It’s one of the simplest joys of summer—watermelon. With its vibrant red flesh, ultra-refreshing texture, and promise of cool relief, it’s a seasonal favorite.

We love it sliced, cubed, or blended into smoothies. But behind its image as a “healthy” fruit lies a lesser-known effect on the body—particularly on blood sugar levels.

A Sneaky Spike in Blood Sugar?

Long praised as a weight-loss-friendly fruit thanks to its high water content and low calorie count, watermelon makes a comeback on every table once temperatures rise. But recent studies are raising eyebrows: this sweet and seemingly innocent fruit can cause a rapid spike in blood sugar—sometimes even sharper than that caused by white sugar.

Why? Because watermelon contains very little fiber and virtually no fat or protein—the very elements that usually help slow down sugar absorption. The result: once it hits your mouth, its natural sugars (glucose + fructose) are absorbed quickly, causing a sharp metabolic spike—especially in people over 50 or those with insulin sensitivity.

A Surprisingly High Glycemic Index

Watermelon’s glycemic index (GI) ranges from 72 to 80 depending on the variety, putting it firmly in the “high GI” category. For comparison, apples have a GI of 38, strawberries 41, and white sugar sits around 65.