Since a vegetarian ketogenic diet is limited to dairy, eggs, nuts, seeds, vegetables, some low carb fruits, and nutrition supplements, it is quite difficult to follow. Has anyone survived a vegetarian ketogenic diet for more than two months?
Let's start by defining the ketogenic diet.
What is a ketogenic diet?
In today's language, a ketogenic diet is any diet plan that pushes the human body into ketosis, a state where ketones are produced. In this state, the body obtains much of its energy from metabolism of dietary fat.
The ketogenic diet (KD) was originally introduced in the 1920s as a therapeutic diet for adults with epilepsy, and that diet required a 4:1 ratio of fat (in grams) to protein plus carbohydrates (in grams). Because a gram of fat provides much more energy than a gram of carbohydrate or protein, the corresponding energy intake ratio would be 9:1 (90% energy from fat). Assuming energy intake of 2000 kcal/day, this diet would include 200 grams fat (1800 kcal), about 40 grams protein (160 kcal) and 10 grams total carbs (40 kcal).
It is not possible to satisfy protein requirements if total carbs are limited to 10 grams/day and only vegetarian foods are consumed.
Since most people aren't presenting with epilepsy and modern interest in the ketogenic diet is motivated by other factors, many people have embraced a more relaxed variant called the Modified Atkins Diet which allows up to 20 grams of net carbs per day. (Dietary fibre is not included when counting net carbs). This is important when trying to include plant-based foods in a ketogenic diet because unlike meat, many plant foods are rich in dietary fibre.
We'll call the diet ketogenic if the daily net carb intake is less than 20 grams.
Can I get enough energy on a vegetarian ketogenic diet?
It may be difficult to obtain sufficient energy on a diet which excludes meat and also limits net carb intake to 20 grams. To answer this question, let's devise a number we'll call the Keto Energy Score (KES) which is the ratio of kcal (energy) to net carbs.
If we need to consume at least 2000 kcal per day, while limiting net carbs to 20 grams per day, then our diet needs to have a KES of 100 or higher. (2000/20 = 100). Any foods that have a KES higher than 100 can be included without limitation. Foods with KES less than 100 need to be limited, otherwise net carbs will exceed 20 grams per day and the diet won't be ketogenic.
To find the KES for any food, divide the energy (in kcal) by the net carbs (in grams). Let's consider some examples below.
KES higher than 100
These foods all definitely fit into a ketogenic diet because their KES is greater than 100, so eat as much as you want. These form the basis of a vegetarian ketogenic diet.
- flax seed (> 100)
- hemp heart (> 100)
- vegetable oil (> 100)
- margarine (> 100)
- butter (> 100)
- whole chicken egg (> 100)
- cheddar cheese (> 100)
These foods can be included sparingly on a ketogenic diet, but they do not form the basis of the diet. Everything in this category must be balanced by also eating something from the first category.
- coconut (85)
- avocado (85)
- almond (60)
- egg white (73)
KES < 50
These foods have a very low KES (Keto Energy Score) because they have a higher quantity of carbohydrates. These must be almost entirely avoided on a ketogenic diet because even a few dozen grams will push daily net carbs over the 20 gram limit.
- tofu (40)
- nutritional yeast (45)
- peanut butter (36)
- whole cow's milk (12)
- broccoli (9)
- sweet bell pepper (8)
- blueberries (5)
- potato (5)
Is it healthy for a lacto-ovo vegetarian to follow Ketogenic diet?
Looking at the results above, it's pretty clear that cheese, and eggs would be very important components of a lacto-ovo vegetarian ketogenic diet because they become the main source of protein. Without these, the diet would be composed of mostly refined oils. (So it would be all but impossible to be healthy on a vegan ketogenic diet that excluded cheese and eggs.)
But even allowing for a pound of cheese and a dozen eggs every day, it would still be very challenging to stay healthy on this diet. Vitamins B1, B3, and B12 would all be in short supply. It would also be difficult to meet requirements for trace minerals copper, iodine, magnesium, manganese, and potassium. There isn't much space in the diet to include other foods, so a multi-vitamin and other supplements would quite likely be necessary to meet recommended daily intake for all nutrients.
It also seems impossible to get anywhere close to the recommended daily intake for dietary fibre (30 grams/day) while following any ketogenic diet, but that isn't unique to vegetarians.
TL;DR No, it is not healthy for a vegetarian to follow a ketogenic diet.
But what about...
Maybe you saw or heard about somebody who said they were doing vegan keto.
- Thomas DeLauer on YouTube posted this apparently "vegan+keto chili" recipe but if you break it down, it has 29 grams of net carbs (52 grams total carbs!) and only 400 kcal which isn't even close to keto (KES=14). Later he suggests relying on flax, chia, coconut, coconut yogurt, high quality low-soy vegan cheese, artichoke, asparagus, nutritional yeast. Of those, only flax seeds (KES>100) properly count as keto. To provide 2000 kcal on those other foods would include somewhere between 32 and 362 grams of net carbs (86 - 450 g total carbs) depending on the actual mix. He says in the video it was only barely possible by eating a lot of protein powder every day. The fact that he measured ketone bodies in his bloodstream was more suggestive of actual starvation than simulated starvation.