Losing body fat usually requires a combination of restricting calories and increasing exercise. However, getting enough sleep might be an important, but sometimes overlooked part of the weight loss equation. Research suggests that short sleep duration might impede fat loss efforts and increase body mass index, or BMI.
BMI
Body mass index is a formula used to determine an individual's body fat based on their height and weight. It is used by physicians and doctors as an indicator of overall health. A BMI between 18 and 25 is considered a normal weight whereas a BMI of 25 or more is considered obese, according to the Mayo Clinic website.
Short Sleep Duration
Scientists from the University of Bergen in Norway investigated the relationship between sleep status and BMI levels. Subjects completed a sleep questionnaire and had their BMI calculated. Sleep duration was divided into the following groups: less than 5 hours; 5 to 6; 6 to 7; 7 to 8; 8 to 9; and 9 plus. Short sleep duration was defined as less than 7 to 8 hours of sleep a night. At the end of the study, which was published in the March 2007 issue of the "Journal of Sleep Research," scientists observed that short sleep duration was associated with a higher BMI.
Leptin and Ghrelin
Researchers from Stanford University in California studied the effects of sleep duration on BMI and metabolic hormones. In the report, which was published in the December 2004 issue of the journal "PLoS Medicine," scientists found that short sleep duration, defined as less than seven hours, was associated with an increase in BMI. In addition, scientists found that short sleep duration caused a decrease in leptin, a hormone that reduces hunger, and an increase in ghrelin, a hormone that boosts hunger. This might explain the increase in BMI.
Increases BMI
Scientists from the University of Iowa explored the relationship between sleep duration and body mass index in a rural population in southeast Iowa. They reported in the September 2006 issue of the journal "Archives of Internal Medicine," that subjects with short sleep duration, defined as less than 6 hours, had a higher BMI compared to those without short sleep duration.
References
- Mayo Clinic: Obesity
- Journal of Sleep: The Association Between Sleep Duration, Body Mass Index and Metabolic Measures in the Hordaland Health Study; B.Bjorvatin et al.; February 2007
- PLoS Medicine: Short Sleep Duration Is Associated with Reduced Leptin, Elevated Ghrelin, and Increased Body Mass Index; S.Taheri et al.; December 2004
- Archives of Internal Medicine: Sleep Duration and Body Mass Index in a Rural Population; N.D.Kohatsu et al.; September 2006
