Overweight women who join a fitness center to lose weight are apt to fail unless they have a workout partner, personal trainer or “life coach” and cut their caloric intake at the same time, according to two researchers from the University of Missouri in Columbia.

The investigators examined the real-life experiences of a group of overweight women who either joined a fitness center or enrolled in Weight Watchers to lose weight.

The results, after 12-weeks, suggest that both weight loss tactics have pros and cons and that a combination of supervised dieting and exercise is apt to yield the best results.

Group support, investigators Stephen Ball and Anne Bolhofner found, is very important to successful weight loss. Most of the women who attended group Weight Watchers sessions stuck with the program for the duration of the study, whereas many of the fitness center-goers dropped out of the study, they report.

In the study, Ball and Bolhofner compared the effectiveness of joining Weight Watchers to joining a commercial gym in 48 overweight and sedentary women. Twenty-four women were given a 12-week membership to Weight Watchers and were told to follow the recommendations of the program, which included weekly weigh-ins, counseling sessions, and a point counting system to monitor calories.

The remaining 19 women were given a 12-week membership to a local fitness center where they were required to do both cardiovascular and resistance exercises at a moderate to vigorous intensity at least three times per week. No specific diet was recommended or encouraged; a trainer offered only basic nutritional advice.

At the end of 12 weeks, 5 of the women in the Weight Watchers group and 10 in the gym group dropped out of the study. The women who went to the gym failed to lose weight, whereas women who went to Weight Watchers lost an average of 5 percent of their body weight, or about 9 pounds, especially around the stomach.

However, neither group saw a decrease in their percentage of body fat. A large percentage of the weight lost in the Weight Watchers group was lean tissue and not fat, which is a concern, Ball noted in a statement.

“Body fat percentage did not improve at all because they lost a much higher percentage than expected of lean tissue,” he explained. “It is advantageous to keep lean tissue because it is correlated with higher metabolism. Losing lean tissue often slows metabolism. What your body is made of is more important than what you weigh,” Ball said.

Most prior Weight Watcher studies have not considered body fat percentage change and only focused on body weight, the investigators note.

Writing in the Journal of Exercise Physiology, Ball and Bolhofner note that they were surprised that body fat did not decrease in the gym-goers by week 12. “The best explanation” for this, they say, is that the amount of exercise was inadequate to elicit changes. It is also possible that the women in this group may not have exercised as intensely or for the recommended duration every session.

They also point out that twice as many women assigned to fitness center workouts as those assigned to Weight Watchers dropped out.

“These results imply that overweight women joining a fitness center with the intent of weight loss or body fat change will likely fail without additional support such as personal trainer, workout partner, or life coach,” the investigators conclude.

“Although commercial weight loss programs typically also have somewhat high drop out rates, the group support associated with Weight Watchers is no doubt a crucial aspect of the program not found in most fitness centers,” the researchers conclude.

SOURCE: Journal of Exercise Physiology, June 2008.