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Late Night Eating: Can It Make You Gain Weight?

Ariel Kanter

March 30, 2010


            There is no doubt that anyone who has ever tried to diet or lose weight has at some point heard, in the process, that they should avoid eating late at night. However, there has been a long-standing debate about whether a correlation between the times of day one eats and weight gain actually exists. This myth has arisen in the past because people have drawn connections between things such as college students, late-shift workers, and obese children and weight gain. In fact, some studies over the years have suggested that circadian rhythms play a role in bodily energy consumption (Chan, 2009). Through many case studies, however, the majority of results have proven either that eating late at night does not have an effect on weight maintenance, or that the information extracted can only be deemed inconclusive.

            Experts at the Oregon National Primate Research Center explain, like many of us have heard, that we have all been told at some point in our lives that eating late at night leads to weight gain (“OHSU Scientists Dispel”, 2008). However, weight fluctuates over weeks and months, not hours, in part because of long-term patterns of both exercise and eating (Rudis, 2010). So, if this is true after all, then why have these correlations been made? After analyzing and perusing a wide variety of case studies on the subject, one overall conclusion has been derived: the issue at hand is not the time that people are eating, but rather it is the fact that people tend to consume worse calories (those high in fat, sugar, and carbohydrates), and more calories, when they eat late at night. The following case studies will reveal just how this conclusion is supported. 

            A number of studies were done over the years, each unique, but all claiming that there is indeed an association between late-night eating and weight gain. In one case, researchers studied the increase in body mass index and waist circumference as a result of working overtime. The scientists presented the subjects with questionnaires consisting of a multitude of different ideas; they asked questions regarding habits of eating breakfast, late night meals, as well as snacking. The experiments resulted in a correlation between overtime and dinnertime, with change in body mass index (BMI) and change in waist circumference. However, the study confirmed a “weak but statistically significant relationship” amongst these properties, which were studied over a three-year period. Consequently, the cross-sectional study found no association amongst them. The experiments concluded that results such of these might have been drawn “due to higher dietary intakes due to stress-induced behaviors like over-eating, or because overtime hours provide for a later dinner time.” Ultimately, even though there was a minor association found, the results were weak; therefore, the connection between eating late and night and weight gain still remains a hypothesis (Nakumora and Shimai, 1998).

            The next experiment that supports that this association is merely a myth is one that was done with mice. Essentially, scientists experimented with two groups of mice over a six-week period, in which both groups were fed diets high in fats. The difference between the groups was that they were fed at different times of the waking cycle. The group of mice that ate at times when they would normally sleep ended up putting on twice as much weight, and this is despite keeping both the activity level and food consumption consistent with the other group. Because of this, they were able to conclude that a correlation does in fact exist (Chan, 2009).

            Although information has been discovered that supports the myth, as one can see from the studies previously discussed, the vast majority of studies completed have proved just the opposite, or inconclusive. This was exemplified in a study comparing the relationship between late night eating and childhood obesity. It was designed to describe proportion of energy consumed from 4 p.m. till 12 p.m. measured in two hour increments in attempt to find the association. “GEE models were used to quantify the proportions and their affects during the different time periods, and dietary intake records were used to calculate the proportions.” The study included 11,072 children ranging from two to eighteen years of age, altogether providing 52,506 food records. The proportion of energy consumed by the children varied by factors such as sex, ethnic groups and age groups between the time increments. The study found that on average, “children classified as being healthy weight consumed 45% of their total daily energy between 4 and 12 p.m., and children classified as obese consumed between 47-49% of energy during the same time period.” After completing all of these measurements, the experiment concluded that the question of the association between circadian rhythm of eating and body weight needs to be further investigated to examine the effect of time of consumption on the risk of childhood obesity (Eng and Wagstaff, 2009).

            The next study on this subject examined weight-related behaviors in college students. This topic seems relevant because people tend to perceive college as time when people gain weight. Many different areas of college life were examined while conducting the study, and one of these included late-night eating. The participants all reported a range of answers as far as weight maintenance: 48% of students gained weight, 18% lost weight, 10% both lost and gained weight, and 24% maintained their same weight that they came to college with. Throughout the study, students would speak about eating late at night for many reasons, including eating for hunger, stimulation, or merely just to be social. After gathering all of this information, experimenters concluded that it wasn’t the late night eating that resulted in weight gain, but rather that the college students were consuming more calories than they would typically because they would indulge in an entirely additional meal, or would eat snack foods that were high in both fat and sugar (Nelson and Kocos, 2009).

            Similar results came from a study examining the common association between late shift workers and weight change. The scientists considered the possible effects of a fixed work shift on body weight; this stemmed from reports from a variety of nurses who entered hospital weight-loss programs after changing from working the day shift into the later night shift. The same nurses were subjects, along with nurses aides and security personnel, who all worked different shifts. Each of these subjects was asked to complete questionnaires divided into four sections: demographics, work and weight history, health or mental history, and sleeping and meal patterns. Despite the results revealing that later shift workers did gain more weight, experimenters drew the conclusion that the weight gain could’ve been related to eating more food and exercising less since starting the shift, or having fewer meals and compensating with a last meal later in the night (Geliebter and Gluck, 2000).

            Clearly, these case studies overwhelmingly support the idea that the myth of late-night eating and weight gain, still today, remains just a myth. Many nutritionists seem to support this conclusion as well, and agree with the fact that the correlation simply arises from the type of food and type of eating people do at later hours into the night. One nutritionist blames the majority of late night eating on emotional factors such as stress and anxiety. She writes that late-night eating can “actually help to feed the vicious cycle of overeating, and eating poor food choices. Poor food choices is a big issue here. For the poorer the choice, the worse the weight gain is going to be, and therefore the overall decline of health. Sometimes, people have a light snack at night, out of hunger. However, others indulge in a literal smorgasbord, sinfully indulging in some of their favorite entrees…but, generally, the late night food devourings is more a part of the negative emotions-one thing leading to another” (Daigneault, 2010). Another nutritionist argues that there might be a correlation, but it is not due to our bodies storing fat late at night, but rather that people cannot control their portion sizes and food choices late at night. “Although scientific studies someday may prove that calories ingested before bed are handled differently than calories ingested at other times, evidence for this commonly held belief is lacking. For now, it's safe to assume that one's weight reflects the balance between calories burned and calories consumed over time, regardless of when you choose to eat” (“Medical Myths”, 2010). As one can undoubtedly see, medicine has yet to prove that the myth really exists, so for now, we must continue to treat it that way.

After collecting a lot of research and data, unfortunately, many of the results still seem to be inconclusive. However, the overwhelming majority of results seem to point in the direction that the time in which you eat has no true effect on body weight status. Based on all of this scientific research, therefore, I would recommend, that if you are going to eat late at night, make sure your food choices remain in line with the amount of calories you would eat on an average during the day. Do not eat a fourth meal late and night, and try not to snack on fattening and sugary foods such and cookies, pretzels, and candies. Because these are typically the foods people are consuming late at night, this is the reason we tend to think that late-night eating causes weight gain. Until scientists can successfully come up with legitimate information to prove otherwise, this myth will remain a myth.










1. Chan, S. (2009, September 4). Eating Late at Night Adds Weight. BBC News.
     Retrieved from


2. Daigneault, T. (n.d.). The Effects of Eating Late at Night. In Helium. Retrieved
     2010, from


3. Eng, S., & Wagstaff, D. A. (2009). Eating late in the evening is associated with
     childhood obesity in some age groups but not in all children: the
     relationship between time of consumption and body weight status in U.S.
     children. International Journal of Behavioral Nutrition and Physical
     Activity, 6(27), 1-8.


4. Geliebter, A., & Gluck, M. E. (2000). Work-Shift Period and Weight Change.
     Applied Nutrtional Information, 16, 27-29.


5. Medical Myths: Eating Before Bed. (2010). AOL Health. Retrieved from


6. Nakamura, K., & Shimai, S. (1998). Increases in Body Mass Index and Waist
     Circumference as Outcomes of Working Overtime. Occupational Medicine,
     48(3), 169-173.


7. Nelson, M. C., & Kocos, R. (2009). Understanding the Perceived Determinants
     Weight-Related Behaviors in Late Adolescence: A Qualitative Analysis Among
     College Youth. Journal of Nutrition Education and Behavior, 41(4 ), 287-292.


8. OHSU Scientists Dispel Late-night Eating/Weight Gain Myth. (2008). Oregon Health
     and Science University. Retrieved from


9. Rudis, J. (2010). True or False: Eating Late at Night Will Make you Gain Weight.
     In Beth Israel Deaconess Medical Center. Retrieved from





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