Why a Low-Sugar or Sugar-Free Diet Could Be a Really Bad Idea

You’ve been told to cut back and even eliminate it—but new science shows that your body actually needs the sweet stuff.

Sugar has become nutrition’s public enemy number one—eating too much is blamed for heart disease, diabetes, obesity, and Alzehimers, among other things—which is why everyone you know is going nuts trying to quit it. But if you’re an active woman, the story is different, and ridding your diet of sugar isn’t just unnecessary, it can actually sabotage your fitness goals, experts say.

You can and should eat sugar before, during, or right after your workout because your brain and muscles need it for fuel, especially if you’re doing intense or lengthy sessions. Without it, you won’t be able to push as hard or go as long, explains Lauren Antonucci, R.D.N., a sports dietitian and nutrition consultant to the New York Road Runners. “For active women, sugar is not the devil,” she says. “It’s something you can use to your advantage to become faster and stronger.” (Here’s how to become more sugar savvy.)

The Workout Loophole

Your body stores carbs, including sugar, as glycogen in your muscles and liver; when you exercise, it breaks them down to give you energy, explains Marni Sumbal, R.D.N., cofounder of Trimarni Coaching and Nutrition. If you’re working out for more than an hour, especially at high intensity, those carb stores can dip too low, making you tired and shaky. That’s when the easily digestible sugars in sports-nutrition products like gels and drinks can give you an assist. Case in point: They helped soccer players maintain endurance, especially during the second half of a game, when fatigue sets in, according to a review of studies published in the journal Nutrients. The boost you get from sugar may also improve your skills, increasing accuracy. But it’s not just athletes who score the benefit: Other research finds that eating sugar right before you exercise helps your routine feel easier.

Without the proper fuel, your workout will suffer—and so will your health, says Sumbal. When your carb stores get depleted, your levels of stress hormones like cortisol spike. Over time, that will make you feel run down and can weaken your immune system. A sports drink can help: Runners who consumed one didn’t experience the cortisol increase that those drinking a placebo did, and their immunity stayed strong, a study published in the Journal of Strength and Conditioning Research shows. The bottom line: Consuming sugar can keep you from getting sick and allows you to recover from exercise more quickly and effectively.

Timing is Key

The trick is to schedule your sugar consumption for specific times to get the best benefits. Here’s your game plan:

  • Before exercising. “If you haven’t eaten in a few hours, your blood sugar will be a little low and you won’t be able to exercise as intensely,” says Sumbal. Have something with easily digestible sugars, like a banana, or even a piece of dark chocolate, first.
  • During your workout. If you’re exercising for 75 to 90 minutes or more (or going really hard, like in an hour-long race), aim for 30 to 60 grams of carbs per hour of exercise. A 20-ounce Gatorade will give you 36 grams; a packet of Clif Shot energy gel has 24 grams. “These products are formulated to have the perfect balance of sugar and electrolytes,” Sumbal says.
  • Your cooldown: You know you’re supposed to eat protein for recovery, but carbs are critical too. They replenish your glycogen stores and cause insulin to rise, which helps shuttle amino acids, the building blocks of protein, into your muscle cells. Pair a food with sugar, like fruit, with a source of protein, such as eggs or nuts, and eat it within 30 to 60 minutes of cooling down. Also effective for recovery: drinking chocolate milk, which contains protein and sugar.

But No, You Can’t Go Whole Hog

In between workouts and on your rest days, minimize added sugars and processed foods to eat more effectively, says Antonucci. It’s fine to have something desserty occasionally (after all, treating yourself is the no. 1 secret to a healthy diet), but too much processed food crowds out important sources of protein, healthy fats, and antioxidants such as lean meats, nuts, and fruits and vegetables—and they keep your energy and hormone levels stable and your immune system healthy. It goes without saying, but opt for fresh, healthy foods whenever you can.