The Logics of Weight Loss (artikkel av Martin Berkhan)

[Niklas]

Synes denne artikkelen var så bra, men litt leit at den ble postet på FB og ikke på bloggen hans. Så jeg valgte å dele den med dere.

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The Logics of Weight Loss: How Your Body Thinks It Should Be Done

Ok, here's a little something I threw together in a jiffy as they say, the kind of stuff that is sciency at points, but without any specific PubMed link or study in place. I write easily if I don't need the formalities that constantly interfere with the writing itself. Most certainly a luxury I shall allow myself here.

In brief, this short article explains the logic of weight loss, the hardwired priorities of our physiology. I think you will find that our bodies are quite sensible and predictable after all is said and done.

This is also what I've found in some of my own mathematics and study - fancy talk for "clients", and how you can rank, classify, and predict a certain outcome that will be true for the great majority. There is no "everyone is different", requiring 29 fat loss routines, etc.

Ok, enough nonsense now, let's see what comes now.

Body fat and fat burning

The greater the body fat mass, the higher the abundance of fatty acids readily available for lipolysis - simply put, the fatter you are, the greater % fat used whenever some calorie deficit is created. Vice versa, of course, as leanness means less fat burning.

Fat burning here is simply the choice of substrates in fuel economy at any given moment - greater fat burning, just think of that as greater % fat used, etc. As you know, we burn a mix of fat, glucose, protein, and this can be roughly measured by R.Q.

Read for some talk about that (R.Q) http://www.leangains.com/2010/11/cheat-day-strategies-for-hedonist.html

Quantifying Fat Burning

So all this sounds simple, quite logical. There's even a formula, a paper with all kinds of long equations, in which we find that ~77 kcal/kg fat mass is a theoretical limit, the maximum of fat from fat stores that you can burn off in a day.

So if you're 80 kg and 15% body fat, you can mobilize 924 kcal per day from your fat stores, about -150 g fat loss per day, according to this formula.

Exceed the number, get a -1500 kcal deficit one day, some 345 kcal or -50 g mass would then come from other fuel sources, protein, etc.

It doesn't take much thinking to have all kinds of questions and doubts about such a formula - I have never used it - but I don't think you should see this as anything else than a Fancy Formula.

It is useful to demonstrate the simple - "the fatter you are/the more you burn" etc - that fact that we simple have to try harder to avoid muscle loss as we lean down. You need to take it real easy in the single-digits, like I've said before.

Fat:Muscle Loss

So body fat by itself spares lean tissue and this is something that has been studied in great detail. In studies on starvation, lean mean lose muscle fast, in contrast to obese men that are not so severely affected, losing mostly fat.

Some figures for reference, from memory, fat loss:lean mass during weight loss in lean men 30-40% lean mass, some 10-20% in obese. This is just Average Joe & Jane, no training, standard diet, meaning a diet quite low in protein compared to what most sensible folks eat.

Ok, so there's seems to be some kind of priority system here in regards to fuel selection, and sure enough it is just that, and it provided a great survival advantage during our evolution.

It's really quite brilliant - like a calculator, thinking way ahead. Very deterministic, unless you do something to affect the process - meaning do some weight training, eat high-protein diet, etc. If you don't, you will lose weight in a very predictable pattern - clearly mapped out in key stuides like the Minnesota Starvation Study.

And the study of metabolism and metabolic fuel economy, in men and women, of varying body fatness, allowed some quantification of fat loss relative to amino acid oxidation (muscle loss) during fasting, prolonged fasting and starvation, i.e. a time period spanning

Evolution and Starvation

So let's see about those losses now. The average human can sustain the loss of one third of his muscle mass, before starvation death occurs.

One third is some critical point, after which the tissues around the heart and other life-supporting tissues start to get catabolized. (And now, since one third is what goes for Average Joe, with his average muscle mass, a large muscle mass, all factors being equal, will be catabolized faster relatively speaking - meaning % muscle loss to fat % loss in starvation. Or % muscle to % fat in a calorie deficit.)

Similarly, a complete depletion of peripheral body fat stores causes death for similar reasons, as fat stores in critical organs, like the brain, the next ones to go after that point.

(Intriguing phenomenon, for the morbid type, is the so called "king penguin syndrome", a peculiar state at the verge of death, that induces a rapid increase in metabolic rate, causing death faster than predicted. It's not quite clear what this is. Doctors at Auschwitz saw this ever so often, and I recall vaguely their tales, 'as if the person is already dead, and wills his body into death by force of will', something along those lines. Anyway, quite random, but that's how it is around here.)

Ok, so to maximize our survival time during starvation, increasing the likelihood of us finding food, and surviing, our physiology is hardwired to select fuels strategically - more fat if you got it, more muscle protein if you got muscle to spare, etc.

This selection of substrates, very precise, has one purpose - maximize survival. You die when:

1. One third of muscle mass is lost.

2. When (almost) all fat is lost.

What good would it be to burn only fat, and die quickly a ripped corpse? No, obviously not so good.

So our metabolism make the right choices, our physiology drags it out, and once we're chewing on those last fat stores - let's say Average Joe, no training, just dropping weight all down to 5% body fat, you've reached a point where muscle mass loss dominate over fat loss. That might not sound like best choices to you, but our DNA hasnät changed much.

So you see, that's why Average Joe & Jane always lose muscle on a diet. It's yet another evolutinary mechanism, quite useless today, some will argue.

Cursed by natural bodybuilders who find their bench dropping 30-40 lbs on that last 4-week stint leading up to the stage - not so strange, when they have only the capacity to mobilize some 400 calories of fat, and their coach tells them to do 2 hours of cardio every morning on a 1600-kcal low-carb diet*. It's just unreasonable, there is no such capacity, and no sense to do it unless you want to lose muscle mass.

Ok then! That's it for tonight, folks. Hopefully you learned something.