Blood Sugar & Watermelon

Carbohydrates in Watermelon

Carbohydrates are what tend to make your blood sugar levels increase after meals, with the exact effect varying based on the food and what you eat with it. Watermelons are made up of 8 percent carbohydrates by weight, all but 2 percent of which consists of sugars. A 1-cup serving of cubed watermelon contains 11.5 grams of carbs, including 0.6 grams of fiber and 9.4 grams of sugars.

Glycemic Index

You can use the glycemic index to estimate how much of an effect a food will have on your blood glucose levels. Foods that have a glycemic index score of 55 and under are low on the glycemic index, while those with a score of 70 or over are high on the glycemic index. Although many fruits are low on the glycemic index, watermelon has a glycemic index of 72, so it is likely to cause your blood sugar levels to spike after you eat it, especially if you eat it by itself.

Reasons for Watermelon's Effect on Blood Sugar

Watermelon doesn't contain starch and only contains a small amount of fiber, so the sugars in watermelon are quickly digested. Certain sugars are also more likely to increase blood sugar levels than others, according to an article published in "The Journal of Nutrition" in April 2009. The sugars in watermelon consist of 54 percent fructose, 25 percent glucose, 20 percent sucrose and 1 percent maltose. While fructose has little effect on blood sugar levels since it has a GI of 23, glucose, with a GI of 100, increases them. Sucrose has a moderate effect, with a GI of 65.

Minimizing the Effect on Blood Sugar

While watermelon may cause blood sugar spikes if you eat it alone, you can minimize this effect by eating a smaller amount of watermelon and by eating it along with foods that don't increase your blood sugar levels, including foods that are low on the glycemic index and foods that don't contain much carbohydrate. Consider making watermelon salsa to serve along with chicken or pork or adding it to a salad along with goat cheese, nuts and greens.