Effects of Sleep on Muscle and Fat

In a study published in Annals of Internal Medicine, researchers looked at the effect of sleep on energy intake and expenditure.

About the study:

  • Ten overweight nonsmoking adults (7 male, mean age 41, mean BMI 27.4)

  • Followed them over 14 days of moderate calorie restriction (identical diets)

  • 8.5 or 5.5 hours of nighttime sleep

  • Measurement of:

    • Fat loss

    • Fat-free loss (muscle mass)

    • Changes in substrate utilization, energy expenditure, hunger, and 25-hour metabolic hormone utilization

The researchers found that while sleeping 8.5 hours each night, greater than 50% of the participants' weight loss was fat.

Reducing sleep to 5.5 hours sleep each night, cut the fat loss to 25%, in other words, they lost 55% less fat than when they were sleeping 8.5 hours, increasing the loss of muscle mass by 60%. Other findings were markers of enhanced neuroendocrine adaptation to caloric restriction, increased hunger, and a shift in relative substrate utilization towards oxidation of less fat.

The authors concluded:

  • The amount of sleep contributes to the maintenance of fat-free body mass at times of decreased energy intake

  • Lack of sufficient sleep may impact the efficacy of diet for weight loss and related metabolic risk reduction

The takeaway from this is that if you are planning to start a weight-loss program, try to make sure you are getting enough sleep each night.

How much sleep should you get? Here are some general approximations, depending on age:

  • Newborn - up to 18 hours

  • 1 to 12 months of age - 14 to 18 hours

  • 1 to 3 years of age - 12 to 15 hours

  • 3 to 5 years of age - 11 to 13 hours

  • 5 to 12 years of age - 9 to 11 hours

  • Teenagers - 9 to 10 hours

  • Adults - 7 to 8+ hours

  • Women during pregnancy - at least 8 hours

See original article:

"Insufficient Sleep Undermines Dietary Efforts to Reduce Adiposity"
Arlet V. Nedeltcheva, MD, Jennifer M. Kilkus, MS, Jacqueline Imperial, RN, Dale A. Schoeller, PhD, and Plamen D. Penev, MD, PhD Annals of Internal Medicine October 5, 2010 vol. 153 no. 7 435-441