The ketogenic diet is one of the most popular diets at the moment. There is a lot of buzz surrounding the diet, positive and negative. A popular negative myth is that a ketogenic diet is too restrictive to be sustainable (or healthy), as it cuts out an entire food group (carbohydrates). But while it does cut back on certain foods, a ketogenic diet is anything but restrictive if you approach it the correct way. For example, a ketogenic diet does not cut out carbohydrates completely.

Many people starting a keto diet may wonder about fruits and vegetables, as they do contain carbohydrates. Fruits and vegetables, which have many healthy advantages, help to round out and complete any ketogenic diet. This post will share what a ketogenic diet is and how you can still enjoy fruits and vegetables in order to keep the diet sustainable.

Scroll down to see a chart of the impact various fruits and vegetables may have on your blood sugar and ketone levels.

What is a ketogenic diet?

First, a ketogenic diet is a high-fat, moderate-protein and low-carbohydrate diet. The goal of the diet is to restrict carbohydrates in order to force the body to switch to the metabolic state of ketosis. Ketosis is an evolutionary mechanism that can occur in a fasting state or when carbohydrates are restricted. Nutritious fats are emphasized as the predominant source of energy, with fats making up 65 to 75% of daily calories in a ketogenic diet. This leaves protein at a moderate intake of 20 to 25% of daily calories and lastly, carbohydrate intake at 5 to 10% of daily calories. 

A ketogenic diet can be used to manage certain health conditions such as epilepsy, type 2 diabetes, insulin resistance and even some cancers such as gliomas. Recently, the most common use for a ketogenic diet is weight loss. When pursuing weight loss, many people who follow the diet focus on strict macronutrient ratios (of fat, protein and carbohydrates) to meet their specific goal. But it can be a big mistake to focus only on the macronutrient numbers and not on micronutrients and their importance in our overall diet. 

Micronutrients are the vitamins and minerals derived from the foods that we eat. Eating a well-formulated ketogenic diet is key to achieving both healthy macronutrient and micronutrient goals.

Sidebar: You can learn about the important micronutrients present in fruits and vegetables here and within LifeOmic’s new LIFE Extend app – browse the fruit and vegetable items in the Healthy Plants pillar within the app and learn more.

LIFE Extend app nutrition tracking pillar.
LIFE Extend app nutrition tracking pillar.

A well-formulated ketogenic diet is more sustainable

A well-formulated ketogenic diet is a nutrient dense diet that includes a variety of well-sourced plant products as well as animal products. It is mostly whole food based and includes a variety of well-sourced meats and animal fats, eggs, dairy, plant-based fats, nuts, seeds, vegetables and some fruit. Following these guidelines ensures variety, texture, flavor, unique plant-based antioxidants and an overall better mix of nutrient density that will make it more sustainable in the long run.

Fruits and vegetables have carbs, so how do they fit into a ketogenic diet?

Fruits and vegetables are a great addition to a ketogenic diet as they provide important antioxidants and micronutrients while minimally impacting insulin production. Fruits and vegetables can also provide fiber and prebiotics (a type of fiber) that can help to support a balanced and thriving intestinal microbiome. Some vegetables, especially dark leafy greens, above-ground and cruciferous vegetables, contain a minimal carbohydrate count while providing a good amount of fiber and water. 

There are two types of fiber: Insoluble and Soluble. Insoluble fiber stays intact in the digestive tract and aids in digestion and waste removal in the colon. Soluble fiber dissolves and becomes like a gel in the digestive tract. This helps to slow down digestion and can minimize food impact on blood glucose. Most vegetables have a large amount of insoluble fiber and small amount of soluble fiber. Fruit tends to have more soluble fiber than insoluble.

When fermented in the gut, insoluble fiber can possibly impact and contribute to the production of ketones. Our gut microbiota can break down fiber into short-chain fatty acids such as butyrate. Interestingly enough, the butyrate produced can be converted to the ketone body beta-hydroxybutyrate and therefore positively affect ketone levels in the body.

Glycemic Index, glycemic load and carb count: Which one matters more?

While eating a ketogenic diet, it is important to take into account the amount of carbohydrates being consumed as ketosis occurs in the absence of carbs. What about glycemic index or glycemic load? You may have occasionally heard these two terms, but what do they mean and if you are already restricting carbohydrates, do they matter? 

Glycemic Index

The glycemic index (GI) of a food is a numerical measurement of the impact that a carbohydrate in that food can potentially have on an individual’s blood glucose level and the extent to which it can raise this level. The scale is numbered from 0-100, with pure sugar being ranked at 100. Carbohydrate-containing foods that are ranked high on the GI scale are digested and metabolized rapidly, resulting in a higher fluctuation in blood glucose levels. Low GI carbohydrates provide a smaller blood sugar fluctuation as they are digested and metabolized slowly. Carbohydrates that rank a 70 or higher are considered high on the GI scale while carbohydrates that rank below 55 are considered low on the GI scale. 

One of the issues that researchers have had with the glycemic index is that it can only tell us one part of the whole picture. Glycemic index is determined by feeding ten or more healthy people a portion of food containing 50 grams of carbohydrates and then measuring the effect on their blood glucose levels over the next two hours.

This may not be the most valid, real-world measure of the impact of the food on blood sugar levels, as 50 grams of carbohydrate of a particular food is not always the typical portion size. It also does not take into account the individual. The effect of food on blood glucose can vary from individual to individual and can also be affected by other factors such as hormones, exercise, medications and activity. 

Glycemic Load

Measuring glycemic load (GL) may be a more accurate picture on how a food can affect your individual blood glucose levels. The GL of a food takes into account the total amount of carbohydrate in and portion size of a food that you will be consuming. A numerical value of 20 or higher is considered a high GL while 10 or lower is considered low. 

Any diet that contains foods that are low in glycemic index and glycemic load is beneficial in the prevention and management of metabolic diseases such as diabetes and cardiovascular disease. Therefore, it can be beneficial to look at both glycemic index and glycemic load in addition to carbohydrate count. 

Here is an example of how glycemic index, glycemic load and total carbohydrate count can all come together: One medium apple has a glycemic index of 38 (low), a glycemic load of 6 (low) and a total carb count of 25 grams (21 net). 

Here is an example of a food with a high glycemic index and how different the glycemic load can be: A cup of chopped watermelon has a high glycemic index of 72, but this serving is considered low in terms of glycemic load with a numerical score of 3. Total carbs for a cup of chopped watermelon is also low at 10 grams total. 

So while the carbohydrates in watermelon may be digested and used as energy in your body more quickly than the carbohydrates in an apple, you may consume fewer carbohydrates with a serving of watermelon than in an apple.

Choosing the right carbs to eat on a ketogenic diet

While the carb count in the apple example above may be on the higher end, it is important to assess your own personal carbohydrate tolerance while eating a ketogenic diet. Ketosis can be achieved differently for every person and the total carb count one can consume while remaining in ketosis can vary anywhere from 20 grams to 50 grams per day.

Fruits and vegetables contain fiber and fiber moderates the rate at which their natural sugars enter your bloodstream. A food that contains a moderate amount of carbs but ample amounts of fiber (usually low GI) can minimally impact ketosis and ketone production. Conversely, a food with the same amount of carbs but a lower amount of fiber, and that is high on the glycemic index, may negatively affect ketosis and ketone levels.

To find your own personal limit, you can experiment with adding in more of the suggested carbohydrates slowly over time and check your ketone levels regularly using a blood ketone meter such as Keto-Mojo.

Glyemic load and carb count of various fruits and vegetables.
Glycemic load and carb count of various fruits and vegetables.

Many fruits and vegetables can fit into a ketogenic diet

You can safely fit a variety of fruits and vegetables into a ketogenic diet while staying under the 50 grams per day threshold of carbohydrates. Fruits and vegetables contain fiber and water while keeping carbs low, so feel free to thoroughly enjoy them alongside other nutrient-dense low carb foods such as nuts and seeds. Here is an example list of fruits and vegetables that you can enjoy on ketogenic diet while taking into account the glycemic index and glycemic load:

  • Apricot (1 apricot, GI = 32)
  • Asparagus (1/2 cup, GI = ~15)
  • Avocado (1 whole, GI < 30)
  • Broccoli (1 cup, GI = ~10
  • Blackberries (1/2 cup, GI = 40)
  • Blueberries (1/2 cup, GI = 53)
  • Brussels Sprouts (1 cup, GI < 10)
  • Cabbage (1 cup, GI < 10)
  • Carrots (1 cup, GI = 35)
  • Swiss chard (1 cup, GI < 10)
  • Cucumber (1/2 cup, GI = ~15)
  • Kale (1 cup, GI < 10)
  • Romaine Lettuce (1 cup, GI < 10)
  • Mushrooms (1 cup, GI = ~10)
  • Peach (1 medium, GI = 28)
  • Peppers (1 cup, GI = 40)
  • Spinach (1 cup, GI < 10)
  • Strawberries (1/2 cup sliced, GI = 40)
  • Tomato (1 cup, GI = 15)
  • Zucchini (1 cup, GI = ~15)
  • Raspberries (1/2 cup, GI < 40)

A large salad with a mix of the above that combines high-fat plants (avocado, coconut, olives and/or their oils) and/or a clean animal protein is a great example of a well-formulated ketogenic meal. I personally love eating sliced avocado, cauliflower roasted in avocado oil and a side of grass-fed beef.

A well-formulated ketogenic diet is one that is nutrient-dense and will offer a safe and sustainable approach to overall health. The goal is to limit carbohydrate sources, not to be afraid of them, especially those that are plant-based.