Staying up late every night and sleeping in is a habit that could put you at risk for gaining weight. People who go to bed late and sleep late eat more calories in the evening, more fast food, fewer fruits and vegetables and weigh more than people who go to sleep earlier and wake up earlier, according to a new Northwestern Medicine study.

Late sleepers consumed 248 more calories a day, twice as much fast food and half as many fruits and vegetables as those with earlier sleep times, according to the study. They also drank more full-calorie sodas. The late sleepers consumed the extra calories during dinner and later in the evening when everyone else was asleep. They also had a higher body mass index, a measure of body weight, than normal sleepers.

The study is one of the first in the United States to explore the relationship between the circadian timing of sleeping and waking, dietary behavior and body mass index. The study was published online in the journal Obesity and is expected to appear in a late summer print issue.

“The extra daily calories can mean a significant amount of weight gain – two pounds per month – if they are not balanced by more physical activity,” said co-lead author Kelly Glazer Baron, a health psychologist and a neurology instructor at Northwestern University Feinberg School of Medicine.

“We don’t know if late sleepers consume the extra calories because they prefer more high-calorie foods or because there are less healthful options at night,” said co-lead author Kathryn Reid, research assistant professor in neurology at the Feinberg School.

The study shows not only are the number of calories you eat important, but also when you eat them -- and that’s linked to when you sleep and when you wake up, noted senior author Phyllis Zee, M.D., professor of neurology and director of the Sleep and Circadian Rhythms Research Program at Feinberg and medical director of the Sleep Disorders Center at Feinberg and Northwestern Memorial Hospital.

“Human circadian rhythms in sleep and metabolism are synchronized to the daily rotation of the earth, so that when the sun goes down you are supposed to be sleeping, not eating,” Zee said. “When sleep and eating are not aligned with the body’s internal clock, it can lead to changes in appetite and metabolism, which could lead to weight gain.”

The research findings could be relevant to people who are not very successful in losing weight, Zee said. “The study suggests regulating the timing of eating and sleep could improve the effectiveness of weight management programs,“ she said.

The findings also have relevance for night-shift workers, who eat at the wrong time of day related to their bodies’ circadian rhythms. “It’s midnight, but they’re eating lunch,” Zee said. “Their risk for obesity as well as cardiovascular, cerebrovascular and gastrointestinal disorders is higher.”

The study included 51 people (23 late sleepers and 28 normal sleepers) who were an average age of 30. Late sleepers went to sleep at an average time of 3:45 a.m., awoke by 10:45 a.m., ate breakfast at noon, lunch at 2:30 p.m., dinner at 8:15 p.m. and a final meal at 10 p.m. Normal sleepers on average were up by 8 a.m., ate breakfast by 9 a.m., lunch at 1 p.m., dinner at 7 p.m., a last snack at 8:30 p.m. and were asleep by 12:30 a.m.

Participants in the study recorded their eating and sleep in logs and wore a wrist actigraph, which monitors sleep and activity cycles, for at least seven days.

Late sleepers function in society by finding jobs where they can make their own hours, Baron noted, such as academics or consultants. “They find niches where they can live this lifestyle, or they just get by with less sleep,” she said.

Northwestern researchers are planning a series of studies to test the findings in a larger community and to understand the biological mechanisms that link the relationship between circadian rhythms, sleep timing and metabolism.
by Marla Paul, health sciences editor, Feinberg School of Medicine. Contact her at

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Thanks for this enlightening article, as a night owl it's good to know! This has implications for those suffering from sleep apnea, as gaining weight often makes sleep apnea worse, so advising s.a sufferers to change their sleeping patterns may be a good option for those who do not want traditional solutions such as CPAP breathing equipme

lol wow unfortunately this article describes me to a tee! I've always loved to sleep late and of course I love my ice cream before bed! This was fine when I was younger but now that I'm getting a little older I'm seeing how this pattern may may it more difficult for me to shed my extra pounds!

I think late sleepers consume the extra calories because they prefer more high-calorie foods. Remember the relationship between chocolate and endorphins.

This is article is so true!! I've always been a night owl and will be working away on my laptop in bed till 2am. I am a single mum of a toddler, and the nights are the only time I get to concentrate uninterrupted. When I put her to bed, I eat to give me fuel, unfortunately they are rarely healthy choices. I just don't want to feel hungry so I can concentrate on my work.

You have provided me a new information - late sleep and late wake up will increase the weight. I will try to avoid this. Thanks for sharing.

This is a very interesting study. However, there are so many variables to consider when doing a study on eating and sleep patterns. For instance, you have to ask yourself why there wouldn't be just as many healthy snacks available to eat for the late sleepers as opposed to the normal sleepers? Does the content in the fridge change for late sleepers as opposed to normal sleepers? I don't think so. The key point missing here is highlighted above in the article and that is, not knowing if the late sleepers actually prefer to consume higher calorie foods as opposed to lower calorie foods. In a study such as this I would have thought that question would have been a good one to ask your 51 participants in the study... Also the normal sleeper is said to go to bed by 12:30 a.m. in the above study, but I would also think that a large portion of the population goes to bed much earlier than that if their working in the morning, more like 9:30 p.m. or 10 p.m. As well I didn't see any mention of what percentage of the 23 late sleepers were obese due to their late sleep patterns, as opposed to how many of the normal sleepers were obese? Or for that matter a percentage of how many in the group of 23 late sleepers were obese as opposed to how many of the 23 late sleepers were normal weight? A more interesting aspect of this study would be to find out what percentage of late sleepers were obese? Perhaps even what percentage of late sleepers over all age groups were obese compared to normal sleepers? It's hard to see the correlation between late sleepers and normal sleepers eating patterns and calorie intakes if you are not 1. asking participants the reasons why they might prefer to eat higher calorie foods at night and 2. comparing the over weight between the late sleepers and the normal sleepers. Just my opinion, but you may want to look at this closer in the next study between late sleepers and normal sleepers.

This bad habit is building in me working late at nights. I guess I never seen people sleeping early these days. Late sleeping is the main reason for weight gain. Another issue faced is once you increase your weight it is very difficult to get to the normal BMI.

This article is very interesting and I can fully relate to it by own experience. I used to go to bed late and due to the inherent eating habits (eating the so-called late-night "snack", e.g.) gained a lot of weight. As soon as I started to go to bed a little earlier (skipping that last meal of the day), positive results showed up in less than 2 weeks.

I have been reading a lot about the link between sleep and weight gain as well as sitting and weight gain. This article just emphasizes the importance of getting to bed early - although we may guess the causes, perhaps we should focus more on the correlations like insurance companies do. Thank you for this excellent post :)

Wow! This blog has almost everything I need for my research about this topic

So which of the fat loss diets are the best? Unfortunately, a large number of fat loss diets have specifically designed a weight loss program to help you achieve weight loss fast, but, many times, these program are damaging to the long term health of a individual and are also not long term.

In a general sense sure, people who are up later probably do consume more calories but I think it's important to differentiate there. It is still the calories and not necessarily the unusual sleep pattern that is causing the weight gain. I know from experience working late shift that I didn't experience any weight gain because the only thing that changed was the hours my routines and eating habits stayed the same.

Personally I think this is key “The extra daily calories can mean a significant amount of weight gain – two pounds per month – if they are not balanced by more physical activity,” I think there are ways to compensate for those of us who are "night owls" I'm 34 years old and rarely go to sleep before 4 AM. I'm up by 9 and usually get in at least a 5 mile run/walk a day. I weighed 355 pounds at my heaviest. I'm currently 235, still overweight but healthy. if anything I sleep less than I did at my heaviest.I'm a freelancer so luckily I can work when I like. I know there will always be exceptions, and maybe I need less sleep because I am healthier. I think there has to be a lot more digging done. I believe it's more about the quality of the caloric intake. Healthy food is just as available as junk food.

I think that the study shows a correlation, but does it really show a causation effect? Is being a night owl a cause of obesity? Or possibly the other way around? It could even be a different factor that causes both. It would be interesting to see if there are any studies that have tracked what happens if a night owl changes their sleep patterns or vice versa.

Totaly agree with the circadian rythym of the body. I was at a job that switched from gravyard shift to day shift hours every two weeks. My body was in turmoil, gaining weight, couldn't sleep. I believe this schedule had a lot to do with developing a rough case of sleep apnea as well.

As a long time sufferer of sleep apnea, I know that snoring is a good sign there might be a problem. I was a horrible loud snorer for many years before I took action. I ended up having a few bouts of atrial fibrillation which was brought up from the sleep apnea. I'm using a breathing machine now and have the apnea under control, and the a-fib episodes have been much fewer.

I am sharing this to a very good friend of mine. Interestingly, is it the same with men?

I never noticed I was snoring until my wife told me on our camping trip she couldn't sleep in the same caravan as me. God bless soundproof motorhomes!