Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
7 Jun

Dear Mark: The Low Carb Flu

Conquering carbs offers a whole constellation of rewards, not the least of which is a steady, brisk energy unlike most people have known before (well, maybe since the whirling age of 10 or so…). People tell me constantly that they can finally make it through the day without being down for the count every midafternoon. They enjoy enough vigor and vitality to weather a whole day’s worth of activity. The busyness of life becomes easier to handle: the energy demands of daily work or business travel, the mayhem and constant commotion of kids, a weekend’s worth of chores and errands, etc. A skipped meal doesn’t suddenly change the agenda to including procuring a bagel or other false pick-me-up. Nonetheless, for some folks, there’s a common, temporary but still bothersome bump in the road on the way to that Primal prize. Though it varies, it often means a couple weeks of mental fuzziness, fog and fatigue. Although your body might be off to the races, your brain can lag behind like a little brother in a stuffed snowsuit. It’s a game of “hey, wait up!”  while the body’s mechanisms and metabolism align themselves. They call it “low carb flu,” and rest assured it’s just as temporary.

Dear Mark,

I just want to know if anyone who has been Primal for some time had any trouble with cognition in the first few weeks. I can hardly think straight, especially after eating, and I am also low on energy. Will this pass??? Besides that, my body feels great!”

Thanks to Jessica for her question in response to Matt Garland’s excellent guest post last week. It’s a common subject of emails I receive.

First off, I should mention that some folks experience the low carb flu, and others don’t. Overall, those who have been lower carb for some time seem to have fewer problems with the transition taking their carb intake down a notch. As rational as it sounds, this trend still isn’t a hard and fast rule. I know a number of Primal adherents who fit this profile and then went on to experience the symptoms Jessica describes. Others I know went from sky high sugars to low carb cold turkey and felt great from day one. Go figure. It might be due to the “sliding  range of genetic variations” I’ll be discussing in an upcoming post.

Although the low carb flu isn’t universal, that doesn’t mean it’s abnormal. For many people, it takes about two to three weeks to move beyond the temporary fog and fatigue. Studies following the physical performance of low carbers showed that initial disadvantages were erased after this window of time. If your body is used to employing easy glucose carbs and now must create glucose from fats and protein (a slightly more complex but entirely natural mode of operation), it can take some time to get up to speed. Rest assured that our bodies can and are doing the job. It simply takes time to work efficiently. The transition actually shifts metabolic related gene expression, increasing fat oxidation pathways and decreasing fat storage pathways. (That’s nothing to shake a stick at!) Within a few weeks, the body should be fairly efficient at converting protein and fat for the liver’s glycogen stores, which provide all the glucose we need for the brain, red blood cells, muscles, etc. under regular circumstances.

The small amount of specifically targeted research on low carb diets and cognition are small and shoddy at best. A recent study, for example, showed minor memory delay during the first week of strict carbohydrate elimination (as opposed to reduction), but further measures were not taken until carbs were reintroduced. By the same token, those on a traditional American Dietetic Association diet exhibited more confusion during the study tests. I don’t think this study offers any legitimate, useful assessment on either diet.

Nonetheless, there’s the sense that we’re stressing the brain and causing damage by not bathing it in a steady supply of glucose. In fact, we may be doing our brains the ultimate favor. Recent research has pegged Alzheimer’s as a kind of “type 3” diabetes, a disease related to insulin resistance. Truth be told, our brains can function on ketones, fat-metabolism byproducts and key energy sources in low to very low carb diets, which some say may be even healthier yet for our noggins. Check out Jimmy Moore’s interview with Dr. Larry McCleary, a respected neurosurgeon and author of The Brain Trust Program: A Scientifically Based Three-Part Plan to Improve Memory, Elevate Mood, Enhance Attention, Alleviate Migraine and Menopausal Symptoms, and Boost Mental Energy.

Keep in mind also that people in low carb transition can genuinely shortchange their physical needs when they aren’t eating enough fat or when they’re pursuing high intensity exercise routines lasting over an hour, which send the body’s glycogen stores into a nosedive to the ground. I hear this from CrossFitters and P90Xers who insist on maintaining their daily high intensity while transitioning to Primal eating. This isn’t to say that you can’t exercise more intensely for longer on a Primal Blueprint diet (although there’s no real need to for perfectly solid fitness), but more than an hour’s time for most folks requires some extra carbs when glycogen is depleted. If you’re bothered by the mental fog even without intensive exercise, ease up on your carb restriction by adding 25 grams or so to see if it makes a difference. Listen to your body and gauge your sensitivity. Rome wasn’t built in a day, and you’re not going to compromise your overall benefit by taking it slowly.

As any Primal buff would attest, this temporary setback pales in comparison to the benefits once the transition has passed. Without the persistent carb-induced peaks and crashes, you should enjoy a measurable boost in energy – steady and stable – in no time. Hang tight, and know you’ll be on the other side of the hill soon! In the meantime, take good care of yourself with a little extra shuteye and maybe some well-timed green tea for a modest boost when you really need it.

Avid Grokkers: what words of experience do you have for Jessica and other new folks at the Primal table? Be sure to share your thoughts, stories and words of wisdom. Thanks for reading and keep your questions coming!

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I’m feeling these exact symptoms right now! This is my second day consuming 68 grams of total carbs (about 1/3 polysaccharides, 2/3 di/monosaccharides). A little bit of regular coffee is helping, along with adequate b-vitamins.ct symptoms now

    Vito wrote on July 14th, 2011
  2. I spent a year+ on Atkins and another year mostly primal so don’t remember carb flu that well, but I think this will help. From time to time I get the “blues” a slight depression and lack of energy without any real cause.
    I eat an avocado. I always feel better within 30 minutes!

    Andrea wrote on August 25th, 2011
  3. I am very new to primal eating, I just started reading the book this week. But as a previous carb addicted vegetarian, I have already made a lot of changes in my diet these past few days. I have been experiencing really bad nausea throughout the day. Waves of it come and go, in the afternoons and at night before bed. I feel better after eating a little chicken and have been trying to resist the urge to snack on a piece of dry toast! Any suggestions/experience with horrible nausea?

    Kat wrote on September 19th, 2011
  4. Hi, I can’t seem to quench my thirst. Help. I am a few weeks into Primal and am losing weitht, too. Yahoo.

    Kay Caringi wrote on September 20th, 2011
  5. I’m avidly reading all these suggestions, but are there any peri-menopausal women out there who started Primal and promptly started getting hot flashes? any advice? I’m slowly getting rid of the “low carb flu” after 4 weeks, NO cravings for carbs, losing weight nicely. Helped by being off sugar for a year which was a gentle weaning process and lost 10kg sloooowly! Thanks to David Gillespie’s book “Sweet Poison”, then I read Gary Taubes books and here I am going Primal.

    JulieMcAra wrote on September 20th, 2011
    • Hi Julie – yes I sweated like crazy start of 2nd week – had to stand outside the hairdresers in Jan in freezing temps to cool off – and I am normally a really cold person. The sweating only lasted a few days though – it started when I’d eaten coconut milk (with coco powder mixed in!) and I think it was the combination of high fat and low carbs that freaked my body out.

      It prob took me about 3-4 months to start to feel how I do now in terms of energy (I’m 9 months in). And it varied. Some days I had way too much energy and had to run up stairs to burn it off. Others I was dragging myself up the stairs – with just no energy. Nowadays the energy is pretty stable, unless I’ve not got enough sleep.

      It changes gradually and you tend not to notice it until one day you suddenly realise you don’t feel like you used to and you haven’t done for ages – you just hadn’t noticed. I think just get on with life and don’t focus too much on it. I may only have lost 8lbs, but I’m 2 dress sizes smaller and still falling – but that’s taken 9 months. It’s not a race and so don’t think about competing with these guys who just seem to lose it in a matter of days! Just remember that getting there slowly is still getting there.

      Debs wrote on September 21st, 2011
  6. I honestly felt like I had the flu, full on, feverish, ached a bit, head hurt – set on a day after I began, but is was gone within 18 hours

    StrongWIll wrote on October 10th, 2011
  7. I’m into my third week of trying the PB lifestyle. I am a lifelong vegetarian so the changes have been pretty drastic for me. Prior to trying PB, I did make some changes to my diet by slowly decreasing my grain intake and introducing fish to my diet. I also quit dairy cold turkey when I started PB.

    I do not eat eggs, poultry or red meat, so my PB style consists mainly of fish and seafood and nuts (which I never ate before because of the high calories). Can I just say that I NEVER FELT SO AWFUL? The first week after about 3 or 4 days into it I had diarrhea. From the second week on the diarrhea stopped but now I have a severe case of constipation and not even laxatives do the job. I am so bloated I feel like I’m about 12 months pregnant (I know that is not possible, but I just wanted to illustrate how bloated and heavy I feel) and every time I eat or drink something my stomach balloons up. When I wake up, my face is all swollen and puffy. I run out of energy very quickly though some days I do have a little more energy. I’ve been tracking my food intake on and my diet is about 60% fat, 23% carbs and 17% protein, give or take some. I try to keep my carb intake to below 100g, but given my meat limitations I find my carb intake stays at about 120-130 grams. Need to work on that although my carb intake consists strictly of vegetables and berries. I am definitely eating enough as I do not go hungry. As a matter of fact, I fear that I am taking in way too many calories- I always end up at about 2000 calories and up which is way more than I am used to consuming (I’m supposed to be at around 1600 or so for weight loss). I don’t eat that much but I find that the fat (mainly consisting of olive oil in cooking and avocado) and the nuts really elevate the calories even though I don’t eat that much in terms of volume.

    I also have a constant buzzing in my head. That is not really the right description, but it is not a headache either. It’s more like a weird lightheaded/dizzy feeling that one would normally feel when hungover.

    Overall, I just really don’t feel very well aside from the sinuses that cleared up after I quit dairy. I think if the bloating, constipation and puffiness would go away, I could really adopt this lifestyle as I really don’t miss the grains so much. I do get hungry quite often and do get sweet cravings at night so I snack on nuts and berries. Another thing is that I find breakfast options quite difficult and end up eating a lot of veggies for breakfast (hence the high carbs). I tried eating eggs for about a week but my body completely rejected it. I started getting so much mucus and my nose was constantly running. I quit the eggs and the mucus cleared up.

    I am thinking that perhaps my body is taking longer to adjust because I have been a vegetarian most of my life and it’s been quite a shock to the system to handle so much protein even though I had slowly introduced fish to my diet prior to PB.

    I am going to stick with this for a while as I think the grain elimination does agree with my body (despite the bloating lost about 2 lbs in these three weeks), just the protein overload is a bit much for the system. I am thinking of reintroducing beans to my diet especially as breakfast options are so limited for me. And no, I will not eat red meat (pork or beef) or poultry not because of ethical issues, but simply because I can’t stand the taste (which is why I have been a vegetarian since I was 8 years old) and my body would go into convulsions if I forced myself to eat them.

    Has anyone had similar issues with the bloating and constipation and if so, how long did it take until you felt better? Anything I can do to alleviate the symptoms in the meantime? Any helpful suggestions would be appreciated!

    Lulu wrote on December 2nd, 2011
    • Lulu, I’m super bloated too, puffy face, etc. It’s been about four days since I’ve been eating very low carb Paleo. I’ve done this before though, and it did go away, but it’s really bad this time. I don’t have constipation, as I’m taking loads of magnesium. I’m also taking stuff to kill candida, so that may be making my symptoms worse. When I was younger, whenever I went low-carb, I’d immediately lose a huge amount of water weight. Not anymore. It seems to take a lot longer before the diuretic effect kicks in for me now. It’s annoying. Are you doing any better now?

      Robin wrote on December 10th, 2011
      • Hi Robin. I’m sorry to hear you are having the bloating and the swelling as well- not fun! I’m at the end of my fourth week and I did start feeling much better toward the beginning of the fourth week. The swelling and the bloating went down quite a bit and my stomach is back to normal level. I don’t have constipation as much anymore although I do have the intermittent attacks of diarrhea still. Magnesium supplements only started working after about 2 weeks or so of taking them.

        I still have very low energy all the time and I am still hungry all the time. But I still feel encouraged now with the swelling and bloating gone. And despite all this and the tremendously high calorie levels for me I still somehow managed to lose another pound this week- probably just the water from the bloating.

        Hang in there Robin, I’m sure you will start to feel better soon!

        Lulu wrote on December 10th, 2011
  8. The day after I wrote that post, I started feeling way better and felt increasingly fantastic all the way up until… christmas vacation :( where of course i ended up eating some things i wouldn’t normally. now i am back to square one. it’s my third day of all paleo eating and i still feel like doodoo: major cravings, fatigued, bloated, etc. i can see the inflammation in my skin and my dull, bloodshot eyes. i only started eating poorly around the 29th (and by “poorly” i mean exquisite gourmet food at the finest restaurants). It’s crazy how 3 and a half days of eating fairly “normal” amounts of sugar and grains will do me in this much. it makes me wonder if i’m just becoming a hypochondriac or orthorexic. You still around Lulu?

    Robin wrote on January 5th, 2012
  9. This explains so much. I’ve felt a little run down since I started this, but I’m determined to go for the full 30 days to test out PB. Carb Flu…

    Zelenn wrote on January 25th, 2012
  10. add me to to roll call of carb flu sufferers. day 19 of whole30, and struggling mightily with thirst, nausea and fatigue. Luckily, the brain and mood still seem to be ok. I’m hanging on for my 30 days, but have no benefits yet, and still feel crappy. I’ve been told you just have to hang on, so I am trying, but it’s rough when you feel awful.

    lawyerhands wrote on January 28th, 2012
  11. I started eating primal at the beginning of December. I didn’t have any troubles until about 10days ago when I started experiencing lots of confusion, intolerance to cold, extreme exhaustion, eyes burning, itchy skin, & abdominal pain. Are these normal effects of going primal? I must note that I had a gradual change and haven’t completely gotten rid of all grains yet.

    Mindy wrote on February 6th, 2012
    • Hi Mindy, you definitely aren’t alone with those symptoms. I also started at the beginning of December but went full-on primal. All my food was organic and all my meats organic and grass-fed. I even swapped over to raw milk. I was eating about 70g protein, 20g carbs and about 130g fat (those Korg calculation tables at the end of the PB book were very handy) – all monitored by fitday, as I had no idea what foods contained. I gave up coffee and tea and replaced fruit with vegetables. Initially, I struggled with the fat concept but food actually tasted so good with it that this was quickly overcome. After a week, my 3 years of bloating and stomach pain disappeared and I was ecstatic. I had about 4kgs to lose and lost most of that in the first 3 weeks.

      However, after that first week, I started to experience the symptoms you’ve described. I would go from shivering to sweating (in a tropical climate), was so tired I couldn’t get out of bed, my eyes were constantly red and burning, I had a head-splitting headache that kept me in bed for a week (thought I was dying), alternating diarrhoea and constipation, always thirsty and my joints were so sore, I felt like I was 110. When I did go to the gym, I had no energy after 5mins of body-weight training and would break out in a cold, clammy sweat and want to throw up. My perfect skin broke out in red rashes and dots and I developed a sensitivity to anything I put on it. Eventually I discovered steaming, apple cider vinegar and sweet almond oil and this has helped my skin immensely. I also started started developing patches of psoriasis on my scalp. Three weeks in, I discovered that I was reacting to dairy and coconut milk and cut those out. Will try again in a month or 2 as the idea of not eating triple cream brie or my newly discovered full-fat organic yoghurt ever again is too depressing to contemplate. I also get these brutally intense, wall-climbing cravings for red wine (I used to drink a glass a day).

      As of about 2 weeks ago, my energy levels have finally picked up and are quite good. I’ve eased up on my gym routine and now incorporate walks on the beach – barefoot. My skin is getting better but still burns if I put anything on it other than oil and apple cider vinegar. My stomach is sometimes queasy but I now make my own bone broth and this is wonderful. I actually crave it. Every day I take a teaspoon of good quality cold liver oil (and 1 or 2 bowls of bone broth), and occasionally also take vitamin b and c. I recently celebrated 4 weeks alcohol free – with a glass of red wine! Given that lemons now taste sweet to me, the flavours in the grenache shiraz mourvedre were out of this world.

      It has been two months and, all in all, the experience has been totally horrid. However, before I started PB, almost everything I ate made me feel sick anyway, so I figured my stomach was in a bad way and wouldn’t heal without a fight. After doing quite a bit of research, I now recognise that these symptoms were simply healing/detox symptoms and my body was/is trying to rid itself of years of accumulated toxins. Admittedly, the severity of the symptoms may also have been lessened if I hadn’t adopted the full-on approach that I did. Interestingly, I didn’t previously eat junk food or sugar and ate healthily accordingly to CW!!! I’m probably not out of the woods yet but I’m well on the way. My stomach thanks me and I’m close to my optimal weight. I have a wardrobe full of clothes that now fit beautifully, I’m much leaner and feeling rather good about myself. I’m also more aware of chemicals and toxins and trying to live in a way that’s kinder to the environment. I’ve also found an amazing butcher (Grass Roots Urban Butchery in Vaucluse) that supplies me with meat, bones and trotters from grass-fed animals raised humanely. I also have no trouble sticking to this way of eating because the thought of going through those rotten symptoms again is the best deterrent. Interestingly, I’m also teaching myself to cook. Being a low-fat adherent for years, I never realised how good food can taste when you start adding fat and eating PB-properly.

      So stick with it Mindy – it’s worth it in the long run.

      p.s. my sister has also started PB and has lost 5kgs of post-baby weight in 5 weeks – with not a single side effect and tons of energy. I guess you can’t win ’em all.

      Wombik wrote on February 6th, 2012
  12. It seems I had the ca-flu for about 4 days after about 3 weeks of going primal. This was about the time I got into rhythm with carb levels. I dropped from 250 carbs pre-Primal, to about 135 the first few weeks, and now hit under a 100 regularly. But interestingly enough, once over the ca-flu I began dropping weight a lot more steadily and quickly. 6lbs in the last week. Feel great. Pushing the word out to family/friends. By the way, I’m from Oxnard CA but living in Guam.

    jamesjaragon wrote on April 6th, 2012
  13. I didn’t get the carb-flu with Paleo diet until I went further with a zero-fruit regimen to get past the plateau and drop some more fat. And then it was pretty mild. A few weeks later I didn’t feel the mental sluggishness anymore.

    lbruce wrote on April 6th, 2012
  14. Just wanted to thank everyone for leaving their experiences and insights here. I’m a week into full on primal living (averaging 60g carbs a day) and the flu hit me like a ton of bricks yesterday!

    I’ve been forgetting little things (like my address), been groggy yet unable to sleep, living in a bit of a haze and, the cherry on top of it all, almost had an “accident” in the supermarket yesterday as my bowels decided it was “go” time without telling me. Can’t make this stuff up.

    I was pretty scared but feel SO much better now that I’m finding out that it will pass. I just hope its quicker than a couple weeks. Thanks all!

    Cole Pouliot wrote on April 9th, 2012
  15. Hi, I am 41 and I cut wheat out of my diet after reading the book “Wheat Belly” about 2 weeks ago. I noticed that my terrible bloating went away. Then my acupuncturist got me the Primal Blue print and I have really limited my Carb intake.
    I have lymphocytic Colitis and all of the info I have received has been counterintuitive to my problems. A nutritionist told me at one point that I would have to eat white bread, gravy and canned food for the rest of my life. SInce every person I have spoken to medically has told me that I should avoid basically every food group (they always contradict the last person I spoke with) I have had to figure things out by listening to my body. But I have not done so great. I never ate the white bread but I have chose to avoid red meats and sugar.
    After cutting out the majority of carbs in the past 2 weeks I began to notice Gall stones coming out. I have lost 6 pounds 191 to 185 in this two weeks which is awesome and is keeping me motivated, But I feel really miserable. I feel so achy and tired. Has anyone had an experience with anything like this? Or gone primal with microscopic colitis?
    Thanks, looking for encouragement and answers.

    Jennifer wrote on April 11th, 2012

Leave a Reply

If you'd like to add an avatar to all of your comments click here!

© 2016 Mark's Daily Apple

Subscribe to the Newsletter and Get a Free Copy
of Mark Sisson's Fitness eBook and more!