This. I read a lot of science and health stuff, and there have been a lot of fascinating articles about obesity over the last few years. It's not nearly as simple as the sanctimonious bigots want it to be.
For example, one study found that it's not just Americans who are fatter. Indeed, it's not even just people who've become fatter. It's also lab animals, many different species, that have become heavier over the decades, even when controlling for diet and exercise. They don't yet know why but speculate it may be certain food additives or the effects of artificial lighting.
I've also seen several articles discussing a link between gut bacteria and obesity. One study found that if they transferred gut bacteria from fat mice into thin mice, the thin mice started gaining weight, even though their diet and exercise remained the same. Other studies found people would often spontaneously start losing weight after procedures that substantially changed their gut bacteria.
Finally, I read that the extremely obese are metabolically different from those who merely carry a few extra pounds (like Mursilis). Diet and exercise works great for those with a few extra pounds. For the extremely obese, however, it works temporarily at best. Less than 1% of the extremely obese succeed with diet and exercise over the long term (either 3 years or 5 years, don't remember). From a medical perspective, such a complete failure rate would normally completely discredit the treatment, yet even many medical professionals cling to their old prejudices.
The bottom line is that while diet and exercise are always a great starting point, the problem with obesity is far more complex than that. Especially for the extremely obese, other treatments are necessary.
On a side note, it's interesting to note how this issue unites ignorant people across the political spectrum. Even the most die hard lefties who denounce bigotry based on ethnicity, color, or sexual preference, are happy to jump on board with smug, anti-fat bigotry. Educate yourselves, gentlemen. It's the best cure for bigotry.