The right diet, a
good cardiovascular exercise program and a full body resistance training
program form the foundation of any weight loss strategy. However, other
lifestyle choices can have a big impact on weight loss success. An example of
one such lifestyle choice is to limit eating after 8:00 PM. This has been
recommended to dieters for generations, but is there any research to back this
up? Do people who eat a lot of food after 8:00 PM really gain more weight? In
this post, we’ll take a look at what the research tells us.
I find this topic
interesting for a couple of reasons. First of all, when I was in high school
and college, I could not gain weight for the life of me. I ate all the time,
but I had a really high metabolism and was extremely physically active, so I
burned off every calorie I put into my body. This probably sounds like heaven
to people who were struggling with their weight, but it wasn’t so great. I was
really, really skinny.
One of my
fraternity brothers told me that to gain weight, I just had to eat 2 peanut
butter and jelly sandwiches right before I went to bed. I told him that those
few hundred calories wouldn’t make a difference because I was already eating a
ton of calories all day. He said it wasn’t just the extra calories, it was when
I was eating them that was so important. I gave it a shot. The summer between
freshman and sophomore year in college, I ate 2 peanut butter and jelly sandwiches
right before I went to bed. I was also working in construction and lifting
weights. I put on 30 lbs. in 4 months!
When I became a
licensed nutritionist and started working with weight loss clients, I found
that a lot of people who were overweight ate a high percentage of their food at
night. Having them stop this habit, in addition to changes in diet and exercise,
helped them to lose weight. I also noticed that clients that made good progress
with their diet and exercise but did not stop eating late at night did not lose
much weight at all. I have been recommending to limit late night eating to my
weight loss clients for over 15 years.
So what does the research have to say about this?
The Research
Surprisingly, I
did not find much high quality research on the topic of late night eating and
weight gain. However, I did find several investigations utilizing weaker study
designs that hint at a potential association.
1) In a recent
cross-sectional investigation published in the American Journal of Clinical Nutrition, 110 college-aged men and
women recorded all of their food intake with a time stamp so that the hour of
consumption could be accurately recorded. When compared to normal weight
subjects, overweight subjects consumed significantly more of their calories 1
hour closer to melatonin onset, which was around 11 PM (Reference 1).
2) Another
cross-sectional investigation published in the journal Appetite showed that protein, fat and carbohydrate consumed after
8:00 PM were associated with a higher BMI in a group of 52 volunteers that
filled out 7 day food logs (Reference 2).
3) This investigation
is a much older study that only had an abstract. I include it here because it
is interesting and I have never seen results like this before. In this study, 9
young men were given the same meal at 9:00 AM, 5:00 PM and 1:00 AM (Reference
3). Energy expenditure was measured by indirect calorimetry for one hour
before, and six hours after consumption. Dietary induced thermogenesis (DIT) of
the meal was calculated as the 3 hours of energy expenditure above basal
metabolic rate.
Morning DIT was
significantly higher than afternoon DIT (P=.04) and night DIT (P=.0002). Afternoon
DIT was higher than night DIT (P=.06). What this means is that these young men
burned a higher percentage of their meal’s calories in the morning than they
did in the afternoon or at night.
Conclusions And Recommendations
The research on
late night eating and weight gain is largely unimpressive. To come to a firm conclusion,
you’d really want to see a number of randomized trials and well-designed cohort
studies showing an association with late night eating and weight gain. To my
knowledge, these studies have yet to be conducted.
What we are left
with are cross-sectional studies that are a much weaker form of evidence. Having
said that, several studies I did find suggest a cross-sectional association
between eating late at night and gaining weight. One study was a trial that
mentions a potential mechanism, but it is so old I could not find the full text
to properly evaluate it.
I would say the
evidence, while weak, is suggestive of a relationship between late night eating
and weight gain. So what are some potential mechanisms at play here?
1) Eating food
late at night simply adds extra calories that you would not consume
otherwise.
2) Food consumed
late at night is of poor nutritional quality and more likely to cause weight
gain. Most people snack on high glycemic carbs like chips, pretzels and dessert
late at night. These calories spike the blood sugar and increase fat storage.
3) Another hypothesis
is that our metabolism slows down quite a bit at night, so more of what we consume
is stored as fat.
4) The thermic
effect of food is lower at night, so more of what we eat is stored as fat.
Despite the weak
forms of evidence and uncertain mechanisms, I still think it is a good idea to
limit eating after 8:00 PM if weight loss is your goal. I have seen this be a
very big part of the equation for many weight loss clients over the years.
References
1) McHill AW, et
al. Later circadian timing of food intake is associated with increased body
fat. American Journal of Clinical
Nutrition 2017; 106:1213-19.
2) Baron KG, et
al. Contribution of evening macronutrient intake to total caloric intake and
body mass index. Appetite 2013;
60:246-51.
3) Romon M, et al.
Circadian variation of dietary induced thermogenesis. American Journal of Clinical Nutrition 1993; 57:476-480.
