People who sleep less than 7 hours or more than 9 hours a night, gain more weight over a period of time and become obese as compared to individuals who log 8 hours every night.

People who want to lose weight or prevent weight gain should not only exercise and eat well, but also sleep.

In a study by Dr. Angelo Tremblay, of LavalUniversityin Quebec City, published in the Journal Sleep, the researchers followed 276 men and women for 6 years. During that time, people who averaged 5 to 6 hours of shut eye a night gained 1.98 kgsĀ more than those who slept 7 to 8 hours, while those who slept for 9 to 10 hours gained 1.58 kgs more than the average-length sleepers.

Short and long sleepers also showed greater gains in fat mass and waist circumference than average-length sleepers, and were significantly more likely to gain 5 kgs or more.

Getting too much or too little sleep somehow disrupts appetite control by causing a reduction in leptin, a hormone that dampens appetite, while increasing secretions of the appetite-stimulating hormone ghrelin.

Short and long sleepers were also more prone to hypoglycemia, or low blood sugar, than average sleepers, which could increase appetite as well.