The Misconceptions of the Ketogenic Diet

by Amylee Amos PhD, RDN, IFMCPNutrition
Sliced avocado

There’s always some new diet trend, and at the moment it’s the Ketogenic Diet that’s making headlines. I constantly see articles from nutritionists, physicians, even food bloggers talking about the ‘keto’ diet. Their opinions seem to run the gamut- the ketogenic diet is either going to save your life and cure you of all that ails you...or it’s going to kill you. What gives? Why so much controversy? Probably because most of the people talking about the ketogenic diet are misguided in their approach. Let's break it down.

Before I get into it, let me make one clear distinction. In general when we talk about diets, we’re talking about food plans. Think, the Mediterranean diet. Lots of vegetables, legumes, olive oil, and fish. Very minimal red meat, sweets, and processed foods. We’re talking about food.

Think, the paleo diet. Lots of wild meats, vegetables, nuts and seeds. No grains, legumes or refined sweets. Again, we’re talking about food.

Now think about what you know of the ketogenic diet. If the words ‘fat’ and ‘carbohydrate’ come to mind, you are already identifying the problem. Fats, carbohydrates, and proteins are not foods. They are macronutrients, which are the building blocks of foods. It's great to know about them and talk about them, but we don’t eat macronutrients in singularity, we eat foods.

Part of the trouble with and the controversy behind the ‘ketogenic diet’ is that it’s not a meal plan- what we’re talking about is not food, it’s metabolism. The term ‘ketogenic’ refers to the physiological state of ketosis.

What is Ketosis?

The goal of a ketogenic diet is to put your body in a state of ketosis. Ketosis refers to a metabolic state of burning through fats as a fuel or energy source. The word ‘ketosis’ comes from the term ‘ketone bodies’ which are produced when the body metabolizes fatty acids to be used as energy. Ketones are produced when the body undergoes a process called beta oxidation, which is cellular fat usage- a normal physiologic process (1). When we consume a wide range of foods, and the body breaks them down into the smallest forms of carbohydrates, fats, and proteins that they're made of, the body chooses to use the carbohydrates as energy. This is our primary fuel source. Carbohydrates, meaning simple starches and sugars, but also fruits and vegetables, are broken down into glucose molecules and used as energy. We store some carbohydrate in our liver in the form of glycogen, and the body is able to use that storage when there isn’t a fresh stream of carbohydrate coming in from food, but we primarily use carbohydrate that we are actively consuming through our diet.

Metabolic Flexibility

Only when the carbohydrates in the diet are insufficient to fuel the body, will our metabolism flip into ketosis and use the fats as energy. Our bodies are designed to be able to transition between these two types of metabolism: lipid (fat) based metabolism and glucose (carbohydrate) based metabolism. In times of famine we are able to maintain ketosis by burning through our body fat stores, but even throughout the day our bodies are designed to be able to switch between using carbohydrate as fuel and fat as fuel. So ketosis is just as natural as running off carbohydrate throughout the day - in fact, breastfed babies are often in ketosis because of the fat content in breast milk (2). My point is, ketosis is a very natural metabolic process.

The issue is, for the most part, we are not transitioning fluidly between carbohydrate and fat metabolism. Or in other words, we are not metabolically flexible. We are firmly stuck in a carbohydrate based metabolism. Think about the last time you ate your standard American diet lunch of a PB&J on white, Diet Coke, and a bag of chips around 12pm, but then felt starving and lethargic around 3pm. Your body had burned through the processed, simple carbohydrates from lunch and because it wasn’t able to efficiently flip into fat burning mode, it sent a message to your brain to get more carbohydrate. Our western diet and sedentary lifestyle have caused us to become metabolically inflexible. In healthy metabolism when we are metabolically flexible, the body is able to efficiently use carbohydrate as energy when it’s present, and fat when carbohydrate is not present (3). In other words, the body should be able to flip in and out of ketosis throughout the day. A nutrition plan that helps induce a state of mild ketosis (or for the sake of clarity, a good ketogenic diet), when done properly, can help retrain the body into a state of metabolic flexibility.

My point in loading you up with all of this physiology is to explain that ketosis is a physiological state. It’s not a group of foods. In order to achieve a state of ketosis you need to be eating a diet rich in fat and lower in carbohydrate. Again, those are macronutrients- not foods. There are many ways to eat a diet high in fat and lower in carbohydrate. Doing this can be health promoting or disease causing. And the same is true of every other macronutrient distribution you can think of!

The Ketogenic Diet

The ketogenic diet is often portrayed as a meal plan made up of coconut oil, butter, and bacon (which, as I'll show you, does not need to be the case). When you start googling the ketogenic diet online, you’ll hear a lot about the macronutrient breakdown. Scanning the internet to write this article, I found websites stating that the keto macronutrient breakdown is 75% fat, 20% protein, and 5% carbohydrates. Other sites educate about the strict 50 grams of carbohydrates per day rule.

These numbers are all so arbitrary. When was the last time you calculated out your macronutrient breakdown? Probably never. And even if you did start calculating it- you’re eating food, not macronutrients, so what do you think is the likelihood that everyday your macro breakdown would be the same? Probably not likely. And for all of these people on the ketogenic diet- are they actually in ketosis? Are they measuring their ketone levels? How do you know that a state of ketosis has been achieved?

A nutrition plan that helps the body achieve a state of metabolic flexibility is optimal. For many people, because our bodies are stuck in the rut of the high refined carbohydrate, standard American diet, a mildly ketogenic diet can be beneficial. But the way we eat to achieve mild ketosis is of the utmost importance. For reasons regarding optimizing cognition, many of my clients eat to achieve a state of mild ketosis. And yet the meal plan they follow is predominantly plant based. They eat a wealth of nutrient packed vegetables (the goal is 10-15 servings per day!). They do this and yet throughout the day they are in mild, nutritional ketosis. If you’ve read even a handful of the blog posts out there about a ketogenic diet- you’re probably thinking I’m full of it. But my clients actually test their blood ketone levels. They use small meters that measure their levels of beta hydroxybutyrate (BHB), which is a type of ketone. So even with all of these vegetables, they are still objectively in ketosis. They eat adequate (but not too much) protein (4), like small low mercury fish, eggs, tofu or tempeh, and grass fed or wild meats. And, of course, they eat a rich amount of healthy fats, such as high polyphenol olive oil, nuts, seeds, avocados, olives, and sometimes coconut or MCT oil. My clients often eat as much as 100 grams of carbohydrates per day- the difference is they’re choosing the right kinds of carbohydrates (from a variety of colorful vegetables!).

This is the biggest issue with the controversy surrounding the ketogenic diet- we’re not all doing it the same way. We know that a diet rich in vegetables is optimal for health. A ketogenic diet can be exceedingly rich in vegetables (again, 10-15 servings of vegetables per day!). It just comes down to what kind of carbohydrates you eat, what kind of fats you eat, and what kind of proteins you eat. Done properly, you can achieve ketosis following a nutrition plan very similar to the widely proclaimed Mediterranean diet.

This is a plant based, whole foods diet, meaning a nutrition plan made up of mostly plant foods with other whole, nutrient rich foods. This nutrition plan allows people who need mild ketosis for health achieve that state, and at the same time it is anti-inflammatory, pro-longevity, and nutrient dense way of eating(4).

What’s the Takeaway?

All in all, if you’re looking to achieve mild ketosis, do so in a healthy way. Don’t sacrifice other factors (like nutrient density from all those plants) for ketosis. Follow a plant based diet, rich in non-starchy vegetables, adequate proteins, and lots of healthy fats. Above all, eat whole foods and avoid the keto products. (Like all energy bars, some of the keto bars can be just as bad for you as a Snickers.) If you want to be serious about maintaining mild ketosis, measure your ketones so that you can be certain you are in the proper range. Pair your plant based, whole food nutrition plan with other healthy lifestyle modifications that increase ketosis, such as regular physical activity and intermittent fasting.

To my knowledge the primary argument of nutrition experts against a ketogenic diet is the limiting of vegetables. I argue, that restriction of vegetables to maintain mild ketosis is not only unnecessary, it's dangerous. The fact is, you can and should be eating plates of vegetables and still be able to maintain mild ketosis if you want to/need to.


  1. Fukao, T., Lopaschuk, G. D., & Mitchell, G. A. (2004). Pathways and control of ketone body metabolism: on the fringe of lipid biochemistry. Prostaglandins Leukot Essent Fatty Acids, 70(3):243-51.
  2. Wu PY, Edmond J, Auestad N, et al. (1986). Medium-chain triglycerides in infant formulas and their relation to plasma ketone body concentrations. Pediatr Res, 20(4):338-41.
  3. Galgani, J. E., Moro, C., & Ravussin, E. (2008). Metabolic flexibility and insulin resistance. American Journal of Physiology - Endocrinology and Metabolism, 295(5), E1009–E1017.
  4. Levine, M. E., Suarez, J. A., Brandhorst, S., Balasubramanian, P., Cheng, C.-W., Madia, F., … Longo, V. D. (2014). Low Protein Intake is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell Metabolism, 19(3), 407–417.