[dbspin]

>by in large, it's calories in vs calories out.

It's absolutely not... I have zero sympathy for the 'fat pride', political fatness etc side of body positivity. But I can confirm both through personal experience and research that your perspective is uselessly reductive. Endocrine disruption, sleep schedule, glycemic index and pharmaceutical drugs can all enormously impact on weight gain and retention. Moreover the 'calories in, calories out hypothesis' (first outlined in this paper from the 1950's - https://academic.oup.com/ajcn/article-abstract/6/5/542/47299...), has been debunked (see this recent met-analysis - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516704/). Weight gain / loss in humans is a dynamic system, where the body will preconsciously adjust activity preferences and metabolic activity to maintain weight homeostasis. There are also enormous interindividual differencies in how the body responds to calorie load - related to genetic and gut microflora differences - https://www.healthline.com/nutrition/gut-bacteria-and-weight... (not a link to a study directly, but links to dozens of stories confirming impact of gut bacteria on weight and overall health). Additionally, we've seen cross species weight gain, including in species that exist outside of human society, indicating that there are environmental factors for cross cultural weight gain beyond worse diets and more sedentary life styles - https://www.science.org/content/blog-post/everything-getting....

[adamdusty]

Your brain may subconsciously adjust your activity as a result of dieting, but that doesn't change the fact that it is physically impossible for your body to store energy you didn't consume.

[tsol]

Your body can speed up or slow down processes to conserve energy. For example, it's much easier to lose weight when you are heavier versus if you are skinny because your body is quicker to slow metabolism. And that is just one factor. Gut microbiome is another.

[adamdusty]

Sure your body could put itself into a coma and conserve all possible energy, and it would still be physically impossible for it to store energy you did not consume.

Your body will never go under such heavy energy conservation that you cannot lose weight, and it doesn't have enough control to do that anyway. At best your body can attempt to slow down your physical activity and slow down digestion for efficiency. Yes as you diet your metabolic rate will decrease, and even if it were to decrease an impossible amount like 50+% you would still be able lose weight by comsuming less energy.

[nailer]

Yes people have different bodies - some slimmer, some less so. No, that doesn't explain why people are suddenly morbidly obese.

[dafneee]

>It's absolutely not

So why do we never find obese people among starving conditions (famines, concentrations camps, etc)

[pjc50]

Because they're starving and their calories are externally constrained. So what?

[guerrilla]

Because it's a necessary but not sufficient condition. You can't store fat if you don't get enough calories, but many people don't store fat at the same rate others do for the same overage.