Teenage girls who go on strict diets, use diet pills or induce vomiting to help lose weight are more likely to gain weight afterward and to be at risk for obesity than those who do not engage in such practices, according to a study by researchers at the University of Texas at Austin and Stanford University.
The study of 692 ninth-grade girls at three high schools in Northern California compared the body-mass index of students engaging in restrictive dietary practices with the index of those who did not. Researchers led by Eric Stice, a psychologist at the University of Texas, asked girls to complete questionnaires annually over four years. Weight and height were also measured annually.
Stice and his co-authors from Stanford found that teenagers who reported strict dieting and radical weight-loss efforts were more likely to gain weight than those who did not take special pains to try to lose weight.
One unexpected finding noted by the researchers, whose study appears in the December issue of the Journal of Consulting and Clinical Psychology, is that girls who exercised to try to control their weight were more likely to gain weight during the study. Stice and his colleagues suggest that this may reflect the growth in bone density or muscle mass that exercise produces.
There are two reasons why weight-reduction efforts might backfire, Stice and his coauthors say. One may be self-delusion common to many dieters: They think they are dieting and exercising more than they actually are. The second may be that some students may have a familial propensity toward obesity.