A study shows that in the general population, people who sleep less than 4 hours a night have a higher risk of obesity than those who sleep 7 to 9 hours a night, while those who sleep only 5 hours a day have a 50% higher risk. 
People who are lack of sleep have the same eating and exercise habits as those who sleep 7 to 9 hours a night.
 the researchers conclude that lack of sleep is easy to make people obese.