I found this really helpful in seeing the importance of calorie intake, and seeing how much your food actually contributes to the function of your major organs.
http://www.womenshealthmag.com/weight-loss/how-calories-work25% to muscles
23% to the liver, pancreas, kidneys, spleen, and adrenal glands
10% to the kidneys
10% to the brain
10% to breaking down the food you just ate
5 to 10% to the heart
2 to 3% to fat cells
See, with only 2% going to the fat cells, if you do not overeat (binge), you may only have 1-2% go to the fat cells, but this does NOT mean you are actually gaining fat mass; your cells are just expanding but can retract quickly. 10% goes to metabolism alone (breaking up the food you ate). Notice 5-10% goes to the heart and 25% goes to the muscles. Since the heart IS a muscle, and a large muscle at that, some of that 25% has to include the heart.