Can Burning the Midnight Oil Make You Gain Weight?

Yes, it can. Researchers have found that night owls—people who routinely stay up late and sleep in the next morning—tend to eat twice as much junk food and weigh more than people who go to bed on the early side and wake up with the sun.

For some people, "early to bed, early to rise" just doesn't cut it. Maybe you stay up well past midnight because you're self-employed or work a late shift and have the opportunity to sleep in until 9 or 10 a.m. or even later during the week. Or maybe you're up late for any number of reasons, but still have to get up early for work or school or to take care of your family, and you somehow get through each day with the help of six or eight cups of coffee. If you're on a late-night schedule and gaining weight, chances are there's a connection.

A Northwestern University study of 52 adults—23 late risers and 28 normal risers—found that those who slept late ate twice as much fast food and consumed an average of 248 more calories each day than the early birds. The night owls also ate fewer fruits and vegetables and drank more non-diet sodas. The late risers were up, on average, until 3:45 a.m. and woke up as late as 10:45 a.m. The normal, or early risers were asleep by 12:30 a.m. and up by 8.

As might be expected, the night owls ate their meals later in the day, with an average breakfast time of noon, lunch at 2:30 in the afternoon, dinner at 8:15, and an evening meal or snack at 10 p.m. The early risers ate breakfast by 9 in the morning, lunch by 1 p.m., dinner by 7 in the evening, and a snack around 8:30 p.m. Those who stayed up late not only consumed more calories each day; they consumed most of them during their late night meals and snacks. While the early birds were sleeping, the owls were eating.

Normally, our circadian rhythm, or internal clock, determines when we fall asleep and wake up, in accordance with the earth's rotation and the rising and setting of the sun. The researchers suggest that when these patterns are disturbed and we don't sleep and eat at normal times, the effect on our metabolism may be weight gain.

One question that is left unanswered in this study is whether night owls tend to be people who intentionally eat more junk food or if they consume these types of foods because that's what is most readily available later at night. Of course, common sense says that if you're routinely eating too much junk food, any time of the day or night, it's time to ditch the ice cream and chips and stock up on fresh fruit and vegetable snacks.



Baron, KG et al; "Role of Sleep Timing in Caloric Intake and BMI" Obesity 2011 Jul;19(7):1374-81 Web 15 Sept 2011

Northwestern University: Night Owls at Risk for Weight Gain 4 May 2011 Web 15 Sept 2011