A person can eat watermelon on a keto diet, as long as they make sure the carbohydrate content fits within their desired macronutrient ratio.

Watermelon is rich in nutrients and can hold a lot of water. For this reason, they are a suitable fruit for maintaining hydration and overall health.

However, as with all fruits, watermelons naturally contain sugars. Therefore, people following a ketogenic diet may worry that eating watermelon could take them out of ketosis, the metabolic process that burns fat instead of carbs.

A ketogenic, or keto, diet is an eating plan containing high amounts of fat, moderate amounts of protein, and very low amounts of carbohydrates.

As sugars are carbohydrates, it is reasonable to assume that watermelons are not keto-friendly.

This article will provide some nutritional information about watermelons and discusses their proper place in a ketogenic diet. It will also list some keto-friendly fruits.

Is watermelon keto? A close-up of watermelons which can be consumed as part of a keto dietShare on Pinterest
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Watermelons contain many different nutrients.

Vitamin C

One cup of diced watermelon provides 21% of a person’s daily requirement of vitamin C. This is an antioxidant that helps the body maintain healthy tissues, blood vessels, and bones. It also assists in forming collagen, healing wounds, and absorbing plant-based iron.

Vitamin A

A cup of diced watermelon also contains around 17% of a person’s daily vitamin A requirement. This helps maintain the immune system and keeps the skin and eyes healthy, among other essential functions.


Red-fleshed watermelons contain high levels of lycopene. This carotenoid antioxidant, which is also in tomatoes and pink grapefruits, gives these fruits their reddish color.

Importantly, lycopene may help protect the body against heart disease and many forms of cancer.


According to the Department of Agriculture, those following a keto diet should note that 1 cup of diced watermelon also contains around 11 grams (g) of net carbohydrates.

Net carbohydrates are the carbohydrates the body actually absorbs from a food source. Within foods, they are the total amount of carbohydrates minus the fiber it contains since fiber is an indigestible form of carbohydrate.

One cup of diced watermelon has 11 g of net carbohydrates because it contains 11.6 g of total carbohydrates and around 0.6 g of fiber.

Ketogenic diets heavily restrict the amount of carbohydrates that a person can eat in a day. In a typical ketogenic diet that restricts carbs to 5–10% of total calories, a person who consumes 2,000 calories a day will only eat between 20–50 g of carbohydrates daily.

This means the amount of watermelon a person can eat on a keto diet while staying in ketosis depends on how restrictive their diet is.

For example, 1 cup of diced watermelon would make up more than half of an individual’s daily carbohydrates if they are aiming for only 20 g of carbs per day.

If a person is aiming for around 50 g of carbs per day, then 1 cup of diced watermelon comprises 23.2% of their daily carbs.

Therefore, there is no conclusive answer to the question of whether watermelon is keto-friendly. A person can eat watermelon and other fruits while staying in a state of ketosis, depending on what else they eat in a day and their daily carbohydrate target.

Whether they remain in ketosis will depend on the macronutrient ratio they are aiming to achieve, as well as what else they want to eat on a given day.


One cup of diced watermelon contains 46 calories. According to a 2019 study, diets that include fruit with high levels of water and fiber could help a person maintain a moderate weight.

The paper suggests that watermelon can promote a feeling of fullness, which researchers call satiety, as its high water content gives it a low energy density proportionate to its volume when compared with many other fruits.

As many people who follow a keto diet do so for weight loss, the high satiety to volume ratio that watermelon provides makes it additionally beneficial.

The most keto-friendly foods are low in net carbohydrates. Many fruits are high in carbohydrates, including fiber and natural sugars. However, some of the more keto-friendly options include:

  • Avocados: Contain around 8.53 g of net carbohydrates per 100 g.
  • Tomatoes: Contain around 3.89 g of net carbohydrates per 100 g.
  • Blackberries: contain around 9.61 g of net carbohydrates per 100 g
  • Strawberries: Contain around 7.68 g of net carbohydrates per 100 g.
  • Peaches: Contain around 10.1 g of net carbohydrates per 100 g.

By comparison, 100 g of watermelon contains around 7.5 g of net carbohydrates.

The ketogenic diet is gaining in popularity. Recently, many people have become interested in severely limiting their daily intake of carbohydrates, usually with the aim of losing weight.

However, it is worth noting that the ketogenic diet can be quite extreme.

Healthcare professionals initially developed the diet as a treatment for epilepsy in children. The average American diet consists of around 55% carbohydrates, while the Institute of Medicine recommend that 45–65% of daily calories come from carbohydrates for a healthy diet. Many keto plans require a person to limit their daily carbs to 5–10% of their total calories, based on a diet of 2,000 calories a day.

There is also some evidence that ketogenic diets can have unwanted short-term effects. These include:

Doctors sometimes refer to these symptoms as “keto flu.” However, they bear no relation to the influenza virus and usually disappear after a few weeks on the diet.

There are also other long-term effects from the diet that may last longer than 2 years, including:

  • various vitamin and mineral deficiencies
  • fatty liver disease
  • kidney stones

Importantly, scientists do not yet know whether keto diets are beneficial for health. This is because dietary science is complex and influenced by many factors. Scientists must conduct long-term studies before drawing conclusions.

Many different factors play into a person’s health. For this reason, it can take a long time for scientists to work out the real effects of a given diet.

Watermelon can be keto-friendly if people eat it in moderation. This rule holds true for many other fruits.

Generally, anyone considering a ketogenic diet should first seek the advice of a doctor, registered dietitian, or both.

This is especially important for people with diabetes, as sudden shifts to a ketogenic diet could cause hypoglycemia.