How much sleep is best for blood sugar and insulin resistance?
About 7 hours and 18 minutes per night. A large study of 23,475 adults found that insulin sensitivity peaked at this weekday sleep duration. Sleeping less or more than this amount was linked to greater insulin resistance, the precursor to type 2 diabetes. The study also found that 1 to 2 hours of weekend catch-up sleep was linked to better numbers if you are short on sleep during the week, while more than 2 hours showed no benefit.
Researchers used data from the National Health and Nutrition Examination Survey (NHANES) spanning 2009 to 2023. They measured insulin sensitivity using a formula called the estimated glucose disposal rate (eGDR), which combines waist circumference, HbA1c (a three-month average of blood sugar), and high blood pressure status into a single score. A higher eGDR means your body handles glucose better. Among all participants, the median eGDR was 8.23, and the median weekday sleep duration was 7 hours and 30 minutes. The study was a one-time snapshot (cross-sectional).
Dr. Kumar’s Take
This study puts a number on something long suspected. Sleep matters for blood sugar, but “get enough sleep” is vague advice. Here, roughly 7 hours and 15 to 20 minutes appears to be the target. The researchers also looked at weekend catch-up sleep, since that is how many people actually live, and found that a small amount was linked to better numbers in short sleepers while more than 2 hours showed no benefit. That said, this is observational data with self-reported sleep times, so the exact numbers are a guide, not a prescription.
What the Data Show
The relationship between sleep and insulin sensitivity followed an inverted U-shaped curve. As weekday sleep increased toward 7 hours and 18 minutes, eGDR rose steadily, meaning glucose metabolism improved. Beyond that threshold, more sleep was linked to declining eGDR scores. This pattern held across the full sample of 23,475 participants aged 20 to 80.
Weekend catch-up sleep told a more nuanced story. Among the 10,817 participants with weekend sleep data, just over 48 percent reported sleeping longer on weekends than weekdays. For people who slept less than the optimal 7 hours and 18 minutes on weekdays, catching up with 1 to 2 extra hours on weekends was associated with higher eGDR, meaning better glucose processing. More than 2 hours of catch-up showed no such benefit, and in a separate analysis it weakened the link between weekday sleep and eGDR. The authors concluded that heavy catch-up sleep may be detrimental for people who already sleep enough during the week.
Who Is Most Affected
The effects of long sleep were not equal across all groups. Sleeping beyond about 7 hours and 18 minutes on weekdays was more strongly linked to lower eGDR in women, in adults aged 40 to 59, and in people with a BMI of 30 or higher. Below that threshold, the benefit of more sleep was similar across most groups and stronger in people with a BMI of 30 or higher.
Important Limitations
This study is observational, so it cannot prove that sleep duration directly causes changes in insulin sensitivity. Sleep times were self-reported, which can be inaccurate. There is also the possibility of reverse causation, where poor glucose metabolism disrupts sleep rather than the other way around. The eGDR formula, while validated, is an estimate and not a direct measurement of how the body processes glucose. These are important caveats to keep in mind before making major changes based on these findings.
Practical Takeaways
- Aim for about 7 hours and 15 to 20 minutes of sleep on weeknights, as this appears to be the range most strongly linked to healthy glucose metabolism.
- If you consistently sleep less than 7 hours on weekdays, allowing yourself 1 to 2 extra hours on weekends may help your metabolic health, but do not overdo it.
- Avoid weekend sleep binges of more than 2 extra hours if you already sleep enough during the week, since the authors concluded it may be detrimental and it showed no benefit.
- Women, adults aged 40 to 59, and people with obesity showed the strongest link between long weekday sleep and worse insulin sensitivity.
- Focus on sleep consistency throughout the week rather than relying on weekends to make up for chronic short sleep.
Related Studies and Research
- One-third of US adults get less than 7 hours of sleep: geographic patterns revealed
- One night of partial sleep loss triggers insulin resistance
- One week of sleep restriction reduces insulin sensitivity in healthy men
- Tart cherry juice improves sleep duration and quality in older adults
FAQs
Is 7 hours and 18 minutes of sleep really better than 8 hours for blood sugar?
According to this study, yes. The data showed an inverted U-shaped relationship, meaning insulin sensitivity peaked near 7 hours and 18 minutes and then declined with longer sleep. This does not mean 8 hours is harmful overall, as sleep benefits many systems beyond metabolism. But for glucose processing specifically, slightly less than 8 hours appeared to be the sweet spot in this large sample. Other factors like sleep quality, consistency, and individual health conditions also play a role that this study did not fully capture.
Can weekend catch-up sleep fix the damage from sleeping too little during the week?
It can help, but only within limits. The study found that 1 to 2 hours of extra weekend sleep was linked to better glucose metabolism in people who slept less than 7 hours and 18 minutes on weekdays. However, catching up by more than 2 hours showed no benefit. This suggests your body benefits from modest recovery sleep, but large swings between weekday and weekend sleep patterns may disrupt metabolic rhythms. The best approach is still to keep your sleep schedule as consistent as possible throughout the week.
Why were women and middle-aged adults more affected by long sleep?
The researchers observed that sleeping longer than about 7 hours and 18 minutes was more strongly linked to lower insulin sensitivity in women and in adults aged 40 to 59, though the study did not fully explain why. Hormonal differences may play a role, as estrogen and progesterone influence both sleep architecture and glucose metabolism. Middle age is also a period when metabolic flexibility naturally declines and insulin resistance becomes more common, which could make this age group more sensitive to sleep disruptions. These findings suggest that women and people in their 40s and 50s may benefit most from paying close attention to their sleep habits.
Bottom Line
Sleeping approximately 7 hours and 18 minutes per night is linked to the best insulin sensitivity, based on a study of more than 23,000 adults. Both too little and too much sleep were associated with greater insulin resistance. If you fall short on weekday sleep, a modest 1 to 2 hours of weekend catch-up may help your metabolism, but sleeping in much longer than that showed no benefit. Consistency matters more than compensation.
