Whey, casein, soy, pea... experts dish on which protein powder is the best for weight loss, muscle gain, and other goals.

If you're looking to lose weight, it might seem counterintuitive to add things to your diet; however, using a protein powder to aid in weight loss might actually be a good idea. The question, then, is: What kind of protein powder is best for weight loss?

There are countless brands and types of protein powder on the market, including casein, soy, pea, brown rice, hemp, and-of course-whey. (Related: Get the Scoop on Different Types of Protein Powder)

Whey (a type of protein derived from milk) has long been the unofficial king of the protein world (thanks to celebrity trainers like Jillian Michaels and Harley Pasternak, who swear by the stuff). Studies have shown unequivocally that whey protein can help build muscle-but is it the best protein powder for weight loss?

"Absolutely," says Paul Arciero, D.P.E., director of the Human Nutrition and Metabolism Lab at Skidmore College. "Whey is perhaps the most effective dietary strategy to aid weight loss. It's the most thermogenic food source you can eat. This means it burns the most calories after you eat it."

It's true: All proteins are more thermogenic than carbohydrates or fats, but research shows that whey is indeed the most thermogenic. One study published in the American Journal of Nutrition found that the thermic effect of whey protein was significantly greater than that of casein or soy protein in lean, healthy adults.

"Whey is one of the most efficient and nutrient-dense protein sources suitable for people who are fitness-focused and seeking weight loss," agrees Ilana Muhlstein, M.S., R.D.N., cocreator of Beachbody's 2B Mindset nutrition plan. "It's a complete protein, easy to find, high in protein, and low in calories, and blends well in different smoothie recipes."

Add whey protein to your meals and snacks, and your metabolism will stay high all day. (There are tons of creative ways to use protein powder in your food-and not just in smoothies.) What's more, whey protein-and really any protein-will keep you feeling full for longer than other types of foods, says Arciero, which means you'll likely snack less. (See: How Much Protein Should You Eat Per Day?)

But there's a third reason why whey protein is recommended for people trying to lose weight: "It's the most effective food you can eat to help you turn on a process called protein synthesis, which starts the building of new muscle," says Arciero. In layman's terms, extra protein will ensure that you hold on to the muscle you already have-muscle mass is often a casualty during weight-loss attempts-and it will help you gain muscle more easily too. This is important because the more muscle you have, the more calories your body burns.

How to Use Protein Powder for Weight Loss

Of course, to get the best results, add exercise. Research published in the Journal of the American College of Nutrition found that strength training plus whey resulted in more weight loss than whey alone.

How exactly do you add whey protein to your diet? "Whey can be easily incorporated into lots of different foods," says Arciero. "You can eat it in a shake or cook and bake with it." (Try this protein pancakes recipe, these protein ball recipes perfect for snacking, or Emma Stone's post-workout protein shake recipe.)

Whey protein powder is sold in health food and vitamin stores and it's also available as an add-on at most smoothie bars. Whey can be separated from milk or harvested during cheese production, but it's low in lactose, which means it may work fine even for people who are lactose-intolerant. The average woman can safely consume 40 to 60 grams of the stuff each day, aiming for no more than 20 grams at a time, Arciero recommends.

If you're looking for a plant-based protein alternative, "I would recommend choosing a vegan protein powder that includes a blend of pea and rice," says Muhlstein. "Including both in one formula can enhance the amino acid profile and create a more neutral flavor profile as well."

By Jessica Cassity for DietsinReview.com