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Is a Very Low-Carb Ketogenic Diet Healthy?

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Is a very low-carb diet suitable for you? What are the pros and cons and what you should expect from it? These and other questions are answered by Franziska Spritzler from Low Carb Dietitian. Franziska is a certified dietitian and has personal experience with very low-carb ketogenic diets!

Very-low-carbohydrate ketogenic diets (VLCKDs) have been around for hundreds of years and were the standard form of treatment for diabetes prior to the discovery of insulin in 1922. William Banting, a British undertaker, deserves credit for developing the first VLCKD for weight loss in the mid 1800s.

Cardiologist Dr. Atkins popularized it again in the early 1970s after reviewing decades-old nutrition research in his attempt to discover a plan that would allow people to lose weight without going hungry – his own Achilles' heel when it came to sticking to a diet. Over the years, the very-low-carbohydrate ketogenic diet has been criticized for being too restrictive, difficult to maintain long term, and unhealthy. However, many people find that this way of eating is the only one that allows them to lose weight and effectively control diabetes.

How is a Very Low Carbohydrate Ketogenic Diet Defined?

Is a Very Low-Carb Ketogenic Diet Healthy?

Although at this time there isn't universal agreement on the term, a few years ago leading researchers in the field of carbohydrate restriction proposed the definition of very-low-carbohydrate ketogenic diets as those containing less than 50 grams of total carbohydrate per day.

However, the degree to which carbohydrates need to be restricted to induce ketosis varies from person to person. Some may achieve elevated ketone levels consuming 60 grams of carbohydrate or more, while others may need to restrict carbs to less than 30 grams or even less than 20 grams to experience the same effect.

A VLCKD is defined as any diet with less than 50 grams of total carbohydrates as defined by Phinney and Volek (or 20-25 g net carbs). There isn't a universal definition of a VLCKD.

Net Carbohydrates or Total Carbohydrates?

Many people count net carbohydrates by subtracting fiber from total carbohydrates, but there are differences of opinion regarding whether fiber should be counted. Soluble fiber may be absorbed and therefore could affect ketosis and blood glucose levels, while insoluble fiber simply passes through the GI tract unabsorbed. Most foods contain both types of fiber, as shown in this comprehensive chart.

In their excellent book The Art and Science of Low Carbohydrate Living, Dr. Steve Phinney and Dr. Jeff Volek recommend 50 or fewer grams of total carbohydrates per day on a LCKD and do not mention fiber or net carbs in this regard. However, it stands to reason that consuming 50 grams of total carbohydrate where half or more of the carbs come from fiber will lead to higher ketone levels than if the same person consumes a 50-gram total carbohydrate diet containing only a few grams of fiber.

Why Follow a VLCKD?

I'm a registered dietitian who eats a diet containing less than 50 grams of total carbs daily and recommends carbohydrate restriction for people who want to lose weight, control diabetes, improve symptoms of PCOS (polycystic ovary syndrome), or experience better overall health. However, there's a lot of controversy around this way of eating. As with any dietary approach, there are advantages and disadvantages to limiting carbs to very low levels.

Benefits of Very-Low-Carbohydrate Ketogenic Diets

You Will Find it Easier to Lose Weight

Is a Very Low-Carb Ketogenic Diet Healthy?

Very-low-carbohydrate ketogenic diets are well-known for their effectiveness at achieving weight loss. The exact mechanism for how this occurs is debated among the experts, but it appears to be a  result of several factors, including increased satiety, lower insulin levels, and increased lipolysis, or fat breakdown.

In fact, in every study – including the “gold standard” for evidence, randomized controlled trials –  VLCKDs perform at least as well and generally better than low-fat diets for this purpose. For instance, the A-Z study followed overweight women randomized to one of four diets: Atkins, Ornish, LEARN, or Zone.

At the end of the year-long study, the  participants on the Atkins diet had lost the most weight, although their carb intake gradually increased from very low levels initially to moderately low (110-140 grams of total carbohydrate) at the one-year mark.

In addition to formal research, there is an impressive amount of anecdotal evidence supporting carb restriction for weight loss and maintenance. For example, the Active Low-Carber Forums website has over 98,000 members, many of whom have lost 50 pounds or more and kept the weight off for several years by adopting a VLCKD.

Your Blood Sugar Levels Will Become more Stable

Is a Very Low-Carb Ketogenic Diet Healthy?

Carbohydrate is the nutrient with the largest impact on blood sugar; for those with diabetes, consuming even modest amounts can raise blood sugar to levels that damage blood vessels and nerves. Elevated blood sugar also places a heavy burden on the beta cells of the pancreas to produce high amounts of insulin in an attempt to shuttle the sugar into the body's cells.

Following a VLCKD is the most effective strategy to reduce postmeal blood sugar response – as well as the safest, given that insulin and all oral diabetes medications carry some risks. Dr. Eric Westman of Duke University has conducted studies in which people were able to reduce or significantly decrease diabetes treatment by following a diet containing less than 20 grams of total carbohydrate per day (in this study and also here).

Your Body Composition Will Probably Improve

Although in some circles low-carb diets have a reputation for inducing muscle loss, research has demonstrated the opposite: A very-low-carbohydrate ketogenic diet promotes  better retention of muscle mass during weight loss and overall improvement in body composition.

Your Risk for Heart Disease May Go Down

People who restrict carbohydrates and increase intake of healthy fats like olive oil, coconut oil, butter, lard, tallow, avocado, olives, and nuts almost universally experience a  drop in triglycerides and an increase in healthy HDL cholesterol. In addition, VLCKDs promote large, fluffy LDL particles (Pattern A) which are relatively benign with respect to heart disease risk, particularly when compared to the atherogenic small, dense type characteristic of Pattern B.

Sounds great, doesn't it? But in the interest of fairness, let's look at potential disadvantages of following a VLCKD.

Potential Side Effects of Very-Low-Carbohydrate Ketogenic Diets

Your LDL Cholesterol Might Go Up

Is a Very Low-Carb Ketogenic Diet Healthy?

Will a very-low-carbohydrate diet raise your LDL cholesterol? Maybe. LDL cholesterol response to carbohydrate restriction is variable; it's believed that roughly 50% of people experience a rise while the other half either see a decrease or experience no change.

However, even if your LDL does go up, it will in all likelihood result in the more favorable Pattern A mentioned above. There is also a  temporary increase in LDL following significant weight loss, so keep this in mind. Finally, the LDL-C in most lab reports may not be accurate. It's calculated using total cholesterol, HDL-C, and triglycerides in what's known as the Friedewald equation, and if triglycerides are less than 100, it will overestimate your true LDL level.

Your Food Choices Will be Somewhat Limited

This is one of the biggest criticisms of low-carbohydrate diets, and there's some validity to it. On a VLCKD, there are several off-limits foods that may include some of your favorites: pasta, rice, bread, most fruit, and sweets. Although there are acceptable substitutes for many of these items, even the most enthusiastic low-carber will admit that there are some foods that simply can't be successfully replaced by a low-carb version, such as bread or baked potatoes.

You'll Likely Develop a Decreased Tolerance for High-carb Foods

Although people respond to carbohydrate restriction differently, generally speaking, tolerance for carbohydrates usually goes down after becoming keto-adapted. In other words, your blood sugar will rise higher after consuming a high-carb item than it would if you followed a regular diet comprised of at least 150 grams of carbohydrate daily.

This is sometimes referred to as physiological insulin resistance in order to distinguish it from the pathological insulin resistance that occurs in Type 2 diabetes, obesity, and metabolic syndrome. Because of this, you're instructed to eat at least 150 grams of carbohydrate for three days prior to taking an oral glucose tolerance test (OGTT), which allows you to regain carb tolerance.

If you took the OGTT (which involves consuming 75 grams of straight glucose) without modifying your very-low-carbohydrate diet, your blood sugar  might potentially rise to the level where diabetes could be diagnosed (200 mg/dL) even if you don't have diabetes.

You might get constipated

Not everyone who follows a VLCKD develops constipation, but enough do to mention it here. Fortunately, it's often temporary and can be remedied by drinking enough fluid, getting sufficient magnesium, and consuming additional salt – at least 1-3 extra grams per day.

Is A Very-Low-Carbohydrate Ketogenic Diet Right for You?

In my opinion, the benefits of keeping your carbs very low outweigh the drawbacks, but whether to follow a VLCKD is a matter of personal choice. If you love high-carb foods and find that avoiding them inevitably leads to feelings of deprivation which results in bingeing, then a carb-restricted diet probably isn't your best choice.

However, if you're trying to lose weight or have diabetes or metabolic syndrome and enjoy rich, luxurious, high-fat foods like cheese, cream, eggs, avocado, and fatty meats – and are willing to give up the aforementioned high-carb foods in exchange – a very-low-carbohydrate ketogenic diet may be the ideal way of eating for you.

Although VLCKDs are safe and healthy for most people, it's important to speak with your doctor prior to adopting a low-carb diet or making other dietary changes.

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Franziska Spritzler, RD, CDE
Registered dietitian, certified diabetes educator and creator of

Franziska Spritzler

Franziska Spritzler, a registered dietitian and certified diabetes educator, is a strong proponent of carbohydrate restriction for people struggling with diabetes, insulin resistance, obesity, and PCOS.

She follows a very-low-carbohydrate, ketogenic diet for blood sugar control and has experienced many improvements in her health as a result of making this change.

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This article was written by Franziska Spritzler, RD, CDE who is a qualified expert. At KetoDiet we work with a team of health professionals to ensure accurate and up-to-date information. You can find out more on the About us page.

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Comments (28)

I have read some other articles about this, and that it can be a successful weight loss plan for those with obesity.   Do you have thoughts regarding calories per day.  Some indicate less than 800 calories per day to start to lose target weight loss, and then gradually increase to maintenance.   Also, do you have meal plans, recipes or know of books with those?

Hi Darlene, I'd discourage anyone to be following a diet with less than <1200 kcal, especially since less than that should be done under medical supervision and used sparingly only in some cases.
You can download our app (free) and calculate your macros to find out your ideal levels:
We do also have the option for premium subscribers to build custom diet plans to fit your macros - as many as you want by using over 1500 recipes. I hope this helps!

My weight recently ballooned to 240 not pretty on a 62 year old 5'-6" frame and to add to that I also had a cardiac event that made me realize that I had to get my poop together!
I have been on a under 20 carb lifestyle for 1 month now and the change has been nothing short of amazing. I have lost 25 pounds so far and I feel 100 % better, my sleep as improved, my blood pressure has dropped considerably, my joint pain has disappeared and in general my everyday aches and pains have improved immensely.
I have to believe the improvement is a result of taking sugar out of my diet...sugar simply put is poison!
My Goal was to drop 50 pounds...halfway there!

Gord, that's amazing and goes way beyond just weight loss, thank you for sharing this with us!

How does ketosis affect Kidney Disease? Do you have any suggested reading?

Hi Meg, there is some information about kidney disease in this post: Ketogenic Diet FAQ: All You Need to Know

Hi are you familiar with KETO RASH? I need urgent help on this, overtime I tried low carb diet, I always got KETO RASH all over my body. Please help me on this.
Many thanks before!

Hi Karen, I don't have personal experience with keto rash but I know that it may help if you increase your carbohydrate intake a little. What's your carb limit? I'd try at least 30 g net carbs per day.

Hi there, Thank you for this article! I am 49 and have had PCOS since I was in my 20s (probably earlier) and was never advised to eat low carb. It wasn't until I researched myself that I found out about the Ketogenic diet. I've been following this or at least low carb/high fat for almost 2 years now, keeping my net carbs under 20, and although I see many health improvements my weight is not moving much. Initially I lost about 20lbs in the first 6 months but then I have been gaining & losing the same 5-10 lbs since. I have a lot to lose (I'm 5'5 and weigh 230) so I just don't understand why the weight is sticking to me. I have my macros set to 75f/20p/5c and often go as high as 80 fat.  Any advise would be greatly appreciated. Thank you! Krista

Hi Krista, have a look at this post, I hope it helps: How To Low Carb: 15+ Common Weight Loss Mistakes
You can also contact Franziska directly (e-mail on her website).

Thank you for this extremely important and clear explanation of the high fat low carbs diet. I manage a large migraine group on FB after having figured out the cause of migraine a few years ago. One of the most important issues migraineurs face is the carbohydrates electrolyte disruptive effects. Glucose takes water out of the cells and pushes sodium out as well, causing edema and lack of voltage for the brain (I enjoyed your increased salt comment! Indeed migraineurs need to do just that!). We constantly fight what I call the "carbs-effect" that without exception leads to a migraine. I really enjoyed your explanation and will share your expertise with my group by sharing this article. I suppose a happy medium is possible to retain a neutral pH body acidity level to remain healthy. Thank you!

Thanks for the article. I am type 2 diabetic and wanted to know if when you say 150gr of carbs for 3 days prior to taking the test you mean a weight of 150 grams or talk about macronutrients, because I ve been eating vlc for a while now and usually every 100 grams of let's say pasta there is only around 70 grams of carbs, and 100 grams of pasta is A LOT of pasta (pasta is just an example, sorry english is not my first language (: )so I would need to double that amount and more for a few days.. ? It kinda worries me to be honest, but I'd be really thankfuk if you made that clear for me please because health comes first 😊
Thank you.

Hi Marta, I believe Franziska was referring to 150 grams of carbohydrates as macronutrients (not pasta, etc) Also, my understanding is that that test is not recommended for type 2 diabetics but only healthy individuals who want to test their carb tolerance.

Im pleased to have come across your site.  Ive tried a commercial VLCD, but struggle with the replacement meals and shakes, to the extent that trying to consume them makes me cringe. I am going to try your approach, as it seems fairly straight forward. Just one question, can I eat pickles??

Hi Edith, that's the best approach to follow - just eat real food 😊 Yes, you can eat pickles too, just avoid products with added sugar / be aware of it.

Nice Article.

Your article is very interesting with lots of if and buts.
My opinion is that low carb.,high fat diet can help lose weight and also help reverse per-diabetes if accompanied with regular vigorous exercise.But should not be continued for life.Once your have reached your weight loss goal,you should add some good carb along with lot of vegetables and fruits(Apple,Berries,Pear) and maintain your desired weight by balanced diet with portion control.

Thank you for your insights. However, unless there is a medical reason for anyone to stop following a low-carb approach (such as type one diabetes in some cases), there is no need to add extra carbs as long as the diet is rich in nutrients.

I am currently 73 years old, 5'4" and currently weigh 153 lbs.  I am on a high protein, low carb program.  (I began 7 weeks ago and weighed 163 lbs.)  My "coach" is very supportive, but I am getting a bit discouraged. My goal was to lose 30 lbs and so I am one-third of the way there.  Today, my coach said something that kind of shocked me.  He said that I am a small woman and based on the amount of fat measured in my body, I should be weighing 82 lbs.  He seemed to acknowledge that that would be unwise, but did believe I needed to lose my goal and maybe more because of that. Is that possible?
They don't seem to want you to exercise on this program, but I am concerned because of my age, that my metabolism is not cooperating.  This week I lost nothing .

Hi Mary, I would be hugely concerned about what your coach has suggested. I don't know enough to tell you how much you should weigh and I'm not a nutritionist but I'd think that your original goal was very reasonable and I'd stick with it - any weight loss is beneficial. I'm about the same height and wouldn't personally go below 115 pounds.  You shouldn't lose too much weight, especially not at your age. I think you can always include some exercise, possibly walking / power walking? Maybe you can try a low-carb, moderate protein, high-fat diet, of course, after consulting it with a specialist.

I'm happy to see the support of experts! It could be quite frustrating to explain to my doc that I'm doing well on a low-carb diet. He doesn't believe I eat all that fat and have normal cholesterol, he probably thinks I'm making it up or that I'm just an "exceptional case". Actually, my HDL has increased which he thought was weird. If only they were willing to do the research and stop judging the atkins diet based on pseudo science funded by the food and pharmaceutical industries.

I know what you mean. I've been looking for a good doctor for a long time. In any case, your health is more important and he will realise it once he sees it improving!

I'm going to print out the article about the Friedewald equation and take it to my doctor--maybe then, she'll quit harassing me about my LDL.  I've been eating ketogenic for about a year, and she's after me for the LDL and the saturated fat...but not a peep about the much-raised HDL or Vitamin D levels.
Referring to my last CMP, all my levels are good except the LDL (131)--now that I know it's been overstated, I'll rest easier, and look forward to the sound of silence from my doctor next time she tests cholesterol.
Another alarming thing is the whole "within range" thing--the lab that ran your test has a range that's made up of prior patients...patients who may have been much sicker than you, thereby skewing the range into the unhealthy territory.  If you're eating cleanly, you should try to aim for the lower end of the "range" so as not to get lumped in with a population of sickies who've managed to move the whole range right out of the truly healthy territory.  DO NOT LET YOURSELF BE COMPARED TO THIS POPULATION--THEY ARE NOT YOUR PEERS!!  This is why you should always aim your results toward the low end of "their" range, and consider that healthy.  Because to you, and compared to other truly healthy, clean eaters, it is.  Compared to obese, sick people, you're running low on the "range."  That's where you want to be until the population at large starts cleaning up its act, and starts skewing the "range" back where it needs to be.
I guarantee you that if a certain lab were to only test Paleo, Primal, and keto eaters, the "range" would look a whole lot different.  Compared to other labs, clean eaters would undoubtedly be flagged as deficient in many areas, and consequently, be prescribed many drugs they don't need.  I imagine vegetarians ans vegans go through this now.

Oh I know, it can be quite frustrating and you sometimes have to look for a long time until you find a lowcarb-friendly doctor.
I have been looking for mine for 3-4 years but I'm very happy with him! My endocrinologist has approved my diet because he actually follows the recent research and has seen the benefits of LCHF. Since I started LCHF, my antibodies have dropped 8 times!!! I have Hashimoto's and the antibodies are now below the "normal" level for this disease. I hope I can reverse it one day completely - I'm slowly getting there 😊
Lab tests are not always what you expect them to be and I had to ask for "special" tests for my thyroid because I know the weak spots in the health system (e.g. only testing the level of T4 hormone and not T3 and antibodies).
About the drugs people often don't need - statins are just a perfect example!

Great article Franziska! I can't believe VCL is not prescribed to all patients with diabetes, PCOS, high cholesterol, etc. I have seen great benefits being on keto for over a year and would never go back. My cholesterol has improved, I lost weight and my blood pressure dropped. It's very easy to stick to, it's actually the only diet I could follow without feeling I'm on any diet.

That's great to hear! I have the same experience - if something, it has helped and improved my health. I don't do very low-carb like below 20-30 grams of net carbs but I still stay in ketosis on most days even at higher levels of net carbs (maintaining my weight). If I feel like I need to lose a few pounds (like it was after Christmas), I just avoid dairy and anything sweet-tasting and stay at about 30 grams net carbs. That's why I have also created my Clean Eating Challenge 😊

I have been addicted to your app just over a month now. I am seeing benefits as I have bipolar 2 and am feeling great.
One question though. I am eating under 15 grams of carbs and follow the diet strictly. I have a ketone monitor and last week registered 1.4 but today registered .5.
Nothing has changed in my diet. Could you shed some light on this for me.
Thanks for a great app

Hi Lynne, is the level of ketones the only thing that has dropped or have you also experienced slow fat loss or other effects related to health? I have written something about ketones here - the level of ketones is not that important and does not always mean a bad thing: Ketosis & Measuring Ketones: All You Need To Know