This is an interesting post about the genetics of being fat. It’s possible that if you had a recent ancestor who went through starvation it altered their genetics and may have passed down genes to you that make you hold on to fat. So this tweet is pretty accurate:
As nice as it all sounds, this is not scientifically accurate. We are all descended from people who survived famines, literally all of us. It does not matter if your immediate ancestors dieted, because almost every one of your ancestors for the last 2,5 million years suffered from malnutrition.
As such, we actually evolved to weather off famine, not just by storing fat, but by being very calorie efficient. The natural state for homo sapiens is being very lean and wiry: Look at pretty much every hunter gatherer human still existing, or who existed in the past. A human being can easily survive and prosper fora day on an amount of food that would fit in their cupped palms. This translates to about 1600 calories for a woman, 2200 for a man, and is enough to perform the hard labor needed for hunting and gathering.
Which explains why study after study shows that being SLIGHTLY underweight, or occasional fasting has great health benefits, from reduced cancer, to longer lifespan.
Biologically, homo sapiens is a savannah great ape, which evolved to be lean, fast, agile, and able to perform extremely long endurance runs on limited energy from foraged food. Our ancestors hunted by running down antelopes until the antelopes keeled over from sheer exhaustion, even if it meant fasting for days until they caught it. That’s the level of exercise your body evolved for. We are born to be marathon runners, not body builders or obese.