It depends on the medical problems the individual is facing.

Overweight people have the problem of a low metabolism due to diets. Which is why diets stop working. So in them, no, a low metabolism isn’t OK, especially because that low metabolism isn’t correlated with hunger signals.

Speaking of animal studies there’s also this idea that in nature everything is cyclical. You’ve got periods of feasting and you’ve got periods of famine. Eating less all the time is probably not good for longevity.

There's also the concept of baseline and highly adaptability to continued circumstances, so presumably metabolism is highly elastic if gradually tuned over the years.

Diets don't cause low metabolism, except in the sense that when you lose weight it takes fewer calories to keep the remaining smaller amount of tissue alive. So as you lose weight, in order to continue losing weight at the same rate you have to keep cutting calories even further.

That the "basal metabolic rate" slows down when dieting is shown by many studies on diet. The weight loss isn't linear and slows down over time, in about 6 months or so, even if the caloric deficit is sustained. Not only that, but the basal metabolic rate stays low even after people start eating normally again.

Here's a study: https://www.ncbi.nlm.nih.gov/pubmed/18842775

Here's another one: https://www.ncbi.nlm.nih.gov/pubmed/23535105

Another interesting finding is what happened with the Biggest Loser contestants: https://www.scientificamerican.com/article/6-years-after-the...

That group on average burned 2607 before the competition, but only about 2000 calories after the competition, even if they continued to do plenty of exercise afterwards. They also regained much of that lost weight.

Thin people shouldn't be giving dieting advice, because the obvious confounder is having a well functioning metabolism, whereas overweight people don't ;-) This is made worse by doctors doing it for the same reasons as everybody else. Until they get fat themselves, realizing only afterwards that gluttony wasn't the problem after all.

You've misinterpreted most of the research. The "Biggest Loser" study has been debunked. https://renaissancehumans.com/biggest-loser-study-calorie-re...

The concept of a damaged metabolism doesn't make sense. Your body doesn't waste energy for the hell of it, there is not even a dial for the metabolism to change. Your organs just perform their functions using energy in the process. An organ can't reduce its energy expenditure without compromising its function. Not to mention that if it were possible to live with less calories, evolution would have eked out that benefit millions of years ago.

It is well known that the resting energy expenditure is a simple function of body composition, with no influence of age, gender or body weight [0]

The first study attributes the drop in energy expenditure to the non-resting energy expenditure, which isn't part of the metabolism. There is no saying that difference in energy expenditure isn't compensated for in real life situations, the study freely admits the difficulty in controlling for it.

The second study shows a drop of energy expenditure of a whopping 2%. Another explanation of the effect could just be that the formula they use to predict the resting metabolic rate is too simple, it literally only uses two variables: fat mass and fat free mass. You wouldn't expect such a simple formula to hold over a wide range of weights, it's surprising that it works so well, to within 2%, in the first place.

The third one, the Biggest Loser study, is the only one of the three that is just plain wrong. I'm very surprised to see it appear on Scientific American. In the study, they invent their own formula for the RMR by doing a multilinear regression in 4 variables on 14 subjects. This formula is different from the usual formulae and tellingly underestimates the caloric need of fat tissue (1.5 kcal/d/kg instead of 3.5 kcal/d/kg or 5.7 kcal/d/kg as in your second study). Then they apply that formula, which was calibrated only on the obese subjects, on the people after they lost weight and compare that to the measured RMR, instead of using a more standard formula, and interpret the difference as metabolic damage. No wonder it doesn't work. If you instead plug in the data in a more accepted formula, you see little difference with the measured metabolic rate. Heck, even I have massive metabolic damage according to that formula, their formula estimates my RMR at a whopping 2460 kcal/d, which isn't my total daily energy expenditure. The measured RMR in the article, 1903 kcal/d, wouldn't be unusual for people of that weight.

That study should have never gotten past peer review, and I don't know why it hasn't been retracted yet.

I don't understand the focus on metabolism anyway. Even if a damaged metabolism existed (it doesn't), that still wouldn't change anything if you ate less. The problem lies in a miscalibration between satiation and energy need, we should be figuring out why some people are more hungry than others, and what we can do to change that.

0: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3139779/

> Not to mention that if it were possible to live with less calories

you don't think eg amenorrhea features?

Doesn't that go in the face of this study?

That is, this study seems to claim that what you eat can impact your metabolism.

No. With a diet the metabolism go much slower.

https://www.scientificamerican.com/article/6-years-after-the...

I'm not an expert in this, but the historical Okinawa diet doesn't have as much in simple carbohydrates compared to other lifestyles[1]. I think calorie intake is a notable aspect like you mentioned, but eating foods with a higher satiety strikes me as making a larger impact as well.

https://en.wikipedia.org/wiki/Okinawa_diet

Nor do the Inuit people. And until yhe introduction of the Western diet, they had very little cardiovascular disease.

It's not that low carb high fat increases from healthy levels, but rather that high carb diets slow down from healthy levels.

But still a very interesting point you make.

Some of the best things in life involved expending a lot of calories. Even if calorie restriction "works" in the sense of slightly extending human lifespan (and there's no real evidence for that yet) it's hard to see that as a net improvement.

I've seen videos of people who are actually trying long term calorie restriction to live longer and they look terrible.

This is about restricting carbohydrates, not all calories.

You can do both. Eat mainly fat and eat less calories.

As anecdotal evidence that's the Inuit diet.

The point was questionning if we should look for increased metabolism or not.

I'm also worried about the increased fat diet that could clog the arteries.

simplified: this, again, is a misconception - fat doesn't per se clog the arteries. LDL (bad) to HDL (good) cholesterol levels do that, which are influenced by a lot of factors, like smoking, alcohol, certain kinds of fats and simple carbs (sugar).

There is no evidence fats clog arteries.

Steve Jobs used to worry about that.

It lead to very unhealthy habits.

From a much broader, evolutionary or theory-of-life perspective.. eating less would a be a step backwards, towards eating nothing - not existing, or pure entropic. Every advance in the development of life is a fight against entropic death- as organisms move farther and farther from this, there will be increasing forces of nature fighting in the opposite direction - that is a sign you are moving in the RIGHT direction.

In mammals at least, smaller organisms have higher metabolic rate. But getting smaller is also developing towards "not existing" :)

Good point. I was struggling with the idea that lower metabolism might mean higher efficiency (like when we started cooking food). And being Paleo/carb restricting could be seen as a step back too!

Maybe we should continue eating processed, insulin spiking, gut destroying foods and see how our body adapts next? (That's not sarcastic, just a proposal) How is our body adapting currently? (Diabetes is not an adaptation)

My take is that lower metabolism is just a lower ‘power saver’ mode for the body, and, like a computer, results in slower ‘processing ‘

Being sedentary leads to a host of maladies, while constantly doing bootcamps, overtraining, pro sports or cross-continental marathons causes enormous oxidative stress, tissue damage and more risks of premature wear, cancer and aging... so there's a happy medium for a healthy, good quality of and longer life.

Also, between catabolic processes that destroy the body to keep it going and binge eating, there's a happy amount of fasting and cutting calories to a sustainable amount... lipogenesis, ULDLs, and VLDLs generally aren't good.

Please cite your evidence that constantly doing boot camps increases cancer risk.