When Americans want to lose weight, they hit the gym. And usually, they fail. Of course they hit the gym. Hundreds of infomercials, billboards and websites tell them it’s the way to get shredded abs and drop unwanted pounds. And they make lots of money, and Americans need more miracle workouts. But what they really need is nutrition. Studies show that diet, not exercise, is the key to weight loss. In a year-long study published in the New England Journal of Medicine in 2011, people who dieted without exercising lost 10 percent of their body weight, while those who exercised without dieting lost only 1 percent of their body weight. In fact, the Mayo Clinic has said “most studies have demonstrated no or modest weight loss with exercise alone … an exercise regimen is unlikely to result in short-term weight loss beyond what is achieved with dietary change.”
Put simply: you can’t out-train a bad weight loss diet. To put some numbers with that, the adage—widely accepted as gospel—is that weight loss is 80-20. That is: 80 percent diet, 20 percent fitness. This rule of thumb is harder to back up with studies, but it works with math. If you need to reduce your overall calorie intake by 500 calories in a day, 80 percent of that deficit (400 calories), would be reduced by diet—say by drinking one less soda and eating one less slice of pizza. Twenty percent of the 500-calorie deficit (100 calories) could be burned off by running about one mile, or walking for 20-25 minutes.
Compare that to an exercise-only approach: To burn an extra 500 calories, you’d need to run about five miles. Or you could ride a stationary bike for 55 minutes. But even that may not be enough—in a study from Arizona State University, dieters who only exercised actually gained weight. The scientists theorized that the women in the study may have compensated for their exercise by overeating, undoing its potential weight loss benefits.
Of course, exercise is good for your heart, muscles, bone density, and one part of your weight loss journey: The Mayo Clinic says it’s key to keeping weight off once you’ve lost it. So aim to perform it as 20 percent of your regime—in the same New England Journal of Medicine study, dieters who did the nutrition and exercise plans together lost 9 percent of their body weight during the study.