Everyone knows that eating a low-fat, low-calorie diet and getting regular exercise helps shed pounds, but a new study led by researchers at Fred Hutchinson Cancer Research Center has found that when it comes to losing weight and body fat, diet and exercise are most effective when done together as compared to either strategy alone.
The results of this randomized trial, led by Anne McTiernan, MD, PhD, director of the Prevention Center and a member of the Hutchinson Center’s Public Health Sciences Division, were published in Obesity.
The majority of women in the study who both improved their diet and who exercised regularly shed an average of 11% of their starting weight, which exceeded the study’s goal of a 10% or more reduction in body weight.
“We were surprised at how successful the women were,” McTiernan stated in the press release. “Even though this degree of weight loss may not bring an obese individual to a normal weight, losing even this modest amount of weight can bring health benefits such as a reduced risk of diabetes, heart disease and cancer.”
The year-long intervention involved 439 overweight-to-obese, sedentary, postmenopausal Seattle-area women, ages 50 to 75, who were randomly assigned to one of four groups:
- exercise only (goal: 45 minutes of moderate-to-vigorous aerobic exercise per day, five days a week, including three days at the Hutchison Center’s exercise facility);
- diet only (goal: 1,200 to 2,000 calories a day, depending on starting weight, and fewer than 30% of daily calories from fat);
- exercise and diet (with the same goals as above); and
- no intervention.
“Although numerous studies have examined the effect of lifestyle interventions on weight, few have focused on postmenopausal women, a group that experiences particularly high rates of overweight and obesity,” McTiernan stated.
At the end of the intervention, the researchers found that the women in the exercise-only group lost, on average, 2.4% of their starting weight (with a mean weight loss of 4.4 pounds) as compared to an average weight loss of 8.5% among women in the diet-only group (with a mean weight loss of 15.8 pounds). The greatest weight loss was achieved by women who both changed their diet and who exercised regularly; these women shed an average of 10.8% of their starting weight (with a mean weight loss of 19.8 pounds). Two-thirds of the women in this group achieved the study goal of losing at least 10 percent of their starting weight.
“This study shows that you get the biggest bang for your buck by combining a healthy weight-loss diet – which in this case meant reducing calories by cutting fat intake and boosting the consumption of low-calorie foods – with regular, moderate-intensity aerobic exercise,” McTiernan stated. “You don’t need to be an athlete; walking, biking or gym cardio machines all work well. Start slowly and gradually increase to 45 minutes of activity a day, more if you are able.”