Producers of soy protein isolate, a high-protein supplement that comes in powdered form, promote it as an aid for gaining muscle and improving body composition. This plant-based protein supplement provides all of the essential amino acids needed to repair build and maintain body tissues, according to the University of Illinois.

Calories

As a low-calorie supplement, soy protein isolate can help you shed some excess pounds. Each serving contains 120 calories, which comprises just 6 percent of the daily suggested intake of 2,000. You can easily burn the 120 calories with exercises, such as a 12-minute jog or a 14-minute swimming session.

Recommended Serving

According to the Food and Drug Administration, consuming 25 grams of soy protein per day may lower your risk for heart disease. Four ounces of firm tofu contain 13 grams of soy protein, a soy burger contains about 10 to 12 grams and 8 ounces of soy milk contain 10 grams. However, when you eat 25 grams of soy protein you consume 45 milligrams of isoflavens. Pennsylvania State University College of Agricultural Sciences reports the weak estrogen content of isoflavens may increase your risk of cancer if you consume more than the safe upper limit of 100 milligrams per day. Fifty-five grams of soy protein contain 99 milligrams of isoflavens.

Carbohydrate Content

Carbohydrate removal during processing increases the protein content of soy protein isolate making it a good choice for low-carbohydrate diets. Carbohydrates provide energy for sports and other forms of exercise, which makes them an important part of a healthy diet. When using a soy protein supplement, add carbohydrate-containing foods, such as fruits, vegetables and whole grains.

Fiber and Fat Content

Protein supplements, including soy protein isolate, do not contain fiber unless the food manufacturer adds it during processing. Because fiber promotes feelings of satiety, soy protein isolate without fiber may not leave you feeling full, which could limit its effectiveness in weight loss plans. Soy protein isolate contains 1.5 grams of fat per serving with no saturated fats. Too much saturated fat may increase your risk of heart disease.