Birth control pills are safe and effective for millions of women, but researchers are still working to understand how the hormones they contain may influence eating behavior.
A new study in JAMA Network Open followed 422 women who were already using combined oral contraceptives, tracking their eating patterns daily for 49 consecutive days. The goal: to examine whether binge-related eating changes depending on whether women are taking hormone-containing pills or hormone-free pills within the same cycle.
In a typical birth control pack, women take about three weeks of "active" pills that contain hormones, followed by about a week of "inactive" pills that contain no hormones.
"Because we tracked the same women day to day, we could see how eating changed with hormone exposure," said Dr. Shaunna Clark , a co-author and associate professor of psychiatry and behavioral sciences at Texas A&M University's Naresh K. Vashisht College of Medicine .
How birth control hormones may increase binge-eating risk
The study used a within-person design, meaning each participant served as her own comparison. Researchers measured emotional eating (overeating in response to negative emotions) while tracking whether each day corresponded to an active or inactive pill.
They found a consistent pattern:
Emotional eating was significantly higher during active pill days than during inactive pill days.
This pattern appeared:
- across two full pill cycles
- in the full sample of 422 women
- and in a subset of women with diagnosed binge eating
Clark says the findings held even after accounting for negative mood, suggesting the change was not fully explained by emotional distress.
"That tells us the hormones themselves may be playing a role, rather than those changes being driven by mood or other factors," she said.
Why birth control may increase binge-eating risk for some women, but not others
The analysis focused on average changes across the group, but the study emphasizes that not all women experience these shifts in the same way.
"Participants ranged in age from late adolescence to young adulthood and were all using the same type of pill, monophasic combined oral contraceptives , which provide a consistent dose of hormones during active pill days," said Clark, part of the research team led by Dr. Kelly Klump at Michigan State University.
Because the study examined within-person changes, it shows that eating behavior can shift alongside hormone exposure, even if the magnitude of that shift differs between individuals.
"These findings show a pattern at the group level," she said, "but individual responses can vary."
Birth control pills linked to binge eating, but not mood or body image
The study does not establish that birth control pills cause binge eating. Instead, it identifies a specific association between hormone exposure and increased emotional eating within individuals.
Importantly, researchers also tested other outcomes:
- Weight preoccupation did not change across pill type
- Mood changes in response to pill type were smaller and less consistent than the changes in eating
Clark says that suggests the effect is relatively specific to binge-related eating behavior, rather than a general shift in mood or body image concerns.
How this study changes what we know about birth control and binge eating
Previous research has shown that binge‑related eating tends to increase after ovulation, when both estrogen and progesterone are elevated.
This study extends that work by showing that synthetic hormones in birth control pills are linked to similar patterns.
By comparing hormone-containing and hormone-free days within the same individuals, the study provides some of the clearest evidence to date that binge-related eating increases during periods of hormone exposure in the birth control cycle.
"Findings like these can help us better understand how different hormone exposures affect eating behavior," Clark said. "Over time, that could help clinicians and patients make more informed decisions about care."
