Like it or not, losing weight comes down to calories. Most soy milk is fortified with calcium and vitamin D to make it nutritionally comparable to cow's milk.
Everybody knows that nonfat cow's milk has less fat - and therefore fewer calories - than 1 percent, 2 percent, or whole milk (which is 3.25 percent fat, in case you wondered). A cup of nonfat cow's milk has 83 calories, compared to 102 calories in 1 percent milk, 122 calories in 2 percent milk, and 146 calories in whole milk. Drink the recommended three cups per day, and you'll end up with 189 additional calories if you choose whole instead of nonfat milk. That might not seem like much, but it adds up over time. If you drink three cups of milk each day, switching from whole to nonfat milk could help you lose almost 20 pounds in a year!
Soy milk comes in a variety of flavors, some with added sugar. Plain soy milk has 100 calories per cup, comparable to 1 percent milk. You can also purchase light soy milk, with almost half the fat of regular soy milk, at 70 calories per cup.
Some research shows that drinking three cups of nonfat milk per day can help some people lose more weight, especially in their midsection. Will the same thing happen if you choose soymilk? The research hasn't been done, so there's no way to know for sure. If you're allergic to cow's milk, choose light soy milk. Otherwise, choose nonfat cow's milk for a healthy, low-calorie beverage two to three times per day.
From a weight loss point of view, it doesn't make much difference. What does make a difference is the number of calories you consume. If you're over the number you personally need for your weight loss program, you're going to find it hard to lose, regardless of where the calories come from. The studies - marketed by the dairy industry - that showed drinking milk helps with weight loss failed to mention that that's only true when you're deficient or low in calcium. Once your calcium intake is normal, adding extra dairy does nothing for your weight loss. People have used both low-fat dairy and soy products to help lose weight successfully. As long as you don't have food reactions to either, the choice is yours. (Both dairy and soy are on the top ten list of most allergenic foods).
The research shows positives and negatives for both soy and dairy. When considering whether to add either of them to your diet, the most important factor for weight loss is total calories and your overall exercise-versus-eating energy balance. It's a matter of taste preference too.
There is some recent research showing that dairy can be an effective weight loss aid. The vitamin D and calcium contained in dairy foods seems to promote weight loss, especially when you compare it to taking mineral supplements alone. Dairy products are a complete source of nutrients - carbohydrates, fat and protein - so they may make you feel fuller for longer and for fewer calories.
Soy has also been shown to be helpful in a diet plan geared toward weight loss. It offers a healthy dose of protein and is relatively low in calories. Adding flavor and texture to it is easy, so it's a good ingredient for a satisfying light meal.
Bottom line: I'm not sure why you have to choose between these two foods. You can include both of these foods in your diet and still lose weight.
