Weight loss doesn't help pregnancy chances, study finds

A randomized study of 379 women with obesity and unexplained infertility found that intensive lifestyle changes that shed pounds led to no better chances of pregnancy and healthy births than simply increasing physical activity without weight loss.

"We have known for decades that obese women often have difficulty getting pregnant," said researcher Daniel J. Haisenleder, PhD, of the University of Virginia School of Medicine's Center for Research in Reproduction. "For this reason, many physicians advise weight loss prior to conception. However, there are few studies that have addressed the issue comparing a healthy lifestyle -- i.e., exercise -- vs. exercise plus weight loss."

Obesity and Pregnancy

The FIT-PLESE study, conducted at nine academic medical centers across the country, divided participants into two groups: Half the women dieted intensely using meal replacements, medications and increased physical activity. The other half simply increased their physical activity without trying to lose weight. After completing the programs, both groups received three rounds of standard infertility treatments.

Women in the weight-loss program ended up losing, on average, 7% of their body weight, while participants in the exercise-only group typically maintained their weights. But, in the end, there were no significant differences between the two groups in terms of the frequency of healthy births. In total, 23 of the 188 women who completed the 16-week intensive weight-loss program ended up giving birth; among the 191 who completed the exercise-only program, 29 gave birth.

The intensive dieting program did offer health benefits for the women who completed it, however. In addition to dropping pounds, they saw a major decrease in metabolic syndrome, a cluster of conditions that increase the risk for serious health problems such as diabetes, stroke and heart disease.

Based on their findings, Haisenleder and his collaborators conclude that the weight-loss program did not make women more fertile or improve birth outcomes compared with simply exercising. They note the health benefits of weight loss may not translate into better odds of getting pregnant.

"Weight loss improved metabolic health in these subjects. Unfortunately the changes seen did not improve fertility," Haisenleder said. "Infertility within this population remains an important health issue, and will require further studies to address the problem in the future."

Funding for the research was provided by the National Institutes of Health's Eunice Kennedy Shriver National Institute of Child Health and Human Development, grants U10 HD38992, U10 HD077680, U10 HD39005, U10 HD077844, U10HD055925, U10 HD27049, U54-HD29834 and R24-HD102061. The project also was supported by the NIH's National Center for Advancing Translational Sciences, grants UL1 TR002014 and UL1 TR001863. Nutrisystem provided discounted coupons, and Fitbit provided discounted Fitbits for activity monitoring.