The study, conducted by researchers at Columbia University's Mailman School of Public Health and the Obesity Research Center, demonstrated a clear link between the risk of being obese and the number of hours of sleep each night, even after controlling for depression, physical activity, alcohol consumption, ethnicity, level of education, age, and gender. The study was an analysis of data taken from the National Health and Nutrition Examination Survey I (NHANES I).

Counterintuitive Results

Specifically, the study found that subjects between the ages of 32 and 59 who slept four hours or less per night were 73 percent more likely to be obese than those who slept between seven and nine hours each night. People who got only five hours of sleep had a 50 percent higher risk than those who were getting a full night's rest. Those who got six hours of sleep were just 23 percent more likely to be substantially overweight.

"The results are somewhat counterintuitive, since people who sleep less are naturally burning more calories," said lead researcher James Gangwisch, a post-doctoral fellow in psychiatric epidemiology at Columbia University. "But we think it has more to do with what happens to your body when you deprive it of sleep as opposed to the amount of physical activity that you get. Other studies have shown that leptin levels decrease and grehlin levels increase in people who are sleep-deprived, leading to increased appetite and consumption."

It's the Metabolism, Stupid

Why would that happen? According to Gangwisch, one possible answer can be found in looking back at our early forebears. "The metabolic regulatory system may have evolved to motivate humans to store fat during summer months when the nights are shorter and food is plentiful, which was a survival mechanism for the body to prepare for the dark winter months when food would not be as plentiful," said Gangwisch. "As a result, sleeping less could serve as a trigger to the body to increase food intake and store fat."

The study was presented as part of a joint effort by NAASO and the American Diabetes Association (ADA) to increase awareness of the rising problem of obesity and its related health problems in the United States.

Obesity May Overtake Tobacco

NAASO and ADA recognize obesity as a significant threat to public health and are cooperating to provide further opportunities for sharing obesity information, increasing obesity awareness and facilitating more research and better clinical care in their joint effort to fight this disease.

According to the Centers for Disease Control and Prevention (CDC), deaths due to obesity - as it relates to poor diet and physical inactivity - may soon overtake tobacco as the leading preventable cause of death. Obesity can significantly increase a person's risk for a number of serious conditions, including type 2 diabetes, heart disease, stroke, high blood pressure and some types of cancer.