• BioBlog: Carbs at Night: Fat loss killer or imaginary boogeyman?

    Posted In: Nutrition  /  Posted On: 08.31.12

    Originally published on http://www.broscience.com

    There are quite a few things that everyone in the fitness industry KNOWS.  You have to eat 8 meals per day, consume 400g+ protein per day, do fasted cardio, use heavy weights to bulk up, and light weights wit 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 that 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 based in little actual research data.  The debate about whether or not it’s ok to have carbs at night has been all but settled in the fitness industry.  You simply can’t consume a shred of carbohydrates at night or you will store fat faster than vampire rises after the sun sets!  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.  So I decided to examine this fitness factoid to determine if eating carbs at night was actually detrimental to your body composition or if it was all fallacy.

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

    In order to properly asses 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 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.  Seems reasonable, but broscience always ‘sounds’ reasonable.  These ‘experts’ 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 less 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?  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% (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).  Ah ha!  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 night time 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 and 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).  These researchers from Israel put people on a calorically restricted diet for 6 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% of the total) at the night.  What they found after 6 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 were 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 6 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 eating I’d be starving!”  Well my friends you are buying into a vicious cycle I’m afraid.  Let me explain: when you eat small amount of food 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 and 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 further 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.

    So what’s the explanation for the night time 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 huh?  Additionally, the experimental group had much higher levels of adiponectin, a hormone associated with increased insulin sensitivity and fat burning.  They also had a trend for slightly higher leptin levels.  Furthermore, the night time 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 time.

    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.  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.  So write it down “Don’t eat carbs at night bro” has officially been BUSTED as BROSCIENCE!

    Literature Cited

    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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    Comments On This Post

    1. avatar

      Layne,

      Doesn’t this kind of coincide with John Kiefer’s thoughts on carb back loading? He advocates consuming the vast majority of carbs (regardless of source) at night. Curious to hear your thoughts.

    2. avatar

      This fits with what I have stumbled onto.

      Fasting until midday and keeping carbs low until the evening meal.

      I have lost significant bodyfat and been surprised by muscle gain considering I only have access to a 14kg kettlebell!

    3. avatar

      Sounds like the Carb Backing Loading theory is golden here… (not that I’ve read much about that) but it seems to talk about similar things.

      Proteins and fats then go crazy with your carbs post-workout which goes into the evening.

      Haven’t shelled out $84 to learn about that yet.

      Figured Layne might come out with a little guide that explains these concepts! :-)

      Great article!!

    4. avatar

      Hey Layne – great stuff as usual. There is research out there like this http://www.ncbi.nlm.nih.gov/pubmed/9040548 that showed having most calories late at night maintained muscle mass better and increased fat loss. There was also another police officer study which I am struggling to find – also found the same thing with better lean mass maintenance when caloric intake was greater at night.

    5. avatar

      Hi Layne this is not something that is directly related but I think it would be a good time to ask. Do you feel that it is more beneficial for one to consume their carbs at breakfast and around their workouts as opposed to spread evenly throughout the day ?

      E.g. carbs at breakfast, alot of carbs pre workout with the remaining carbs consumed in the form of quick carbs in pwo shake and slow carbs in ppwo meal ?

      I’d like to know the answer for when in calorie surplus and also deficit, thanks Layne !

    6. avatar

      Layne please would you be able to do an Article purely reviewing John Kiefer’s work on Carb Back loading?

      You two are some of my favorite writers and I would love to hear why your opinions differ when both of you claim your work is based on science.

      I am completely confused why there isn’t agreement between the two of you.

      From this article and from your interview with Propane Fitness it seems like your arguing that your not sure whether Carb-Backloading will make a huge impact on your physique it terms of fat loss, while retaining muscle but I would like to hear you both debate about this as you’ve only referenced one piece of research which supports Carb-Backloading, but Kiefer seems to have given 20+ research articles.

      Once again – a confused reader.

      Ps. Thanks for all the work you put in and your Youtube videos are really inspirational, the ideas of outworking and having passion are really pushing me through life at this point in time.

    7. avatar

      Many boneheads are involved in bodybuilding who never have and never will have any interest in educating themselves in the science and questioning with a critical mind the claims many take as “fact”.

      You debunk this claim and many others have. But I am thoroughly appalled at the amount of people in my gym at least who maintain such false notions. I ask “Are these the people reading this and learning?” The cleverer people will naturally gravitate towards the truth, but those seems to not be the majority.

      Everyone has the ability to become a bodybuilder. Not everyone has the ability to become a neuroscientist. I think this is the root of the problem. Bodybuilding represents the average person in the street who is uninformed at even the most basic level about nutritional science. Destroying broscience is slow and tedious progress(no doubt you know this!).

      • avatar

        Jesus, you sound like a lot of fun at parties.
        I haven’t cringed at a comment so self inflated in an eternity.

        I’m sure it would be especially entertaining to see your physique or see your lifts.

        Why you have such an inaccurate portrayal of body builders we may never know. However, to dismiss them as boneheads, doing things anyone could do and being wrapped in their ideology is absurd. It is because they are busy accomplishing things, not reading articles online that their ideas on carb intake hhaveyet to shift.

    8. avatar

      Hi Layne most information on nutrition and carbs relates to training 5-7pm. However I train/lift at 7-7.30am. I’m more alert, have more energy and focus to follow PHAT which has given me greater gains.

      Back to you article above, I mostly have my carbs 9am pwo and 10.30am pwo meal and rarely with 7.30pm dinner. I don’t eat any carbs pre wo say 6-6.30am as I feel sluggish in the gym.

      Whats your thoughts on your article for someone who trains 7am.. Could 80% (200g) eaten PM really increase strength and fat loss??

      Cheers Layne upfront for any advice and thoughts

    9. avatar

      too much for my little mind to read. wore me out. Your articles and video blogs would be well served by an intro summary and an exit summary. simple tools in a crowded internet.

      • avatar

        You can’t be serious. First, without the references or citations, this would just be more broscience. Secondly, these references are solid and so are the conclusions drawn. To me this is internet gold. Something shorter and less challenging doesn’t bring us any closer to the truth.

    10. avatar

      Given the refractory nature of MPS and the ramifications of this article, would it be wrong to surmise that for optimum body composition one might want to replace intermittent fasting with intermittent CARB fasting (e.g., carbs at dinner only, but two other protein and fat meals, all spaced 4-6 hours apart?

    11. avatar

      So a decent recommendation would be protein shakes (or meat) every couple of hours throughout the day, and a high carb meal for dinner?

      For carb sources, usually glucose and starches seem to be recommended vs things higher in fructose. Unfortunately, that seems to make fruits (and even vegetables) a less attractive proposition. Do you have any thoughts or science on the matter?

      Thank you for your blog, and for replying to so many of these nitpicky questions.

    12. avatar

      excellent writing as always, Layne. I think your new blog with these articles and videos was really a smart path to go down.

      I feel like Martin at leangains has been talking about this for a while. I’m glad to hear you chiming in about it since I regard your opinion on these issues very relavant.

      I personally have had great success by always skipping breakfast. I simply eat about a 1000 calorie lunch and then a big ol 3000 calorie dinner.

    13. avatar

      Hi Layne,

      This is a very interesting article, thanks. I have recently read Gary Taubes’s book “Why we get fat: And what to do about it” and it has really opened my eyes regarding the whole insulin and carbs debate.

      Since reading it, I have gone on a sort of Keto diet, very similar to Atkins, where I have reduced my carb intake to between 20 and 40g a day and imcreased my saturated and natural fats. And I have lost 8kg in about 2 months.

      But I do weight training 5 times a week (and recently started your PHAT – omg my lower back…anyway i digress) and im worried about the lack of carbs leading to a lack of energy in the gym.

      So i would like to know your thoughts on the Keto diet and building muscle? How important are carbs in your diet if you are doing heavy lifting, and can your body not get that glucose from the extra oils and protein you are eating?

      I hope you can help me with this, ive scoured the net for info on it and i keep coming up with ‘carb cycling’.

      regards,
      chris

      • avatar

        I would be interested in Layne’s thoughts on this as well. I have been following this ketogenic approach, coupled with Starting Strength style training, to lose weight without losing (and hopefully gaining) lean muscle.

        Personal success? 10kgs in 2 months so far, and I feel A LOT stronger! And cutting out the carbs definitely helps me with hunger control.

        I have read quite a bit on nutrition and weight loss (including people like Aragon), and I am just not convinced that we need the carbs.

        I would appreciate any thoughts on this.

        Cheers
        Swiss Mike

        • avatar

          Perhaps you’re being too literal, Layne. The commenter is responding to what you said about consuming carb meals every 2-3 hours — that it trains your body to be hungrier and to crave carbs more often. Sure, a biologist might not use the term “efficiency” here, but this isn’t a biologist, it’s a blog commenter.

          Here’s the question rephrased: Do you suggest spacing carb meals out more than 2-3 hours? If so, how far?

    14. avatar

      Hi Layne,
      I would like to know how the glycemic index of a carbohydrate food might affect this study? In terms of the nighttime group vs throughout the day carb group? Hopefully I don’t confuse you with my question.
      Thank you for your time and I look forward to you answer!

    15. avatar

      “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.”

      I’m pretty sure that’s the opposite of what you meant to type.

    16. avatar

      Does eating carbs before bed affect growth hormone release while sleeping+? Or is that another myth? How can you maximise natural growth hormone release?

    17. avatar

      Well written article! I’m glad I see what has been known in the science world for a while is getting spread by more that don’t care to get criticized by mainstream believers. This article sums up 80% of how my clients have such a high success rate long term. To add to this the psychological impact is tremendous as well. It allows clients also to use what makes them feel good at the end of the day to wind down. The people reading this article that doubts it should try it because most of you have yo yo weight over the last few years doing different methods of eating. So you don’t go off trying it and it not work one very critical part wasn’t mentioned. Law of Thermo dynamics – cals in to cals out! You have to still make sure you are at a caloric deficit every 24 hrs. If any one wants to see a more real life result of how applying cals in to cals out, no supplements other than vitamins, and eating how it fits the best for you on an individual basis checkout my site and look at the before and afters.

    18. avatar

      Fenugreek has been used either short-term to boost milk supply or long-term to augment supply and/or pumping yields. There are no studies indicating problems with long-term usage. Per Kathleen Huggins “Most mothers have found that the herb can be discontinued once milk production is stimulated to an appropriate level. Adequate production is usually maintained as long as sufficient breast stimulation and emptying continues” .:`,

      My own online site http://healthmedicinebook.comap

    19. avatar

      Interesting article! I suffer from IBS and always thinking of lowcarb, as I seem to be better then. Still worried about my metabolism… Thanks for sharing!

    20. avatar

      Good article. It did alleviate some of my fears about consuming carbs at night. From my readings I have come to the conclusion that if you eat a three meal per day (breakfast, lunch, dinner) each with lean protein source, complex carbs, veggies and then supplement between meals with a protein source to get to your goal grams per day all while achieving your daily caloric intake then you should have results. This article is important to me since now I do not feel like I am taking a step back when I include complex carbs in my dinner. Thanks, Layne

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