Hormones, not calories determine the weight.

This era of genome mapping, nutrigenomics, and stem cell research has made this clear that the little messenger called hormones carries information from your body to your mind and vice versa. Hormones control every aspect of how we gain weight and how we lose it. It also determines how we store this fat in our body.

100 calories of carb are not the same as 100 calories of protein. Some food release fat-burning hormones and some release fat-storing hormones. Diet cola and artificial sweeteners are 0 calories and would have been perfect for weight loss but still, it makes you fat. The reason is the so-called diet soda/cola when consumed has an impact on the hormone insulin. The sweet taste is understood by your body as sugar and hence the release of insulin by the pancreas.

Consumption of protein increases glucagon and leptin hormones which help in fat burning. Whereas consumption of carbs leads to a spike in insulin levels, which leads to the storage of fat.