Wednesday, January 15, 2014

Eat Late, Gain Weight?

You may have been warned at some time in your life not to eat at night or after [insert Magical Hour After Which All Food Consumed Turns To Fat here] or else you will gain weight. While I can only surmise about the origin of this assumption, I might venture to guess that a food intake cut-off time came about as the result of somebody's diet protocol, a technique of which was likely put in place to reduce overall caloric consumption--agreeably, not a bad strategy to help moderate intake. Unfortunately, the idea must have gotten twisted over time into the lore it has since become: eat at night and you're doomed for weight gain, no matter what! But like numerous other urban legends of nutrition, the science behind the eat-at-night-and-get-fat warning just is not there. Let's take a closer look.  

First, it is key to understand that the total number of calories you consume and the amount of physical activity you partake in over the course of weeks and months is largely what affects your weight trend: if you take in more calories than you burn over time, the excess energy will be stored as fat. As long as you remain in energy balance over time, it won't make much difference whether you stop eating at 7 pm each day or consume all your daily calories late into the night.

Next, your body doesn't process food less efficiently at night, nor does it somehow simply and preferentially store all night calories as fat (although if it did it would most likely be to punish you for eating so late, you bad person--take that!). Additionally, keep in mind that while you may stop moving, your body does not stop when you are asleep. Your heart continues to beat, blood circulates, lungs function, digestion proceeds, and your brain keeps working. This all takes energy — meaning you are still burning some calories. 

In a 2006 paper published in Obesity Research, primate researchers observed how much, what, and when 16 monkeys ate over one year, as well as tracked weight changes, and found that the monkeys who consumed most of their food at night were no more likely to gain weight than monkeys who didn't eat at night, suggesting that there is no inherent correlation between time of day and weight gain. Even though humans aren't monkeys, the researchers believe that their study still helps dispel the notion that eating at night inevitably causes weight gain.

While the hours at which you eat throughout the course of a day do not independently and affirmatively cause weight gain in people who are not exceeding their energy needs, it does appear that when you choose to eat throughout the day (your eating pattern) may be a predictor of overall caloric intake and, subsequently, weight statusResearchers at the University of Texas-El Paso studying how time of day influenced self-reported food intake in 867 free-living individuals found that those who ate more earlier in the day ate less overall, while those who ate more at night consumed more calories overall. Researchers speculated that the individuals consuming a greater proportion of daily calories in the morning were provided a beneficial level of satiety which helped moderate the amount of food ingested over the rest of the day. If you are overweight and tend to eat a large proportion of your daily calories at night, it might be wise to think about shifting your eating pattern.  

So, while eating at night is not, as a stand alone, going to make you fat, there are some important points to consider when it comes to eating late and the potential for weight gain:

1. If you stay up late and don't get enough sleep, you may be more susceptible to weight gain. In a recent in-laboratory study with 225 healthy, non-obese individuals, researchers observed a significant weight gain in subjects who spent only 4 hours in bed (from 4 am to 8 am) compared to those who were in bed for 10 hours each night (from 10 pm to 8 am). Caloric intake increased in the sleep restriction group due to increased food consumption during the hours of additional wakefulness. 

Indeed, sleep deprivation seems to be increasingly linked to obesity. Other research has indicated that lack of sleep may cause alterations in glucose metabolism, contributing to insulin resistance, and potentially leading to increases in appetite.  

2. Emotional or mindless eating at night can be a big contributor to an excess calorie intakeIt's rare that I see an overweight or obese client who doesn't report struggling with this.  Emotional or mindless eaters typically eat out of habit or because they are stressed, tired, bored, or are using food to fill an emotional void. Foods usually eaten during these times are high in calories, nutrient-poor, and very easy to over-consume (highly palatable) such as chips, cookies, chocolate, ice cream, fast food, and highly-processed convenience foods. This kind of night eating CAN cause weight gain, as it usually results in a daily caloric surplus.

3. If you don’t have a consistent and regular eating schedule during the day, you may end up overly-hungry at night. Being famished can hinder your judgement--leaving you more likely to make suboptimal eating choices and/or consume larger-than-necessary portions. If this behavior becomes a regular pattern, it can eventually lead to undesirable numbers on the scale.

What else can you do to avoid falling into detrimental eating habits that can contribute to weight gain?

·      Restrict late-night meals and snacks but not because your body automatically converts nighttime calories to unwanted pounds. Rather, not eating after a certain hour of the day can help to minimize or eliminate the possibility of munching on extra food, which may otherwise send your daily calorie input beyond its limit.

·      If you don't have a regular daily eating pattern, try eating 5-6 smaller meals and snacks spread evenly throughout the day and see if it curbs an excessive hunger in the evening.

·      Make sure you include adequate protein, fiber, and healthy fats for dinner. Incorporating all of these nutrients can help you feel more full and eliminate late-night hunger.

·      Don't eat while sitting at the computer or watching TV. Instead, tune into your meals by making it a rule to eat in the dining room or at the kitchen table.

·      Get help with emotional eating. This is a very difficult issue for many people. Your registered dietitian can assist you in breaking through this problem and/or point you to additional professionals who can help. 

In summary, keeping the causes of weight gain and the basic formula for weight loss shrouded in mystery is a very good tactic for the diet and fitness industry, but these enigmas are often just illusions. As usual, the keys to weight control boil down to how much you eat coupled with your overall dietary choices--your weight doesn't give a damn what time it is.


Andrea M, Spaeth DF, Dinges NG. Effects of experimental sleep restriction on weight gain, caloric intake, and meal timing in healthy adults. SLEEP. 2013;36:981-990

Castro JM. The time of day of food intake influences overall intake in humans. J Nutr. 2004;134:104-111

Sullivan EL, Daniels AJ, Koegler FH, Cameron JL. Evidence in female rhesus monkeys (Macaca mulatto) that nighttime caloric intake is not associated with weight gain. Obesity Res. 2005;13:2072-2080


  1. Great post. For some years I was of the 'It doesn't matter when you eat school', but because of research in the last few years (including the study you cited) there may just be merit in trying to avoid eating too much later at night even if you are still close to energy balance over a 24-hour period.

    Study by "Garaulet M et al. Timing of food intake predicts weight loss effectiveness. International Journal of Obesity 2013;37:604-611." looked at 420 people who were following a 20-week behavioural treatment for obesity. Each person was grouped as an early or late eater based on the timing of their main meal of the day which was lunch for this mostly Mediterranean group of volunteers.

    At the end of 20 weeks, the late lunch eaters lost significantly less weight than the early lunchers – amounting to 2.2 kilograms. What was surprising was that there were no differences in the total amount of food eaten, dietary composition, energy expenditure, appetite hormones and sleep duration between the two groups. The late eaters though were more likely to be late evening diners and to have a minimal breakfast or skip it altogether.

    1. Thanks for the comment Tim! I agree there may be merit to avoid eating late but from the research I've read, the benefits seem to be derived from including breakfast, consuming more protein earlier in the day, obtaining a greater level of satiety (thereby influencing circulating satiety hormones), genetic variance in clock genes (as the Garaulet study points out), and existing disease states of late eaters, among other factors.

      The Garaulet study is quite interesting--thanks for pointing that out, I hadn't come across it! It does look like the late eaters in that study ate less protein at lunch, had less weight to lose to begin with (based on BMI & body fat %), and interestingly that group was also more likely to have markers of insulin resistance--all factors that could have influenced their lesser weight loss.

      I also can't help but be critical of all studies relying on self-reported intake (the Castro study I cited is another example), but I think they can still provide some insight into what may or may not be going on.

      Lots more to learn for sure. ;)