[crazygringo]

There are a lot of people who insist that calories must be equal in terms of weight loss/gain, or else there would be violation of the laws of thermodynamics or something...

To quote Gary Taubes, who tries to puncture this myth:

The reason people believe we get fat because of overeating and sedentary behavior is because they believe the laws of thermodynamics somehow dictate this to be true. In particular the first law, which tells us that energy is conserved, so if a system takes in more energy than it expends, the energy contained in the system has to increase. If that system happens to be our fat tissue, than the fat tissue accumulates fat. That’s the logic. So if we eat more than we expend, we get fatter and the logic turns this around to say that we get fat because we eat more than we expend. And so, overeating and sedentary behavior are the causes. This is the logic that leads virtually every government health agency and independent health organization (the AHA, the AMA, you name it) to have some variation of this World Health Organization statement on its website or in its promotional material: “The fundamental cause of obesity and overweight is an energy imbalance between calories consumed on one hand, and calories expended on the other hand.”

[neutronicus]

People talking like you can perform a thermodynamic analysis of nutrition is definitely a pet peeve as a physicist.

[mathewsanders]

+1 it drives me crazy too. Calories are a unit of stored energy. Wood has plenty of calories (great for fires) but if you eat a bunch of bark you're not going to store that weight, you're just going to make yourself sick.

[kyberias]

I don't understand how this quote from Taubes proves anything. If I stop eating, I will lose weight and eventually die. Also, if I eat more, I will gain weight. Thus calories must have SOMETHING to do with weight, right? I think Taubes is fighting a straw man here: I haven't heard anyone argue that eaten calories are stored in 1:1 ratio. But they have some causal relationship.

[travisp]

Sure, if you stop eating you will lose some weight and die. But, you can die of starvation while obese. In animal studies, it is possible to reduce calories and the animals won't lose weight or to add a lot of extra calories and not become obese.

Calories have something to do with it because they are one part of the equation. Calories in does equal calories out. Calories In = Calories Stored + Calories Expended. But, the mistake is in thinking that the law of thermodynamics means that the type of calories in doesn't impact the ratio of calories stored/expended -- the variables are not independent. The content of the food you eat impacts: your hunger, your energy level, fat storage rates, and your metabolic rate, all of which mean that attempting to cut or add calories may not have the expected impact depending on what the food is.

[kyberias]

BTW, could you refer to some of these animal studies that show that reducing calories does not impact the weight? I hope the animals in question are not for example ants but more like primates or something resembling humans.

[kyberias]

Got it. I've heard that theory before but never have I seen any substantial evidence. I accept that the food I eat might have some effect on my "hunger" and "energy level". Which in turn could make me eat more or exercise less. That doesn't really have anything to do with calories per se. Many other causes have the same effect, e.g. psychological or hormonal situations. However, the real argument seems to be that what one eats impacts one's "fat storage or metabolic rates". That's hard to believe. It would be interesting to see some hard evidence to support that claim. The present study tries to give some results, but I think the sample rate is insufficient. I've seen much evidence to the contrary.

[travisp]

The idea that carbohydrates impact fat storage through insulin is one of the main arguments put forward by Taubes in his book, and he provides a lot of evidence and studies to back up his assertion. He may be wrong (and he somewhat acknowledges this and calls for proper studies to be done), but it's worth reading if you want to understand what the argument is.

[bitdiffusion]

If you read the whole article, Taubes isn't saying that there is not a link between calorie intake and weight-gain - what he is saying is that it's not "causal" in any useful sense. Why exactly overweight people consume more calories is still a mystery and it's a gross oversimplification to discuss the law of thermodynamics when considering "why someone is overweight".

[kyberias]

I haven't heard anyone but Mr. Taubes "discussing the law of thermodynamics". For me, there is zero mystery why obese people are fat. They have eaten and continue eating more (calories) than other people. And they will get less obese if they eat less. What exactly is the mystery here?

[planetguy]

Yes as and no. Fundamentally weight gain/loss really is a matter of calories in vs calories out; if you're burning more calories than you're consuming then you're gonna be losing weight. It's akin to saying that all you need to do to win at golf is to hit the ball really hard towards the hole -- true, but not necessarily good advice.

The reason sometimes we put too much emphasis on the basic-thermodynamics side of things is that we're busy fighting a war against dumb fad diets.

But once you acknowledge the basic calories in vs calories out principle, you can start thinking about what foods make it easiest to maintain a caloric deficit. Even the most 'traditional' of health authorities acknowledge that this is a factor, which is why they won't say "Hey, whatever, eat three slices of chocolate cake a day and nothing else". The first factor is making sure you get sufficient nutrition along with your calories, the second is making sure you feel full while maintaining a caloric deficit. There's a growing acknowledgement that low-carb diets can help with both of these.

This study suggests a third factor: that eating a low-carb diet can actually boost your base metabolic rate. How? Not sure. It would be interesting to see whether it gets replicated in a larger scale study.

[rprasad]

Other studies have explained/tried to explain how the low-carb diet (i.e., Atkins) work. The basis gist of those studies is that the body burns fat reserves instead of carbs. Burning fat requires more energy than burning carbs, which increases the body's BMR.