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Balancing Your Energy Sources: There’s No Magic Formula

Steer clear of one-size-fits-all formulas to balance carbs, fat and protein in your diet.

When nutritionists say to eat a balanced diet, they typically mean to balance the three macronutrients: carbohydrate, protein, and fat. But how exactly should you balance them?

No Magic Ratio

Some sports nutrition experts have recommended a 50/25/25 diet in which you get 50 percent of your daily calories from carbohydrate and 20 percent each from fat and protein. Advocates say endurance athletes need to consistently maintain this ratio of the three macronutrients to perform optimally in training. The idea here is that the heightened focus on carbohydrate, the body’s main fuel supply, is ideal for sustaining highly active individuals.

Other experts recommend a more evenly balanced 40/30/30 diet, getting 40 percent of your daily calories from carbs. And still others promote different ratios. But while they may disagree on the specifics, there seems to be an undergirding belief among some experts that there exists some perfect balance of macronutrients that optimizes endurance training performance.

Guess what? There isn’t.

“Percentages are meaningless, because it is the absolute amount of carbohydrate and protein that matters,” says Asker Jeukendrup, Ph.D., an exercise physiologist at the University of Birmingham in England and one of the world’s leading experts on the effects of different amounts of carbohydrate and protein intake on endurance performance. “How much you need depends on your goals and the amount of training you do.”

In other words, what matters is not the relative proportions of carbs, fat, and protein you eat, but rather the basic quantity measured as total calories or grams. And since macronutrient needs vary depending on training volume, there is no single macronutrient ratio that could possibly meet the needs of every athlete.

A Better Way to Measure

Picture: Getty Images

So what are the right amounts?

“Typically, carbohydrate needs will vary from 5 to 10 grams per kilogram of body weight per day with training ranging from one hour per day to five hours or more,” says Jeukendrup (editor’s note: 1 kg = 2.2 lbs).

Unlike protein and fat, carbs are not used structurally in the body — they are used strictly for fuel. Therefore, the more active you are, the more carbohydrate you need, with the hardest-training athletes requiring twice as much carbohydrate as the lightest trainers. Studies have shown that athletes who fail to increase their carbohydrate intake sufficiently to match increases in their training volume do not perform as well.

Protein needs also vary with training volume, although somewhat less. Traditional recommendations call for one gram of protein per kilogram of body weight daily for recreational endurance athletes, increasing to 1.5 g/kg/day for serious competitors. But in a recent study, Jeukendrup found that going all the way up to 3 g/kg/day helped a group of elite cyclists to better handle the stress of an especially hard block of training. This is an extreme case, but it demonstrates that the carbohydrate and protein recommendations for athletes should be considered minimums. It’s fine, and sometimes beneficial, to get more than the recommended amounts as long as it doesn’t cause you to regularly consume too many additional calories.

And fat? Dietary fat needs are less sensitive to fluctuations in training volume. According to Jeukendrup, you can trust that your fat needs will be met if you get the right amount of carbs and protein and simply let fat account for the remainder of your daily energy needs.

Getting the right balance of macronutrients requires a little math, but it beats using a one-size-fits-all formula that doesn’t really fit all.

Daily Carbohydrate Needs

Training Volume (Hours/Day) Carbohydrate Needs
1 5 g/kg
2 6 g/kg
3 7 g/kg
4 8 g/kg
5 9 g/kg
>5 10 g/kg