Potential Problems With Severe Carbohydrate Restriction


First, let’s talk about ketogenic diets, which require reduction of digestible carbohydrates to 50 grams a day or less for most folks.  The iconic ketogenic diet is the induction phase of the Atkins diet, which restricts carbs to a max of 20 g daily.  Note that the average American eats 250 to 300 grams of carb daily.

Your body gets nearly all its energy either from fats, or from carbohydrates like glucose and glycogen. In people eating normally, 60% of their energy at rest comes from fats. In a ketogenic diet, the carbohydrate content of the diet is so low that the body has to break down even more of its fat to supply energy needed by most tissues. Fat breakdown generates ketone bodies in the bloodstream. Hence, “ketogenic diet.” Also called “very-low-carb diets,” ketogenic diets have been around for over a hundred years.


Very-low-carb ketogenic diets have been associated with headaches, bad breath, easy bruising, nausea, fatigue, aching, muscle cramps, constipation, gout attacks, and dizziness, among other symptoms. “Induction flu” may occur around days two through five, consisting of achiness, easy fatigue, and low energy. It clears up after a few days.

Other effects that you might not even notice immediately (if ever) are low blood pressure, high uric acid in the blood, excessive loss of sodium and potassium in the urine, worsening of kidney disease, deficiency of calcium and vitamins A, B, C, and D, among other adverse effects.

A well-designed ketogenic diet should address all these potential issues.  My Ketogenic Mediterranean Diet is an example.  I followed it for for six months and blogged about it.  (The KMD is not a paleo diet.)

Athletic individuals who perform vigorous exercise should expect a deterioration in performance levels during the first three to four weeks of any ketogenic very-low-carb diet. The body needs that time to adjust to burning mostly fat for fuel rather than carbohydrate.

Competitive weight-lifters or other anaerobic athletes (e.g., sprinters) will be hampered by the low muscle glycogen stores that accompany ketogenic diets. They need more carbohydrates.


Long-term effects of a very-low-carb or ketogenic diet in most people are unclear—they may have better or worse overall health—we just don’t know for sure yet. Perhaps some people gain a clear benefit, while others—with different metabolisms and genetic make-up—are worse off.

If the diet results in major weight loss that lasts, we may see longer lifespan, less type 2 diabetes, less cancer, less heart disease, less high blood pressure, and fewer of the other obesity-related medical conditions.

Ketogenic diets are generally higher in protein, total fat, saturated fat, and cholesterol than some other diets. Some authorities are concerned this may increase the risk of coronary heart disease and stroke; the latest evidence indicates otherwise.

Some authorities worry that ketogenic diets have the potential to cause kidney stones, osteoporosis (thin, brittle bones), gout, deficiency of vitamins and minerals, and may worsen existing kidney disease. Others disagree.

It’s clear that compliance with very-low-carb diets is difficult to maintain for six to 12 months. Many folks can’t do it for more than a couple weeks. Potential long-term effects, therefore, haven’t come into play for most users. When used for weight loss, regain of lost weight is a problem (but regain is a major issue with all weight-loss programs). I anticipate that the majority of non-diabetics who try a ketogenic diet will stay on it for only one to six months. After that, more carbohydrates can be added to gain the potential long-term benefits of additional fruits and vegetables.

Or not.

People with type 2 diabetes or prediabetes may be so pleased with the metabolic effects of a ketogenic diet that they’ll stay on it long-term.

Steve Parker, M.D.


30 responses to “Potential Problems With Severe Carbohydrate Restriction

  1. I’m a type 2 diabetic and have been eating low carb for 2 1/2 years and am quite comfortable with this style of eating. Have lost 30 pounds and my A1C is 5.6. Hope to lower it further. For me, for the long term, I am eating more like 50-75 grams of carb a day with occasional days of eating treats, AND occasional days of eating closer to 20 grams of carb. It varies, just like it does on a standard American diet. If I go on vacation my weight tends to go up with restaurant eating but I am able to bring it right back down. One of the BIGGEST benefits of low carb eating is appetite control. You just don’t have that awful craving anymore. Portion sizes are much lower too yet you feel perfectly satisfied between meals. And once adapted, I find that when I DO have a treat, like the maple danish I had yesterday, it tastes overpoweringly too sweet and actually not pleasant. Of course I’ll have another one someday, but the experience was not as pleasant as it was in the past and I feel NO DESIRE to have another in the foreseeable future. That memory of being sickeningly too sweet stays in my mind and when I think of how it raises my blood glucose, it’s easier to avoid it. EVERYONE should try cutting back on the carbs. You DON’T have to go to 20 carbs to benefit. Atkins NEVER recommended permanent intake of 20 carbs a day. My opthamologist attacks Atkins! He knows next to nothing about human metabolism and Atkins has been dead for decades yet he carries on about low carb eating. Most of patients in the waiting room are overweight and diabetic of course because they are older and were never told to reduce their carb intake. Absurd. It makes me so angry when health care people issue a blanket indictment of low carb eating without even defining their terms. Lowering your carb intake to 100 or even 125 carbs a day is far better than eating 300 or 400 grams a day. How can that be as terrible as physicians and dieticians would have you believe? It’s ludicrous and a public health disaster.

    • Agree with everything you said, Frank. Just one minor nitpick: Dr. Atkins has not been “dead for decades” as you stated. In fact, he died in July 2003, just under 10 yrs. ago. So yes, I get your point, it’s been quite a while, but it’s hardly been “decades.”

    • Frank, you may be helping many folks with T2 diabetes by sharing so much. Many thanks.


  2. 5 1/2 years at sub 30 grams per day…130 lbs gone, feel fantastic, completely healthy… more energy than EVER in my life and I’m now 52.

  3. There doesn’t appear to be any physiological gap from eating ketogenically, except if you don’t get enough sodium. I read pretty much all of your concerns as fears and not proven fact. Most of us eat more vegetables than your average western citizen, and studies show our systemic saturated fat is actually lower than someone eating high carb; which makes perfect sense when you learn that excess carbs get converted to palmative acid, a saturated fat. Beef is only 40% saturated. It appears moot anyway as Krause has shown saturated fat is not even associated with heart disease, and if it was, nobody has yet demonstrated how it even causes harm.

    Your real concern seems to be the ability to stick with it. Of course it’s nearly impossible. Our food guidelines demonize the plan. They want us to limit saturated fat to 7%. Really? Some days I eat 70%. And my doctor thinks I’m killing myself. He can’t show me any science; the fact that all of his cardiologists believe it is enough for him. Ever try to tell a dietitian you eat ketogenically? It’s like telling the pope you are an athiest. A lot of support there. And then there are people like you,a medical doctor with a book to sell. Line up all teh doctors, the Ozes, the Parkers, and especially the Cornell school of idiots — the China Study hacks, and shoot them all. Yes, browse the internet, turn on a televeision, listen to a radio, or be in the same room as a health professional without recieving the message you are killing yourself. Do you really think people not sticking to a ketogenic diet is physiological? Or is it all of this versimilar bombardment?

    But then there’s the people like me that actually read science, listen to all sides of the discussion, ask questions, corroborate and validate evidence, and make up our own minds based on the best facts. We don’t seem to have any trouble sticking to it. And my recessed retinopathy, my great A1C, my lost weight, my higher energy and happiness, my improved sexual functioning, my improved athletic performance — OMG how that’s improved –thanks my good senses. I’m almost five years at it.

    • Good points Cafe although I like Steve! But as I mentioned, even my opthamologist carries on about low carb and he clearly knew NOTHING about current carb and fat diet research and opinions from our conversation. You are right, people are INUNDATED with negative misinformation about eating low carb and as I said, there isn’t even any mention by ANY doctor I have talked to who defined what he or she means by “low carb” when they condemn it. My doctors are always AMAZED at my results, but they don’t want to hear how I did it since it’s against EVERYTHING they currently believe.

    • Congratulations, cafemol.
      BTW, my understanding is that Krause is one of the leading human lipid experts in the U.S.
      Re: that 7% saturated fat number: in almost three decades of medical practice, I’ve never run across a patient who calculated their percentage of total calories from saturated fat.


  4. Reaching my 3-year anniversary- and can say without reserve that I will eat some version of a low carb diet for the rest of my life. The benefits are huge. Lowered borderline hypertension to normal- “desirable” blood lipid levels- great energy. No cravings for sweets.
    I eat out two or more times a week. Very easy to do low carb if you know how to order. Just don’t judge by what you feel the first couple of weeks. Get through those and you’ll feel amazing.

  5. The ketogenic diet saved my life. Having hypertension, the side effect of lowered blood pressure made mine normal. Weighing in at my heaviest of 275, the side effect of my body burning it’s own fat was not a bad thing either, I had plenty for my body to live off of. I’ve gone from size 24 to size 10. Then there is the whole T2 Diabetes thing… My hbA1c continued to go up with 3 medications and a low fat diet and heart healthy whole grains, For 22 months now, my hbA1c has been that of a non-diabetic. As for the long term sticking to it, well, I believe that my T2 is in remission. I do not want to be morbidly obese again, relying on medications to keep me alive. I stick to it because I don’t want to suffer from the symptoms and complications. I will stick to it the rest of my life because I really had no life prior.

    The ketogenic way of eating taught me more about my body and my sickness than my diagnosing doctor ever did. It gave me my life back.

    My doctor “prescribed” Atkins because it was my only hope. I don’t think she thought I would stick to it because, yeah, most people don’t. For me it was not only intervention but a bit of hope. I thought the progressive nature of my diseases would be the death of me. The old me let Diabetes control my life. The new me doesn’t let any food control her quality of life.

    As for long term, it will be 2 years in April. There are certain foods that I will never be able to eat again. I have no problem with that because there is no food that tastes as good as being able to run and play with my grandchildren in the fresh air.

    • So true MJohnson…doctors and dieticians tell you to eat whole grains and low fat-high carb and then they medicate for the high A1Cs they know will come. They aren’t stupid, they know their diet will cause high blood glucose but they all are still convinced that the greater risk is higher fat in the diet supposedly causing heart disease, an increasingly unsupportable supposition, while diabetic complications from high A1Cs are an ABSOLUTE CERTAINTY. To me that does NOT make sense. Bully for you! So happy to hear you are doing so much better…have a steak and asparagus ON ME!

      • In 2009, I spent 80 hours reviewing the literature on dietary fat and associated heart disease. That’s when I let go of my fear of dietary fat, saturated or not. Most physicians don’t have the time or inclination to do that review. I hope the medical schools are bringing up the next generation of doctors without fat phobia.


    • That’s inspirational, mjohnson.

  6. My experiences lies somewhere between the above comments.

    ~18 mos low to very-low carb, ranging from 25 – 75 g per day depending
    Weight drop from 255 to 185 lbs
    A1c down from 7.4 to 5.4 (the high value was with very strict adherence to the ADA diet guidelines – what a bunch of hogwash)
    Lipids mixed (triglycerides down to 47. TC up to 220, ratios fine – not worried but my GP is)

    Also, adding sporadic, intense exercise (boxing, cross-fit) has been easier. Apparently fewer carbs = more energy,

    Other minor complaints are pretty much gone.

    Pretty much the only problem I’ve had is the occasional low blood sugar reading, easily fixed with half an apple or a bit of dark chocolate.

  7. I’m not diabetic or even pre diabetic, but I have been on a very low carb ketogenic diet for nigh on two years. I plan to eat this way for the rest of my life. Do I fall off the wagon occasionally? Yes, not so much because I crave carbs but because outside of my home, options aren’t always ideal. But I always get right back on with no problems. I don’t think you have to be diabetic to appreciate the benefits of a ketogenic diet or stick with it.

  8. My biggest concern with ketogenic diets is kidney function, and to a lesser degree the liver. I keep a record of spaced CMPs noting: indirect markers to the best of my limited knowledge: creatinine, BUN, etc.

    However, I don’t know how accurate this is to monitor kidney function since 1) you’re going to have elevated nitrogen and uera on a high protein diet, and if you workout probably creatinine too. Not to mention the equation used for GFR is still an “equation” based on the general population; I’m not sure how accurate that would be for an athlete or those involved in strength routine. Again I’m not a doctor and not knowing what to look for hinders my ability to monitor my health, and I would like for someone who is a doctor tell me what is too high or low, especially for GFR. The problem with most doctors I have tried to discuss this with is they are all normally against low carbohydrate dieting and instead they recommend the typical FDA diet of high carbohydrate and little protein when I go to discuss it.

    I tried to alternate diets before too, but I continue to gain and fail miserably. The fact is ketogenic diet is the only one that works and I hate to quit it because of deteriorating kidney function or something of that nature, at least the liver has the ability to regenerate to some degree. Losing kidney function, and more importantly being on dialysis is not my goal but weight loss is.

    Any advice?

    • Why did you say “high protein” there? A good low-carb high-*fat* diet is moderate protein, and no threat to the kidney. Unless you’re building muscle, about one gram per kilogram of lean tissue per day suffices, so for me around 80-100g of protein, and that’s about all I was eating before.

    • Hi, Kris.
      Ketogenic diets don’t cause any adverse liver effects to my knowledge. In fact, they’re a good way to counteract the fatty liver that is so common in Western cultures.
      Regarding assessment of kidney function, I suggest a baseline 24-hour urine collection for creatinine clearance and total protein. These can be repeated in the future if needed. My favorite “quick and dirty” kidney function test is simply serum creatinine. As you imply, folks who do resistance training and have higher than average muscle mass will tend to have higher serum creatinine levels, which is not a bad thing if it only reflects high muscle mass.


      • Thank you Dr.Parker for replying. I appreciate your professional opinion about my health concerns. I will do just that and monitor serum creatinine,

  9. Been on LCHF 3 years and I have long-term effects, I could stop taking meds for bloodpressure+ DM2+ allergies, lost weight, feel so much alert, need less sleep, can enjoy good food with good conscience, have not had flu or stomach flu, have become more aware of organic, proper food and so on. I think the best thing with this that I dont need any meds anymore

  10. A ketogenic diet isn’t high in protein. In fact it may be lower in protein intake than what a lot of people eat on the standard modern diet. The body needs very little protein (between 0.6 to 1 gram per 1 lb of lean body mass) and a ketogenic diet is perfectly adequate. I’ve been on a ketogenic diet for 9 months, lost 23Kg of weight, lowered my BP, got my blood sugar under control (I’m pre T2D), regained my energy and physical endurance, lost my allergies, migraines and gained back my health.

    Downside? I’m getting tired of telling doctors to STFU and pass me the butter.

  11. Thank you all for your response(s)

    Well perhaps my concept of high protein diet is incorrect, I apologize. I consider 1g per LBM high protein, so for a 170 that is 170 grams of protein. According to FDA’s guidelines protein requirements it will be around 80 grams~ per an average male diet. That’s almost double that of the FDA hence my thinking of high protein diet.

    However most sports nutritionist recommend around 1g per 1lb of LBM and more protein in a caloric deficit(I assuming for protein sparing effects via buffering calories), I understand the point for a ketogenic diet is lower carbohydrates intakes and higher fat to buffer that but still protein(or fat) will generally be higher in this diet setup than normal carbohydrate based diets so this is why I said high protein.


    Still regardless kidney function is a concern for me. Rather on a PSMF or Ketogenic diet.

    • randalschwartz

      Uh, I think Claude mistyped when he said “between 0.6 to 1 gram per 1 lb of lean body mass”. I’ve heard the rule as “0.6 to 1 gram per *kilogram*”, which would cut your numbers by a factor of 2.2. And no, I’ve never heard anyone advocating an *increase* in protein on a LCHF diet, unless they were already below the “body cannibalizes your own muscles to get essential proteins” level, which is what that number represents.

  12. I did not see in any of the references any info on the
    Eskimo diets which if I am not mistaken exclusively
    meat and fat. My recollection is that the old traditional
    eskimos did not have CHD. For me personally, I find I
    can keep every thing simple by simply eating lean meats
    and vegetables and nuts along with low or no fat dairy.
    That naturally rules out the high glycemic foods and I
    also agree that having gone a long time without, I no
    longer crave the old popular empty carb foods like bread,
    cereal and crackers and sweets etc.
    I do not have diabetes but I have decided that it is best
    that I follow a diabetic/paleo diet as it makes perfect sense to me that the blood sugar spikes from processed
    carbs over time will wear out our pancreas. I have told
    my friends to stop eating morning cold breakfast cereals
    because of the overwhelming carb content. What I am
    barely reconciling is the need for some sugar in the
    bloodstream especially for physically strenous events
    and I have read that the brain needs blood sugar to
    function at hi levels. The ketogenic adherents I think
    may be taking it a bit too far. I have a question ….
    if no carbs are eaten and only meat and low fats etc.
    the body digests some of the protein for energy
    right ? Therefore a greater amount of protein needing
    to be eaten to prevent our body canabalizing on our
    muscle stores. I’d like to relate a story about the
    so called hitting the wall that athletes refer to when
    they run out of muscle glycogen. I was beginning to
    take long bicycle rides ( 4 and 5 hours) and one day
    I neglected to bring my bagles or fig newtons or gatorade
    etc. All I had was water and after riding at about 18 mph
    for a little over an hour…. in a matter of about ten seconds my strength was weakened to only being able
    to pedal about 8-10 mph. My body literally quit working.
    A 15 min rest and a few borrowed candy bars built
    my energy back up. Dont ever underestimate the
    effect of what I think is the ketogenic result of not enough
    carbs. ( this did make me wonder about dogs metabolism in the 1000 mile Sled Dog race… They only
    feed them meat and fats )

    • Gregory, thanks for commenting. I agree that high-level athletes (and mid-level?) may need more oral carb grams than other folks. Jeff Volek and Stephen Finney may well disagree (check their books at Amazon). Athletes on a very-low-carb diet may need 4-6 weeks to adjust to low carb consumption.

      Yes, our bodies will make blood glucose from ingested or body tissue proteins as needed to keep blood sugar over 60 mg/dl or so. If we don’t eat enough protein, the body canabilizes its own tissue proteins. We can also make some glucose from the glycerol backbone of trigylcerides (fats).


  13. Mechelle Meixner

    Exactly a year ago I found out that I was diabetic. That day I stopped eating all grains, flours and sugars. Soon, I switched to 70% fat, no more than 70 grams of protein and 30 to 50 grams of carbs per day. Very easy to eat this way. When I crave something that I don’t normally think of as food, I eat a bite or two of it. Usually I don’t want more than that.

    Today I am not on any meds. My A1c is 5.3, blood pressure 110/60, trigs are 43, HDL 83, and I am no longer anemic, depressed or Vit D deficient. Of course, I feel great! It was very comforting to me to read the above responses as I had so much trouble finding a doctor who didn’t think that I was crazy!

    It is only hard to eat this way if you eat seed oil fats or just don’t eat enough saturated fat. If anyone is having too many cravings, they probably need to add more sat fat! When you get enough fat, your health just keeps improving, your food cravings disappear, and you have enormous amounts of energy and focus and drive… (And whole, real food is really the only food that I usually want to eat. Hard to believe, but every month it gets easier and easier to live this lifestyle).

    Also, essential reading: anything by Volek and/or Phinney. Finally, Jimmy Moore’s Ask the Experts podcast was truly life-changing for me. Anyone who wants more info, inspiration, and to not feel alone on this journey to health has got to check Jimmy’s podcasts out!

    Steve Parker, thanks for this excellent blog!

    • Thanks for the compliment, Mechelle. And for sharing your experience. I wish my carb cravings went away on a high-fat diet, but that wasn’t my experience. I just have to deal with them.