The myth of “calories in, calories out”

cw: weight loss, exercise

If you’ve spent any time researching how to change your weight, be it to lose or gain, you’ve doubtless encountered the pervasive myth of “calories in, calories out” or CICO. The short version is that as long as you burn more calories than you bring in, you’ll lose weight, and as long as you eat more calories than you burn, you’ll gain. And, like any health related advice that fits on a business card, it’s wrong. Or at least a vast simplification of an enormous and complex system that can’t be cut down to a four-letter acronym.

There are people who can granularly track every single calorie that comes into their body, calculate their TDEE (total daily energy expenditure), do the recommended 200-300 fewer calories a day, and still not lose weight. And if you spend any time in the comments section of the internet, such as Reddit or Twitter, anonymous internet bros will blame the person not losing weight for cheating on their food or having a lack of willpower. But that ain’t it.

In 2015, in the journal Exercise and Sport Sciences Reviews, Pontzer suggests a different explanation for how we burn calories—that our bodies adapt to limit burning calories as we exercise more. As he says “However, as the body adapts to higher levels of [physical activity] to maintain [total energy expenditure] within a homeostatically constrained range, the effects of increased [physical activity] will diminish. Specifically, the Constrained [total energy expenditure] model expects the effects of exercise interventions to diminish at higher levels of [physical activity] and across longer periods of measurement.”

In a review of his theory by Ravussin and Peterson explain “Although it is known that extra calories burned through exercise often do not translate into weight loss, the lack of exercise efficacy — those “missing calories” — has been attributed to compensation through increased food intake. However, Pontzer argues that the missing calories can be explained by a decrease in nonactivity energy expenditure, particularly resting energy expenditure, rather than an increase in food intake.”

This ties to the idea of having a “slow” or “fast” metabolism, but perhaps is more accurately considered as a “metabolic set point”, which is one of the many weight loss theories that bubbles up now and then. It posits that by making a small weight change, and then keeping it off for an extended period (6+ months) your body then resets what it thinks as normal.

The other big piece of evidence pointing to a more complex take on calories is the fact that it’s not just humans that are getting heavier overall. Generational weight gain has been observed in a number of species including primates, lab rats, and pets (though it should be noted that the author behind this study consults for food groups, including Coca-Cola*)

Another study, cited in the Atlantic, showed that even given the same caloric intake and exercise levels, someone in 2006 would be 10% heavier than someone in the 1980s.

There is no weight that is better than another weight. Being heavier or lighter doesn’t make you a better or worse person. But for people who do want to restructure their body, for whatever reason, they are not helped by folks spouting overly simplistic explanations for what the research seems to suggest is actually a hugely complex and multivariate issue.

Note: I’m not a doctor. Or a personal trainer. Or a dietician. Or a scientist. Please don’t listen to me for advice.

*[via Vox]