Poor sleep doesn't just derail your own diet — it can derail your partner's too, according to a study led by researchers at Concordia University published this month in the journal Annals of Behavioural Medicine.
The research team, led by Concordia psychology PhD candidate Maegan Dymarski and corresponding author Jean-Philippe Gouin, followed 204 cohabiting couples in Canada for three months. Each partner filled out questionnaires about sleep and diet at the start of the study, after one month, and after three months, and kept daily diaries tracking their efforts to eat healthily during the first two weeks. Nearly all participants, about 96%, said they were actively trying to improve their diets, and at least one partner in each couple had a body mass index of 25 or above.
People with a sleep-deprived partner were essentially saying they have less confidence in their ability to follow a healthy diet, so they engage in less effort to do so.
Jean-Philippe Gouin, Concordia University
The researchers found that when one partner slept poorly, both people reported putting in less effort toward healthy eating and feeling less confident they could stick with it, even the partner who had slept fine. The team's explanation centers on shared meals and shared kitchens: a tired partner, the study suggests, is more likely to bring home convenient, calorie-dense food such as chips, crackers, or chocolate, making it harder for both people to eat the way they intended.
Women in the study reported healthier diets and more consistent effort overall than men, though the researchers found gender did not change the basic sleep-to-diet spillover effect between partners. The authors, whose work was funded by the Social Sciences and Humanities Research Council of Canada, caution the study is observational and based on self-reported data, so it cannot prove poor sleep directly causes worse eating, only that the two consistently move together within couples, a point echoed in subsequent coverage of the findings.
The findings add to a growing body of research treating household diet and sleep as a shared, rather than individual, project within a household.
