Seven hours of sleep may be the optimal duration for maintaining metabolic health, with both short and excessive sleep associated with increased insulin resistance, according to a new cross-sectional study.

Investigators analyzed data from nearly 25,000 participants in the National Health and Nutrition Examination Survey (NHANES) to examine whether sleep duration was associated with estimated glucose disposal rate (eGDR), a marker of insulin resistance.

“We found a significant inverted U-shaped relationship between how long people sleep on weekdays and their insulin resistance,” lead author Zhanhong Fan, MMed, and senior author Feng Zhang, PhD, of the School of Nursing and Rehabilitation at Nantong University in Nantong, China, told Medscape Medical News.

“We also discovered that the effect of weekend catch-up sleep is conditional — for those who don’t get enough weekday sleep, modest ‘catchup’ of 1-2 hours was beneficial, but for those who already sleep enough or for anyone engaging in excessive catch-up sleep, weekend catch-up sleep was associated with negative metabolic effects,” they said.

The study was published online in BMJ Open Diabetes Research & Care.

Investigating Real-World Sleep Patterns

Sleep duration is a “fundamental regulator of metabolic homeostasis, with profound implications for glucose metabolism,” the authors wrote. Both sleep deprivation and excessive sleep have previously been linked to increased risk for type 2 diabetes.

“While it’s well known that sleep duration affects metabolic health and insulin resistance, most studies look at average sleep or don’t account for the common modern habit of sleeping less during the workweek and trying to compensate on weekends,” Fan and Zhang said. “We were motivated to understand this real-world pattern.”

The investigators used eGDR, a validated clinical marker calculated from waist circumference, hypertension status, and A1c levels. The measure has increasingly been used to estimate insulin resistance and predict mortality risk in patients with metabolic syndrome.

They analyzed data from NHANES 2009-2023, which included questions about weekday or workday sleep duration. Beginning in 2017, the survey also collected information on weekend sleep duration.

Among 23,475 participants (51.16% male; age, 20-80 years), median weekday sleep duration was 7.5 hours (interquartile range [IQR], 6.0-8.0). Among the 10,817 participants with weekend sleep data, the median weekend sleep duration was 8.0 hours (IQR, 7.0-9.0), and nearly half (48.29%) reported engaging in weekend catch-up sleep.

A Delicate Balance

After adjusting for demographic and lifestyle factors, the researchers identified an inverted U-shaped relationship between weekday sleep duration and eGDR. The curve’s inflection point occurred at 7.32 hours of sleep per night.

Among participants sleeping fewer than 7.32 hours, each additional hour of sleep was associated with a 0.273-unit increase in eGDR, indicating greater insulin sensitivity (P < .001). However, among those sleeping more than 7.32 hours, each additional hour of sleep was associated with a 0.222-unit decrease in eGDR, suggesting higher insulin resistance (P < .001).

Weekend sleep patterns showed similarly nuanced effects. Among individuals sleeping less than 7.32 hours on weekdays, modest weekend catch-up sleep of 1-2 additional hours was associated with higher eGDR levels (beta-coefficient = 0.296; P = .002). Catch-up sleep of less than 1 hour was also associated with improved eGDR levels (beta-coefficient = 0.249; P = .005).

However, among those whose weekday sleep already exceeded 7.32 hours, weekend catch-up sleep had no significant association with eGDR. Moreover, sleeping more than 2 additional hours on weekends strengthened the negative association between weekday sleep and eGDR levels (beta-coefficient = -0.568; P = .005). 

“This suggests that longer weekend sleep duration may exacerbate the negative correlation between weekday sleep duration and eGDR, potentially leading to worsened blood glucose control,” the authors wrote.

Moderation Appears Key

The study’s cross-sectional design limited causal interpretation, and the authors acknowledged that reverse causality cannot be excluded. Self-reported sleep data may also introduce bias.

Nevertheless, Fan and Zhang believed that the findings have practical implications.

“The goal should be consistency and adequacy rather than extremes,” they said. “We should advise patients that aiming for around 7-7.5 hours of sleep on weekdays is a reasonable target for metabolic health.”

They also advocated individualized guidance regarding weekend sleep.

“For patients who chronically under sleep during the week, catching up an extra hour or 2 on weekends may offer a real, measurable, metabolic benefit,” they said. “However, for patients who already get sufficient sleep, or for anyone sleeping in for more than 2 extra hours, we should counsel against it, as this ‘social jetlag’ and circadian disruption may actually be harmful.”

In other words, the authors said, “you cannot fully ‘bank’ sleep or completely undo a week of poor sleep with a single weekend of oversleeping.”

Expert Commentary

Commenting for Medscape Medical News, Josiane Broussard, PhD, associate professor in the Department of Health and Exercise Science at Colorado State University in Fort Collins, Colorado, echoed the authors in noting the study design limits the conclusions that can be drawn.

Because the analysis is cross-sectional and relies on self-reported data, it “can’t really establish cause and effect,” Broussard said. In addition, she noted that eGDR is an indirect surrogate marker for insulin resistance, “so the findings should be interpreted cautiously.”

Nevertheless, the findings align with Broussard’s experience.

“In both research and clinical settings, short sleep is commonly associated with poorer metabolic health and greater cardiometabolic risk, and the association between very long sleep and worse outcomes is also something we see.”

For most adults, she said, “aiming for around 7-8 hours of sleep per night remains a reasonable target for supporting overall metabolic health.”

Broussard said habitual short sleepers should receive broader lifestyle and cardiometabolic risk counseling, whereas patients reporting very long sleep durations should be evaluated for underlying conditions such as sleep disorders, depression, medication effects, or chronic illness.

“Maintaining a regular and consistent sleep schedule is likely the most beneficial approach,” Broussard said.

William Horton, MD, MSc, chair in the 2026 American Association of Clinical Endocrinology Diabetes Disease State Network and associate professor of medicine, endocrinology, and metabolism in the Division of Endocrinology and Metabolism at the University of Virginia School of Medicine in Charlottesville, Virginia, told Medscape Medical News that the intriguing findings “highlight a time-tested maxim: moderation is key.”

The study is “another data point highlighting the potential positive impact of appropriate sleep — generally 7-9 hours depending on the source — on glycemic control and insulin sensitivity,” said Horton.

“Importantly, the study suggests that a modest amount of weekend catch-up sleep may have added benefit for those who don’t achieve adequate weekday sleep,” he said, “although confirmation of this finding in a dedicated trial is still needed.”

This work was funded by a grant from the National Natural Science Foundation of China and the Postgraduate Research & Practice Innovation Program of Jiangsu Province. The authors, Broussard, and Horton reported having no relevant financial relationships.

Batya Swift Yasgur, MA, LSW, is a freelance writer with a counseling practice in Teaneck, New Jersey. She is a regular contributor to numerous medical publications, including Medscape and WebMD, and is the author of several consumer-oriented health books as well as Behind the Burqa: Our Lives in Afghanistan and How We Escaped to Freedom (the memoir of two brave Afghan sisters who told her their story).