> Nutrition is confusing because we’re not used to looking at lots of tiny effects adding up to something large.

This. I think is always more complicated than we think.

And one thing that many times is left out of the discussion is that some foods may have different effects on one individual than others. I was once looking for videos that talk about this and after watching too many, the only one found was :

“What is the best diet for humans? | Eran Segal | TEDxRuppin” https://www.youtube.com/watch?v=0z03xkwFbw4

When explaining their studies, at one point he said “It was not just about the food, it was also about the person eating it”

I recently spent some time in Argentina where Coffee and Mate are very heavily consumed.

I didn't not see many fat people let me tell you.

I suspect that People who "need" coffee a lot, dont sleep properly which has a much stronger relationship to weight gain than caffeine.

certainly if I get back into bad habits like late nights and using coffee as a crutch i put weight back on.

Could it be that they might be adding cream/milk/sugar to their coffee?

It would appear you feel for big sugar's game

> Eg. High saturated fat intake causes about a 20% increase in heart disease mortality.)

Not true. That was thoroughly disproved over the last 10 years of studies. (Sugar and industrial seed oils are the real problem)

https://www.nih.gov/news-events/news-releases/news-womens-he...

http://www.drbriffa.com/2010/01/15/two-major-studies-conclud...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5437600/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4532752/

https://www.ncbi.nlm.nih.gov/pubmed/21118617

https://www.ncbi.nlm.nih.gov/pubmed/30084105

https://www.diabetes.co.uk/news/2017/apr/artery-clogging-sat...

mate?

If you consume more calories than you use, you gain weight. Fat accumulation or loss is simple physics. Caffeine may have some small impact as do other stimulants, but often you see people consuming caffeine with large amounts of sugar or carbohydrates and rarely do you see those same people immediately jumping rope for 3 hours to burn off the equivalent excess calories.

> If you consume more calories than you use, you gain weight.

People throw around this idea as if it was simple.

Just the concept of calorie, which is bound to water temperature changes, is at most a vague second or third order approximation of a body’s energy intake. Petrol would be of super high calorie for instance, but it makes no sense for the body.

We have no clear idea of what any food gives as energy to a body, nor how each body reacts differently to any food, nor how much of that goes out, when that potentially stored energy is used in what amount (would CO2 production measurement help in this regard ? even if so but then it might be get rid of in unexpected ways)

So while the in/out idea may not be completely wrong, it’s effectively useless to anyone seriously thinking about diets.

I'm mostly agreeing with you, but I think you may be going slightly too far.

If you absorb more calories than your metabolism burns, then you gain weight. Variables are:

- Calorie content of food.

- Ability of your body to absorb those calories. This includes what form the calories are in (petrol, obviously, doesn't work), but also may include your gut biome, and perhaps other person-specific issues.

- Your activity level (not just exercise, but non-exercise physical movement as well).

- What your food does to your metabolism.

Sure, if you eat too much of the wrong things, it hurts. If you exercise, it helps. But it's much more complicated than that.

> Fat accumulation or loss is simple physics.

No, it isn't. The biochemistry controlling nutrient uptake or release by different tissues is incredibly complex and nowhere near fully understood, which is part of the reason that studies like this one are interesting. We don't really know how any given calorie surplus or deficit maps to subcutaneous fat vs. visceral fat vs. thermogenesis vs. muscle vs. fatty liver. We don't really know why some people develop T2D at a normal weight, some people only develop it if they're obese, and some people never develop it despite being morbidly obese.

Pretending that this is a simple and solved problem doesn't really help anybody except authors of diet books.

Well not quite, it's never really as simple as that.

People with bowel issues for example might actually consume vastly more calories than their peers but not gain as much weight due to their body being less efficient in converting caloric intake into fat. People with a fast metabolism might burn more calories per day at rest than others as well, and some of the complex interactions could involve interactions with caffeine.

If people are gaining weight rapidly it's always a good idea to look at the whole picture rather than just caloric intake because that can mask the true underlying causes.

If you consume more calories than you use/poop, you gain weight.

FTFY

(of course I’m discounting weight gain due to fluid accumulation if you have circulatory problems or ascites)