Short sleep blunts insulin and stokes appetite, and adding sleep cut calories

Key takeaways

• In a 1999 University of Chicago study, six nights of four hours in bed left healthy young men taking about 40% longer to clear blood sugar after a carb-heavy meal¹.
• Pooled lab studies found that people who were short on sleep ate about 385 more calories a day without burning more⁴⁵.
• In a 2022 trial, adults with overweight who got about 1.2 hours more sleep a night ate about 270 fewer calories a day than a control group⁶.
• In a 2019 lab study, sleeping in on the weekend didn’t protect insulin sensitivity, and on some measures it made things worse⁸⁹.
• Sleep apnea is common in people with type 2 diabetes and often undiagnosed, so loud snoring, gasping or choking sounds, and frequent daytime sleepiness deserve a checkup¹¹¹².

In 1999, 11 healthy young men checked into a sleep lab at the University of Chicago for 16 nights, eating the same meals throughout. For six of those nights, they were allowed only four hours in bed, from 1 a.m. to 5 a.m.¹.

By the end of that stretch, their blood sugar control had slipped badly. After a high-carbohydrate meal, they took about 40% longer than usual to bring their blood sugar back down¹. Both the insulin they released and their response to it fell by about 30%¹.

On morning tests, these lean, healthy volunteers would have met the criteria for impaired glucose tolerance, an early warning sign on the road to diabetes¹. Then they slept up to 12 hours a night for a week, and the changes went away¹.

That study, led by Eve Van Cauter and published in The Lancet, helped launch a long line of research on sleep and metabolism. Since then, the findings have pointed one way: short sleep makes your body handle sugar worse and nudges you to eat more. The hopeful part is that one of the best recent trials found the reverse: adding sleep made people eat less.

Six short nights pushed healthy young men toward prediabetes

To understand the finding, start with insulin, the hormone that moves sugar from your blood into your cells. Insulin sensitivity describes how well your cells respond to it. When sensitivity drops, the body has to make more insulin to do the same job, and blood sugar stays high longer.

In the Chicago study, the short nights also raised levels of the stress hormone cortisol in the afternoon and evening and lowered a thyroid-signaling hormone¹. The researchers said the overall pattern looked like aging¹.

The study was small, and four hours a night is extreme, so researchers have since tested milder losses.

A realistic sleep cut still raised insulin resistance

At Columbia University, Marie-Pierre St-Onge’s team recruited 38 healthy women who usually slept at least seven hours¹⁰. Each woman spent six weeks on her normal schedule and six weeks going to bed 90 minutes later, which cut her sleep to about six hours. The order was set by chance¹⁰.

That mild cut, the kind many people live with, pushed insulin resistance up almost 15% across the group. Among the 11 women past menopause, the rise topped 20%¹⁰.

Fasting insulin rose more than 12%¹⁰. Average blood sugar stayed stable, and the changes weren’t explained by gains in body fat¹⁰. The study was published in Diabetes Care in late 2023 and funded by the National Institutes of Health (NIH)¹⁰.

Stable blood sugar may sound reassuring, but the women’s bodies were working harder, making more insulin to keep sugar in range. St-Onge has warned that, over years, that kind of strain on insulin-making cells could lead toward type 2 diabetes¹⁰. That is a projection, not something the six-week study measured.

Quality matters, not just hours

Deep, slow-wave sleep seems to matter, too. When researchers selectively suppressed deep sleep in volunteers for three nights, their insulin sensitivity fell by about 25%¹¹.

Short sleep turns up hunger, though the hormone story is messier

In 2004, the Chicago team ran a second experiment. Twelve healthy young men spent two nights with short sleep and, in a separate period, two nights with extra sleep, while the team controlled their food and activity².

After short sleep, leptin, a hormone that signals fullness, fell 18%. Ghrelin, a hormone that drives hunger, rose 28%². The men rated their hunger 24% higher. Their appetite for calorie-dense, high-carbohydrate foods rose 33% to 45%².

The same year, researchers at Stanford University and the University of Wisconsin looked at 1,024 adults in the Wisconsin Sleep Cohort³. People who slept five hours had about 15% less leptin and 15% more ghrelin than people who slept eight³. Body mass index, a measure of weight for height, was lowest at about 7.7 hours of sleep³.

Why the hormone explanation is only part of it

That neat hormone story has proved harder to pin down:

• The Wisconsin study was a snapshot, so it couldn’t show which came first. It used one morning blood sample and didn’t measure appetite³.
• It found no link between sleep length and insulin or blood sugar levels³.
• When King’s College London researchers pooled sleep studies in 2016, they offered the hormones as just one possible explanation. Another: a separate study found stronger brain reward responses to food in sleep-deprived adults⁵.

The bottom line on intake is clearer than the mechanism. The King’s College analysis combined 11 studies with 172 people⁴⁵.

People who slept 3.5 to 5.5 hours ate about 385 more calories a day than people given 7 to 12 hours in bed, and they didn’t burn more energy to make up for it⁴⁵. That’s about four and a half slices of bread⁵. They ate a bit more fat and less protein⁴.

Most of those studies lasted one day to two weeks, in labs⁵. Labs are useful, but they aren’t kitchens at home.

Adding sleep cut calories in real life

That’s why a 2022 trial stood out. Esra Tasali and colleagues at the University of Chicago, with Dale Schoeller of the University of Wisconsin–Madison, recruited 80 young adults with overweight who usually slept less than 6.5 hours a night⁶. Recruitment materials didn’t mention the sleep intervention, so people wouldn’t change their habits before the study began⁶.

Everyone slept in their own beds and ate as usual, with no food diaries⁶. After two weeks of baseline tracking, half got a single personalized counseling session on sleep habits. The others carried on as before⁶.

The counseling group slept about 1.2 hours more per night⁶. They also ate about 270 fewer calories a day than the control group, and some cut as many as 500⁶.

The team measured intake with doubly labeled water. In that method, people drink water tagged with stable isotopes, harmless markers that urine tests can track, to show how much energy they burn. Combined with changes in body energy stores, that reveals how much they ate⁶.

Tasali said limiting electronic devices before bed appeared to be a key change, though the study didn’t formally test it⁶. She was also clear that “this was not a weight-loss study”⁶.

The university projected that, if the effect lasted, it could mean about 26 pounds lost over three years. That’s an extrapolation from two weeks, not a result⁶. The trial was funded by the NIH⁶. A larger, longer study is the next step.

Sleeping in on weekends didn’t undo the damage

Many people try to repay a short week with long weekend mornings. In 2019, Chris Depner and Kenneth Wright at the University of Colorado Boulder tested whether that works⁸⁹.

They kept 36 healthy adults, ages 18 to 39, in a lab for about two weeks, with food, light and sleep closely monitored⁹. After baseline testing, the volunteers were split into three groups⁸⁹:

• Control: up to 9 hours of sleep a night.
• Short every night: up to 5 hours.
• Weekend recovery: 5 hours for five nights, then a weekend of free sleep, then two more short nights.

Both short-sleep groups snacked more after dinner and gained about 3 pounds on average⁸.

Whole-body insulin sensitivity fell 13% in the group that stayed short every night⁸⁹. In the weekend group, it fell by 9% to 27%, according to the university; the NIH summary gives the top figure, 27%⁸⁹. Only the weekend group lost insulin sensitivity in the liver and muscles⁸⁹.

The weekend helped a little while it lasted, with less night snacking. But the habit returned as soon as short nights resumed⁸⁹.

The two official summaries disagree on how much extra sleep the weekend brought: 66 minutes on average, says the university, or about 3 hours over two nights, says NIH⁸⁹. Both call it modest. The volunteers’ body clocks also shifted later, making it harder to fall asleep Sunday night⁹.

Depner said the team “didn’t see any benefit in any metabolic outcome” among the weekend sleepers⁹. Wright’s advice was to aim for about 7 hours on as many nights as possible⁹. He suggested weekend sleep might still help people who lose sleep only once in a while, but the study didn’t test that⁹.

The study was small, lab-based and short, but it suggests consistency matters more than catching up. A future article in this library covers sleep schedules in depth.

Sleep apnea and diabetes often travel together

Obstructive sleep apnea is a common sleep disorder that brings repeated drops in oxygen and broken-up sleep through the night¹¹.

In studies that measured sleep overnight in people with type 2 diabetes, about 71% had sleep apnea, according to a 2012 review by S. Pamidi and Esra Tasali¹¹. Yet in one large primary care analysis, only 18% of patients with diabetes had an apnea diagnosis¹¹.

Whether apnea causes diabetes is still unproven. Long-term studies are mixed¹¹. Treatment with CPAP, a mask that keeps the airway open with gentle air pressure, has also given mixed results for blood sugar. In that review, only three of nine sham-controlled trials found a benefit, and results seemed to depend on using the machine more than four hours a night¹¹.

In 2008, the International Diabetes Federation urged doctors to screen people with either condition for the other¹³. If you have diabetes or prediabetes and any of the warning signs in the box below, ask about a sleep study. A future article in this library covers sleep apnea.

Night shifts and a mismatched body clock

Timing matters, not just hours. In a 2009 study at Brigham and Women’s Hospital, 10 healthy volunteers lived on 28-hour “days” for 10 days, so they slept and ate at shifting times¹⁴. Their leptin dropped, and 3 of the 10 had after-meal blood sugar in the prediabetes range⁷¹⁴. Their daytime blood pressure rose, too⁷.

In 64,615 women in the Nurses’ Health Study 2, the link between night shifts and type 2 diabetes depended on each nurse’s natural body-clock type¹⁵. Night owls who worked only day shifts had about 1.5 times the odds of diabetes, compared with women in between¹⁵. That study was funded by the National Institute for Occupational Safety and Health and was observational, so it shows links, not cause¹⁵.

Future articles in this library cover irregular work schedules and the body clock. For eating late, see the library’s article on intermittent fasting.

How strong is the evidence?

Claim	Rating	What it rests on
Short sleep weakens insulin sensitivity in healthy people	Strong evidence	Several controlled lab studies, from severe to mild sleep cuts1910
Short sleep makes people eat more	Strong evidence	A meta-analysis of 11 lab studies45
Lower leptin and higher ghrelin explain the extra eating	Promising but early	Small lab study and a snapshot study; other mechanisms possible235
Adding sleep cuts calories in short sleepers	Promising but early	One well-measured two-week trial6
Extra sleep leads to lasting weight loss	Not enough evidence	Only projections so far6
In a controlled lab trial, a weekend of recovery sleep protected insulin sensitivity during a short-sleep week	Evidence says no	The one such trial (36 adults, 2019) found no metabolic benefit; real-life and occasional short sleep weren’t tested89
Treating sleep apnea improves blood sugar	Promising but early	Mixed trials; nightly use seems to matter11

A metabolism-friendly sleep checklist

Use this as a quick self-check. Each item comes from the studies above.

• I get about 7 hours or more most nights, not just on weekends⁹.
• My bedtime and wake time stay within about an hour across the week, so I’m not relying on weekend catch-up⁸⁹.
• Screens go off a while before bed, the change the Chicago trial flagged⁶.
• I’ve stopped my after-dinner snacking, the habit short-sleep volunteers fell into⁸.
• My sleep is deep and unbroken most nights, or I’ve asked a clinician why it isn’t¹¹.
• If I have diabetes or prediabetes, I’ve been asked about snoring and sleepiness¹¹¹³.

A two-week sleep extension plan

This plan borrows the shape of the 2022 Chicago trial: watch first, then change one thing⁶. It’s a personal experiment, not a treatment.

Week 1: observe. Change nothing. Each morning, write down when you went to bed, when you got up and how you felt. Note any after-dinner snacking. Don’t count calories or weigh yourself daily. The trial’s volunteers didn’t log food, either⁶.

Week 2: add sleep. Using your week 1 average, aim for 45 to 60 extra minutes a night.

1. Keep your wake time fixed and move bedtime earlier in two steps of about 30 minutes.
2. Set a screen cutoff 30 to 60 minutes before the new bedtime⁶.
3. Close the kitchen after dinner, since late snacking rose with short sleep⁸.
4. Make the bedroom dark, cool and quiet enough to stay asleep.
5. Keep weekends within an hour of your weekday times⁹.

At day 14, compare. Are you hungrier in the evening, or less? Is your energy steadier? If thoughts about food or weight start to feel hard to manage, stop and reach out. The National Alliance for Eating Disorders helpline is 1-866-662-1235.

Sleep belongs with food and movement

Natural health has always treated the body as a whole, and this research backs that up. Food and movement get most of the attention in metabolic health, but these studies suggest sleep belongs on the same list.

There’s no product to buy here. The most promising intervention in this article was one conversation about sleep habits, followed by earlier, screen-free bedtimes⁶. That is prevention the way many readers already like it: simple, cheap and in your own hands.

Questions readers ask

The bottom line

Sleep is part of your metabolism. In lab studies, short nights weakened insulin’s effect, even when the sleep loss was modest, and pushed people to eat more. Sleeping in on weekends didn’t reverse the damage in the best test so far.

The encouraging news is that the reverse seems to work, too. In a real-world trial, short sleepers who added about an hour of sleep ate less. Aim for a steady seven or more hours, give screens an earlier curfew, and get checked if snoring or daytime sleepiness suggests apnea.

Related reading

• Sleep saves what you learned today, while the brain-cleaning story is less certain
• Modest goals cut diabetes risk 58% in a landmark trial, and yours can be just as small
• Intermittent fasting ties ordinary dieting in trials, which can be good news
• Glucose sensors catch every spike, and in healthy people most spikes are normal
• One in seven workers clocks in during off-hours, and sleep is the first thing to anchor

Sources

1. University of Chicago Medicine. “Lack of Sleep Alters Hormones, Metabolism, Simulates Effects of Aging” (on Spiegel K, Leproult R, Van Cauter E, “Impact of Sleep Debt on Metabolic and Endocrine Function,” The Lancet, 1999). October 1999. uchicagomedicine.org
2. Spiegel K, et al. “Brief Communication: Sleep Curtailment in Healthy Young Men Is Associated With Decreased Leptin Levels, Elevated Ghrelin Levels, and Increased Hunger and Appetite.” Annals of Internal Medicine, 2004 (abstract via QxMD). pubmed.ncbi.nlm.nih.gov
3. Taheri S, Lin L, Austin D, Young T, Mignot E. “Short Sleep Duration Is Associated With Reduced Leptin, Elevated Ghrelin, and Increased Body Mass Index.” PLoS Medicine, 2004;1(3):e62. doi.org
4. Al Khatib HK, Harding SV, Darzi J, Pot GK. “The Effects of Partial Sleep Deprivation on Energy Balance: A Systematic Review and Meta-Analysis.” European Journal of Clinical Nutrition, 2017;71(5):614-624 (Nutrition Evidence record). nutrition-evidence.com
5. King’s College London. “Sleep Deprivation May Cause People to Eat More Calories.” November 2, 2016. kcl.ac.uk
6. University of Chicago Medicine. “Getting More Sleep Reduces Caloric Intake, a Game Changer for Weight Loss Programs” (on Tasali E, Wroblewski K, Kahn E, Kilkus J, Schoeller DA, “Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings,” JAMA Internal Medicine, 2022). February 7, 2022. uchicagomedicine.org
7. MedlinePlus, National Library of Medicine. News report, March 2, 2009, on Scheer FAJL, et al., Proceedings of the National Academy of Sciences, 2009 (archived copy).
8. National Institutes of Health. “Weekend Catch-Up Can’t Counter Chronic Sleep Deprivation” (on Depner CM, et al., Current Biology, 2019). NIH Research Matters, March 12, 2019. nih.gov
9. University of Colorado Boulder. CU Boulder Today news story on weekend catch-up sleep (on Depner CM, et al., Current Biology, 2019). February 28, 2019. colorado.edu
10. Columbia University Irving Medical Center. “Shortening Sleep Time Increases Diabetes Risk in Women” (on Zuraikat F, Laferrère B, Scaccia S, et al., Diabetes Care, 2023). November 13, 2023. cuimc.columbia.edu
11. Pamidi S, Tasali E. “Obstructive Sleep Apnea and Type 2 Diabetes: Is There a Link?” Frontiers in Neurology, 2012;3:126. frontiersin.org
12. MedlinePlus. “Sleep Disorders.” National Library of Medicine, updated December 4, 2025. medlineplus.gov
13. Sleep Review (Reuters Health). “Patients With Obstructive Sleep Apnea Should Be Screened for Type 2 Diabetes” (on the International Diabetes Federation consensus statement). June 2008. sleepreviewmag.com
14. Harvard Gazette. “Researchers Find Potential Cause of Heart Risks for Shift Workers” (on Scheer FAJL, et al., PNAS, 2009). March 2009. news.harvard.edu
15. Vetter C, Devore EE, Ramin CA, Speizer FE, Willett WC, Schernhammer ES. “Mismatch of Sleep and Work Timing and Risk of Type 2 Diabetes.” Diabetes Care, 2015;38:1707-1713 (CDC Stacks, NIOSH-funded). stacks.cdc.gov