Any food, eaten in excess, will make you gain weight, which includes foods made from soy. That doesn't mean that soy is inherently fattening, though; in fact, many soy-derived foods have nutrients that actually help with weight control. You can include soy in diets for weight gain or loss; the results you get depend on your individual needs and the total calories and quality of your diet.
Weight Gain and Loss Basics
No single food will make you gain weight -- or lose it. It all depends on how many calories you're eating each day as compared to how many you burn. Eat more than you burn, and you'll gain weight; eat less, and you'll lose.
For example, a slightly active 37-year-old man who is 6 feet tall and weighs 185 pounds needs about 2,900 calories to maintain his weight. Each pound stores 3,500 calories, so if he routinely eats more than that -- say, 3,400 calories, or an extra 500 calories daily -- he'll gain about a pound each week. If he eats less than that -- for example, 2,500 calories daily, or 500 calories fewer than he needs -- he'll lose a pound of week.
Your individual calorie needs depend on your size, activity level, gender and age, and you can use an online calculator to figure it out. Then add 250 to 500 calories to your daily goal for safe weight gain, or remove 500 to 1,000 calories for safe weight loss.
Calories in Soy-Based Foods
Soy foods are moderately high in calories, which means they can help you gain weight, but they could also fit into a restricted-calorie weight-loss diet. A cup of tempeh, for example, supplies 320 calories. If you add a cup of tempeh to your daily diet, you get enough extra calories to gain a little more than a half-pound per week; however, it you budget the calories for the tempeh in a restricted-calorie diet, you won't gain weight.
Eat a cup of firm tofu, and you'll take in 176 calories along with beneficial nutrients like protein, calcium and iron. Soybeans also supply calories and nutrients; a cup of green hulled edamame beans contains 376 calories and more than your entire vitamin C needs for the day, while a cup of cooked mature soybeans supplies 298 calories and around half your daily iron needs. Drink a glass of soy milk, and you'll get 131 calories, plus protein and essential minerals like manganese and selenium.
Potential Benefits for Weight Control
Soy-based foods are usually high in protein, which makes them beneficial for weight loss. Protein-rich foods have a high thermic effect, which means you'll burn fat and calories during digestion -- more than you would in digesting fat or carbohydrates. Soy is just as beneficial for weight loss as other sources of protein, as long as you're restricting your calorie intake, reports a literature review published in Obesity Reviews in 2008. A cup of tempeh, for example, provides 31 grams of protein; a cup of soy milk supplies 8 grams of protein, and a cup of cooked mature soybeans contains 29 grams.
Eating soy also increases your fiber intake; edamame, for example, has 43 percent of the daily value for cup. Fiber makes your food more filling and controls blood glucose levels, which prevents blood sugar crashes that trigger hunger pangs. Mature soybeans supply 41 percent of the daily value for fiber per cup; tofu contains 8 percent of the daily value; and soy milk contains 6 percent of the daily value per cup.
Healthy Soy Serving Tips and Suggestions
Use soy as the main source of protein in healthy dishes like stir-fries and casseroles. Tofu readily soaks up the flavors from other ingredients, so it can work in virtually any dish. Try tearing chunks of tofu into bite-size pieces and sauteing them with red peppers, spinach and curry spices for a nutritious tofu breakfast scramble, or bake slices or cubes of tofu to add to salads. Edamame and mature soybeans work well in chillis and soups to add heartiness, plus protein and fiber to make your meal more filling. Tempeh's naturally nutty flavor works well in sandwiches and wraps -- pair it with pea sprouts or microgreens, tomatoes and a black olive hummus in a whole-grain tortilla or on whole-wheat bread for a flavorful meal you can enjoy on-the-go.