How was your study designed?
GANGWISCH: We looked at sleep hours in relation to body mass and found that people were more likely to be obese if they had shorter nights of sleep. Those who reported an average of two to four hours of sleep were 73 percent more likely to be obese than people who got 9 to 10 hours. People who reported getting 5 hours were 50 percent more likely to be obese.
What's the mechanism behind this?
GANGWISCH: Studies on this in 2003 at the University of Chicago found that people's appetites went up when they were deprived of sleep, and they craved sweets and salty food.
HEYMSFIELD: Those who are normally restrained eaters aren't when deprived of sleep. The cognitive impairment makes you susceptible to bad judgment.
How do you know obesity is caused by lack of sleep and not vice versa?
HEYMSFIELD: The NHNE study shows that if you're sleep deprived your eating behaviors won't be normal. But we don't know which comes first. So we look forward to more research.
What can people do to stay on an even keel in terms of eating and sleep?
HEYMSFIELD: If you're working against deadlines and not sleeping much, your eating behavior can be disturbed. You want to watch impulses you might not normally respond to.
GANGWISCH: Patients need to think about healthier sleep practices. Things your grandmother would have told you: Go to bed at the same time every night. Have your bedroom dark. Don't drink coffee or alcohol before bed.
The data that you based your study on end in the 1980s.
Would the results be different now?
GANGWISCH: Probably worse. Stores are open all night; there's the Internet, dual-income families, more shift workers. Many more of us are getting less sleep and many more are becoming overweight.
It sounds too good to be true: Spending more time in bed just might help you stay slim. A study conducted by Dr. James Gangwisch and Dr. Steven Heymsfield of Columbia University and presented Nov. 17 to the North American Association for the Study of Obesity found that the less sleep subjects reported getting, the more likely they were to be obese. Based on data from the government's National Health and Nutrition Examination survey of 18,000 adults in the '70s and '80s, the study suggests that "increasing sleep could augment increasing physical activity and improving nutrition," to help fight fat, says Gangwisch. Here, PEOPLE contributor Nina Burleigh debriefs the research team.