[yaakov34]

It is a fact that the effect exists, but I think that you are also victim to the popular idea that this effect is extremely powerful or even overwhelming, making "taking care of yourself" a powerful morality tale. Here is a quote from a large study:

"having a BMI between 30 and 35 shortened life by an average of 0–1 years, having a BMI between 35 and 40 shortened life by 1–3 years, and having a BMI above 40 shortened life by 1–7 years"

(This is easily googlable, I don't want to turn this message into a journal article)

Note that the error bars on the effect are quite large (1 to 7 years even for extreme obesity). Now it's true that a lot of things hide in an "average", and there is a lot to discuss here, and I am definitely not discouraging anybody from acquiring healthy habits and lifestyle, but... it's just not a simple story of reward for virtue and punishment for sins. Genetic factors which we have no control over probably have a greater effect. Which is not a story that people want to hear.

[1123581321]

Sure, I understand what you are saying. Those are actually significant findings, though. Keep in mind how good we are at keeping people with progressed heart disease alive. The relatively few years' reduction in lifespan masks, in my cases, early onset of heart disease and years of expensive emergency response, frequent hospitalization, transplants, reduced quality of life, and so on. Better is to look at large meta studies about bmi, smoking, diet, and physical activity as they affect rates of disease as well as mortality. I quickly searched and found many results.

Respectfully, I haven't said anything about living until a very old age. I am only talking about a few diseases and I understand there are a lot of ways to die. I have also said the morality of not trying to extend lifespan is subjective.

[treehau5]

What about going the other way? how does having a BMI of 25 to 30, 20 to 25, 15 to 20 work?

[yaakov34]

The same study says that low BMI is also associated with lower lifespan, and the statistically optimum BMI for white people is 23 to 25 (there are racial differences in all the numbers, which I think also challenges the idea of assigning moral qualities to them).

However, I don't know if I would give too much thought to the effect for low BMI - it could just be that people with extremely low BMI tend to have some disease process which causes that; only a small minority of them are rail-thin athletes. For high and extremely high BMI, there are known causal mechanisms for disease, so it's a different story.

[shanacarp]

We have a huge environment we live in, plus we shape are environment to an extraordinary high degree. Furthermore, we're actually quite sensitive as organisms to those changes, including in ways where it's only now coming out in some cases because our previous equipment wasn't sensitive enough to register what was happening. We also actually know very little about genetics, genomics, and epigenetic despite posturing that we do. That's why the error bars are big

Fundamentally, actually shrinking that error bar for many diseases is one of the biggest hard science and math problems of the future.

It's going to be so exciting!