There is no evidence that calorie restriction makes you live longer. The human body is remarkably adaptive to what it is given. If you restrict calories, the body simply turns down the amount of energy it burns. If you're hungry, then you should eat something rather than put your body in a heightened state of stress. Cortisol in the blood has long term negative effects and can actually lead to weight gain. The problem is not number of calories but quality of calories. No one has become obese on a pure carnivore diet and it's not because they count calories or restrict themselves. But fat people today eat processed sugar and seed oils which disrupt the satiety signals so they always feel hungry.