Our bodies are genetically adapted to a starvation diet. Even when food is no longer a scarcity to most, the body’s mechanisms still functions to store/convert to fat as much of food as possible.
The only ways this system can be changed are either through drastic diet control coupled with strict, rigorous exercise(not the 20-minute-walk-per-day nonsense), artificial gene/body manipulation, or wait for natural selection to start taking out the morbidly obese ones before they reproduce, leaving the lean ones to be allowed to have more offspring.
Actually it’s a lot easier than that. The trick is to NOT go into a starvation diet. You actually need to eat MORE than that, that’s why they call the diet eat less exercise more. Eating next to nothing triggers the starvation mechanisms which not only impede weight loss but do incredibly bad things to your body. You want to cut your calorie intake just enough so it’s less than your burning but not so much your body freaks out. It’s not really that hard, you just have to pay attention. And actually the 20 minute walk per day thing isn’t nonsense at all, it’s a good solid addition of calorie burning, sure it might not be enough to give you stellar results, but the target is 2 pounds a week anyway so people shouldn’t be that addicted to stellar results.