You probably know that whey protein should be your top protein choice when you're trying to build muscle, but you may not know that it should actually be your top choice when you're on a weight-loss diet, too! Yes, this fast-digesting protein king actually packs a powerful appetite-suppressing punch, contrary to the fact that liquids (and whey in particular) digest quickly.

Whey protein has been shown to positively impact the hunger hormones in your gut, the appetite control center in your brain, and to have a helpful impact on blood glucose levels (which has a positive impact on appetite, and in turn weight loss). It's even been shown to be a superior appetite suppressant compared to casein protein in the short term.[1]

How Whey Helps You Lose Fat

1. Increases Appetite Suppressing Hormones

Whey protein is composed of several bioactive compounds, or small molecules that exert powerful effects in your body. Glycomacro peptide (GMP) is one that may play a major role in suppressing your appetite. GMP has been shown to increase secretion of the gut hormone cholecystokinin (CCK).[2] CCK plays a major role in sending satiety signals to the brain, which may help encourage you to put your fork down and make weight loss easier.


A study in the journal Appetite found the presence of GMP in whey protein to have a major impact on keeping appetite at bay.[3] Researchers provided subjects with a regular whey protein or a GMP-depleted whey protein before they sat down to an all-you-can-eat meal. Subjects who drank the GMP-depleted whey ate significantly more than the traditional whey group, which researchers attributed to the appetite-suppressing impact of GMP.

2. Signals Fuel Availability in the Brain

Whey protein contains more leucine (a critical branched-chain amino acid) than any other protein source.[4] Beyond its muscle-building role, it's thought that leucine may have a direct impact on appetite, too. In a study published in Journal of Science, researchers injected one group of mice with supplemental leucine and another with a control, and then exposed them to unlimited food after a brief fasting period.[5] Both groups gained weight over the next 24 hours, but the mice injected with leucine gained one third of the weight of the control group!

There seems to be a complex relationship between leucine, mTOR (the master growth regulator within cells that plays a role in initiating muscle protein synthesis), and the hypothalamus (where the appetite control center in the brain is located). Researchers suspect that mTOR has a fuel-sensor role and helps to regulate appetite.

When you consume leucine-rich whey, the leucine serves as a signal of "fuel availability" to the mTOR complex. As a result, mTOR sends a signal to the hypothalamus to downregulate appetite, helping you feel full!

So, in addition to helping with weight loss, this nutrient could help you avoid packing on unwanted weight in the first place. In other words, it's not just about calories in versus calories out, the kinds of amino acids you have on board make an impact, too.

h whey, the leucine serves as a signal of "fuel availability" to the mTOR complex. As a result, mTOR sends a signal to the hypothalamus to downregulate appetite, helping you feel full!

3. Stabilizes Blood Glucose

Hunger is one consequence of low blood-glucose levels. After a meal, particularly one rich in carbohydrates (especially simple carbohydrates), blood glucose levels spike. However, shortly after, insulin levels rise in order to keep blood glucose levels within a normal range. A rapid rise in blood glucose and the subsequent insulin response can lead to a dip in blood glucose shortly after.

This sets the scene for hunger to take over, and is a big reason diets that call for a low number of daily carb grams are popular for weight loss. When you're always hungry, it becomes a real struggle to adhere to your calorie budget and lose fat.


Gram for gram, protein goes a lot further in stabilizing your blood glucose than carbs. Whey protein in particular can help to curb the hunger response, ultimately promoting steady blood glucose and appetite for hours after eating so you can keep your hunger—and calories—in check.

Whey has a profound effect on the release of two incretins: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).[6-8] Incretins work to enhance the insulin response to a meal to ensure proper blood glucose control.

Rather than a massive spike in blood glucose and insulin, followed by a spike in hunger soon after, whey helps you remain on an even keel in terms of both energy and appetite. Plus, GLP-1 and GIP both function to suppress appetite and slow gastric emptying.[9-10]

How to Get Whey Protein in Your Diet

If the idea of chugging a liquid to reach your weight-loss goals doesn't appeal to you, consider making healthy protein pancakes, protein pizza crust, or homemade protein bars. You can even stir 10 or 20 grams of whey protein powder into your oatmeal. It doesn't matter how you get the nutrients in whey, just that you get them in!

If you decide to take the liquid route, consider using a blender and adding ice to your shake. The blender will help incorporate air, which will add volume to the shake without adding calories. The ice will further thicken your shake and help increase fullness.

Wrapping Up

In addition to helping you gain weight in the form of muscle, whey protein can be a powerful tool during weight loss because it can help your body regulate hunger. You'll feel more satisfied on fewer calories, so it will take less willpower to lose fat and stick to your diet.

Learn More

  1. Bendtsen, L. Q., Lorenzen, J. K., Bendsen, N. T., Rasmussen, C., & Astrup, A. (2013). Effect of dairy proteins on appetite, energy expenditure, body weight, and composition: a review of the evidence from controlled clinical trialsAdvances in Nutrition: An International Review Journal4(4), 418-438.
  2. Burton-Freeman, B. M. (2008). Glycomacropeptide (GMP) is not critical to whey-induced satiety, but may have a unique role in energy intake regulation through cholecystokinin (CCK)Physiology & behavior93(1), 379-387.
  3. Veldhorst, M. A., Nieuwenhuizen, A. G., Hochstenbach-Waelen, A., Westerterp, K. R., Engelen, M. P., Brummer, R. J. M., ... & Westerterp-Plantenga, M. S. (2009). Effects of complete whey-protein breakfasts versus whey without GMP-breakfasts on energy intake and satietyAppetite52(2), 388-395.
  4. Bucci, L., & Unlu, L. (2000). Proteins and amino acid supplements in exercise and sport. Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition, 191-212.
  5. Cota, D., Proulx, K., Smith, K. A. B., Kozma, S. C., Thomas, G., Woods, S. C., & Seeley, R. J. (2006). Hypothalamic mTOR signaling regulates food intakeScience312(5775), 927-930.
  6. Hall, W. L., Millward, D. J., Long, S. J., & Morgan, L. M. (2003). Casein and whey exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetiteBritish Journal of Nutrition89(02), 239-248.
  7. Veldhorst, M. A., Nieuwenhuizen, A. G., Hochstenbach-Waelen, A., van Vught, A. J., Westerterp, K. R., Engelen, M. P., ... & Westerterp-Plantenga, M. S. (2009). Dose-dependent satiating effect of whey relative to casein or soyPhysiology & Behavior96(4), 675-682.
  8. Nilsson, M., Stenberg, M., Frid, A. H., Holst, J. J., & Björck, I. M. (2004). Glycemia and insulinemia in healthy subjects after lactose-equivalent meals of milk and other food proteins: the role of plasma amino acids and incretins.The American Journal of Clinical Nutrition80(5), 1246-1253.
  9. Yabe, D., & Seino, Y. (2011). Two incretin hormones GLP-1 and GIP: comparison of their actions in insulin secretion and β cell preservation. Progress in Biophysics and Molecular Biology107(2), 248-256.
  10. Edholm, T., Degerblad, M., Grybäck, P., Hilsted, L., Holst, J. J., Jacobsson, H., ... & Hellström, P. M. (2010). Differential incretin effects of GIP and GLP‐1 on gastric emptying, appetite, and insulin‐glucose homeostasis. Neurogastroenterology & Motility22(11), 1191-e315.

About the Author

Paul Salter, MS, RD

Paul Salter, MS, RD

Paul Salter, MS, RD, CSCS, received his BS in dietetics from the University of Maryland and his MS in exercise and nutrition science from the University of Tampa.

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