Rhubarb is most often stewed, baked or preserved in jams or jellies. Because of its tart, acidic flavor, it is typically sweetened with sugar or honey, though doing so can more than quadruple its calorie content per serving, points out Dianne Lamb of the "Brattleboro Reformer." Without added sweeteners, cooked rhubarb is low in calories and rich in essential nutrients such as dietary fiber, potassium, vitamin C and calcium. Use cooked, unsweetened rhubarb as an ingredient in sauces for fish or meat, or prepare it with fruits like strawberries, apples or pears for a sweet but low-calorie topping for ice cream or in baked goods.
Total Calorie Content
A single cup of cooked rhubarb that includes no added sugar contains approximately 50.4 calories. According to the U.S. Department of Agriculture, this amount is roughly equivalent to the calories you would receive from consuming 1 cup of cooked chopped broccoli, 1 cup of chopped raw carrots, 1 cup of raw, peeled apple slices or 1 cup of cooked yardlong beans.
Calories from Fat
Rhubarb is very low in fat: 1 cup of unsweetened cooked rhubarb provides only 4.3 calories from fat, or about 11 percent of the vegetable's total caloric content. Most of rhubarb's fat calories come from polyunsaturated fat -- approximately 2 of the 4.3 calories -- with a small amount also contributed by monounsaturated and saturated fat. Rhubarb does not contain any cholesterol.
Calories from Carbohydrates
A 1-cup serving of cooked rhubarb without any added sugar contains nearly 11 grams of total carbohydrates, which supply 43.6 of the 50.4 calories per cup of the vegetable. Rhubarb has 4.3 grams of fiber in each cooked cup, though fiber does not contribute any calories to the total amount. The bulk of rhubarb's carbohydrate calories is supplied by simple sugars such as fructose.
Calories from Protein
Rhubarb is low in protein, with each cup of cooked, unsweetened rhubarb containing about 2.2 grams of protein, or 8.8 calories. This amount is 17 percent of the caloric content of each cup of plain, cooked rhubarb. The protein in rhubarb is incomplete -- the vegetable does not provide all of the amino acids that your body requires every day. Eating a wide variety of plant products regularly can ensure that even people who don't consume any animal products can get adequate protein.