Carbs At Night: Fat Loss Killer Or Imaginary Boogeyman?

Most fitness enthusiasts learn early on to treat late-night carbohydrates like a nightmare waiting to happen. But what does science 'real science' have to say? The answer may surprise you.

There are quite a few things that everyone in the fitness industry "knows." You have to eat eight meals per day, consume 400g+ protein per day, do fasted cardio, lift heavy weights to bulk up and light weights with high reps to tone up ... oh wait, those are all broscience!

Don't get me wrong, bodybuilding and fitness have been on the cutting edge of many dietary and training interventions to which mainstream science is only now catching up. Unfortunately, the vetting process for many of these protocols isn't exactly stringent. Thus, many things become accepted as fact, when in reality they are broscience. The debate about whether or not it's okay to have carbs at night has been all but settled in the fitness industry. The consensus is: You simply can't consume a shred of carbohydrates at night or you will store fat faster than a vampire rises after sunset!

That is, according to many fitness "experts" out there, most of whose credentials are worth about as much as a thin sheet of slightly used one-ply toilet paper. In this article, I will look into this fitness factoid to determine if eating carbs at night is actually detrimental to your body composition or if it is all broscience.

The debate about whether or not it's ok to have carbs at night has been all but settled in the fitness industry.
"The debate about whether or not it's ok to have carbs at night has been all but settled in the fitness industry."

So where did this "no carbs at night" thing come from?

In order to properly assess this fitness "fact," we need to understand why limiting carbs at night is recommended in the first place. Most "experts" who recommend limiting carbs at night do so because their assertion is that since you will be going to sleep soon, your metabolism will slow down and those carbohydrates will have a greater chance at being stored as fat compared to if they were consumed earlier in the day, where they would have a greater probability of being burned. This seems reasonable, but broscience always does. They also often assert that insulin sensitivity is reduced at night, shifting your carb-storing directionality towards fat and away from muscle.

Let's tackle the issue of metabolic rate slowing down at night time first. The logic behind this theory seems reasonable enough: You lie down in a bed and don't really move, just sleep, so obviously you are burning fewer calories than if you are awake doing stuff. Even if you are just sitting in a chair or couch resting, you have to burn more calories than just sleeping right?

"The Idea that you should avoid carbs at night because your metabolism slows down and you won't 'Burn Them Off' definitely doesn't pass the litmus test."

At first glance this seems to jive with work from Katoyose et al. which showed that energy expenditure decreased during the first half of sleep approximately 35 percent.1 However, these researchers did show that during the latter half of sleep energy expenditure significantly increased associated with REM sleep. So, there are rises and falls in sleeping metabolic rate (SMR), but what is the overall effect? Interestingly, at the very least it does not appear that the average overall energy expenditure during sleep is any different than resting metabolic rate (RMR) during the day.2,3 Additionally, it appears that exercise increases sleeping metabolic rate significantly, leading to greater fat oxidation during sleep.4 This seems to be in line with data from Zhang et al. which demonstrated that obese individuals had sleeping metabolic rates lower than their resting metabolic rates, whereas lean individuals had sleeping metabolic rates significantly greater than their resting metabolic rate.3 So unless you are obese, not only does your metabolism not slow down during sleep, it actually increases!

The idea that you should avoid carbs at night because your metabolism slows down and you won't "burn them off" definitely doesn't pass the litmus test.

So the whole "don't eat carbs at night" thing is definitely broscience, right?

So far, the fear of carbs at night certainly smells like broscience, but before we render a verdict, let's examine things further. There is also the issue of insulin sensitivity and glucose tolerance to address. This is where things get interesting. Compared to morning meals, levels of blood glucose and blood insulin definitely remain elevated longer with evening meals.5,6 Aha! There it is, proof, that you shouldn't consume carbs at night right? Not so fast. Though insulin sensitivity and glucose tolerance appear to be worse at night compared to a morning meal, it is important to keep in mind that a morning meal is after an overnight fast and the fast may improve insulin sensitivity. Perhaps a more fair comparison is a mid-day meal vs. a nighttime meal. In this case there is actually no difference in insulin sensitivity or glucose tolerance.5

Therefore, it appears that insulin sensitivity and glucose tolerance are not necessarily impaired at night, but rather are merely enhanced by an overnight fast.

Does any of this science mumbo jumbo actually make a difference?

While it is great to talk about mechanisms and nitpick every intricate detail about metabolism, at the end of the day, we have to examine whether or not any of this stuff makes any difference. Fortunately for us, a recent study published in the Journal of Obesity examined this very question.7 Researchers from Israel put people on a calorically restricted diet for six months and split them into two groups, a control group and an experimental group. Each group consumed the same amount of calories, protein, carbohydrates, and fat but they distributed their carbohydrate intake very differently. One group (control) ate carbs throughout the day, whereas the experimental group consumed the majority of their carbohydrate intake (approximately 80 percent of the total) at the night. What they found after six months may shock you.

Not only did the experimental group consuming the majority of their carbs at night lose significantly more weight and bodyfat than the control group, they also experienced better satiety and less hunger!

Whoa, hold up. Less hunger? I don't buy it

You heard me right, they were less hungry. Now I'm sure all of you that have been following typical fitness protocols where you eat six times per day and have most of your carbs earlier in the day are thinking, "Man, if I went more than 2-3 hours without carbs, I'd be starving!" Well, my friends, you are buying into a vicious cycle. Let me explain: When you eat small amounts of carbs frequently, you are basically titrating in glucose to your system.

To dispose of this glucose, your body releases insulin to drive blood glucose into cells. Over-secretion of insulin, however, may cause hunger to rise (typically about 2-3 hours post meal, the approximate time course of an insulin response), but—no problem—you are eating every 2-3 hours anyway, right? Just titrate in some more glucose. Unfortunately this makes you crave and consume glucose like clockwork. It tricks many people into thinking that they need carbs every 2-3 hours or they would be hungry when, in fact, the opposite is true.

If you ate carbs less frequently with more time between carb dosings, you would be less hungry because your own body would ramp up systems that deal with endogenous glucose production, and keep your blood glucose steady. When you consume carbs every 2-3 hours however this system of glucose production (gluconeogenesis) becomes chronically down regulated and you must rely on exogenous carb intake to maintain your blood glucose levels. Now if you transition from eating carbs every 2-3 hours to further apart for the first few days you may be hungry until your body has adjusted to using gluconeogenesis to maintain blood glucose rather than just eating carbs every 2-3 hours, but once you do adjust, you will find that you are far less hungry.

Bringing things full circle, this is exactly what the researchers found! These subjects were hungrier in the first week of the diet compared to 90 and 180 days into the diet where they were much more satiated.

When you eat small amounts of carbs frequently you are basically titrating in glucose to your system.
"When you eat small amounts of carbs frequently you are basically titrating in glucose to your system."

Control group

So what's the explanation for the nighttime carb group losing more body fat and being more satiated than the control group (maybe we should call them the "bro" group)? The researchers postulated that more favorable shifts in hormones may be the difference. The baseline insulin values in the experimental group eating the majority of carbs at night were significantly lower than those eating carbs during the day.7 So much for carbs at night decreasing insulin sensitivity, right? Additionally, the experimental group had much higher levels of adiponectin, a hormone associated with increased insulin sensitivity and fat burning. They also trended toward slightly higher leptin levels. Furthermore, the nighttime carb munchers had lower levels of LDL (bad) cholesterol and higher levels of HDL (good) cholesterol.

Overall, the people eating the majority of their carbs at night lost more bodyfat and had better markers of health by the end of the study than those who ate more of their carbs during the day.

So what's the verdict?

I am not ready to say that we should all be eating the majority of our carbs at night. I would like to see this study repeated but with a bolus amount of carbs eaten at one meal in the morning to properly compare it to the single high carb meal at night, whereas the previous study compared a bolus night time carb meal vs. several feedings of carbs throughout the day. It may very well be that the beneficial effects of the diet in this study was more associated with limiting carb dosing (and insulin secretion) to a single bolus rather than spreading them throughout the day.

"Overall the people eating the majority of their carbs at night lost more bodyfat and had better markers of health bey the end of the study than those who ate more of their carbs during the day time."

However, I think what can be said with relative certainly is the notion that consuming carbohydrates at night will lead to more fat gain, or impair fat loss compared to consuming them at other times of the day, is false. Write it down: "Don't eat carbs at night, bro" has officially been busted as broscience!

This article was contributed to Bodybuilding.com via Broscience.com

References
  1. Katayose Y, Tasaki M, Ogata H, Nakata Y, Tokuyama K, Satoh M. Metabolic rate and fuel utilization during sleep assessed by whole-body indirect calorimetry. Metabolism. 2009 Jul;58(7):920-6.
  2. Seale JL, Conway JM. Relationship between overnight energy expenditure and BMR measured in a room-sized calorimeter. Eur J Clin Nutr. 1999 Feb;53(2):107-11.
  3. Zhang K, Sun M, Werner P, Kovera AJ, Albu J, Pi-Sunyer FX, Boozer CN. Sleeping metabolic rate in relation to body mass index and body composition. Int J Obes Relat Metab Disord. 2002 Mar;26(3):376-83.
  4. Mischler I, Vermorel M, Montaurier C, Mounier R, Pialoux V, Pequignot JM, Cottet-Emard JM, Coudert J, Fellmann N. Prolonged daytime exercise repeated over 4 days increases sleeping heart rate and metabolic rate. Can J Appl Physiol. 2003 Aug;28(4):616-29.
  5. Biston P, Van Cauter E, Ofek G, Linkowski P, Polonsky KS, Degaute JP. Diurnal variations in cardiovascular function and glucose regulation in normotensive humans. Hypertension. 1996 Nov;28(5):863-71.
  6. Van Cauter E, Shapiro ET, Tillil H, Polonsky KS. Circadian modulation of glucose and insulin responses to meals: Relationship to cortisol rhythm. Am J Physiol. 1992 Apr;262(4 Pt 1):E467-75.
  7. Sofer S, Eliraz A, Kaplan S, Voet H, Fink G, Kima T, Madar Z. Greater weight loss and hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner. Obesity (Silver Spring). 2011 Oct;19(10):2006-14.

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Competitive Bodybuilder Layne Norton teaches bodybuilding tips and tricks for success

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dbman4

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dbman4

Literally the best article on bb.com I've seen in a long time (backed up by a bodybuilder, a doctor who has his phd in studying nutrition and bcaa's and it's riddled with sources and credibility. BB.com Please use Layne more and structure your articles more like this one. I don't even care that it's almost half a year old haha

Sep 4, 2012 6:30pm | report
 
RobinOlds

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RobinOlds

One of the best evidence based articles I have ever seen on here. We need more of these.

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Sep 4, 2012 7:11pm | report
 
phenomenon777

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phenomenon777

totally agree.

Dec 16, 2012 8:18am | report
Spawn8214

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Spawn8214

You would really like Jim Stoppani's articles. He is one of the most well decorated PhD's who contribute on here, and he has the body to prove his works as well (it annoys me when I see really fat guys talking about the best way to lose fat...)

Jan 15, 2013 9:21pm | report
NDeeps27

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NDeeps27

Dr. Layne Norton to the rescue once again. Great article

Sep 4, 2012 8:41pm | report
 
ronnioron

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ronnioron

myth buster to say the least....wow that laid to rest some reall mumbo jumbo goin in my head....i can stop stuffing chickens at nite and maybe eat some decent food for a change or even go out...there u go i said it...

Sep 5, 2012 1:00am | report
 
teslation

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teslation

as far as i would say anything, the best thing so far is to go carb cycling and whether u do it at night or morning its all good and i really liked the article but if ur not sure then go with carb cycling low day/high day/ no day

Sep 5, 2012 3:25am | report
 
geohhh

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geohhh

The real Mythbusters! very useful article!

Sep 5, 2012 4:09am | report
 
Joedzilla

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Joedzilla

Broscience or not, for me not including carbs in my last meal works pretty well, and i noticed the difference when i starting doing it.

What i have in my last meal to be crunchy are almonds and nuts.

Sep 5, 2012 7:21am | report
 
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kelseykumquat

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kelseykumquat

Ridiculous. OF COURSE if you're on a restricted calorie diet, you'll lose weight. It doesn't matter if you eat ONLY carbs and ALL of them before bedtime. Throughout the day, you're burning more calories than you consume.
Also, you did not address the relationship between GH and Insulin (you know, the hormone triggered by carbs?). How can I take the best advantage of the GH surge I receive when I fall asleep if Insulin is restricting it?

Sep 5, 2012 8:15am | report
 
whodathusker

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whodathusker

Check out the references...the amount of food in the restricted diet was the same for each group. The only difference was when the foods were consumed. This may not be the end all be all, but at least it is backed by SOME information and not just "word of mouth".

Sep 5, 2012 10:59pm | report
kelseykumquat

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kelseykumquat

My point is, they would've lost weight Anyway, because both groups were on restricted-calorie diets. The point I'm getting at is not all of us are trying to lose weight; and in fact many of us are trying to put on muscle. If you consume carbs before bedtime, the subsequent insulin spike interferes with your body's GH output, thereby hindering your body's ability to build lean muscle; not to mention the many other benefits of GH. So, yea, maybe don't be afraid to eat some carbs before bedtime (if you're only trying to lose weight, and don't care about some of that weight being muscle). But this is information is misrepresented, and many of the people that take this as great news are just happy to see some information that tangently justifies eating in a way they like, while ignoring the potential drawbacks.

Sep 6, 2012 8:15am | report
ameyp97

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ameyp97

good article!!!!

Sep 5, 2012 11:14am | report
 
Holly444

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Holly444

Thank goodness we've got Layne contributing to bb.com. What a great article. I have recently been experimenting with meal timing and carb timing, etc. I've found the statements of this article to be completely true.
Thanks for sharing!

Sep 5, 2012 11:57am | report
 
ELew

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ELew

I always thought that eating carbs frequently throughout the day did not help weight loss - even if the total carbs and calories where the same.

Sep 5, 2012 2:13pm | report
 
cambodiangrl189

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cambodiangrl189

very interesting, maybe i can dip into the bread jar at night and not feel too guilty lol

Sep 5, 2012 3:29pm | report
 
ozzyaaron

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ozzyaaron

Awesome article and makes sense. Just going to chase up that journal reference to see what types of carbs they included.

Sep 5, 2012 4:03pm | report
 
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Bodice

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Bodice

This is a pretty ballsy article. It's great seeing things like this.

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Sep 5, 2012 7:06pm | report
 
kilgore55

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kilgore55

Great article people read it out more it says the lower calorie didn't loose more the ones who ate more at night did fn dumb a$$e$

Sep 5, 2012 7:10pm | report
 
KCBadBoy

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KCBadBoy

Good article is good!

Sep 5, 2012 7:32pm | report
 
AlwaysSwoleUp

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AlwaysSwoleUp

This jives with Keifer's carb back-loading

Sep 5, 2012 7:44pm | report
 
kish996

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kish996

Your logic is flawed. You stated that lean individuals had a higher metabolic rate while sleeping than obese individuals and therefore were increasing their metabolic rate while sleeping. They may burn more calories while they sleep than an obese person but there would be a similar comparison made during the day. It is nonsense to think that you burn more calories while you sleep than when you are awake. Furthermore, I lost 62 lbs in 10 weeks using Kris Gethin's program on BB.com using exercise, small portioned meals, and no carbs after 6 p.m. While I cannot put a specific number on the effect that spaced out meals and cutting carbs at night had on weight loss I can say that I am living proof that this strategy DOES work

Sep 5, 2012 9:59pm | report
 
klip2006

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klip2006

Perhaps it was the overall diet and exercise not the fact that you cut carbs after 6pm that made you lose 62lbs. Just sayin...

Sep 6, 2012 5:23am | report
bbassitt32

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bbassitt32

@klip2006. Finally someone who has a in intelligent rebuttle. Its like the person that gives up alcohol, revamps their diet, and dedicates themselves to a workout plan, and then tries to say that it was all their post workout, ect. Its not one thing its the whole cumulative effect.

Sep 19, 2012 2:06pm | report
michaeloey

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michaeloey

U can't say that the method that layne mentioned is flawed just because u r using the opp approach n ge great results... U might get better results using this approach.... I get really lean while on high carb diet, but i can't say that ketogenic or lower carb diet is crap, just because high carb diet works for me.....

Oct 15, 2012 11:33pm | report
Showing 1 - 25 of 63 Comments

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