  Of course there will be, but the ceiling that can be reached is genetically influenced.

I am something of a believer in the role of genes in performance, as you may recall from our talent vs training debate.  The failure of science to discover that gene, I believe, is more a function of genetic complexity combined with our limited ability to understand it.  As mentioned in the genetic debate, it takes 300,000 gene variants to explain only 50% of something like height.  Only 45% of training response can be explained by vast gene arrays.  How much more complex might performance be?

2011 produced some of the first scientific evidence that the response to training was strongly influenced by genes.  That is, it was found that individuals who had a certain number of specific genetic variants (called SNPs) were "high-responders", whereas those who lacked these specific gene variants saw almost no change in their VO2max or performance after months of training (the "low responders").  You can read more on this study here.  What hasn't been done yet is to show whether these SNPs are present more in certain populations than in others.  That's the study that would show whether the probability of discovering a high responder (and thus potential great runner) is greater in some groups than others.  Of course, as molecular methods improve, and genome-wide association studies become more powerful, these potential links will become clearer.

The fact that Jamaica and the USA dominate sprints and that east Africa dominate distance running is one of the most intriguing areas of exercise physiology.  And exercise economics, when you look at things like incentives, culture, economic factors.  The addition of genes to this mix is what makes Kenyan running so fascinating.

Until those answers are provided, we have only questions and theories.  There's no doubt however, about who the team to beat is in international running.  The only question, for the rest of the world, is "How"?

Barcelona - changing the way coaches approach sport

The second winner of the Team of the Year award is Barcelona's all conquering football team.  On the surface, that's an easy award to give out, because Barcelona have been exceptional.  In 2011, they won the Champions League, Spanish League title, World Club Championships, and a host of other trophies, bringing to 12 (out of a possible 15) the number of titles they've won under coach Pep Guardiola.

The fascinating thing for me, at least from a sports science/management perspective, is the manner in which they have achieved this success.  Yes, they have some of the greatest players in the world - the Player of the Year award title for 2010 (awarded in 2011) was a straight shootout between three Barca players in Lionel Messi, Xavi and Andres Iniesta (Messi won it).  But the Barcelona "way" is so distinctive that it has begun to inspire coaches and sports administrators from other sports to want to imitate it.

Much has been written about the Barcelona style of football, and their now legendary youth academy, La Masia (one such story can be read here), which produced Messi, Xavi, Iniesta, Puyol, Pique, Febregas, Busquets and Valdez of the current typical starting 11.

Barcelona's movement off the ball, the positional awareness of the players, the work rate when not in possession, and the ability to manipulate space and defenders are the "buzzwords" that I've heard a great deal around the sport of rugby, for example!  One rugby coach has expressed that it is his vision to be the "Barcelona of Sevens rugby", such is the influence of Barcelona on other coaches.

And why not?  Barcelona's dominance has been complete and distinctive, technically speaking, to the point that their opposition have likened playing them to playing against Playstation figures.  I'd be going beyond the limits of my own football knowledge to describe the technical characteristics of what the players learn at La Masia, and at the senior team, the specifics of what make them so remarkable.

The success of the club is again not the product of any single factor (in the same way that Kenyans aren't great runners for one reason alone).  So the Barcelona approach to youth development, their focus on skill and movement rather than size, strength and speed, and their desire to teach sportsmanship and creativity ahead of winning are only part of the mix.  Not one of these factors should be viewed as a competitive advantage, however - they are all easily replicated, in theory anyway.

The youth academy concept is now so common in sports, particularly football and rugby, and many of the elements and principles are shared, at least on paper.  The ethos of youth development is not unique, and nor is the attitude that "we invest in the person, not just the player".  This approach to youth-development is now accepted as best-practice, and every academy will have a code of conduct that dictates how young players are to be taught and managed.  So again, simply following the "recipe" doesn't guarantee the end-product.

The challenge for other coaches and sports administrators, even in sports like rugby, who want to imitate the Barcelona way, is to recognize how difficult it is to develop the culture that underscores the technical excellence and the on-field results.

Nevertheless, the Barcelona model will continue to be discussed, and attempts made to imitate it.  It is the sincerest form of flattery.  What we (the outsiders) see is the end result, which is sometimes breath-taking.  The 5 goal demolition of Real Madrid in 2010, the 4-0 defeat of Santos in the Club World Championship final in December, and the defeat of Manchester United in the Champions League Final at Wembley are some of the highlights from Barcelona's on-field "end product".  Whether the system can be reverse engineered, I have my doubts, but when a team is held up as the gold standard for how to play, then they're worthy of "Team of the Year".

Ross