Psychology Department

Health Psychology Home Page

Papers written by students providing scientific reviews of topics related to health and well being

  HomeWeight LossAlternative Therapy | Supplements | Eating Disorders | Fitness | About this Page |


Does Night-time Snacking Cause Weight Gain?

Vicky Ruleman

November 11, 2008



            There has been much debate as to whether eating before bedtime causes weight gain.  Some claim that eating before bedtime causes a person to gain weight because the body does not have an opportunity to burn these calories, and the extra calories will be stored as fat.  Others claim that eating before bedtime does not cause weight gain as long as the daily energy intake matches the daily energy expenditure.  However, they say that eating before bedtime is linked to weight gain because people who eat before bedtime often consume unneeded calories in a “fourth meal.”  The goal of this paper is to investigate if eating before bedtime causes weight gain or a higher BMI by looking at scientific literature.



What’s on the Web?


Oprah’s Boot Camp


Oprah’s Boot Camp says that a person should not eat weight three hours before bedtime in order to lose weight.  This rule is one of several rules of Oprah’s Boot Camp to lose weight.  No scientific experiment was conducted, but the website points to several people who have been able to lose weight successfully.  Because there was no follow-up study and the no eating before bedtime was only one rule of the boot camp, the results cannot be trusted.  Also Oprah and her company are trying to promote her TV show and earn a profit, so their motives might be skewed.


New York Times


On the New York Times website, Dr. Aronne is quoted as saying that eating before bedtime does not necessarily lead to weight gain, but people who eat before bedtime usually eat more and thus gain weight.  The article also says that studies of college students who eat before bedtime have shown that they are more likely to gain weight.  Dr. Aronne further says that eating before bedtime has been linked to metabolic syndrome and insulin resistance and if a person eats extra calories before bedtime the body stores them as fat.  There was no experiment conducted, but this article relies on the expert opinion of Dr. Aronne, director of the comprehensive weight loss control program at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.  The evidence presented in the New York Times is not concrete because this is only one person’s judgment.  The New York Times, like all other newspapers, has an agenda to sell papers, so that is one of their primary motives.  


            Fox News,2933,401841,00.html


Cheri L. Collier, adjunct professor at Case Western Reserve University’s School of Medicine, describes her recommendations for avoiding the freshman fifteen.  One thing she advises is avoiding eating three hours before bedtime because that can lead to weight gain and inability to fall asleep.  There was no experiment cited, but Cherri L. Collier is the Nutrition Services Manager for the Centers for Community Health at MetroHealth Medical Center, Cleveland, Ohio and has been the principal investigator for many research projects on clinical nutrition.  The evidence on Fox News’ website is not very reliable because the results and designs of Cherri Collier’s experiments are not described.  Fox News has an agenda to attract viewers, and their primary interest is not in conducting or verifying scientific research.


            Health Magazine



Elisabetta Politi, nutrition manager at Duke Diet and Fitness Center, Duke University's weight-management center, advises a person trying to lose weight to eat the most food earlier in the day.  She says that the calories you eat earlier in the day help you eat less at night.  Thus, eating earlier in the day as opposed to later in the day helps reduce the total calories consumed in a day.  There was no specific experiment conducted; the article relies upon the opinion of Elisabtee Politi.  The evidence on is not reliable because it is only based on one person’s opinion, and no results of experiments are cited.  In addition, Health magazine runs this website, and this company has a motive to sell magazines by promoting ways to lose weight.  The weight loss methods might not be based on science but might instead be based on appeal to consumers.




An article entitled “9 Surprising Facts About Your Stomach” written by Colette Bouchez and reviewed by Louise Chang, MD, says that eating before bed does not make you gain weight faster than if you eat the same foods during the day.  In this article, Mark Moyad, MD, director of preventive and alternative medicine at the University of Michigan Medical Center in Ann Arbor, is quoted as saying, “It's the total amount you take in over a period of time compared to how much you burn that determines if you will gain weight. There is no science to show that eating at a specific time of the day can influence weight gain on its own.”  However, NYU director of pediatric gastroenterology Joseph Levy, MD, says that eating before bedtime can make digestion more difficult and cause gas, bloating, and heartburn.  Again, no experiment was conducted, but the article relies upon the opinion of two physicians.  While the evidence presented by Dr. Moyad is logical, the article still does not cite results of experiments and is not completely reliable.  WebMD claims that its motive is to provide quality health information, and the material online is reviewed by four physicians on the Independent Medical Review Board.


Scientific Research


“Association between Eating Patterns and Obesity in a Free-living US Adult Population”


Ma et al investigated eating patterns such as eating frequency, the temporal distribution of eating events across the day, breakfast skipping, and number of meals eaten away from home and the relation to obesity (2003).  Residents of Worcester County, Massachusetts, aged 20-70 years old who had telephone service were eligible to participate.  Individuals taking certain medications, working night shifts, at risk for hypercholesterolemia, on weight-loss diets, or suffering chronic illness were excluded.  Minority groups were also specifically recruited.  Subjects were seen at a clinic for a baseline interview and every three months over the next year.  Every three months, blood samples were taken for serum lipid assessment and body weight was measured.  The participants were also asked to recall dietary intake for a 24 hour period from two randomly selected weekdays and one weekend day.  The participants also reported at what times they went to bed and woke up every day.  At the end of the study, 138 subjects who completed less than ten 24-hr dietary recalls were excluded from the study.  Thus, 499 men and women with a total of 6,931 dietary recalls were included. 

The interval between the last meal and bedtime was calculated and analyzed using a t-test, but there was no significant association between this interval and obesity.  However, this study says that further research is needed to examine the carbohydrate percentage of the last meal and obesity. 


            “Eating Patterns and Dietary Composition in Relation to BMI in Younger

and Older Adults”



Howarth et al compared eating patterns and dietary composition with BMI in younger adults (20-59 years, n = 1792) and older adults (60-90 years, n = 893) (2007).  Subjects for the study were chosen only if they provided height, weight, time of consumption for all eating occasions, dietary recalls, and plausible reported energy intakes.  Pregnant women, those on medically related diets, and people without access to suitable food were excluded.  Subjects were divided into younger adults (20-59) and older adults (60-90).  The subjects self-reported the type of eating occasion at which food was consumed: breakfast, brunch, lunch, dinner, supper or snack.  Approximately 20% of eating occasions were recorded.

            The BMI was calculated based on self-reported height and weight.  The energy intake and dietary composition during two days were calculated as average daily values and by eating occasion.  Total daily energy intake, eating frequency, meal skipping, and snacking were self-reported.  Multiple regression analysis was used to compare eating patterns such as meal and snack frequency with BMI.  Regression models were controlled for other factors including age, sex, presence of chronic disease, and ethnicity.

            The results of this study found that total energy intake, rather than intake during a particular eating occasion, was positively associated with BMI for both age groups.  Furthermore, this study found that increased energy intake later in the day was not associated with a higher BMI or energy intake for either age group. 


            “Circadian Rhythms of the Spontaneous Meal Pattern”


John de Castro investigated the relationship between circadian rhythms and meal patterns (1987).  Eight male and thirty female undergraduate students volunteered as subjects of the experiment.  Subjects were given a diary and asked to record food intake, time consumed, and amount consumed for nine consecutive days.  Then, the subjects met with the experimenter to clarify any ambiguous data.  The times between the termination of the prior meal and the onset of the next meal were calculated.  This postmeal interval in minutes was divided by the meal size in kcal to find the satiety ratio.   Next, the mean satiety ratios were calculated according to 6 three hour time periods beginning at 0600 and ending at 2400.  These mean ratios were plotted against the time interval.

            The satiety ratio was found to be highest during the earliest time period (1.2 min/kcal) and lowest during the latest time period (~.38 min/kcal).  While this study does recommend caution when interpreting these results because of the shorter meal time intervals later in the day, the results seem to indicate that food eaten earlier in the day as opposed to later in the day is more satisfying.  This suggests that food eaten earlier in the day can reduce total energy intake and food eaten later at night can increase overall intake. 


            “The Time of Day of Food Intake Influences Overall Intake in Humans”



            John De Castro investigated whether circadian rhythms affect food intake (2004).  It was hypothesized that the amount of food eaten earlier in the day reduces the overall intake and the amount of food later in the day increases overall intake because satiety ratios decrease during the day.  In a double-blind study, 867 individuals consisting of 375 men and 492 women participated as subjects.  The mean age was 36.3 +/- 13.8 years and the mean BMI was 24.5 +/- 4.3 kg/m2.  The subjects were given a diary and asked to record amounts of food and beverages consumed, times consumed, how the food was prepared, and self-ratings of hunger, thirst, and depression.  They recorded this data for seven days, and two of the people present with the subject when he or she was eating were asked to verify the information reported. 

            The percentage of daily food intake in each of the five time periods (0600 to 0959, 1000 to 1359, 1400 to 1759, 1800 to 2159 and 2200–0159 h) was calculated.  Total energy, fat, and carbohydrate amounts were calculated.  Dietary energy densities (MJ/g) were also calculated for all periods as the total food energy ingested (MJ) divided by the total weight (g) of everything ingested during the period.  These dietary energy densities were analyzed using ANOVA.  The satiety ratios, which describe how long the individual will wait to eat again per amount eaten in the meal (min/MJ) were calculated, and a t-test was conducted to analyze this data.

            The study found that the subjects of this study consumed more energy during later periods in the day with peaks at lunch and dinner.  The satiety ratios were found to be significantly greater in the first period, decreasing throughout the day.  Like the previous study, this suggests that food eaten earlier in the day can reduce the total energy intake of the day, and food eaten later at night is not satiating and can increase overall intake.


“The Effects of Equal-energy Portions of Different Breads on Blood Glucose Levels, Feelings of Fullness and Subsequent Food Intake”


Holt, Brand-Miller, and Stitt compared the effects of seven different breads and their satiety indexes on fullness and total daily energy intake (2001).  Ten healthy subjects participated and fasted for ten hours one night.  The next morning the researchers performed baseline satiety readings and took fasting blood samples of the participants.  The participants ate a test bread, and satiety ratings were collected at 15-minute intervals over the next 120 minutes.  A satiety index (SI) of the bread was calculated by dividing the area under the 120-m satiety response curve (AUC) for the test bread by the satiety AUC for the reference bread (regular white bread) and multiplying by 100%. 

The SI scores of the breads ranged from 100% to 561%, with white bread having the lowest SI.  The greater the SI of the bread consumed, the less energy intake was consumed at the test meal afterwards and throughout the day.  


Summary of Scientific Research


            Ma et al found no significant association between the time interval of the last meal and bedtime and obesity (2003).  Howarth et al found that energy intake later in the day did not correlate with a higher BMI (2007).  Rather, greater total energy intake is correlated with a higher BMI.  John DeCastro found that satiety ratios are greater earliest in the day and decrease throughout the day (1987, 2004).  Holt, Brand-Miller, and Stitt showed that a greater SI index from a piece of bread is associated with less energy intake throughout the day (2001). 




If overall energy intake matches energy expenditure, then weight will remain stable (Howarth 2007).  However, food eaten at night is less satiating, and food eaten earlier in the day is more satiating (DeCastro 1987, 2004).  More research needs to be done in order to explore why food eaten at night is less satiating.  Holt, Brand-Miller, and Stitt have shown that greater satiety index of bread consumed is associated with lower energy intake throughout the day (2001).  Thus, energy consumed earlier in the day is associated with less total energy intake, and energy consumed later in the day is associated with more total energy intake.  In order to consume appropriate energy intake, it seems advisable that a person should eat more food earlier in the day and less at night.  However, a night-time snack will not lead to weight gain as long as the snack did not cause the person to exceed needed energy intake. 




Literature Cited,2933,401841,00.html tricks/


De Castro, J.M. (1987).  Circadian Rhythms of the Spontaneous Meal Pattern, Macronutrient Intake, and Mood of Humans.  Physiol Behav., 40(4), 437-46.


De Castro, J.M. (2004).  The Time of Food Intake Influences Overall Intake in Humans. J Nutr., 134(1), 104-11.

Holt, S.H., Brand-Miller J.C., Stitt, P.A. (2001).  The effects of equal-energy portions of different breads on blood glucose levels, feelings of fullness and subsequent food intake. J Am Diet Assoc., 101(7), 767-73.

Howarth, N.C., Huang T. T-K., Roberts, S.B., Lin B. H., McCrory M.A. (2007). Eating Patterns and Dietary Composition in Relation to BMI in Younger and Older Adults.  Int J Obes (Lond), 31(4), 675-84.

Ma, Y., Bertone, E.R., Stanek, E.J., Reed, G.W., Hebert, J.R., Cohen, N.L., Merriam, P.A., Ockene, I.S. (2003). Association Between Eating Patterns and Obesity in a Free-living US Adult Population.  Am J Epidemiol, 158(1), 85-92.




Psychology Department

The Health Psychology Home Page is produced and maintained by David Schlundt, PhD.


VuLogoVanderbilt Homepage

Return to the Health Psychology Home Page
Send E-mail comments or questions to Dr. Schlundt