Exercise or Diet Alone Isn’t Enough to Prevent Disease, Study Shows

Health food or exercise alone isn’t enough to prevent chronic disease, new research shows. Contrary to popular belief, you can’t outrun the toll of a poor diet — and healthy eating, on its own, won’t ward off disease.

Most people know that working out and eating well are critical components of overall health. But a sweeping study published this week in the British Journal of Sports Medicine suggests that hitting the gym won’t counteract the consequences of consuming fat-laden foods, and mainlining kale can’t cancel out sedentary habits.

“Sensationalized headlines and misleading advertisement for exercise regimens to lure consumers into the idea of ‘working out to eat whatever they want’ have fueled circulation of the myth about ‘exercise outrunning a bad diet,’” the study authors wrote.

Previous animal studies as well as a few human ones have backed this up, suggesting that, at least in the short term, strenuous exercise can counteract the effects of overeating.

So an international team of researchers examined data from nearly 350,000 participants collected from the U.K. Biobank, an enormous medical database with health information from people across Britain, and followed up over a decade-long period. The study participants, median age 57, were healthy at the outset of the study, meaning they were not diagnosed with conditions like cardiovascular disease, cancer or chronic pain.

Analyzing self-reported questionnaires, the experts broke people’s diets down by quality. For instance, high-quality diets had at least 4.5 cups of fruit and vegetables per day, two or more servings of fish per week, less than two servings of processed meats per week and no more than five servings of red meat per week. The study did not measure discretionary foods like soft drinks or desserts, said Melody Ding, the lead author of the study and an associate professor at the University of Sydney.

The researchers also measured activity levels using responses from another questionnaire that asked about the total minutes participants spent walking and engaging in moderate physical activity, like carrying light loads or biking at a steady pace, and vigorous physical activity that lasted more than 10 minutes at a time. The authors wrote that it was the first study to examine diet and exercise alongside both general mortality and specific lethal diseases, like cancer.

Not surprisingly, people with both higher levels of physical activity and better quality diets had the lowest mortality risk. Overall physical activity levels were associated with a lower mortality risk, but those who regularly engaged in vigorous exercise — the kind that makes you break a sweat — had a particularly lower risk of cardiovascular disease mortality. And even just 10 to 75 minutes per week made a difference.

Regardless of your diet, Dr. Ding said, “physical activity is important. And whatever your physical activity is, diet is important.”

“Any amount of exercise is protective,” said Salvador Portugal, a sports health expert and assistant professor in the Department of Rehabilitation Medicine at NYU Langone Health who was not involved in the study. But you can’t rely solely on your workout to maintain good health, he added.

These findings underscore what many doctors have seen in practice, said Dr. Tamanna Singh, co-director of the Sports Cardiology Center at Cleveland Clinic who was not involved with the study. For instance, she said, there are many components of heart health, and “optimizing one thing is not going to necessarily improve your cardiovascular risk.”

She sees patients who classify themselves as amateur or professional athletes and are shocked when they suffer cardiovascular events, she said, without considering their diet. “Often they’ll come to me after an event and say, ‘I work out so much. Why did I have a heart attack?’”

On the flip side, even those with the most nutritious diets in the study saw considerably worse outcomes without some form of regular fitness regimen.

That doesn’t mean people can’t treat themselves after a workout, Dr. Singh said. (She’s a marathon runner herself, and she looks forward to nachos after a long run.) “If you are, for the most part, intentional about what you put into your body and intentional with how you move your body, you’re doing enough.”

The study highlights the importance of viewing food and exercise as components of holistic health, Dr. Ding said, instead of calculating how many miles can “cancel out” a cookie.

“It’s not just about burning calories,” she said. “We need to shift that thinking.”