Study suggests extreme dieting lowers sleep quality, with women more strongly affected

A new study suggests that extreme dieting may actually worsen sleep quality, especially for women.

A joint research team led by Prof. Park Min-seon of the Department of Family Medicine at Seoul National University Hospital and Prof. Seo Min-jeong of the Department of Family Medicine at SMG-SNU Boramae Medical Center announced the findings on Tuesday after analyzing dietary habits and physical activity levels among 13,164 adults who participated in the Korea National Health and Nutrition Examination Survey, an annual nationwide government health review.  

The study examined the relationship between energy intake-expenditure balance and sleep duration. Unlike previous studies that analyzed eating habits or physical activity separately, this research evaluated how the balance between the two factors affects sleep using large-scale national data.

The researchers calculated an energy balance index by subtracting basal metabolic rate and physical activity expenditure from total daily calorie intake, then divided participants into four groups.

After adjusting for multiple variables, including age, body mass index, smoking, alcohol consumption, diet quality and compensatory weekend sleep-ins, the team assessed the risk of “short sleep,” defined as sleeping six hours or less per day.

The findings showed that among women, the group with the most balanced energy intake and expenditure had a 29 percent lower risk of insufficient sleep than the group with the most severe energy deficit.

Women in groups that consumed slightly more or substantially more energy than they expended also showed lower risks of insufficient sleep — 25 percent and 24 percent lower, respectively — than the severe energy-deficit group.

Notably, the group with the most balanced energy intake and expenditure showed greater sleep benefits than the group with the highest calorie intake. The findings suggest that sleeping better is not simply about eating more, but about maintaining a healthy balance between calorie intake and energy use.

The same association was not observed among men.

The research team attributed the gender-specific findings to differences in neuroendocrine and immune regulation.

During sleep, the body uses roughly 400 calories to activate immune cells and reduce inflammation. When calorie intake becomes too low, the body activates the hypothalamic-pituitary-adrenal axis — the body’s stress-response system — triggering the release of stress hormones such as cortisol that can interfere with deep sleep.

Researchers attribute the result to women tending to react much more strongly than men to fluctuations in metabolism- and immunity-related hormones such as cortisol, leptin and estrogen, leading to a sharper deterioration in sleep quality when the body lacks enough energy for overnight recovery.

“This study confirms that extreme dieting focused only on eating less or increasing exercise can actually harm sleep,” Park said. "To protect sleep health, people need personalized health strategies that consider factors such as sex, occupation and activity level when balancing calorie intake and energy use."

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.

BY KIM NAM-YOUNG [[email protected]]