Watermelon: What Is The Glycemic Index?

Watermelon glycemic index GI

What is the glycemic index of watermelon? Can you eat watermelon if you have high blood sugar? Does watermelon raise blood sugar levels? Does watermelon lower blood sugar? How much watermelon can you eat? Can you make watermelon lower glycemic? And which is the best watermelon color to eat?

What is the glycemic index?

The glycemic index is a scale that measures the effects of foods on blood sugar levels. More exactly, the glycemic index determines how much the carbohydrates in food raise blood sugar levels. Designed as a numerical scale, the glycemic index assigns numbers to foods based on their effects on blood sugar. The number assigned to a food is referred to as the glycemic index score or value, or GI score or value.

Watermelon glycemic index

The glycemic index goes from 0 to 100, 0 being the lowest value which indicates minimal to no effects on blood sugar and 100 being the highest value represented by the pure sugar glucose whose glycemic impact is maximal. Foods ranked 0 to 55 are low glycemic index or low GI. Foods with a score of 56 to 69 are moderate glycemic index or moderate GI. Foods with a score of 70 and up to 100 are high glycemic index or high GI.

To achieve good blood sugar control and not experience spikes in blood sugar levels and associated fluctuations in energy levels, you have to eat predominantly foods that are low glycemic. Low-glycemic foods affect blood sugar the least and are preferred in a generally healthy diet. Conversely, high glycemic foods affect blood sugar to great extents and are best consumed infrequently and in small amounts. Find out more about the glycemic index.

Glycemic index of watermelon

Watermelon is classified as a high glycemic index food and is one of the few fruits that are high GI. The glycemic index of watermelon is 72, an average value estimated for all varieties of sweet watermelon, including pink and red, yellow watermelon, white watermelon and orange watermelon. While generally seen as a healthy fruit, and full of benefits for health, watermelon has a significant impact on blood sugar levels.

Watermelon glycemic index GI

Why is watermelon high glycemic?

What makes watermelon a high glycemic food is not purely its content of carbs or sugar. Watermelon only has 7.55 grams of carbohydrates per 100 grams of fruit and just 6.2 grams of these are sugars. The content of carbs and sugar is quite low for a fruit, especially one as sweet as watermelon.

By comparison, sweet cherries have 16 grams of carbs for every 100 grams of fruit of which 12 to 13 grams are sugars, and cherries glycemic index score is one of the lowest of all fruits: 20 to 25. Similarly, nectarines have 9.4 grams of carbs per 100 grams of fruit and 8.4 grams of these are sugars, more than watermelon. Yet the glycemic index score of nectarines is only 40, a lot lower than that of watermelon.

The difference is cherries and nectarines have more dietary fiber to limit the glycemic effects of digestible carbohydrates. Dietary fiber slows down digestion and the rate of sugar absorption into the bloodstream, lowering the glycemic impact of foods.

Watermelon is naturally very low in dietary fiber with just 0.4 grams of fiber per 100 grams, and high in water at over 91 grams of water per 100 grams. There is little in it to slow down the rate of sugar absorption into the bloodstream, hence the higher glycemic impact and high GI score.

Does watermelon raise blood sugar?

Eating watermelon raises blood sugar levels quickly and measurably. The fruit provides digestible carbohydrates and simple sugars, and very little fiber, fat or protein to slow down the rate of sugar absorption into the bloodstream. Despite not actually being high in carbs or sugar, the small amounts that you do get from the fruit get absorbed quickly and raise blood sugar levels just as quickly.

Watermelon glycemic score per servingĀ 

The effects of watermelon on blood sugar are directly proportional to intake. That is, how much watermelon you eat at once determines how much it will raise your blood sugar levels. This is known as the glycemic load which is a numerical scale similar to the glycemic index, but which considers serving size when estimating the glycemic impact of a food.

That means that the more watermelon you eat at once, the higher the rise in blood sugar levels. Conversely, the smaller the serving size, the more limited the effects on blood sugar.

Can you eat watermelon with diabetes?

Even fruits that are high glycemic such as watermelon, bananas and cantaloupe are permitted in a diabetic diet. The only rule is to eat small amounts at once. Small portion sizes compensate for the high glycemic index scores as they limit how many carbs and how much sugar you get from the fruit and reduce the effects of the fruit on blood sugar levels. So you can eat watermelon even if you have diabetes, and still enjoy good blood sugar control, so long as you only eat small amounts at once.

How to lower the effects on blood sugar of watermelon

If you want to enjoy good blood sugar control and prevent fluctuations in blood sugar levels, but still eat watermelon, then there are some tips that can help you!

  1. Have small servings of watermelon to limit you carbohydrate intake and prevent spikes in blood sugar.
  2. Eat one serving of fruit at a time to avoid carbs cumulating and raising blood sugar levels too much.
  3. Avoid eating watermelon on an empty stomach – an empty stomach will digest the carbs in the fruit quickly and absorb the sugars obtained from them just as quickly, resulting in a fast rise in blood sugar levels.
  4. Eat watermelon after a meal consisting of lean protein and low in carbs to enjoy macronutrient balance and satiation and reduce the glycemic impact of the fruit.
  5. Have your watermelon with a source of lean protein or fat such as a few raw nuts and seeds – the protein and fat in raw nuts and seeds slows down digestion and the absorption of sugar into the bloodstream, reducing effects on blood sugar.