Which class of nutrients is the body's primary source of energy?

A) Proteins
B) Carbohydrates
C) Lipids
D) Vitamins

Carbohydrates are the primary energy source for the body.Carbohydrates perform several functions.They supply energy for muscle and organ function,spare protein,and enhance insulin secretion.Carbohydrates are more easily and quickly digested than are proteins and lipids,fuel strenuous short-term skeletal muscle activity,and provide nearly all the energy for the brain.If carbohydrates are not available,proteins and lipids (fats)can also be used for energy.Proteins primarily perform the following functions: build tissue and maintain metabolism,immune systems functions,fluid balance,and acid-base balance.They are a secondary energy source.The primary functions of lipids include supplying the body with essential nutrients,acting as an energy source,providing flavor and satiety,and providing insulation.Although vitamins provide no energy,they are critical in regulating a variety of body functions.