Every day each person needs to sleep, then you know how long to sleep helps to keep you slim? Recently, Canadian scientists unveiled the secret: every night to sleep 7-8 hours is not easy to get fat. 276 of the age of 21 to 64-year-old adults, a body weight measurement and long-term follow-up survey. The study found that nighttime is less than 6 hours sleep or more than nine hours of the people, than the night sleep of 7-8 hours heavier. Experts say that sleep can affect weight, because sleep affects hormones levels of the human body.