It's obviously thermodynamically possible for your body to be more or less efficient at metabolizing energy from the food you consume. The remainder will be exc

It's obviously thermodynamically possible for your body to be more or less efficient at metabolizing energy from the food you consume. The remainder will be excreted. Someone who is lactose tolerant will gain more weight from a glass of milk than someone who is lactose intolerant because they are capable of getting energy from the lactose. The person who is lactose intolerant literally will shit those future pounds off.