it's certainly true though that as your weight decreases the amount of energy it burns also decreases, and there can be additional backlash in terms of the body

it's certainly true though that as your weight decreases the amount of energy it burns also decreases, and there can be additional backlash in terms of the body severely reducing the metabolism (and the resulting lethargy/etc can complicate efforts to exercise/etc). Furthermore metabolism varies in general by age, gender, and genetics in general. and on the flip side, the amount of energy you absorb varies by the type of molecule the body is metabolizing, and also the leading indicators are that the gut microbiome plays a huge amount in determining how much energy the body absorbs. Two people can absorb several hundred calories' difference from eating the same diet and the same quantity, and over a scale of a week+ that turns into pounds gained or lost. "CICO" is a massive oversimplification of an incredibly complex set of chemical processes. Like yes obviously your body cannot violate the laws of thermodynamics but we've just agreed that two different people will neither take in nor burn out the same amount of calories from doing the exact same things! Again, two people could eat the exact same things in the same amounts and exercise the same amount, and potentially gain a pound every week while another person holds weight. And the problem is that this oversimplified advice gets translated into oversimplified medical recommendations/etc, and an incredible amount of moral opprobium. Fat people are an easily visible target and are systematically discriminated against - they are paid less, they have worse interpersonal outcomes, and they receive worse medical care. The first answer of a doctor to a fat person is always "lose weight" - I have a relative whose complaints were ignored until she finally had a volleyball sized ovarian tumor removed in a hysterectomy - and that goes doubly for women in general, whose medical complaints are downplayed/ignored in general. And - not that it matters - but fat people have lower lifetime health spending. They're not "costing you" anything, not that that is ever a good reason to abuse a group of people, but our healthcare spending is hugely back-loaded towards end-of-life care, the third knee replacement and the two weeks in the hospital with congestive lung failure, all tend to be avoided by fat people. They die early and don't incur those expenses. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2225430/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2225430/ On a personal level, "what can I do to improve my own health", yes, the answer is correct that for your own personal metabolism the only thing you can do is to reduce your caloric intake. But everything past that, we're gradually realizing it's been horribly oversimplified by this idea that humans are the same as a blast calorimeter. It certainly doesn't apply on population-wide scales, there have pretty obviously been dietary shifts (massive increases in consumption of HFCS and other processed sugars) and potentially microbiome or hormonal shifts due to chemical exposure that have compounded these issues and exacerbated the decrease in activity. And that is certainly obscured (and attempts to study and remediate it stymied) by the "just eat less than you burn bro!" that is so popular.