According to the U.S. Department of Agriculture National Nutrient Database, there are 42 calories in each cup of spaghetti squash. As it is almost 92 percent water in weight, this accounts for the low number of calories.
While low in calories, spaghetti squash is also low in fat, with less than half a gram of fat per cup serving. This makes it an ideal vegetable for those on weight-loss or weight-management plans. Spaghetti squash contains many valuable nutrients, including folic acid, potassium and vitamin C. This particular squash is lower in carbohydrates than other types of squash, with only 10 grams per cup serving, useful for those following low-carb or diabetic meal plans.