Macronutrients (macros) are typically defined as the three substrates that are used by the body for the production of energy. Those energy substrates are carbohydrates, fats, and proteins. Together, the macronutrients create the caloric total for a food.

Carbohydrates (Carbs)

Carbs are converted to the simple sugar, glucose. Glucose is a sugar molecule that is present in all body tissues. When at rest, glucose is stored in the muscles and liver as a more complex sugar called glycogen. Glycogen is stored in muscles and is used to form ATP (adenosine triphosphate), which is the compound that the body derives its energy from.

Glycogen stores can become depleted from long intense exercise. You may have heard of the phenomenon called ”hitting the wall”. Hitting the wall is normally a phrase used by long distance runners who hit a point where it feels like their bodies are giving out on them. Hitting the wall occurs when an athlete’s glycogen stores are depleted however this occurrence is usually only seen in long distance runners.

1 carbohydrate is equal to 4 kcals or Cals.


Fats provide energy during long bouts of exercise. Fats are less readily available than carbs in the body. The reason for that is the process that fats must undergo to be transformed into energy is more complex than that of carbs. Fats must be broken down from their original complex form (triglyceride) into glycerol and free fatty acids. Those free fatty acids can then be used by the body to form energy.

Fats do more than just provide energy. Some types of fats (phospholipids) form protective sheaths around nerves, while others serve as the building blocks of important hormones (estrogen and testosterone).

A fat is equal to about 9 kcals or Cals.


Only under extreme circumstances is protein required for energy creation. In order for protein to be used as energy, it must be converted into glucose or free fatty acids (FFAs). Without conversion to glucose or FFAs, only amino acids can be utilized for energy.

Proteins shine as building blocks. Protein can serve as the foundation for creation of new tissues. Specific proteins called enzymes speed up or slow down the chemical reactions occurring in the body.

Protein is equal to about 4 kcals or Cals.


Q: Do I need to take carbs right after a workout to restore my glycogen stores?

A: Only under two circumstances. If you did intense cardio (cardio uses up significantly more glycogen than weight training does), and if you train more than once per day. Otherwise, there’s no need to “restore glycogen.” The human body is very good at maintaining glycogen stores and will restore them in less than 24 hours.

Q: Do I need to take protein shakes?

A: No. If you can consume all of your protein needs with whole foods, then you most certainly should do that instead. In fact, research suggests that whole protein sources (like chicken and fish) are better at supporting muscle building than protein shakes.

Q: Everyone says fats are bad. Is that true?

A: Fats are a necessary part of the diet. There are unhealthy forms of fat (mostly found in fried foods). However, the kinds of fat that you find in nuts, fish, and oils are healthy and should be consumed for healthy hormone production.


Kenney, W. Larry; Wilmore, Jack; Costill, David (2011-11-18). Physiology of Sport and Exercise, Fifth Edition. Human Kinetics.