I don't think a source should be necessary for this, though I did bother to include one. Obesity hardly existed in e.g. the fifties, and that was certainly not for a shortage of food. And the individuals of healthy weight did reproduce, in great numbers. The sudden emergence of a massive genetic disorder makes no sense.
On the other hand people started becoming fat once quick, cheap, food that sacrifices healthfulness for flavor and price became ubiquitous. And in contemporary times we've subsidized the pants off corn resulting in things like high fructose corn syrup being in practically everything. And of course it would be remiss to not consider the great changes in the engineering of foodstuffs and the corresponding change in the status quo of herbicides with us also consuming trace amounts in massive quantities, as a generational experiment.
[1] - https://www.cdc.gov/genomics/resources/diseases/obesity/inde...
https://www.ncbi.nlm.nih.gov/pubmed/8327020
It seems to be plausible, that by adapting a healthy diet, at least the risk can be lowered and the onset delayed.
But my impression is, that a lot of factors, like poison from the environment (not only food and water, but also through the air) in combination with deseases, allergies and maybe medications etc, come together with genetic preconditions.
Probably for most of us its more important to undertand that genes are not a death sentence, they are triggered by environmental factors.
Obesity is also genetic, some persons body cant cope with the standard western diet.
But if they adapt their diet they will most likely never get obese, and get heart disease and diabetes as a result.
Your thoughts?