Female Hormones Don't Cause Overeating And Weight Gain

In a study conducted by Christine L. Pelkman, a Penn State doctoral candidate in biobehavioral health, women ate about 4 percent more but also burned about 4 percent more calories during the premenstrual phase of their menstrual cycle. Suppressing the cycle with a contraceptive drug didn't significantly alter food intake, change food preferences, or cause weight gain.

The study was the first randomized, placebo-controlled investigation to examine how eating and calorie burning are affected both by the menstrual cycle and by a popular injectable long-acting contraceptive drug, Depo-Provera, in the same women. According to the Alan Guttmacher Institute, more than a million American women used Depo Provera in 1995, the most recent year for which statistics are available.

"The theory has been that if you administer contraceptive hormones, you lower a woman's basal metabolism and she will gain weight," Pelkman says. "We saw no dramatic increase in calorie intake and didn't see a dampening of the number of calories the women burned. There were no changes in food preferences or diet composition either."

She adds, "There was no shift in chocolate intake or in how much they liked chocolate. No shift in their taste for sweet foods in general. No shift in carbohydrate preferences."

The Penn State researcher will present her findings July 7 at the annual meeting of the Society for the Study of Ingestive Behavior in Clearwater, Fla.,in a paper, "Reproductive Hormones and Eating Behavior in Young Women." Her co-authors are Robert Heinbach, Penn State physician, and Dr. Barbara Rolls, who holds the Guthrie Chair in Nutrition and is Pelkman's dissertation adviser. Pelkman will be honored at the meeting with a Young Investigator Award.

The study was conducted with 20 healthy women between the ages 20 and 35 who ate all of their meals and snacks for three days at the Penn State Food Lab during two different phases, near the beginning and end, of two consecutive menstrual cycles. They also took sensory and other tests during the three-day sessions.

In the pre-contraceptive phase of the study, the women both ate and burned more calories in the luteal phase or second half of their menstrual cycle when the natural production of the hormone progesterone reaches a peak just before the onset of menstruation. Following the administration of either the contraceptive or a placebo, the women repeated the three-day eating and testing sessions at the Food Lab at two-week intervals for two more menstrual cycles.

The women who received the contraceptive did not eat more, in fact, they gained less weight, about three quarters of a pound (.3 kilogram), than the women who received the placebo who gained about a pound and a quarter (.5 kilogram) at the study's end. Neither of the weight gains were statistically significant.

"There are lots of misconceptions and myths out there about hormonal contraceptive drugs causing weight gain. Our study shows that this does not necessarily happen with Depo Provera," Pelkman says. "The finding illustrates the fact that you have to look at the risks associated with this easy method of birth control in a complete and careful way when deciding whether or not to take it."

Pelkman was also honored for her work, which forms the basis of her dissertation, with first prize in the Health and Life Sciences Division at Penn State's Graduate Research Exhibition. The Medical Research Council of Canada has also awarded her a three-year post-doctoral fellowship to study at Penn State after she receives her doctoral degree in August.

A Canadian from Waterloo, Ontario, Pelkman now resides with her husband and daughter in Pennsylvania Furnace, Pa.