Biology isn't the only reason women eat less as they near ovulation, a time when they are at their peak fertility.
Three new independent studies found that another part of the equation is a woman's desire to maintain her body's attractiveness, says social psychologist and assistant professor Andrea L. Meltzer, Southern Methodist University, Dallas.
Women nearing ovulation who also reported an increase in their motivation to manage their body attractiveness reported eating fewer calories out of a desire to lose weight, said Meltzer, lead researcher on the study.
When women were not near peak fertility -- regardless of whether they were motivated to manage their body attractiveness, near peak fertility but not motivated to manage their body attractiveness, or using hormonal birth control, they were less likely to want to lose weight and didn't reduce their calories, Meltzer said.
"These findings may help reconcile prior inconsistencies regarding the implications of ovulatory processes," said Meltzer. "The desire to manage body attractiveness was a motivational factor for desired weight loss when women are nearing ovulation."
The research was funded by the National Science Foundation.
The findings are published in the journal Personality and Social Psychology Bulletin. The article, "A psychophysiological mechanism underlying women's weight-management goals: Women desire and strive for greater weight loss near peak fertility," is published online in advance of print at http://bit.
The authors note that their study adds to a growing body of ovulation research, particularly as it relates to women's health and weight management.
Previous studies in the field have found that women, and many non-human mammals, consume fewer calories near peak fertility.
They've also found that ovulation shifts a woman's goals to attract a partner, motivating her to enhance her appearance to compete for men.
The authors note, however, that studies by other researchers attribute those ovulatory shifts in eating behavior solely to physiological factors related to an interaction between the nervous system and the endocrine system.
But Meltzer and her colleagues say the new findings suggest an additional reason, one that is related to cultural norms and influences that dictate one way women may enhance their attractiveness is by managing their weight: Ovulating women may be motivated to lose weight and eat less if they are also motivated to improve their body attractiveness.
"Indeed, in our research we saw that shifting levels of hormones interacted with women's desires to manage their body attractiveness, which predicted an important behavior -- eating less," Meltzer said. "These findings illustrate that broader social norms that dictate that thin women are more attractive can play a role, in addition to physiological factors."
Meltzer's co-authors on the study are James K. McNulty, Florida State University, Saul L. Miller, University of Kentucky, and Levi R. Baker, University of North Carolina at Greensboro.
Findings are confirmed across three independent studies.
The three independent studies involved three different groups of women.
The first study followed 22 heterosexual women who were not using hormonal contraceptives and found they desired greater weight loss when they were closer to ovulation than when they were not.
The second study followed 92 heterosexual women, some who were using and some who were not using hormonal contraceptives. Its findings replicated the findings of the first study: Women who were not using hormonal contraceptives near peak fertility reported wanting to weigh less. In contrast, women in the study using hormonal contraceptives -- which act on the endocrine system to disrupt the menstrual cycle and prevent pregnancy by altering hormonal fluctuations -- didn't demonstrate a desire to lose weight.
A third study followed 89 married women and found that those who were not using hormonal birth control were the ones most motivated to restrict eating during peak fertility, but only when they were more motivated to maintain their body attractiveness.
"Not only did the primary effect replicate across three independent studies," the authors said, "it emerged in two samples of undergraduate women from different universities and a sample of married women and did not vary across participants' weight using two samples of women who had a normal weight on average and one sample of women who were overweight on average."
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