If you wanted to gain one pound of body fat, you would have to consume about 3500 calories more than you burned in any given time frame. Many adults gain one pound each year. Therefore, if all the weight gained was fat, over the course of the year their consumption netted 3500 calories greater than those used – end of story. The warning is that people who gain weight often gain lean body mass (LBM) even if they don’t exercise. Why? Because as weight increases, your body adds small amounts of muscle, bone, etc. With the body fat (generally 1/4 muscle and 3/4 fat) in order to carry the now heavier body through life. Therefore, we often use the formula of roughly 3000 calories per pound of weight gain. Muscle weight is primarily comprised of water and its dry weight (protein) contains 4 calories per gram vs. the 9 calories per gram that fat holds. Thus muscle can yield around 800 calories per pound when including the water weight. Additionally, when we project muscle gain within any goal, we make calorie adjustments based on these numbers.