The Truth About Carbs, Protein and Your Performance

What percentage of my diet should come from carbohydrates? ? Should I exercise on empty? ? How much protein should I eat after I lift weights? ? Is whey the best source of protein?

These are just a few of the questions addressed at the 27th annual meeting of SCAN, the Sports And Cardiovascular Nutritionist's practice group of the American Dietetic Association ( More than 400 sports dietitians gathered to learn the latest news from prominent sports nutrition researchers. I hope this information will help you choose a winning sports diet.

Carbohydrate Update

Louise Burke, PhD, Director of Sports Nutrition at the Australian Institute of Sport, addressed the following questions:

What's the best percentages of carbohydrates, protein, and fat for a sports diet: 40-30-30 or 60-25-15?

Neither! A better approach is to define nutrient needs according to body weight. For example, the International Olympic Committee developed these guidelines:


Intensity of exercise                 gram carb/kg body wt         gram carb/lb body wt

Low intensity                                      3-5 g                            1.5-2.5

Moderate (~1 hour/day):                     5-7 g                            2.3-3.2

Endurance (1-3 hours/d):                    6-10 g                          2.5-4.5

Extreme  (>4-5 hours/d):                     8-12 g                          3.5-5.5


How much should I eat during exercise?

During exercise that lasts one to two and a half hours, you want to target 30 to 60 grams of carbohydrate (120 to 240 calories) per hour. That's about one to two gels or 16 to 32 oz. of a sports drink per hour (after the first hour, if you ate a pre-exercise meal or snack).

During endurance exercise, 60 to 90 grams of different sources of carbohydrates (such as sports drink, banana, gummy candy) per hour is appropriate, as tolerated. Consuming the higher end of the range (90 g, as compared to 60 g) is associated with greater stamina and endurance.

How long does it take to refuel from exhaustive exercise?

If you eat a carb-rich sports diet, you can replenish depleted glycogen stores in 24 to 36 hours post-exercise (with no exercise during that time). While it's important to pay attention to your recovery diet, most athletes do not need to eat immediately after exercise unless they are doing double workouts. (Within an after exercise, yes; immediately, no.)

What can I do if I cannot tolerate any food during exercise?

Try mouth swishing with a sports drink. This sends a message to the brain that energy is forthcoming and you'll feel more energetic. Swishing can enhance performance by 2 percent to 3 percent if you are exercising on empty and have not eaten pre-exercise—as often happens with morning exercisers. (Swishing seems to be less beneficial after a pre-exercise meal, but more research is needed to verify those findings.)

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