When it comes to leading a longer, healthier life, a new study published in iScience suggests exercise may be more important than weight loss, especially among those who are overweight and obese, Gretchen Reynolds reports for the New York Times.

Study details & key findings

For the study, Glenn Gaesser, a professor of exercise physiology at Arizona State University, and Siddhartha Angadi, a professor of education and kinesiology at the University of Virginia, analyzed more than 200 meta-analyses and individual studies related to dieting, exercise, fitness, metabolic health, and longevity. The studies included tens of thousands of men and women, most of whom were obese.

Through their review, Gaesser and Angadi found exercise and fitness levels had significantly greater benefits to obese people's health than losing weight.

As a whole, the studies found that sedentary, obese individuals can lower their risk of premature death by 30% or more after they begin exercising and improving their fitness—even if their weight does not change.

According to Gaesser, this reduction in risk of early death puts active, obese individuals at a lower risk of death than people who are considered to be normal weight but do not exercise.

By contrast, some studies found that heavy people who lose weight by dieting, not illness or exercise, lower their risk of premature death by around 16%—while other research included in the review found that weight loss among those who are obese did not reduce mortality risks at all, Reynolds reports.

"Compared head-to-head, the magnitude of benefit was far greater from improving fitness than from losing weight," Gaesser said.

How exercise—not weight loss—benefits health

Previous studies have also shown that overweight and obese individuals with health problems— such as high blood pressure, poor cholesterol levels, or insulin resistance—can significantly improve their health after they begin exercising regardless of whether they lose any weight, Reynolds reports.

In addition, some research suggests using dieting as a repeated measure to lose weight may contribute to subsequent health problems. In several studies included in the researchers' review, people who lost weight by dieting often regained the pounds before trying to lose weight again. According to Reynolds, this "yo-yo" approach to losing weight can contribute to metabolic conditions, such as diabetes and high cholesterol, and lower life expectancy.

However, Gaesser said exercise can help prevent those same conditions, as well as potentially change a person's fat stores. Exercise can help obese people lose visceral fat, which raises the risk of Type 2 diabetes and heart disease, Reynolds writes.

In addition, a few studies in the review suggested exercise can alter molecular signaling inside fat cells to potentially improve insulin resistance, regardless of a person's weight. "It looks like exercise makes fat more fit," Gaesser said.

Ultimately, Gaesser said the new review suggests that people do not need to lose weight in order to be healthy. "You will be better off, in terms of mortality risk, by increasing your physical activity and fitness than by intentionally losing weight," he said. (Reynolds, New York Times, 9/29)