You can see that fat contains more than double the calories per weight. The assumption is that consuming fat, which contains more calories, will cause more weight gain. But what is rarely factored into this equation is the hormone piece of the puzzle.

Insulin is the most powerful "fat-making hormone." It will convert food into fat easily. It is triggered by:
Sugar Carbohydrates (including grain carbs, fruit juice, and starchy carbs (potato, rice, and corn).
Excess protein.

Interestingly, fats are neutral and are not triggered by any of the fat-storing hormones.

Growth Hormone (GH) is the most powerful "fat-burning hormone." It will trigger the fat-burning process. It is triggered by protein (small amounts).