Essentials: The Science of Eating for Health, Fat Loss & Lean Muscle | Dr. Layne Norton

Energy Balance and Energy Utilization00:00

A calorie is a unit of energy of heat. The potential chemical energy exists in the bonds of macronutrients in food. By digesting, assimilating, and metabolizing nutrients, the body creates energy, primarily in the form of ATP (adenosine triphosphate), which serves as the body's energy currency. Protein gets converted to amino acids that can be used for muscle protein synthesis or other tissue protein synthesis, and can also be converted through gluconeogenesis to glucose. There are also ketogenic amino acids. Fatty acids create energy through beta oxidation, where fatty acids are broken down two carbons at a time to produce acetyl-CoA, which enters the Krebs cycle to produce hydrogen ions that power ATP production.

Components of Energy In and Energy Out02:30

The energy-in side of the equation is more difficult to track than commonly thought. Food labels can have up to a 20% error. There is also a distinction between energy and metabolizable energy. Insoluble fiber is not digestible, and carbohydrate or protein can be bound up in plant structure making it inaccessible to digestive enzymes. This reduces metabolizable energy. Evidence suggests that based on individual gut microbiome composition, some people may be better at extracting energy from fiber than others.

If food labels are consistently off and tracking is consistent, individuals can eventually determine their actual intake. The energy-out side of the equation is more complicated. Resting metabolic rate (RMR) accounts for 50-70% of total daily energy expenditure. Sedentary people have RMR as a higher proportion of total expenditure, while active people expend a greater percentage through physical activity.