Science May Soon Give Us Pills That Make Us Exercise

> But "calories in - calories out" is a simple statement of conservation of energy.

At the physical thermodynamical level, yes. But estimating "calories in" from food intake and estimating "calories out" from exercise apparently have +/-50% error if you take the numbers from the food packaging and from an exercise book respectively, if you actually measure them for a specific person (which is exceedingly hard, almost never done properly, and always takes for granted assumptions that are not proven -- see my answer to DanBC down this thread)

I should have been more precise: "calories in - calories out = calories stored" is a tautology given conservation of energy, as you alluded. But it turns out to be a very inaccurate prediction if weight gain if you assume "calories in"="what's written on the food label", "calories out=what's written in an exercise book about your exercise", and "calories stored=9kcal/g per body weight gained". All 3 are bad measurements, that somehow work out for the majority (60%-90% of the population, depending on how you set your error bars), but break for a minority.

If conservation of energy did not work for 10% of particles, physicists would look for a better description. Somehow, nutrition "experts" are allowed to hand wave the inaccuracies and are given a free pass as scientists. They aren't.

I'm guessing he's referring to Gary Taubes and the book, Good Calories, Bad Calories. It was a big thing years ago, and I would have also assumed most people knew about it. One of the basic ideas is that calories in - calories out = fat is an oversimplification and ignores the complexities of the way our bodies process different foods. In other words, the argument isn't trying to break the laws of physics, it's just arguing where the energy is actually going in your equation.

The book itself is lengthy and comprehensive. He cites a lot of research to make his case, and the citations are available in the book.

With that said, I don't think calories in - calories out is wildly inaccurate, and I don't believe Taubes makes that case.

> You fail to provide any references to these documented examples.

Do you know _why_ people believe the "standard" model to be true? Sometime around 15 years ago, assuming this to be true, I was looking for a repeatable experiment to demonstrate this -- after all, this seems to be such a basic truth that such an experiment must be described, is that not true?

Well, turns out that this is a result of very fragile argumentation, basically:

1) This is how how much energy is released by oxidation from wide classes of fat, protein and carbohydrates, as can be readily verified with a calorimeter.

2) cells generally use oxidation as the mechanism to produce energy.

3) The human body is very efficient.

While 1) is generally true, if you take it as is, you should be able to feed off paper - cellulose is a carbohydrate, and gives ~4kcal/g of energy when oxidized in a calorimeter. But somehow you cannot. You have to take someone's word that only monosachrides and polyssachrides can be oxidized for energy. (A recent Lyle McDonald booklet I read gave references to recent data showing that some people derive 2kcal/g of "dietary fiber" (e.g. cellulose) - totally outside the standard assumed theory)

2) is generally true, but there are some cases (most notably, but not only, cancerous cells) in which the energy production mechanism is not oxidation. This is much less efficient, and generally produces just 0.7kcal/g of sugar.

3) is generally true. But lack of the right enzymes (which are not necessarily available, and when available may take up to 3 weeks to ramp up production for a new food) or other environmental issues can very significantly reduce food uptake.

Furthermore, the body is able to modulate thermogenesis to the point that any measurement that does not take into account continuous body and environmental temperature is looking at half the data.

> or can eat less calories than they burn and gain weight.

Well, there is a sense in which "calories in - calories out" is meaningful, which is the thermodynamic sense. It's just that the "calories list" on food packaging and "calories in " in the thermodynamic sense are at odds, and "calories out" and general calorie-used tables for exercise are at odds.

Sadly, I didn't keep the references when I was following them, but MGU had done a lot of relevant studies. If you are really interested, follow the references from Seth Roberts' "What makes food fattening" (available as PDF, especially Michel Cabanac and Robert Israel), Stephen Guyenet's descriptions of non-industrialized cultures (Many of which had very significant dietary intake but no obesity problem, until they started with industrial farmed grains). If you want actionable advice, read about Dave Asprey's "BP diet" (and follow his references for the science), and even Tim Ferris "slow carb diet". Both consistently produce impossible (from a classical nutrition theory) results, including e.g. Dave's no-exercise-4500-calories-a-day diet on which he remains super lean.

> Wait, what? That makes no sense at all.

Don't take my word for it. Try to figure out why you believe carbohydrate=4kcal/g, protein=4kcal/g, fat=9kcal/g, alochol=7kcal/g, and nothing else matters. You'd be surprised at what you find.

> (Also, what happened to the other 30%??)

There are about 10% of people from what I can tell for which standard models break so badly that they attribute it measurement errors, malfunctioning metabolism or various other ghosts. (data that seems to be discarded by researchers because it doesn't fit priors). It's hard to know, because .. this data is generally ignored by anyone doing large controlled studies.

The other 30% fit within "standard" acceptable error bars, but are not well described by the theory. 60% or so seem to be perfectly well described by theory.

When you dive into it, a lot of accepted wisdom about medicine and nutrition is faith based rather than evidence based, including quite a bit about vitamin B12 sourcing, stomach ulcers, cholesterol, salt, vitamin D, sunlight, allergies and a whole lot more -- energy metabolism in the real world is just another one of these.