Fasting Tracker

Quick answers

Trouble sleeping while fasting?

Fasting itself rarely ruins sleep. What surrounds it often does

What the trials show

Many people worry that going to bed with an emptier stomach will keep them awake. The research is reassuring. A review of six randomized trials of time-restricted eating lasting at least 8 weeks found it doesn't typically worsen sleep, although a few studies saw small changes in either direction 4.

Key study

Early, late or your choice: sleep stayed the same

  • Randomized trial
  • 197 adults in Spain
  • 12 weeks

Adults with overweight ate within an 8-hour window that started before 10 a.m., after 1 p.m., or at a time they chose, or kept their usual habits. Sleep, measured with activity sensors, didn't change in any group compared with usual habits, and neither did mood or quality of life.

Clavero-Jimeno et al., JAMA Netw Open 2025

Even with alternate-day fasting, a tougher plan, fewer than 1 in 10 people had trouble staying asleep, and none had trouble falling asleep 5. Our guide to sleep and fasting goes deeper.

What often gets in the way

Caffeine first. Black coffee helps many people through the morning of a fast, but timing matters. A large dose of caffeine, about four cups of filter coffee, disturbed sleep even when taken 6 hours before bed 2.

Then a big last meal. A short eating window can mean a large dinner. In a Japanese study, people who went to bed less than 3 hours after dinner had about seven times the odds of reflux compared with those who waited 4 hours or more 3. It was an observational study, so it can't prove cause and effect.

Alcohol helps you fall asleep faster, but disrupts the second half of the night 6.

Going to bed hungry can too. If your window ends very early, or your last meal was small, hunger can wake you. And poor sleep makes the next day harder: after two short nights, young men had 28% more ghrelin, the hunger hormone, and felt 24% hungrier 7.

Fasting and sleeping well

  1. Finish your last meal at least 3 hours before bed 3.
  2. Have your last coffee or strong tea at least 6 hours before bed 2.
  3. Make your last meal filling, with protein and fibre, so hunger doesn't wake you 8.
  4. If you wake up hungry, try a glass of water or a cup of herbal tea.
  5. Keep alcohol early in your window, if at all.
  6. After a bad night, it's fine to shorten the next day's fast.

If you work nights, see intermittent fasting for shift workers: a steady routine matters more than a perfect window.

When to see a doctor

  • Poor sleep lasts for more than a few weeks or affects how you function during the day.
  • You snore loudly, stop breathing or gasp in your sleep, or wake unrefreshed however long you sleep.
  • You take insulin or other diabetes medication and wake up sweaty, shaky or with a racing heart: these can be signs of low blood sugar at night. Eat, check your glucose and talk to your care team 9.
  • You have insomnia or another sleep disorder: ask your doctor before changing your eating times.

Sources

  1. Clavero-Jimeno A, Dote-Montero M, Migueles JH, et al. Time-Restricted Eating and Sleep, Mood, and Quality of Life in Adults With Overweight or Obesity: A Secondary Analysis of a Randomized Clinical Trial. JAMA Netw Open. 2025;8(6):e2517268. doi.org/10.1001/jamanetworkopen.2025.17268
  2. Drake C, Roehrs T, Shambroom J, et al. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. J Clin Sleep Med. 2013;9(11):1195-200. doi.org/10.5664/jcsm.3170
  3. Fujiwara Y, Machida A, Watanabe Y, et al. Association between dinner-to-bed time and gastro-esophageal reflux disease. Am J Gastroenterol. 2005;100(12):2633-6. doi.org/10.1111/j.1572-0241.2005.00354.x
  4. Bohlman C, McLaren C, Ezzati A, et al. The effects of time-restricted eating on sleep in adults: a systematic review of randomized controlled trials. Front Nutr. 2024;11:1419811. doi.org/10.3389/fnut.2024.1419811
  5. Hoddy KK, Kroeger CM, Trepanowski JF, et al. Safety of alternate day fasting and effect on disordered eating behaviors. Nutr J. 2015;14:44. doi.org/10.1186/s12937-015-0029-9
  6. Ebrahim IO, Shapiro CM, Williams AJ, et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res. 2013;37(4):539-49. doi.org/10.1111/acer.12006
  7. Spiegel K, Tasali E, Penev P, et al. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846-50. doi.org/10.7326/0003-4819-141-11-200412070-00008
  8. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015;101(6):1320S-1329S. doi.org/10.3945/ajcn.114.084038
  9. National Institute of Diabetes and Digestive and Kidney Diseases. Low Blood Glucose (Hypoglycemia). U.S. National Institutes of Health. www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/low-blood-glucose-hypoglycemia
  10. Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. doi.org/10.3390/nu11040873

A note on health

Fasting Tracker is designed for general wellness and is not a medical device. Fasting is not right for everyone. If you are pregnant, diabetic, have a history of eating disorders or take medication, talk to your doctor first, and before any extended fast.