If you assume (incorrectly, as science has proven) that the human body can metabolize 100% of the energy it consumes, your worst case scenario is your caloric intake. In practice, since you're not receiving 100% of that energy, you're actually better off. Figure out your BMR (basal metabolic rate) and add your estimated calorie expenditure and consume fewer calories than that. The fact that not all those calories are actually used by the body makes it even easier to stay below your daily energy requirements. Thanks for the reply