The protein powder industry is vast, comprising dozens of options that range from whey to casein formulas. The latter is a great option for individuals on weight-loss journeys due to being slower to digest than whey. After researching the market for high-quality protein powders and consulting nutrition experts, our expert gear and wellness editor chose Optimum Nutrition’s Gold Standard 100% Casein Powder as his top pick for weight loss. Its formulation is simple and utilizes high-quality ingredients to support muscle recovery, and its casein protein digests more slowly than whey, which in turn helps curb your appetite.
Optimum Nutrition’s Gold Standard 100% Casein Powder is our top choice for weight loss due to its clean casein protein that’s slow-digesting to help curb cravings.
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Optimum Nutrition’s casein protein powder, which was deemed the best formula for weight loss in our protein powder roundup, stands out mainly for its sustained amino acid release, creamy texture and rich flavor. Its slow-digestion properties also make this pick ideal to use before bed to support muscle recovery overnight. Plus, it has a comparatively clean formulation: “Optimum Nutrition has really high quality control, making it one of the cleanest options regarding additives,” says dietician Janelle Bober of Dietician Live.
Optimum Nutrition Gold Standard 100% Casein Protein Powder (2-Pound)
Protein per serving: 24 grams | Serving size: 1 scoop (34 grams) | Protein source: Micellar casein | Ingredients: Natural and artificial flavors, no added sugar (uses sucralose) | Servings per container: 25 | Flavors: 4, including Chocolate Supreme and Creamy Vanilla
Best for:
Keeping you fuller for longer than whey protein powdersFans of a thick, smooth shake texture and rich chocolate or vanilla flavorsA nighttime snack that still supports muscle recovery
Skip if:
You don’t prefer thick shakesYou don’t like artificial flavors/sweeteners
Optimum Nutrition Gold Standard 100% Casein Features
Casein: A Complete Protein That Boosts Metabolism
The not-so-secret ingredient that helps control appetite in this formula is the micellar casein, which is a milk protein. Casein is a high-quality, complete protein because it consists of all the essential amino acids you need to maintain lean muscle, says certified fitness and nutrition expert Sarah Pelc Graca. “This is important for weight management because keeping muscle mass helps boost your metabolism (compared to fat) while you are consuming fewer calories,” she explains.
Casein isn’t the only high-impact ingredient in Optimum Nutrition’s formula, though. “It also has a decent dose of magnesium (85 mg) and zinc (11 mg), which support muscle function, sleep, recovery and hydration,” says Bober.
Casein Also Helps You Feel Fuller For Longer
Casein is also a slow-digesting protein, taking several hours to break down. “Think of it like an extended release medication—it helps you feel fuller for longer,” Bober says. Protein availability is sustained over extended periods of time, which, she explains, “supports lean mass preservation and helps with long-term metabolism through satiety.”
This characteristic is particularly helpful for individuals who want to cut down on snacking between meals or tend to indulge in late-night munching, according to Graca. “Some people even turn it into a high-protein dessert at night (yum!), which also helps satisfy sweet cravings without hindering progress,” she adds.
Bonus Benefits For Weight Loss
Another benefit to casein being a slow-digesting protein is that it won’t impact how you metabolize overnight. “Controlled studies show it doesn’t change your resting energy expenditure at night when you’re digesting and resting, so there’s not a big shift in metabolic adaptation,” says Bober, adding that this is particularly noteworthy for people with insulin sensitivities or obesity. This is also why many users consume it before bed: Your muscles continue to draw from sustained protein availability overnight to keep rebuilding, which can help decrease muscle soreness the day after.
Optimum Nutrition’s casein formula also exceeds the minimum grams-to-calorie ratio that Bober recommends if you’re looking to lose weight. “I recommend a 10% grams-to-calorie ratio for weight loss, so if you have a serving with 240 calories, 24 grams of protein would be ideal,” she explains. And since this protein powder has 24 grams of protein per 120 calories, it exceeds Bober’s criteria: “A high-protein, calorie-restricted diet is the gold standard for weight loss,” she says.
The nutritional information for the Chocolate Supreme flavor of Optimum Nutrition’s Gold Standard 100% Casein protein powder.
optimum nutrition
Creamy Texture And Rich Flavor
Fans of thick, extra-creamy protein shakes will like this casein protein powder. “It mixes more like a pudding when you use less water or milk,” says Graca. Casein protein powder is also a lot smoother compared to plant protein powders, which tend to be grainy, adds Bober. Tom Ahmad, certified sports nutritionist with Same Day Supplements, agrees—and vouches for the Chocolate Supreme flavor, which he’s used several times. “It’s smooth, enjoyable and thick, making it a perfect filling nighttime shake or snack that can also support recovery,” he notes.
Reasons You May Not Like This Formula
While all three experts recommend Optimum Nutrition’s Gold Standard Casein protein powder for its high-quality protein, creamy consistency and smooth flavor, it’s not for everyone. If you’re not a fan of very thick shakes, opt for a powder that uses a faster-digesting protein like whey (see our top pick from our best protein powders roundup, the Optimum Nutrition Gold Standard Whey Protein Powder). That said, most reviews say this formula is easy to mix with water or milk and blends reasonably well in shaker bottles.
Further, while this formula is one of the cleanest on the market, it still uses some artificial flavoring and the sugar substitute sucralose. The majority of reviewers find the flavors pleasantly sweet but not cloying (particularly the Chocolate Supreme and Creamy Vanilla varieties) and appreciate that it only contains 1 gram of sugar; a few others, though, say they can taste a bit of the artificial flavoring. Further, anyone with sensitivities to either of these ingredients should find an alternative product.
Final Thoughts
Before you decide on this particular protein powder, Bober has one last bit of advice: “Make sure you tolerate it well and consider whether you want plant-based or animal-based protein, plus look at the vitamins and minerals present.” But overall, if you’re looking for a high-quality protein powder and are on a weight-loss journey, Optimum Nutrition’s casein formula is a smart choice, says Graca. “It is especially useful for those who struggle with hunger between meals or want a filling evening snack that aligns with their goals.”
If weight loss isn’t your primary goal—maybe its muscle building, or simply adding more protein into your day—there are other formulas to consider. See our guide outlining popular kinds of protein powders to find the best product to suit your needs.
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This story was written by Forbes Vetted home updates writer Fran Sales. An avid researcher and product tester, Sales is experienced at conducting rigorous deep-dives and expert interviews for complex subjects, from robot pool vacuums to window air conditioners.
It was reviewed by Forbes Vetted gear editor Cam Vigliotta, who’s been evaluating and testing outdoor, training and wellness equipment for the past six years. He has a degree in kinesiology, which gives him unique insight into how protein powders can help with muscle recovery and complement your dietary goals.
To make sure the Optimum Nutrition Gold Standard Casein formula is the best in its category, we consulted three nutrition experts for this review: Janelle Bober, MS, RDN, a registered dietitian nutritionist at Dietician Live, a telehealth provider that offers personalized dietician services; Sarah Pelc Graca, CPT, PN-L1, a fitness and nutrition expert at Strong With Sarah LLC; and Talib “Tom” Ahmad, NASM, CNC, a certified sports nutritionist and SEO manager at Same Day Supplements.