Poor sleep is known to lead to poor diet quality. But as a new Concordia-led study of co-habitating couples shows that poor sleep can affect not only an individual's food choices, but their partner's choices too. Because couples that sleep together very often eat together, one partner's unhealthy food choices can have a ripple effect on the eating habits of the other partner, the researchers say.
The study, published in the journal Annals of Behavioural Medicine, found that poor sleep was linked to a reduced ability to stick to healthy eating goals. People who slept poorly reported making less effort to eat well and feeling less confident in their ability to maintain healthy eating habits. The partner who slept well reported similar effects.
In other words, sleep is not just an individual health issue, according to corresponding author Jean-Philippe Gouin, a professor in the Department of Psychology.
"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," Gouin says. "This is likely because the sleep-deprived partner was more likely to expose them to highly palatable and calorie-dense food: things like crackers, chips, chocolate or candies."
Jean-Philippe Gouin: "People with a sleep-deprived partner say they have less confidence in their ability to follow a healthy diet, so they engage in less effort to do so."Self-reported habits reveal gender differences
The study followed 204 couples living together in Canada over three months. Both partners completed questionnaires about their sleep and diet at the beginning of the study, after one month, and after three months. Participants also kept a daily diary for the first 14 days, in which they recorded different aspects of their efforts to eat healthily.
The participants were, on average, 42 years old. At least one person in each couple was overweight or obese (meaning they had a body mass index of 25 or over) and trying to improve their diet or physical activity. Nearly 96 per cent of participants said they were actively trying to change their diets.
Overall, participants' diet quality improved modestly during the study, while sleep quality did not change significantly. Women reported healthier diets and stronger efforts to maintain healthy eating habits than men, but the researchers found no evidence that gender changed the way one partner's sleep affected the other's diet.
The researchers caution that the study does not prove that poor sleep causes unhealthy eating. Since the study was observational and relied on participants to self-report, the researchers say future studies could use more objective measures to track sleep and diet. Examples include examining factors such as household food choices, meal planning, partner support and conflict.
Treating sleep as a shared concern
The team says the findings could point to a possible new approach to improving dietary habits. Treatments that improve sleep, such as cognitive behavioural therapy for insomnia, could be studied as a couple-based health intervention.
If improving one partner's sleep also improves the other partner's ability to maintain healthy eating habits, then treating sleep as a shared concern could offer benefits for both people, they explain.
"We need to consider the social contexts in which poor eating habits are taking place," Gouin says. "That can involve asking how a partner is influencing one's eating behaviour, whether intentionally or not."
"If we want to make changes that are long-lasting, both partners need to work together to change the home and food environment so that it is easier to maintain healthier habits over time," he says.
The study was led by Maegan Dymarski, Concordia PhD candidate. Tamara Cohen (University of British Columbia), Noémie Carbonneau (Université du Québec à Trois-Rivières) and Kaberi Dasgupta (McGill University) also contributed.
The study was funded by a Social Sciences and Humanities Research Council of Canada (SSHRC) Insight Grant.
Read the paper: "Dyadic associations between sleep quality, diet-related self-regulation, and diet quality in couples"
