Whey and casein are dairy-based proteins, naturally found together in milk. When isolated and sold as dietary supplements, each has advantages for weight loss, and neither holds a clear upper hand. If you’re considering using either protein, carefully study supplement labels to get nutritional details for the brand you choose, and get approval from your doctor before making any major changes to your diet.
Milk Protein Basics
Milk proteins such as whey and casein have the ability to preserve lean muscle mass and improve metabolic health during the weight loss, according to research published in 2013 in the journal “Nutrition & Metabolism." They can’t take the place of calorie reduction or exercise, but when compared with protein supplements from other sources, milk proteins have been shown to stimulate greater body fat loss and overall weight loss when used as part of a reduced-calorie diet.
Whey Pros and Cons
In a study published in 2011 in the “American Journal of Clinical Nutrition,” participants who took whey experienced greater fat oxidation and thermogenesis than those who took casein. Fat oxidation refers to the body's process of breaking down fatty acid molecules into smaller components that can be used for energy, and dietary thermogenesis refers to the body's energy expenditure from metabolizing the foods you eat. Whey is a “fast-acting” protein, so your body absorbs and digests it more rapidly than casein, making it more satiating in the short term. However, that also means whey may not keep you full for as long as casein can.
Casein Pros and Cons
As a “slow-acting” protein, casein is more satiating than whey in the long term, which can help with controlling hunger and cravings. For that reason, registered dietitian Nanci S. Guest recommends it over whey for weight loss efforts. In a study published in 2010 in the journal “Arquivos Brasileiros de Endocrinologia & Metabologia,” normal-weight subjects who supplemented their diets with casein without attempting to cut calories ate less than subjects who supplemented with whey. The study took place over a short-term period of only seven days, however.
Several independent research reviews have concluded that neither whey nor casein holds a clear advantage over the other when it comes to weight loss and weight maintenance. Some protein supplements combine the two. According to registered dietitian Dr. Jeff S. Volek, since casein is digested slowly and whey is digested quickly, it may be better to use a combination of both rather than just one, especially if your weight loss plan involves regular exercise. The "Nutrition & Metabolism" research review also reports that skim milk with whey and casein proteins has been shown to contribute to decreased calorie consumption more effectively than either protein alone.