I saw this going viral:
This is a good visualization of why those who say “calories in = calories out” actually are arguing that calories out are inflexible, because the only intervention they advocate for is reducing calories in.
“You could eat less…”
You can change calories out!! https://t.co/UQzQ7FbNQW
— anabology (@anabology) December 13, 2024
The above tweet illustrates how proponents of CICO tend to focus on the calories-in “CI” side of the equation and ignore the calories-out “CO” half, such as metabolism. However, aside from the occasional anecdotal evidence, there is scant to no evidence to suggest it’s possible to meaningfully raise “CO” without also getting fatter in the process. There is no reproducible diet or other method that appreciably raises “CO” in a general population or even replicates at an anecdotal level.
The guy who posted the tweet, @fire_bottle, despite being held up as an expert and selling product on his website that he claims helps at improving metabolic dysfunction, is still fat. So if such a way exists to increase “CO” safely and easily, he hasn’t found it. He’s not wrong in so far that metabolic dysfunction plays a role in obesity, but the sad reality is there may be no way to fix it. GLP-1 drugs such as Ozempic work on that “CI” part, but drugs that target “CO” tend to be of limited efficacy and possibly unsafe.
The reality is, “CO” is largely innate. That is, for a given bodyweight, how many calories an individual burns is determined almost entirely by genes. Controlling for key factors such as weight, height, activity level, and gender, this varies considerably at an individual level, similar to IQ. And also like IQ, there is nothing that can be done to raise it meaningfully, except for perhaps tons of stimulants and drugs as as DNP or clenbuterol, which are unsafe when used for weight loss purposes.
No one knows why humans vary so much in metabolism, such as which genes are to blame, similar to how humans vary so much in intelligence, also due to genes. You hold the environment constant, yet humans vary so much in terms of BMI. It’s not like food scarcity can be blamed as in prehistoric times, yet in spite of abundance and modernity, a fifth of Americans are still neither obese or overweight, and others are morbidly obese.
Trying to raise “CO” with cardio is not uncommonly offset entirely or to a large extent by adaptive thermogenesis, meaning your body burns fewer calories at rest in such a way that your “CO” is unchanged despite expending more effort. This is corroborated by many studies, such as famously by the recent work of Herman Pontzer. What he found is that humans exhibit a sort of constrained energy expenditure, meaning that burning more calories through exercise is offset by burning fewer calories at rest, such as reduced NEAT, within the constraint of one’s energy curve. And also, increased hunger afterwards. Eating a cup of oats or yogurt after a long walk or run will easily negate those extra burned calories from cardio.
Building muscle also does not work that well. Not only does this lead to increased hunger, but muscle burns little calories, at just 6kcals/day per pound of muscle. Not to mention, the vast majority of drug-free individuals will add only small quantifies of muscle with training. Sure, strength training has benefits, such as reduced risk of falls by improving leg strength and balance, but weight loss is typically not among them.
To get an idea of how inconsequential this is, consider a bodybuilder with 50 extra pounds of muscle compared to a control group, which is an outlier even by bodybuilding standards and would be a very impressive physique. The extra 300 calories he burns is still within a single standard deviation even at his original weight. So maybe going from 2,500kcal/day to 2,800kcal/day, which is within normal for a man at 180 lbs instead of 230 lbs. So 3/4 of a McDonald’s cheeseburger of extra calories for a hulking 50 extra pounds of muscle.
Finally, there is also no evidence to suggest it’s possible to raise metabolism by changing macros (e.g. high fat vs. low fat) [1], or by overeating to kickstart a sluggish metabolism into overdrive in the hope of inducing an ‘afterburner effect‘ when calories are restricted. Any increase of metabolism by overeating is offset by weight gain. This is sometimes called a ‘refeed’, and as to if it works, likely not. As soon as you stop eating at a surplus, your metabolism again drops fast, so no afterburn effect. All you’ve done is set back your progress.
Either you’re on a diet or not. Diets have a high failure rate for a reason: feeling hungry is unpleasant and it does not go away without eating more, which axiomatically means you’re no longer dieting. There are no hacks or tricks to chasing that elusive metabolism boost that will allow one to consume more food without also gaining weight. This is why Ozempic works consistently, by restricting “CI”, when these other strategies fail or success is limited to irreproducible anecdotal evidence.
[1] There is a high thermic effect of protein, at 25-30% vs 5-10% for carbs and 2% for fat, but the evidence is lacking that high protein diets outperform others.