This might seem counterintuitive. After all, fat contains nine calories per gram, whereas carbohydrates and proteins contain four calories per gram. If calories were the only thing to consider, it would stand to reason that if you eat fat, you’re going to gain weight because of the higher caloric load.
However, there are many other factors. For one, fat is a structurally integral part of cell membranes in our bodies. Fats are necessary in order to properly digest and use those all-important fat-soluble vitamins: A, D, E and K. Also, the digestion of fat does not trigger the hormonal response that creates fat storage - but SUGAR does. Sugar releases hormones in the body that actually trap body fat and save it, which leads to weight gain. In fact, the fat in a sweet treat will actually help to slow down that sugar spike that comes after eating sugar, and thus reduce the insulin surge, mitigating some of the ill-effects of the sweet. This is why the whole fat-free dessert idea might not be such a good one.