What's your view on calories in vs calories out theory?

I think that theory is true, to an extent. If I ate 15 chicken breasts in a day, I would most certainly not feel healthy. However, I eat a high-fat, low-carb diet and find that what I WANT to eat is consistently under my caloric goal. For me, it's not so much that I eat low-carb because that means I can eat more, but that I feel fuller and more energetic longer if I've been loading up on avocado, coconut oil, full-fat yogurt, and steak. But my goal is different--I'm not trying to be "low-carb," I'm trying to eat a minimally processed diet, which means cutting out cereals, bread, and so on. Which leads me to eat more meat, veg, fruit, and simple carbs like quinoa and farrow. I'm eating to support my strength and fitness goals, which means less crap, more FOOD! If it seems like there's no way you could ever give up processed carbs, that means you're addicted The longer I went eating high-fat, high-protein, the less I crave sugars and starches.

I don't think calories in and calories out is nonsense. I think both of these views are compatible, in that eating a high-fat, high-protein, low-carb diet makes it easier to fall within my goal caloric range.

Well first of all I refuse to believe a single random person who supposedly did a test on himself. Without controlled environment and professional people who check him, without specific recorded data. I bet he did not recorded how much of all of that was water weight, fat, how much was daily calories burned from exercise, how high was his metabolism, did he took any specific medications, etc. If we even assume he simply does not talk pure nonsense and even did the test in first place. This is not how studies are made. All the legit research I trust shows that it is indeed all about calories in vs calories out. There have been made some researches to prove otherwise but non of them succeeded to do so. So I don't think it's even right to call it "calories in vs calories out theory" cos it is not just a "theory", we have a scientific proof of that.

That beings said, of course things like hormones and how much energy is necessary to digest some type of foods is a factor. And person with health some problems or hormonal differences might not lose weight whatever he does, or might lose more. But in that case it isn't only about calories in vs calories out, is it? It's completely different discussion...

http://www.cnn.com/2010/HEALTH/11/08/twinkie.diet.professor/

It's calories in vs. calories out for weight loss.

But when trying to maximize fat loss while minimizing lean tissue losses, the quality of the calories comes into play.

the laws of thermodynamics are not "a theory" that's why they're called the laws of thermodynamics, not the theory of thermodynamics.

but there is confusion on what exactly "calories in v calories out" means, so I'll clarify:

Some people think that when you say "calories in v calories out" works for everyone, without exception, that it means that you can put anyone's numbers in a calorie calculator, subtract a percentage and they'll lose weight on that number. That is *not* what it means. The calorie calculators will not work for everyone........................ but that does not mean that calories in v calories out isn't true for them.....

.....calories out = the total number of calories your body uses (burns), including everything you do and everything your body does to keep itself alive. Calories in = calories from food that your body uses (or from a drip feed, if that's the case). If these two numbers are equal, you will stay the same weigh (NOT including water weight fluctuations). If more is going out than in, then you'll lose weight. If more is going in than out, you'll gain weight (yes both of those don't include water weight fluctuations either). The weight gained or lost in each case could be fat or muscle, that depends on *how* you lose/gain the weight.

So what about people for whom the calorie calculators don't work? Well the above is still true, but they may have a slow metabolism (which could be due to medical issues) which means that the *calories out* side of the equation is lower than it should be, i.e. the body isn't using as many calories as it should be, and it's much harder to eat little enough to be eating less than you burn off. In this case, it's *not* a good idea to simply eat less and less, you need to fix the metabolic issue, i.e. get the body back to burning the right amount of calories for you. In some cases continuing to eat less and less results in the metabolism slowing even more. So in those people it may be the case that "just eat less than you burn" isn't the best advice, but it does not mean that calories in v calories out isn't true for them. It means that the way to make a deficit is to increase the calories out part of the equation, not to eat less (in some cases that may mean medical intervention, e.g. treatment for hypothyroid).

There are other situations where calories in v calories out may appear not to apply, e.g. if someone has a problem that their gut is not absorbing the food. They could be eating 3000 calories a day, burning just 1800 a day, and still losing weight, but the reason for that is that the calories are not actually going in, the body is not absorbing or using them. In situations like these (which are rare but do happen) the person is just pooping out a lot of the calories they eat, instead of absorbing and using them. If they're losing weight given the numbers I said, they may only be absorbing half of what they eat, i.e. 1500 calories a day, which is less than what they're burning (1800 cals/day) and so they lose weight. BTW if this is the situation you need to see a doctor ASAP as this is a serious medical issue, I just used it as an example of when calories in v calories out may appear to not be true.

So anyway, yes calories in v calories out is a) not just a theory and b) really does work for everyone, but there are various factors that mean that actual weight loss (or weight gain) advice is not so straight forward for everyone as simply putting your numbers in a calculator and eating a percentage less than the number it spits out. Even without medical issues, those calculators are based on averages, so you have to just use them as a starting point and adjust your calorie goal based on real world results. (but if your real world results suggest the calculator is waaaay off, that might be indicative of a medical problem)

It's calories in vs. calories out for weight loss.

But when trying to maximize fat loss while minimizing lean tissue losses, the quality of the calories comes into play.

QFT

Gary Taubes has written extensively on the question and argues against calories in vs calories out. Might want to check out: http://garytaubes.com/

gary taubes is famous for his pseudoscience. try human physiology 101 instead. taught by university professors who have a vested interest in their students learning correct information so they can pass exams on the subject.

People who bring up "the laws of thermodynamics" are not thinking it through enough.

If I eat "3,000 calories" of... stuff... and do "2,000 calories" of... stuff... I'll gain weight, right? THERMODYNAMICS!

...What if I have diarrhea? Some quantity of the food I put into my mouth will come out the other side without full digestion. So I "ate 3,000 calories" and I "burned 2,000 calories", and I didn't gain weight. How did I not violate the laws of thermodynamics? By putting the other 1,000 calories into the toilet. Obviously, people don't normally have diarrhea, but people *do* normally excrete food that is less-than-100% digested.

Okay, that's gross, let's think about something else. Let's say I eat 2,000 calories, and you eat 2,000 calories. We are the same weight, and we do the same activities. At the end of the experiment, we should both be the same weight, right? We started at the same weight, we ate the same calories, we did the same activities. Calories in, calories out! But we don't weigh the same, even after you account for the toilet. What gives?

...Did you check our body temperatures? Hey, you ended up an ounce lighter than I did, and your body temperature is half a degree higher. Where did that heat come from? It came from your calories. Your body maintained a higher temperature than mine, which required it to burn more calories, which left fewer calories to turn into fat. People have natural variations in body temperatures -- not every is 98.6, all the time, every day. THERMODYNAMICS dictates that the heat has to come from somewhere.

And it's not just the differences in our bodies. Not all foods make their calories equally available. If I drank 500 calories of pure sugar-water, my body would absorb that pretty well and I would get pretty close to 500 calories of energy (or fat) out of that. If I swallowed a condom filled with 500 calories of petroleum jelly, I would get pretty close to 0 calories of energy out of that. There's no violation of thermodynamics, here -- as I said before, the missing calories are in the toilet. Some foods are easy for your body to rapidly digest, others may not be fully digested by the time they end up in the toilet.

Thermodynamics doesn't have a thing to do with it.

Thermodynamics doesn't have a thing to do with it.

That's absolutely incorrect. One just needs to account for all effects in their energy balance. That is, energy expended by metabolic activty must be added to the "energy out" term, as does energy radiated out via a person's skin, as does energy lost in diarrhea. If one accounts for everything, it will work.