I think I am missing something.
Are you saying you'd rather be in Kenya, where you have almost zero options for improving your quality of life, given a disease that is for all intents and purposes permanent?
Exercise moderately and eat healthier are probably the most important "preventive" means of health care. Even for conditions that aren't directly related to being overweight or lacking exercise, it can help immensely to correct those two issues.
I'd love to hit he market every other day and have lots of good home cooked meals. But my wife and I work 50-60 hours, and need to have the 2 year old in bed by 8:30. That means out the door at 7, home by 5:30, dinner on the table by 6:30.
I'd love to cook awesome meals and play old man basketball. When do I do that?
As you would suspect, the United States has significantly fewer acute diseases than India, which in turn has significantly less acute disease than Kenya. BUT for chronic conditions, the numbers (relative to population size) are pretty much the same across the board. The distribution of chronic disease is slightly different depending on wealth (diabetes vs obesity vs malnutrition vs heart/lung disease like cancer vs liver disease from alcohol, etc) but they are almost entirely preventable often with "just" some life style changes (I'm oversimplifying, but the vast majority of the conditions are considered very preventable). With the United States spending nearly a fifth of its GDP on medical care we STILL have just as big a problem with chronic disease as Kenya, a country where the average income is under $10/day.
Preventive medicine is almost definitely its own health risk but when you look at what we're trying to combat and just how intractable the problem is here in the US, let alone globally, it starts to look like a very acceptable risk.
[1] http://www.tedmed.com/talks/show?id=7333
[2] http://www.who.int/topics/global_burden_of_disease/en/