If you want to build muscle, lose fat and maximize your performance, you have to know what to eat—and when to eat it. Called nutrient timing, this involves eating specific types of foods when your body is best able to use its nutrients.
The science behind nutrient timing comes down to hormones. Hormones are responsible for muscle growth, bone growth and fat loss, among other bodily functions, and the key hormone in nutrient timing is insulin.
According to Dr. John Berardi, founder of Precision Nutrition, insulin is a storage hormone because it is responsible for feeding carbs, amino acids and fat into the body's cells. Insulin has the capability to increase fat cells' storage to the same extent as it does with muscle.2
The body releases insulin after eating carbohydrates. Simple carbohydrates such as white potatoes, white bread and fruits cause a bigger insulin spike than do complex carbohydrates such as oats, pastas and vegetables. As few as 250 calories of carbohydrates can spike insulin.3
After a weight training session, your muscles are running on empty. Carbohydrates consumed post-workout are used to replenish this energy supply, which means there isn't much left over to store in fat cells. This means the best time to spike your insulin is after a workout, when muscles readily take in nutrients for repair.4
In contrast, on rest and non-training days, there's no need to store nutrients because nothing is lost. Knowing this, here are general rules for nutrient timing to build muscle and lose fat:
Consume higher carbohydrate, higher protein and lower fat. Keep total carbohydrate intake around 1.0 to 2.0 grams per pound of bodyweight. For example, a 200-pound person should intake 200 to 400 grams of carbohydrates.
Take in higher fat, higher protein and lower carbohydrate. Main carbohydrate intake should come from trace sources such as cruciferous vegetables and nuts, totaling around 0.5 grams per pound. A 200-pound person should intake 100 grams of carbohydrates.
On average, consume lower insulin levels. Your main source of carbohydrate should come post-workout. To lose weight by cutting calories, try this formula for total caloric intake: (Bodyweight x 16) x .8 = Daily Calories
Take in higher insulin levels throughout the day. Here's a recommended formula for total caloric intake: (Bodyweight x 16) x 1.2 = Daily Calories
Gaining Muscle and Losing Fat
Prompt higher insulin levels after a workout and lower insulin levels at all other times. Follow the muscle gain recommendations on high intensity workout days, and the fat loss recommendations on rest days.
Good carbohydrate sources on training days are pastas, rices, potatoes, oats, fruits and other wholesome, natural foods. Eat lean proteins such as turkey, chicken, whey protein and milk. On rest days, stick to vegetables of all types, meats, cheeses and nut butters. Also, a general rule is to get one gram of protein per pound of bodyweight.
Those wanting to lose fat should limit carbohydrate consumption to immediately post-workout. Those looking to gain muscle should eat more carbohydrates all day to take advantage of the anabolic effect of insulin (meaning it stimulates growth). And those looking to both build muscle and lose fat with nutrient timing should settle somewhere in between, consuming copious carbohydrates post-workout to repair and refuel the body.
1) Ludwig DS, et al. "High glycemic index foods, overeating, and obesity." Pediatrics 1999 Mar;103(3):E2.
2) Lee ZS, et al. "Plasma insulin, growth hormone, cortisol, and central obesity among young Chinese type 2 diabetic patients." Diabetes Care 1999 Sep;22(9):1450-7.
3) Holt S, Miller J, Petoc P. An insulin index of foods:the insulin demand generated by 1000-kJ portions of common foods. American Journal of Clinical Nutrition 1997;(66):1264-76.
4) Thomas DE, et al. "Carbohydrate feeding before exercise: effect of glycemic index." International Journal of Sports Medicine 1991 Apr;12(2):180-6.
Anthony Mychal is a writer, athlete consultant, teacher and coach. He has a B.S. in health and physical activity and an M.S. in health and physical education; and he studied under James Smith and Buddy Morris at the University of Pittsburgh. In his free time, he publishes a blog with his musings on athletic preparation at anthonymychal.com.