Combining diet and exercise is the most effective means to lose weight than following either of the strategy individually, finds a new study.
The majority of women in the study who both improved their diet and exercised regularly shed an average of nearly 11 percent of their starting weight, which exceeded the study's goal of a 10 percent or more reduction in body weight.
"We were surprised at how successful the women were," said lead researcher Anne McTiernan at Fred Hutchinson Cancer Research Center.
"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 four groups:
1. 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);
2. diet only (goal: 1,200 to 2,000 calories a day, depending on starting weight, and fewer than 30 percent of daily calories from fat);
3. exercise and diet (with the same goals as above); and
4. no intervention.
At the end of the intervention, the researchers found that the women in the exercise-only group lost, on average, 2.4 percent of their starting weight (with a mean weight loss of 4.4 pounds) as compared to an average weight loss of 8.5 percent 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 exercised regularly; these women shed an average of 10.8 percent 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.
The women who were assigned to the non-intervention control group, who did not change their diet or activity level, on average lost less than a pound - a statistically insignificant decrease.
"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," said McTiernan.
The results were published online April 14 in Obesity.