In other studies from Dr. Gaesser’s lab, though, overweight and obese people with significant health problems, including high blood pressure, poor cholesterol profiles or insulin resistance, a marker for Type 2 diabetes, showed considerable improvements in those conditions after they started exercising, whether they dropped any weight or not. Seeing these results, Dr. Gaesser began to wonder if fitness might enable overweight people to enjoy sound metabolic health, whatever their body mass numbers, and potentially live just as long as thinner people — or even longer, if the slender people happened to be out of shape.
So, for the new study, which was published this month in iScience, he and his colleague Siddhartha Angadi, a professor of education and kinesiology at the University of Virginia in Charlottesville, began scouring research databases for past studies related to dieting, exercise, fitness, metabolic health and longevity. They were especially interested in meta-analyses, which pool and analyze data from multiple past studies, allowing researchers to look at results from far more people than in most individual studies of weight loss or exercise, which tend to be small-scale.
They wound up with more than 200 relevant meta-analyses and individual studies. Then they set out to see what all of this research, involving tens of thousands of men and women, most of them obese, indicated about the relative benefits of losing weight or getting fit for improving metabolisms and longevity. In effect, they asked whether someone who is heavy gets more health bang from losing weight or getting up and moving.
The contest, they found, was not close. “Compared head-to-head, the magnitude of benefit was far greater from improving fitness than from losing weight,” Dr. Gaesser said.
As a whole, the studies they cite show that sedentary, obese men and women who begin to exercise and improve their fitness can lower their risk of premature death by as much as 30 percent or more, even if their weight does not budge. This improvement generally puts them at lower risk of early death than people who are considered to be of normal weight but out of shape, Dr. Gaesser said.