My thoughts on the Ketogenic Diet

By Alexandra Caspero on July 26, 2017

A registered dietitian’s thoughts on the ketogenic diet. Including what works, what doesn’t and what’s best for longevity and chronic disease prevention.

My thoughts on the Ketogenic Diet

You’ve heard of the ketogenic diet, right? Once used primarily to treat seizure disorders, the keto diet almost exploded with popularity overnight. It seems that just about everyone is trying this diet, or at the very least, curious on the claims.

Typically, I keep my opinions on fad diets to a minimum. I do believe that there isn’t a perfect ‘diet’ for everyone, as finding what foods makes you feel your best is a personal choice. As I’ve expanded upon in my diet story, this was true for myself as well. Therefore, when a friend asks me for my thoughts on something, I may give a snippet here or there, but I try to refrain from going into “preacher” mode.

Nutrition is hard. Mostly, because food is so incredibly personal. I’m reminded of this fact almost every time I tell someone new that I don’t eat meat. Their response is typically something like, ‘well, I’m never going to give up bacon.’ Or, ‘I could never do that, I’m an athlete and need too much protein.’ Or, something to that effect. The point being is that when I let people know about my personal diet choices, it doesn’t require a defense on why they want to eat meat. It’s OK. I’m not asking you to change. The same can be true when providing a differing opinion of someone’s diet.

But, the point is there- the immediate, visceral reaction to another’s diet choices. We all likely do it, perhaps, without even realizing. It’s also why I think nutrition can be a tricky subject to navigate. Often, we have to navigate around the emotion wrapped up in food choices.

As I’ve received many requests over the past month to discuss my thoughts surrounding the ketogenic diet, I suppose it’s time to do so. As a disclaimer, my general point of view and thoughts on the ketogenic diet is from my experience as a Registered Dietitian. As this diet can be used for various medical conditions, please discuss any changes with your medical team before making them.

The Basics

Years ago, when I worked as an adjunct nutrition professor, I would always discuss the concept of ketosis with my students when we addressed carbohydrate metabolism and low-carb diets. This was before keto was cool. At least, in my nutrition circles. Ketosis was generally seen as a negative, altered metabolic state. One that was essential for survival following a very, very low carbohydrate diet.

After doing a quick google search this morning, it seems like the keto diet has different parameters, depending on which expert or blogger you choose to follow. While billed as a low-carb diet, it’s more than just cutting out ‘white flour products,’ which I saw on quite a few websites. To follow a keto diet, you have to actually enter ketosis. As I’ll explain below, this is only possible on a very restricted carbohydrate intake, limiting all forms of grains, fruits and vegetables.

In a metabolic nutshell, your body prefers to run on glucose. It’s the preferred energy metabolite for the aerobic Kreb’s cycle and electron transport chain, of which your body is able to produce maximum amounts of ATP. Yes, you are able to use both protein and fat in this cycle, but it’s more costly and not preferred. This is especially true of muscle cells, which can utilize carbohydrates much more efficiently than protein or fat. This is only true in red blood cells and brain tissue; those cells can only use glucose for energy.

When you eat a very low carbohydrate diet, your body eventually runs out of the glucose that it can quickly use. Remember, we don’t store glucose well in the body. It’s found in small to moderate amounts in liver and muscle cells (in the form of glycogen), along with blood sugar levels.

When you eat food, blood sugar levels increase, allowing cells to uptake glucose to use for energy. In the absence of blood glucose, eventually, you’ll start to break down protein and fat for energy. This alternative breakdown of fat produces a by-product called acetyl-coA, which can be used to create ketone bodies to then enter the Krebs cycle to produce energy. When the rate of ketone bodies exceeds the rate of utilization, their concentration in blood increases, causing ketonemia. The same happens in ketonuria, an excess of ketone bodies in the urine.

I know, I’m giving you a little biochemistry but also trying to keep things fairly simple. Essentially, this overall production of ketonemia and ketonuria is what we are referring to as ketosis.

Remember when I said that brain tissue prefers only to run on glucose? Well, this is the reason behind why ketosis happens. It’s a shift that’s essential to provide fuel to the brain in the absence of carbohydrates. It’s also the basis behind why the diet has been traditionally used in various neurological disorders, though that’s not anything that I’m going to dive into today.

When did carbs become so vilified?

Was it Atkins? I would bet if I polled a group of people, they would tell me that white rice is less healthy than bacon. Somehow, somewhere, this became a ‘known’ thing. Which, of course, isn’t the truth.

I was dining out with some friends a few weekends ago, and one of the husbands ordered a burger with bacon and cheese, no bun. The remarks from the others around the table were of praise, telling him how ‘good’ he was being by not having the bun along with his cheeseburger.

Huh? I felt like I had been dragged into opposite day, though I know this is a belief held by so many.

Let’s first talk about carbohydrates. There is a difference between a chocolate chip cookie, brown rice and an apple; anyone who tries to convince you otherwise needs a refresher course in biochemistry. I dislike that all carbs have been lumped together in one category, completely eschewing the health benefits that carbohydrates offer.

I’m not going to try and make an argument that a cupcake is a health food. It’s not. I could make the argument that eating a cupcake every now and then is needed to prevent binge eating or restriction, and I’ve written enough on those topics here.

Instead, I’m going to make the argument that carbohydrates are not only good for you, but they are the cornerstone of the diet that promote health and longevity. I firmly believe that most of our health ailments, especially in the United States, are due to over-nutrition: too many calories, too much saturated fat, too much sugar and not enough nutrients.

We are severely lacking in fruit and vegetable intake. Depending on which study you look at, the standard American diet contains french fries as the most consumed ‘vegetable,’ over-consumes intake of calories and protein and barely gets in 1 serving of green vegetables per day. So, it’s hard for me to make the argument that we need more protein and fat and less nutrient-dense carbohydrates for health.

I’ve yet to see any conclusive research showing that a higher protein/fat diet is better for longevity and reduction of chronic diseases (mostly diabetes, heart disease and cancer) compared to one of mostly plants. I’ll address weight loss in a moment, but for now, I want to focus on health. While I don’t think everyone needs to be vegetarian, there is ample research showing that adding in more plants to the diet helps in both of these areas.

As I’ve mentioned several times before, I’m a huge fan of The Blue Zones research. Essentially, a meta-analysis of longevity research, asking the question- ‘what habits will help increase life-span?’ The longest-lived are getting roughly 95% of their calories from plants with only 5% from animal products.  They eat a high-carb diet, about 65% of their diet coming from whole grains, beans and starchy tubers.

I’m in favor of cutting down on sweets and processed grains. I’m not in favor of cutting down on carbohydrates from whole grain, legume, fruit and vegetable sources. Removing these foods from the diet, especially in favor of animal proteins, decreases soluble and insoluble fiber, micronutrients and antioxidants.

So, how does the keto diet fit into this? As I mentioned before, to truly enter ketosis, you have to drastically reduce your carbohydrate intake, anywhere from 30-50g a day as a maximum. Since the diet is based on when your metabolic shift happens, there isn’t a standard of ‘how much’ to follow.

Whatever your exact number ends up being, it’s almost impossible to get enough of these essential nutrients. High-protein and high-fat foods, especially of animal origin, don’t contain fiber (hello, gut health! More on that below), many vitamins or antioxidants. We need more plants in the diet, not less.

Weight Loss vs. Health

I think the main reason that a keto diet is so appealing is that when it comes to weight loss, it does work. This is true with most low-carbohydrate diets. Compared to other low-calorie diets, people tend to lose more weight on a low-carb diet in the first six months, though those numbers tend to even out over time.

We often equate weight loss with health, but that shouldn’t be the case. You can lose weight eating nothing but Pringles and diet soda, but you won’t be any healthier. I know that’s a hard argument to make when you see the scale continue to go down, but what’s happening on the outside is not always a reflection of what’s happening on the inside. Conversely, you can also gain weight eating nothing but ‘healthy’ foods.

I see this over and over again in my private practice. Clients who have spent decades on fairly low-calorie, processed diets and can’t understand why their blood results aren’t the picture of health. On the outside, they look like wellness role models, on the inside, they are just as unhealthy as my over-weight clients. Of course, I’m painting with a broad brush, but I think it’s important to dissect the difference between weight loss and overall health. Sometimes they overlap, but they don’t have to.

One of my thoughts on the ketogenic diet is that yes, it can help with weight loss, but that’s not everything. I’ve yet to see strong evidence that it helps reduce chronic disease and improve longevity as most of the research shows just the opposite.

I hate diets

When I bring up the idea of weight loss vs. health with my clients, the typical response I get is this, ‘What if I go on a keto diet (or other diet) to lose the weight and then start working with you for maintenance?’ As I mentioned before, my goal is not to convince you to eat a certain way. It’s to meet you where you are and help with your immediate needs.

I don’t advocate a diet plan that I don’t think is going to serve your overall goals, even in the short term, but I understand this desire. Overall, I hate diets. All diets. I don’t care if it’s Jenny Craig or Keto or some latest detox fad. I don’t like diets for several reasons, but I mostly don’t like that they don’t teach you the skills you need for a lifetime of a healthy eating.

I want to you to find an eating plan that’s sustainable. That doesn’t have to change based on various goals and can work across all stages of life. That criteria cuts out a lot of traditional fad diets; the ones that make you follow a certain plain but don’t provide skills for when the diet ends.

To me, the keto diet is the same way. It’s also why the weight loss tracking for individuals that follow a low-carb diet (in any form) evens out with other diets after just one year. Most agree that it’s because it gets harder to adhere to and follow the restrictions.

What about gut health?

I’m going to end with what I think is the most compelling reason not to follow a low-carb diet of any measure, keto included: gut health.

I truly believe that we are only in the infant stages of what we know about the role of the microbiome. In the past five years alone, the research has exploded, and we are learning more and more about connections we didn’t even think possible. Just this past month, I’ve attended presentations on the microbiomes role in heart disease, gene expression and the immune response.

Here’s what we do know. In order to feed the healthy gut flora, you need to give it food. While probiotics receive more attention these days, certain fibers are the workhorses in maintaining a healthy gut microbiome.

One study showed that adding more fiber to the diet can trigger a shift in the microbial profile, transitioning it from an obesity profile to that of a leaner physique. Another recent study shows that when microbes are starved of fiber, they can start to feed on the protective mucus lining of the gut, possibly triggering inflammation and disease. Research published last year in the journal Gut, showed a link between a low fiber diet and ulcerative colitis, a chronic bowel disease.

In particular, microbes feast on fermentable fibers, which come mostly from vegetables and whole grains, that resist digestion by human-made enzymes as they travel down the digestive tract. They arrive in the large intestine relatively intact, ready to be enjoyed by the microbes there.

The standard American diet is very low in fiber, averaging just 10-15 grams a day. This is well below recommended amounts of 30-35g a day, which is still a modest amount. Because of the very low carbohydrate parameters set forth for a keto diet, it’s almost impossible to get this much fiber without adding more vegetables, beans and whole grains. And, in the researched world of benefits, even the 30-35g a day is fairly low.

The quick take-away

Thought on the ketogenic diet? I don’t recommend it, not even in a short-term approach. While the evidence is there for quick-weight loss, that doesn’t pan out over the long-term. Additionally, there is a difference between weight loss and health, and the keto diet doesn’t inspire confidence in the latter. Most research continues to show that for longevity and reduced chronic-disease, eating a mostly plant-based, high-fiber is superior.


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Meet Alex Caspero

Alex Caspero is a Registered Dietitian, New York Times Bestselling Chef, and mom of two. She aims to cut through the nutrition noise by providing real-life, nourishing tips for body and mind. Learn more about Alex.

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    1. Joe/Peggyjo
      March 7, 2022 AT 9:49 am

      Thank you very much for your research and honesty. Was curious and thinking about purchasing the KETO diet plan but after reading your article, will stay with the plant based diet.
      May God Bless.

    2. Alameen
      July 9, 2020 AT 12:40 am

      Great article. Thoroughly enjoyed it. I especially liked the Blue zone link. Reminds me of the Green zone…. which is the location of the earth orbit around the sun and how it’s the sweet spot for our existence. Very informative. Has made me reevaluate a lot of my eating habits.

    3. Adam VanDusen
      September 20, 2018 AT 9:07 am

      I know this is an older post but I just wanted to share my story. I am all for a vegan diet or a Keto diet. I feel that mixing fats with sugar is the real reason that we have an obesity problem. I had blood work done before keto and 8 weeks into Keto. My cholesterol dropped 50 points and my triglycerides went from 324 to 170. I also lost 24 pounds in that time. I went from being newly diagnosed as diabetic to normal non-diabetic. My mother has lost over 100 pounds on a Keto “diet” and has stopped needing any medication at all. My exercise was consistent throughout with zero increase in activity. I have also found it really easy to make this life change as I no longer crave sugar(took about 3 weeks). I don’t know why we (vegan and keto) fight about which lifestyle is better when we should be focused on sugar being the main enemy of weight gain. Vegan is a good lifestyle, keto is a good lifestyle. SAD is BAD!

    4. Brianna Meghawache
      February 10, 2018 AT 3:55 pm

      Wow I love your posts! Looking forward to reading more! May I reference you when I blog about this on my site?

    5. Jan
      January 27, 2018 AT 7:53 pm

      Thank you! Excellent post! So happy to read about real science and common sense on the internet.

      1. Alex
        January 28, 2018 AT 10:35 am

        Thanks Jan!

    6. Linda
      November 26, 2017 AT 12:35 pm

      I have been a vegetarian for nearly 45 years (most of my life). I’ve also been vegan off-and-on during that time, for sometimes years at a time. However, high carb veg(etari)an eating didn’t help my weight. Late last year, my BMI was around 45. I embarked on a ketogenic vegetarian diet on January 1st. I’m down nearly 60 pounds (BMI: 34). Increasingly, my ketogenic diet is becoming more plant-based as I learn how to do that. And why does keto work for me? It drops my appetite to a manageable level, so I can consistently eat at a calorie deficit. It also helps attenuate cravings for refined carbs. I never binge anymore, when that was a regular occurrence several times a week pre-keto.

      1. Alex
        November 26, 2017 AT 3:09 pm

        Hi Linda, thank you so much for sharing your story. I love hearing about your experience, thanks for your comment.

    7. Gregory Stacey, MA RDN
      August 1, 2017 AT 10:18 am

      Another issues with the Keto diet is high intake of processed foods (oil). When on a Keto diet you cannot take in the requisite amount of fat from whole food sources (nuts, seeds, olives, coconut, avocado, etc….) as your carbohydrate and protein intake will increase too much and take you out of Ketosis.

      You are forced to take in oils. Of course, plant oils are superior to animal fats but ALL oils are processed foods and merely a remnant of the perfectly packaged whole food source.

      1. Alex
        August 1, 2017 AT 12:36 pm

        Hi Gregory- Yes! Such a great point. Thanks for including this.

    8. Stephanie C.
      July 27, 2017 AT 6:30 am

      I am so glad to see this. Almost every woman in my office is doing this and it is awful. They’re some big girls too, me being the thinnest (though still overweight). I’m working on weight loss, but I’m doing my best to take an intuitive approach this time, which sometimes means I’ll eat a doughnut. My choices are criticized daily and it has been difficult, seeing the weight drop off of them at a more rapid pace than mine. However, I remind myself that they had significantly more weight to lose in the first place (I’m overweight. They’re all morbidly obese.), and I’m doing it in a way that doesn’t leave me cranky, unhappy or craving things that I then eat and feel bad about, or feel the need to vilify to justify my refusal to consume.
      I follow several RD blogs and I’ve been hoping that someone would cover Keto, because in my head it didn’t make sense, but I don’t have the education to support my gut feeling. Reading this has confirmed my personal beliefs, backed with the science, education, and years of experience that I just don’t have. Thank you so much for taking the time to write this. I knew that what was going on around me wasn’t good for me, but having the hard nutritional facts makes it a lot easier to be comfortable with my decision.

      1. Alex
        July 28, 2017 AT 11:07 am

        Hi Stephanie, thanks so much for reaching out. I think that’s the hardest part with some of these fad diets, they can work for weight loss, but it doesn’t always mean it’s the healthiest approach. I try to explain that often with my clients, the difference between ‘weight loss’ and ‘health.’ Unfortunately, for many, the idea of weight loss is often more appealing than trying to change habits and mindset in a more sustainable way. I get that drive, but as I mentioned in this post, I don’t think going into ketosis is the way to do it. Keep doing what you are doing! Alex

    9. Erin
      July 26, 2017 AT 1:35 pm

      Great post! I would completely agree. Keto should be used as a therapeutic diet only, not for weight loss. I outwardly cringe when people tell me that they are trying a keto diet for weight loss. Not only is it possibly damaging to health, it’s just unsustainable. Not to mention, is there not research on this diet where study participants actually died? Very insightful, though. Thanks for sharing!

      1. Alex
        July 28, 2017 AT 11:09 am

        Ah! I didn’t hear about that one, gosh, so sad. Yes, it can be useful when used under careful monitoring, but not something I would recommend at ALL just for weight loss.

        1. Erin
          July 30, 2017 AT 10:28 am

          Oh I wish I could say this wasn’t true, but I just had a dialogue with a stranger on the internet whose daughter was prescribed a keto diet for weight loss by her PCP. It just about made me want to pull my hair out. Docs should absolutely be deferring to RD’s for their patients who need to lose weight through dietary means. Not to mention, this doc is probably not checking labs periodically while the patient is on this diet. That is what’s infuriating to me.

          1. Alex
            August 1, 2017 AT 12:45 pm

            Oh wow, that completely breaks my heart. For so many reasons… I completely agree- hopefully Mom will help get her the care that she needs. I’ve had a few clients recently come to me after their MD’s had prescribed a ‘paleo’ diet, a ‘vegan’ diet or a ‘keto’ diet. I know that we all mean well, but it often feels like some MD’s are just relaying what they think is best, without any follow-up or guidance.