Every month, a woman rides a roller coaster of hormones. As progesterone and estrogen rise and dip, she fights a swell of five pounds around the hips, thighs, buttocks. She can turn, on a dime, from an ascetic to an uncontrollable fiend, craving double malted milkshakes and rich chocolate cakes. Throw contraceptives into the loop and the hormone coaster becomes even more unpredictable, intensifying the cravings and increasing the swell.
And so the myths begin.
In a study conducted by Christine Pelkman, now a postdoctoral researcher in nutrition, women taking the contraceptive Depo Provera didn't eat more, burn less, or gain weight compared to women who received a placebo. They didn't eat any more chocolate than the women on placebo either.
Pelkman provided food to 20 young, healthy women for three days during two different phases of two menstrual cycles. She also measured their resting energy expenditure on the first morning of each session. "The study was tightly controlled," says Pelkman. "The women were all healthy and of normal weight, with normal eating patterns." Pelkman monitored the same women after they had received an injection of Depo-Provera or a placebo, again for two cycles. Depo-Provera, a popular contraceptive that is injected into a woman's arm every three months, suppresses the menstrual cycle by preventing the ovaries from releasing eggs.
Pelkman found that food intake and energy expenditure decreased during the first two weeks of the menstrual cycle, or the follicular phase, when the egg develops in the ovaries and estrogen levels peak. "It's known as the anorectic effect of estrogen," says Pelkman. Food in take and energy expenditure increased during the last weeks of the menstrual cycle, or the luteal phase, when the corpus luteum develops in the ovary and progesterone levels are high. "Women do eat more calories during the luteal phase, but they burn more too" Pelkman explains.
During each three-day session, Pelkman prepared breakfast, lunch, and dinner, and packed snack boxes with foods the women selected from menus that included chocolate chip cookies, fresh fruits and vegetables, candy, yogurt, pudding, diet soda, chips, pretzels, and orange juice. She measured each woman's resting energy expenditure before breakfast. "We'd have them lie on a bed and rest for 20 minutes." (At times, Pelkman had to wiggle their toes to keep them from falling asleep.) "Then we'd put a clear hood over their heads for 40 minutes. A machine circulates air through the hood and then measures the amount of carbon dioxide the woman produces. From the carbon dioxide measurement, we can calculate how many calories she burns." Pelkman found that the women ate about four percent more but also burned four percent more calories during the premenstrual phase of their menstrual cycles.
"We know that the menstrual cycle affects energy regulation," says Pelkman, "but what happens to appetite and metabolism when contraceptive drugs suppress that cycle?"
"There's a popular myth among women that contraceptive drugs cause weight gain," Pelkman continues. "One theory is that shutting down the menstrual cycle lowers metabolism. Another theory says it causes women to eat more."
Pelkman found that suppressing the cycle with the contraceptive drugs didn't significantly alter food intake, or cause weight gain. "Depo-Provera is progesterone, but that doesn't mean it's going to make you blow up, because the estrogen levels stay the same," says Pelkman. "Women on Depo have normal levels of estrogen."
"That's not to say that some women won't gain weight," says Pelkman. It just means that as a group, any fluctuations in the women's weight were statistically insignificant, part of the random weight fluctuations that all normal women experience. "If a woman comes to me and asks if she'll get fat taking Depo-Provera, I'd say: 'I don't know. Try it. My data would suggest no.'
What about cravings?
"Every woman had chocolate at least once during the study," says Pelkman. But none of them showed a preference for chocolate or sweets during a specific menstrual phase or after receiving the contraceptive drug.
"Women need to consider the whole picture when they choose a contraceptive," says Pelkman. "My findings should dispel the myth that Depo will automatically make you fat. In a controlled study, I found that it didn't cause weight gain.
"But my study is just one piece of the story," Pelkman adds. "We need more longterm studies with larger sample sizes."
Christine L. Pelkman received her doctorate in biobehavioral health from the College of Health and Human Development in August 1999. She is now a postdoctoral fellow in the nutrition department, 226 Henderson Bldg., University Park, PA 16802; 814-863-8481; firstname.lastname@example.org. Her advisor, Barbara J. Rolls, Ph.D., is professor of nutrition, biobehavioral health, and behavioral science, 226 Henderson Bldg.; 863-8572; email@example.com. Rolls and Robert Heinbach, M.D. (122 Ritenour Bldg.; 863-2633; firstname.lastname@example.org) were coauthors on a paper, "Reproductive Hormones and Eating Behavior in Young Women," that Pelkman presented at the 1999 meeting of the Society for the Study of Ingestive Behavior in Clearwater, FL. Pelkman's three-year postdoctoral fellowship was awarded by The Medical Research Council of Canada. Depo-Provera is a registered trademark of the Pharmacia & Upjohn Company.