Butternut squash is a starchy vegetable. It belongs to the winter squash family, which falls into the same dietary category as potatoes, corn, and peas. One cup of cooked butternut squash contains about 22 grams of carbohydrates, a significant portion of which comes from starch. That said, it sits on the lighter end of the starchy vegetable spectrum, with fewer calories and more fiber than most of its counterparts.
Why Butternut Squash Counts as Starchy
Vegetables are generally split into two camps: starchy and non-starchy. Non-starchy vegetables like broccoli, spinach, and bell peppers tend to have very few carbohydrates per serving, usually under 5 grams per cup. Starchy vegetables pack considerably more, and butternut squash clears that threshold easily. A cup of raw butternut squash cubes has about 16 grams of carbohydrates and 2.8 grams of fiber. Once cooked, that number climbs to around 22 grams of carbs per cup, with 7 grams of fiber.
Johns Hopkins lists winter squash (including both butternut and acorn varieties) alongside potatoes, corn, and peas as common starchy vegetables. This classification matters most for people managing blood sugar, counting carbs, or following meal plans that treat starchy vegetables differently from leafy greens or cruciferous vegetables.
How It Compares to Potatoes
Butternut squash is starchy, but it’s not in the same league as a potato. A cup of cooked butternut squash delivers 82 calories and 22 grams of carbs. A medium baked sweet potato, for comparison, has 103 calories and 24 grams of carbs. A russet potato runs even higher, typically landing around 160 calories and 37 grams of carbs per medium potato.
The fiber content is where butternut squash really separates itself. Those 7 grams of fiber per cooked cup are unusually high for a starchy vegetable and help slow digestion. This means the starch in butternut squash doesn’t hit your bloodstream as quickly as the starch in a white potato would. If you’re looking for a lower-calorie swap for potatoes that still feels satisfying and substantial, butternut squash is one of the better options.
Blood Sugar and Glycemic Impact
Boiled butternut squash has a glycemic index of 51, which falls in the low range. For context, foods with a GI under 55 are considered low, meaning they raise blood sugar gradually rather than causing a sharp spike. White potatoes, by comparison, often land between 70 and 90 on the glycemic index depending on preparation.
The combination of moderate starch, high fiber, and a low glycemic index makes butternut squash a reasonable choice for people with diabetes or insulin resistance. It still raises blood sugar more than non-starchy vegetables would, so portion awareness matters. But it behaves quite differently in the body than refined starches or even other starchy vegetables like white potatoes and corn.
Butternut Squash on Low-Carb Diets
Whether butternut squash fits into a low-carb or ketogenic diet depends on how strict your carb targets are. A half-cup serving contains about 12.6 grams of total carbs and 8.7 grams of net carbs (total carbs minus fiber). On a standard keto diet with a 20 to 25 gram daily net carb limit, even a half cup takes up a significant portion of your budget.
For moderate low-carb diets that allow 50 to 100 grams of net carbs per day, butternut squash fits comfortably. It works well as a side dish or added to soups and stews in controlled portions. Many people on low-carb plans use it as a substitute for higher-carb starches like pasta, rice, or potatoes, since a serving delivers that satisfying, starchy mouthfeel for substantially fewer carbs.
The Starch in Butternut Squash Is Not All the Same
Not all starch behaves identically in your digestive system. Some of the starch in winter squash is resistant starch, a type that passes through the small intestine without being fully digested. Resistant starch acts more like fiber than traditional starch. It feeds beneficial gut bacteria and has a smaller effect on blood sugar. Research on winter squash starches has found that certain varieties contain notable levels of resistant starch, particularly after cooking and cooling. This is the same phenomenon that makes cooled potatoes and reheated rice slightly lower on the glycemic index than freshly cooked versions.
In practical terms, this means a butternut squash soup that’s been refrigerated and reheated may have a slightly gentler impact on blood sugar than squash eaten straight from the oven. The difference isn’t dramatic enough to restructure your meals around, but it’s a useful detail if you’re already paying close attention to glycemic control.