For patients at risk of developing type 2 diabetes, doctors automatically recommend making two lifestyle changes: losing weight and increasing exercise. Now a new study from Saint Louis University suggests these two health fixes are not interchangeable. When it comes to reducing diabetes risk, the study authors say, exercise offers distinct and separate benefits from weight loss, and so a combined approach is best.

Dr. Edward Weiss, associate professor of nutrition and dietetics, and his colleagues enlisted the help of 52 middle-aged men and women. All of the participants were sedentary and overweight. The researchers first recorded the participants’ insulin sensitivity levels, a marker for diabetes risk that measures how effectively the body is able to use insulin, and then assigned each participant to one of three groups. While all three groups followed a program designed to help participants lose six to eight percent of their weight, one group focused on calorie restriction, the second group on exercise, and the third on a combination of both.

As Weiss explains, calorie restriction improves glucoregulation — the maintenance of steady levels of blood sugar in the body — simply by leading to weight loss, while exercise improves glucoregulation through both weight loss and other independent mechanisms.

“This means that even if you don’t lose weight, exercise helps,” Weiss stated in a press release. Even more, the researchers believed, separate from the results of the combined effort group, the exercise-alone group would show greater improvements in glucoregulation than calorie restriction-alone group.

So what did the efforts of three separate groups teach the researchers? Both exercise and calorie restriction had positive effects on each participant’s insulin sensitivity. Surprisingly, the exercise-alone group did not "win" against the calorie restriction-alone group. However, the participants who both exercised and lost weight saw two times the improvement in insulin sensitivity than either of the single-approach groups.

“On the surface it may seem obvious, and yet there are a lot of people who believe that if they maintain a healthy weight, it doesn’t matter what they eat,” Weiss said. “And others have an appropriate food intake but don’t exercise.”

We all will be healthier, then, if we both exercise and eat the right amount of food. “There is more to be gained by including both approaches in your life,” Weiss added.

Source: Weiss EP, Albert SG, Reeds DN, et al. Calorie Restriction and Matched Weight Loss From Exercise: Independent and Additive Effects on Glucoregulation and the Incretin System in Overweight Women and Men. Diabetes Care. 2015.