A new editorial appearing in the journal BMJ doubles down on Astorino's comments. The belief that exercise can offset a crummy diet is one of the biggest mistakes people make when it comes to their health and disease risk, the editorial's authors say.
"The idea that you can eat what you like as long as you exercise is misleading and unscientific," says Aseem Malhotra, MD, a London-based cardiologist and coauthor of the editorial. "You cannot outrun a bad diet."
Malhotra's editorial points out that, during the past 30 years, physical activity rates haven't changed even as obesity and diabetes rates have skyrocketed. Sugar and refined carbohydrates—not too little exercise—are the biggest drivers of poor health and obesity, he says. (Check out these 25 simple ways to beat a sugar craving.)
Ironically, many athletes suck down sports drinks and other sugary, carb-heavy snacks because they believe their bodies need these energy sources in order to perform. This kind of "carbohydrate loading" can put athletes—even marathon runners and triathletes—at risk for insulin resistance and type 2 diabetes, the editorial argues.
More evidence in favor of diet's importance: A recent report in the journal Obesity Reviews found regular exercise by itself—that is, not in combination with diet changes—rarely leads to significant weight loss, and sometimes results in weight gain.
On the other hand, numerous studies have linked diet improvements to weight loss and lower rates of death and disease—regardless of the participants' exercise habits.
All that said, regular exercise is extremely important if you want to live a long, healthy life. Many studies have shown physical activity safeguards your heart and brain from disease, including Alzheimer's. Exercise also protects your joints from arthritis and pain. More research shows you're more likely to stick with diet changes if you're also working out regularly.
So ideally, your health goals will include eating a proper diet and partaking in regular physical activity. "To optimize health, some aspect of exercise training must be included," Astorino says.
MORE: 5 Ways to Lose Wight That Don’t Involve Diet or Exercise
But if you're wondering which is more essential—or you just don't have the willpower to tackle healthier diet and exercise goals at the same time—focus first on improving your diet, Malhotra says.
