>>1649265Your gene's control the potential of how fat or skinny you can be, the rest is determined by your environment. If a person is unlucky enough to be born with DNA such that they have a tendency to retain fat, and they then couple that with high-fat diet, you can probably guess what will happen.
On the other hand, a person born with DNA such that their body's cells tend to use fat more quickly could eat a diet high in fat and be less likely to put on weight.
>nobody was THIS obese in the 1800sFast food and cars (at least commercially) didn't exist back then, and the only methods of transport were horseback (if you could afford a horse) or your own feet, so even if you had genes that caused your body to tend to retain fat, nobody was really able to eat enough fat each day to become overweight.
