What should I eat and drink before and after working out
What should I eat and drink to refuel after working out?
It’s always nice when science tells you what you want to hear. That’s why several studies in the past few years touting low-fat chocolate milk as a perfect post-workout elixir have been greeted so enthusiastically. Chocolate milk is convenient, cheap, and tasty, so what’s not to like? But you have to be cautious when you take research done on competitive athletes and try to apply the results to casual exercisers. The basic principles are the same, but new research—and common sense—suggests that those whose main goal is to lose weight should chug milk with caution.
Post-exercise nutrition has two primary goals. First, you want to recharge your body’s depleted energy stores so that you’re fresh and recovered before the next workout—whether that’s coming later the same day or later in the week. Second, you’re maximizing your fitness gains by providing the raw materials your body needs to synthesize the contractile proteins that increase strength and the mitochondrial proteins that boost endurance. “It’s a continuum between short-term recovery and long-term adaptation,” says Trent Stellingwerff, a Canadian scientist in the performance nutrition group at the Nestlé Research Center in Switzerland.
The key factors to consider are when and what you eat. For the first half-hour after exercise, the body is processing nutrients to repair itself at a dramatically elevated rate. After about two hours, this “window” is closed and the opportunity for any accelerated recovery is lost. This is where high-tech recovery bars and drinks can be useful, since they’re easy to have on hand immediately after you finish exercising—though it’s also easy to pack a sandwich in your workout bag.
In the past, conventional wisdom held that weightlifters should ingest protein to build muscle, while endurance athletes should focus on carbohydrates. Now researchers agree that both macronutrients are important no matter what type of exercise you’re doing, Stellingwerff says. Recent studies suggest that you should aim to consume about one gram of carbohydrate and 0.3 grams of protein per kilogram of body weight during the first hour or two after a typical cardio workout.
Some sports drinks tout very specific carb-to-protein ratios that companies say will optimize recovery and adaptation. Endurox, for example, has a 4-to-1 ratio—which happens to be the naturally occurring ratio in chocolate milk. In truth, “there’s no magic ratio,” says John Ivy, an exercise physiologist at the University of Texas at Austin and author of Nutrient Timing: The Future of Sports Nutrition. “Anywhere in the range from 2.5-to-1 to 4-to-1 works well,” he says. For very long workouts lasting a few hours or more, a higher ratio of up to 6-to-1 may be appropriate, Stellingwerff adds.
Whatever the ratio, the idea that the body needs fuel immediately after exercise is now widely accepted. But some people take this advice too enthusiastically, as research at the University of Massachusetts at Amherst’s Energy Metabolism Laboratory has shown. One of exercise’s prime benefits for those seeking to lose weight is that it heightens insulin sensitivity, which helps to clear sugars from the bloodstream. Researchers at Amherst asked 16 sedentary, overweight subjects to walk on a treadmill for an hour a day at a moderate pace, burning 500 calories. Half the participants replaced the lost calories by drinking a sports drink and eating immediately after the workout, while the other half were given nothing. Surprisingly, while insulin sensitivity spiked 40 percent in the abstaining group, no improvement at all was seen in the group that refueled.
These results suggest that if you’re trying to lose weight rather than trying to win races, you might be better off skipping the post-workout snack. That doesn’t necessarily mean fasting completely: Ivy points to other studies showing that people who take in a small amount of protein after exercise are less likely to overeat several hours later. But the basic message is clear, Ivy says: “If you’ve gone out and burned 300 calories by walking for 30 minutes, don’t refuel by taking a 500-calorie dietary supplement.” Let the magnitude of your workout dictate the size of the chocolate milk carton.
A POST-WORKOUT SNACK
How to get one gram of carbohydrate and 0.3 grams of protein per kilogram after exercise
• For a 120-pound person
• A tuna sandwich and a 16.9-ounce sports drink
• A cup of oatmeal with milk and an 8-ounce sports drink
• For a 175-pound person
• A protein sports bar and a 25-ounce sports drink
• Spaghetti with lean meat sauce and a cup of low-fat milk
How much should I drink to avoid dehydration during exercise?
It’s the first lesson you learn about exercising in the heat: if you don’t drink enough, you’ll get dehydrated, and that will force you to slow down. By the time you feel thirsty, we’re told, it’s already too late. But some exercise physiologists, led by South African researcher Tim Noakes, have reached an alternative conclusion. It’s not being dehydrated that actually slows you down, Noakes argues; rather, it’s letting yourself get thirsty that signals to your brain to put the brakes on.
The idea that drinking according to thirst isn’t enough to replenish your sweat losses is supported by plenty of research. For example, a 2007 study by researchers at the Gatorade Sports Science Institute found that experienced runners who were allowed to drink as much as they wanted during a 75-minute run replaced only about 30 percent of the fluid they lost by sweating. The conclusion the Gatorade scientists drew from this study is that we should plan to drink much more than thirst alone dictates—but Noakes disputes this interpretation.
The initial studies linking dehydration with impaired performance date back to World War II, as researchers sought to give U.S. military forces fighting in desert or jungle conditions an edge over their enemies. Since then, dozens more studies have shown that if you dehydrate someone (by administering a diuretic, for example), their exercise performance will suffer. Similarly, when subjects aren’t allowed to drink during prolonged exercise, their performance is decreased. Based on these studies, researchers concluded that sweating out more than about 2 percent of your total body weight will slow you down.
But the subjects in all these studies are not just dehydrated; they’re also forced to become thirsty. None of the studies show that subjects who drink freely according to thirst (and thus fail to replace their sweat losses) perform any worse than subjects who drink enough to replace all their sweat. Both thirst and the slowdown that eventually follows are the body’s way of protecting itself in advance from damaging dehydration, Noakes argues. The flaw in the conventional studies is illustrated by a 2006 study in which subjects were told in advance whether or not their fluid intake would be restricted during a 50-mile cycling trial. When they knew they wouldn’t be able to drink freely, the subjects biked more slowly right from the start of the trial, long before any physical effects of dehydration could have had an impact.
In Noakes’s “central governor” theory, the brain monitors signals from various parts of the body with the goal of reducing exercise intensity before the body is in any danger of damaging itself. As fluid levels drop—but before they reach the point at which performance would be compromised—the central governor responds by initiating thirst and reducing intensity. In this picture, you won’t slow down unless you actually feel thirsty, no matter how much fluid you’ve lost. Studies of endurance athletes show that the thirst mechanism varies greatly between individuals: some drink very little during races, while others drink a lot. Interestingly, the fastest finishers tend to also be the most dehydrated—a finding that lends support to Noakes’s argument.
Until a few years ago, few researchers paid attention to Noakes’s ideas. But the potentially fatal dangers of drinking too much—which were first pointed out by Noakes in the 1980s but ignored for nearly two decades—have caused a re-evaluation of hydration guidelines. Most authorities still recommend aiming to limit sweat losses to less than 2 percent of your body weight, but the consensus is no longer as strong. In that light, it’s worth considering the advice Noakes gave in a 2007 article in Medicine & Science in Sports & Exercise: “Drink according to the dictates of thirst. If you are thirsty, drink; if not, do not. All the rest is detail.”