"The law of energy balance says that if you’re in a surplus, excess calories will be sent into fat stores. That’s more or less true for a couch potato. The law of energy partitioning says that if you’re in a surplus, but you’re weight training, some of those excess calories will be sent to your muscles for repair and growth. Imagine two people following the same meal plan with a calorie surplus. One lifts weights and the other doesn’t. The one not lifting weights gets fatter. The one lifting weights not only doesn’t get fatter, he gets more muscular by eating more!
This partitioning of calories and nutrients is even more interesting in the other direction. Two people go on the same meal plan in a calorie deficit. One person is lifting weights and the other isn’t. They’re both going to lose weight. The real question is, what kind of weight will they lose? The person not lifting weights loses lean body mass. The person lifting weights loses fat and keeps his lean body mass - he might even gain a little.
Two people. Same diet. Totally different results. This is more proof that weight loss and body transformation are not the same and that nutrition goes far beyond calories in versus calories out. It’s what your body does with the calories that counts." - Tom Venuto, Burn the Fat, Feed the Muscle
To learn more, check out his new book, "Burn the Fat, Feed the Muscle: The Secrets of the Leanest People in the World".