Does Late-Night Eating Cause Weight Gain?

Screen shot 2009-11-11 at 12.10.50 AMWhen it comes to fitness and health myths: which ones are true, and which ones are full of ****?

As you all know, this whole diet/fitness process is a constantly-evolving learning process for everybody, myself included.  I’m always trying to find ways to get smarter, learn more, save time, and get better results faster.

Enter today’s topic.  Last week, I received an email from long time Nerd Fitness reader Jerry, who wanted me to look into the whole “late night eating myth” and find out the impact of eating late at night.  As Jerry pointed out, “Steve, you’ve said it yourself – try to limit carbs late in the afternoon, and eat a bigger breakfast, but have you ever found scientific proof to support this?”  You know what Jerry?  I haven’t!  Thank you for calling me out and making me earn my money…well I don’t exactly make any money yet, so thank you for making me earn your attention.

The Late Night Eating Myth

As the story goes, you should cut back on eating (carbs especially) after a certain time in the day in order to lose weight.  Because you’re active during the day and less active at night, you’re more likely to burn off those calories during the day and less likely to burn them off at night.  If they don’t get burned off, then they turn to fat.

I’ve heard this from everybody, from fitness industry experts to actors like Daniel Craig (who wouldn’t eat carbs in the afternoons and evenings to prepare for his role as James Bond), and it seems to work for them.   I’ve seen the articles and heard the stories and passed this information onto others.  However, as Jerry stated before, I made the mistake of not digging in to find the truth before endorsing the message.  I put on my research hat (which strangely resembles a Red Sox hat) and went to work; here is what I’ve found.  Not surprisingly, I found articles that both supported and disproved the myth, which I discuss below.

Late Night Eating DOESN’T Cause Weight Gain

The first study that was brought to my attention came from the University of Oregon:

“We’ve all been told at one point in our lives that we should avoid eating meals late at night as it will lead to weight gain. However, our research in rhesus monkeys, which are considered an excellent model for studying primate (man and monkey) obesity issues, showed that eating at night is no more likely to promote weight gain than eating during the day.

491412087_bf19adbe8fAccording to the study, after providing the monkeys with a special diet, scientists observed them for a year and this was their results:

It was really interesting to see that the monkeys who ate most of their food at night were no more likely to gain weight than monkeys who rarely ate at night,” said Elinor Sullivan, an OHSU graduate student conducting research along with Cameron at the Oregon National Primate Research Center. “This suggests that calories cause weight gain no matter when you eat them.

Not so fast ELINOR, if that is in fact your real name.  There are quite a few things about this study that didn’t leave me 100% convinced.  First of all, monkeys might be similar to people genetically, but the fact remains that they’re monkeys, not people.  Secondly, there were some other red flags:

To conduct this research, scientists studied 16 female rhesus monkeys that were placed on a high-fat diet similar in composition to the diet normally consumed by humans in the United States and other Western countries. During the study, all of the monkeys had their ovaries removed – this simulates a menopause-like state in female monkeys similar to human female menopause. In lower animals both high fat diet and decreased ovarian function lead to weight gain.

My first concern is the diet: correct me if I’m wrong, but I’m pretty confident that most people in the US are eating more high-carb diets then high-fat diets.  I’d guess most overweight people are probably both high fat and high-carbs, but I’d like to see an exact breakdown of what they ate.  Secondly, I understand this is a study on weight gain, but I don’t know what kind of variables get introduced when the ovaries of a monkey are removed.  Frankly, I don’t want to know.

This study essentially proved that “late night eating doesn’t cause extra weight gain,” but it was conducted on post-menopausal monkeys.  One of my life lessons has always been “don’t trust post-menopausal monkeys.”  Not what happened after last time.

Late Night Eating DOES Cause Weight Gain

Searching for “late night eating” does cause weight gain studies, I stumbled across this article over on FLEX from May of 2006.  According to them:

For bodybuilders who want to lose body fat, FLEX has consistently recommended avoiding carbs at night–if you’re able to replenish your muscle and liver glycogen throughout the day, then the excess you consume in the evenings will more likely be converted to fat.

A study performed by Swiss researchers also concluded that carbs should be avoided in the evening. Subjects who ate a carb-rich meal (spaghetti and carrots) two to three hours before bedtime had both higher body temperatures and heart rates than subjects who instead ate a big carb meal in the morning. These physiological factors could [my emphasis] interfere with sleep, ultimately having a negative impact on fat loss and muscle growth.

First of all, this comes from a magazine called “Flex” (COME ON). I rarely trust any bodybuilding magazine, as most of them are run by supplement companies.  The glycogen part makes sense to from a bodybuilding perspective (email me if you want to know why), but I’d guess few of you want to be bodybuilders.  Now, I tried to track down the Swiss study referenced (but not cited) and I couldn’t find it, which would lead me to throw it out completely.  However, let’s say for the sake of the article that the study is true.  Before I could use take this study as fact, I’d need to more information than just if they ate a big dinner vs. a big breakfast.  Did they eat more often during the day as well? Were these people who were trying to lose weight, or just random people off the street?  So many questions!

I then found THIS article in the Wellness blog section of the New York Times: According to a study conducted by Northwestern University, “mice who ate when they normally would have been sleeping posted an average 48% increase in body weight. The mice who ate on a regular schedule had an average increase of 20%of body weight.”  Both groups of mice were fed a similar amount of food.  Pretty substantial, right?  So why don’t I buy this study?

To begin with, I think mice are an even worse research specimen than monkeys when trying to compare to human physiology.  Next, I’d guess the mice with the mixed-up sleep schedules probably dealt with non-optimal sleep conditions.  As many of you know, not getting enough sleep can lead to stress which lead to weight gain.  Lastly, all they say is “high fat diet.”  What percentage of fat constitute a high fat diet?  What kind of fat?  What else was in there?  Were these normal lab mice, or amazing mice like Mickey?  I need to know these things.

So Which Is It?

Honestly, I’m not thrilled with ANY of the studies listed above. There are far too many variables, too many monkeys, and too many mice for me to take any of them seriously.  Luckily, I found a few articles that made sense to me and passed the skeptic test.  My favorite article on the topic came from Australia (woooo down under).  This is from a study done by Dr. Kangaroo (just kidding).  Rather than quote it, I’ll give you the gist:  essentially, the timing of your meal doesn’t matter; it all comes down to calories in, and calories out.

To further solidify this position, I’d like to reference another article (that uses ACTUAL HUMAN RESEARCH – w00t).  According to the study here, the diet diaries of 800 people were tracked over a set period of time:

Their food and calorific intake was assessed for each of five, four-hour periods stretching from 6 am to 2 am the following day. The results of this study showed that those who had consumed the bulk of their food near the end of the day ate, on average, significantly more calories than individuals who ate more substantial amounts of food early on.

Notice it doesn’t say “those who ate more later in the day gained weight.”  It says that those who ate more later in the day tended to eat significantly more calories  than those who ate more earlier in the day.  There’s no mention of a physiological difference in people’s metabolism.  Moral of the story?  Calories in, calories out.

This makes sense to me. It’s what we consume over the entire length of the day that determines if we gain weight or lose weight.  It’s not the times of the meals, but the total quantities of the stuff in all of the meals.  There are so many variables when it comes to how humans work – until more studies are done with ACTUAL people who ate the same amount as other people, but at different times of the day, I can’t say with a clear conscience that your metabolism processes food differently in the afternoon or evening compared to how food is processed in the mornings.

Why It Works for So Many People

I believe the reason “no carbs after 4PM/5PM/8PM etc.” works for so many people is because carbs are generally loaded with calories.  A giant bag of animal crackers is like 1500 calories, and a giant bag of lettuce is like 100 calories.  If you have eaten close to your calorie consumption goal for the day during the daylight hours, munching down on a carbohydrate-loaded dinner will certainly tip the equation towards “Calories Consumed” and you will gain weight.

As stated above, people who wait until the very end of the day to eat their main meal are generally so hungry by then that they overeat, consuming too many calories.  Others that eat huge breakfasts and healthy-sized meals throughout the day are less likely to be starving when dinner rolls around so overeating is less likely.  Until proven otherwise, I believe your metabolism processes all food at a constant rate – it’s what you eat between waking up and going to sleep.  It turns out I was giving out correct advice, but I was right for the wrong reasons.  Now I know, and knowing is half the battle.

My Advice

Moving forward, I recommend that you find an eating schedule that works for you. I have a friend whose wife cooks him amazing dinners every night, but he’s worried the carb content will make him gain weight.  I told him that if he wants to eat a big dinner with the family (and not have to sleep on the couch), he should concentrate on eating low-calorie, high-energy meals (loaded with lean meats, vegetables, and fruits) for breakfast and lunch.

If you want to lose weight, you need to keep track of what you’re putting in your body. Eating late at night isn’t the cause of your weight gain because of anything physiological; it’s because when you eat late at night you’re probably overeating.  If you’re worried about weight gain and you want to eat a big dinner, you need to be more thoughtful of what you eat the rest of the day.  Find something that works for you.  Honestly, just use common sense!  Be mindful of what you shovel down your throat.

Don’t want to count calories? Cut out the processed carbs (breads, rice, wheat, cookies, crackers, etc.), stick with vegetables and fruits and lean meats, and you’ll be hard-pressed to overeat.  When it comes to food, veggies are the best: high in energy, low in calorie content.  That’s efficiency in it’s most natural form.

Don’t want to change what you eat or count calories or stop eating late at night? You’re on the wrong site, go play some more Call of Duty: Modern Warfare 2 (WHICH IS AWESOME), and then come back when you’re ready.

Your Thoughts?

What do you guys think?  Have you tried the no-carb at night thing?  Do you have to eat late-night meals due to work?  Are there factors I’m leaving out, or articles I’m not referencing that I should?


Moving forward, I already have two future myths that I plan on discussing:

  • Does more meals spread throughout the day help with weight loss? (I bet you can see how this one will turn out based on today’s myth)
  • How much protein do you really need every day to build muscle?

Let me know if there are other myths you want me to look into.  I’ll do my best to prove or disprove them.


picture from Yasin Hassan, Chi Liu

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  • I never completely understood the idea behind Late Night Eating being so bad. As long as you stay within your limits throughout the day I didn't think it would matter when I ate. I never really thought about the different compositions of foods and how they may play a part though (just like 1500 calories in kit kat bars isn't the same as 1500 calories in vegetables).

    My main meal of the day is still dinner, but I'm trying to be reasonable about it and not snack afterwards, which happened often. I'm also eating smaller, better meals throughout the day to help cushion any blow dinner may bring.

    I'd be curious to see the posts about the two myths (meals spread throughout the day and how much protein), I'd also like to see what you find out about the intermittent fasting that you were talking about in the last posts comments.


  • jdmaxwell

    Yeah the calorie in and calorie out makes the most sense and has been around for long time, people just get on these quick fixes and fad diets and forget about common sense and basic mentalities. Good post. Keep on keepin on!

    Oh and MW2 is amazing. What console do you have it on?

  • NerdFitness

    Diet fads come and go…but the ratio of calories and calories out never really changes. Great point.

    I didn't get a chance to play it last night, just watched one of my roommates play for about an hour. We have it for the 360.

    -NF Steve

  • bkinch

    The reason that restricting food at night works for me is simple: I would normally consume most of my calories between dinner time and going to bed, either in the form of alcohol or snacks, or a charming combination of the two 😉 I could easily double my calorie intake during this time. Now I chew sugarfree gum at night. Sometimes a ridiculous amount of gum, lol.

    I will scout around and try to find it, but I know there was a pretty good study showing that low carbers who ate a high carb breakfast and then cut carbs the rest of the day lost more weight than those who ate low carb all day.

  • jozmo

    Daniel Craig told you that?! That's awesome!

    Good post. I agree that the problem isn't necessarily eating late, but what you eat late.

    As a father, the evening meal is a sacred time for the family to sit and eat TOGETHER. My kids would burn my wife and I at the stake if we just pushed salad on them every night at 6 PM. So there's always noodles, rice, etc. We value and emphasize this connecting time and put good food on the table.

    The key is hitting the gym early, being disciplined & wise on breakfast & lunch, controlling portion size, and not being stupid with late-night snacks.

    That and a lot of MMA fighting with my 7 and 5-yr old boys keeps the weight going down and the strength going up.

  • I love eating late and I've never been able to see a real difference brought on by the timing (even when I lived in the Mediterranean where everybody eats late). I think you're right in your conclusion, Steve, it's a lot more about what you eat than when. If anything, the “gurus” who yell about not eating late (carbs or otherwise), I think are probably trying to just get people to cut down their intake, period.

  • NerdFitness

    Thanks B, let me know if you track down that article. And whatever works for you, keep doing it!

    -NF Steve

  • NerdFitness

    Hey Jozmo,

    I wish Daniel Craig told me that. He seems like a cool dude, plus he's James Bond, so he probably knows lots of attractive ladies. Win win!

    As for dinner, I hear ya – most of the time, its not even about the meal, it's who you spend it with. This is why dinners in Spain take like 73 hours and start at 10PM.

    Love the MMA fighting with the kids. I remember my brother and I used to try and beat up my dad when I was a little kid. Didn't work out so well for us.

    -NF Steve

  • NerdFitness

    You got it Porter. Calories in, calories out.

    -NF Steve

  • JFreedom

    It really doesn't make a whole lot of sense that eating the same amount of food during day but at different times would cause one to gain weight. I can see how it may affect your sleep patterns and whether you have more energy, but it doesn't make sense that it'd be a primary cause of weight gain.

    And…. booya MW2! I'll be on tonight takin' out some durka's on the 360 😛

  • I keep mentioning the same book but there's a very interesting chapter in “Good Calories, Bad Calories” that discusses eating times (doesn't matter, according to his research). Additionally, I've seen a few commenters mention the idea of “calories in, calories out”. The idea being that the body respects the laws of thermodynamics. This makes intuitive sense to me but, according to the studies summarized in that book, isn't the case at all. Instead, the author feels that the research suggests that it's the quality and type of calories as opposed to the quantity or timing of those calories.

    This makes me sound like an insufferable know-it-all but I really couldn't be more convinced by the evidence presented in this book.

  • NerdFitness

    Hey Jordan,

    Thanks for the comment man. Looks like I need to get through Good Calories,
    Bad Calories a little quicker. Gary's the man, too bad his book is so damn
    long and thick and dense!

    -NF Steve

  • nina

    Late night eating is such an issue for me bc my sleep schedule is so off. I also wanted to add that our body has a pineal gland -which is our body's way of figuring out what time of day it is, responding to the amount of serotonin in our brain. The pineal gland sets one's circadian rhythm's process of catabolism (breaking up of products). This is highest within the first 8 hours, and lowest from 4pm-midnight. Therefore, at night time, our body's breakdown of fat is lowest, due to the fact that our pineal gland is percieving less light at that time and it is switching over to anabolism. Sorry , being a med student, this is the only way i can figure these things out, I always know there is some hard science to explain anything. Great article once again!

  • nina

    How about “those that consume 1-2 servings of milk daily are more likely to shed more weight”
    Eliminating all fat out of diet better, or important to take in healthy fats to lose weight?
    An apple a day keeps the doctor away

  • menopauseweightgain

    Your post was very refreshing. Thanks for sharing

  • Vikki

    I agree with not eating before I go to bed, not because I think it will make me gain weight, but because I get hunger pains so bad it wakes me up in the middle of the night. I'm not talking about the psychological “I need food” kind either, it's hunger hungry. It's painful, so I avoid eating at night as much as possible.

  • Vikki

    I agree with not eating before I go to bed, not because I think it will make me gain weight, but because I get hunger pains so bad it wakes me up in the middle of the night. I'm not talking about the psychological “I need food” kind either, it's hunger hungry. It's painful, so I avoid eating at night as much as possible.

  • Grismar

    Interesting read, but of course there's little scientific merit in cherry-picking studies. To say something conclusive, the best thing to do would be to setup your own research and compare that to existing literature, in an attempt to better understand -why- eating at night might differ from eating at other times.

    Second best would be to find as much research as you can (not just a pro and a con) and see how they compare, make a statistical analysis of their findings in a way that puts the combined data a in a comparable perspective.

    So, interesting question: if you look at all (or at least most) of the studies, which conclusion is favored statistically and which reason emerges from that analysis?

  • Barry Bland

    Dude such timely advice and on point. It had to be said… I expect I will be getting in heated discussions with Personal Trainers and “Nutritionists” after posting this online.

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