Can whey change how hungry you feel?

THE SHORT VERSION

• In a 2003 experiment, people ate less at a buffet after a whey drink than after a casein drink with the same amount of protein. A separate experiment in the same paper found higher gut hormone responses and greater reported fullness with whey.
• Whey can influence appetite-related hormones and short-term fullness. Feeling fuller, though, does not guarantee eating less or losing weight over time.
• A hormone reading, a fullness rating, and the food actually eaten are separate findings. Results also depend on the dose, the timing, and who was studied.
• The question to ask: what did the study measure, in whom, and with what serving?

Ninety minutes after a protein drink, participants in a nutrition study were offered a buffet. Researchers wanted to know how much they would choose to eat. The two drinks supplied the same amount of protein, but one was whey and the other casein. Participants ate less after the whey drink.¹

That raises a question protein grams alone cannot answer: can the source of a protein change how hungry you feel afterward? Human studies suggest it can, under some conditions. Following that answer takes us from digestion into the signals the gut sends to the rest of the body.

Digestion also produces signals

Digesting protein releases amino acids and peptides that can influence hormone release. These responses help coordinate digestion, appetite, and how the body handles nutrients after a meal.²

Two hormones come up often in whey research. Cholecystokinin (CCK) takes part in digestion and in signals linked to fullness. Glucagon-like peptide-1 (GLP-1) also contributes to appetite regulation and helps coordinate the insulin response to food.^1,2

A third is glucose-dependent insulinotropic polypeptide (GIP). Like GLP-1, it is an incretin: a gut hormone that helps stimulate insulin release in response to nutrients. A rise in GIP shows a hormonal response. By itself, it does not show greater fullness.²

Ghrelin, often called a hunger hormone, generally rises before meals and falls after eating. Researchers study whether a protein changes that pattern alongside other hormone signals, reported hunger, and food intake.²

What happened before the buffet

The buffet experiment was part of research published by Hall and colleagues in 2003. Participants drank a whey or casein drink with 48 grams of protein and roughly 400 calories. Researchers call a food or drink given before a test meal a preload.¹

In a separate experiment in the same paper, the whey preload produced higher circulating amino acid concentrations and larger CCK, GLP-1, and GIP responses than casein. Participants also reported greater satiety, the fullness that lasts after eating, with whey.¹

The researchers proposed that amino acid delivery, CCK, and GLP-1 could help explain the response. The experiments link protein type with short-term appetite, while leaving room for several contributing mechanisms.¹

Dose and timing matter here. A drink with 48 grams of protein followed by a buffet 90 minutes later describes one particular experiment. It cannot show how every whey-containing snack or drink will affect hunger across an ordinary day.

Feeling fuller and eating less are separate findings

Researchers assess appetite in different ways. They may ask people how hungry or full they feel, measure what they eat at a later meal, or track their intake over weeks. Each approach answers a different question.²

Pal and colleagues compared whey, casein, and a glucose control in a 12-week trial of adults with overweight or obesity. At weeks six and twelve, the whey group reported greater satiety and fullness before lunch than the casein and control groups.³

Yet the whey group did not have lower energy intake or body weight over the twelve weeks compared with the casein group.³

Feeling fuller was a finding in its own right. A lasting difference in eating or weight needed separate evidence.

Where glycomacropeptide fits

One candidate in the appetite story has an unusually long name: glycomacropeptide, or GMP. It is a fragment of kappa-casein that can enter the whey fraction during cheesemaking. A peptide’s parent protein and the ingredient it ends up in can therefore differ.⁴

Researchers have asked whether GMP contributes to whey-related satiety, including through CCK. Human findings have been inconsistent. Studies also differ in who takes part, how much they receive, and how long they wait before the next meal.⁴

In a randomized crossover experiment, Keogh and colleagues tested two GMP preparations, GMP-depleted whey, and glucose on separate occasions. Twenty men with overweight or obesity completed the study.⁵

The researchers found no significant differences between treatments in CCK, reported satiety, or food eaten at lunch three hours later.⁵

A study in 22 normal-weight women approached the question from another angle. Whey drinks with high or low GMP content both reduced intake at a test meal two hours later by about 18% compared with carbohydrate or GMP alone.⁶

Appetite ratings did not differ between the drinks. The authors concluded that GMP did not appear to account for whey’s effect on satiety in their experiment.⁶

Together, these results leave GMP as a subject of investigation, rather than an established explanation for every appetite response to whey. The preparation, dose, comparison drink, and wait before the next meal all matter.^4,5,6

What three studies measured and found

The studies tested different preparations in different people, so their results are not directly comparable. Hall’s hormone and fullness findings came from a separate experiment from the buffet test.^1,3,5

Returning to the question of hunger

Whey can influence appetite-related hormones. In some human experiments, it has increased reported fullness or reduced intake at a later meal. Those outcomes need to be considered separately.^1,2,3

Related reading

• How whey protein is digested
• How to choose a protein drink

References

Educational content. The Fountain is written to explain, not to make health claims about any product. This article summarizes published peer-reviewed research. Nothing here is medical advice.

1. Hall WL, Millward DJ, Long SJ, Morgan LM. Casein and whey exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetite. British Journal of Nutrition. 2003;89(2):239–248. https://doi.org/10.1079/BJN2002760
2. Bendtsen LQ, Lorenzen JK, Bendsen NT, Rasmussen C, Astrup A. Effect of dairy proteins on appetite, energy expenditure, body weight, and composition: a review of the evidence from controlled clinical trials. Advances in Nutrition. 2013;4(4):418–438. https://doi.org/10.3945/an.113.003723
3. Pal S, Radavelli-Bagatini S, Hagger M, Ellis V. Comparative effects of whey and casein proteins on satiety in overweight and obese individuals: a randomized controlled trial. European Journal of Clinical Nutrition. 2014;68(9):980–986. https://doi.org/10.1038/ejcn.2014.84
4. Foisy Sauvé M, Spahis S, Delvin E, Levy E. Glycomacropeptide: a bioactive milk derivative to alleviate metabolic syndrome outcomes. Antioxidants & Redox Signaling. 2021;34(3):201–222. https://doi.org/10.1089/ars.2019.7994
5. Keogh JB, Woonton BW, Taylor CM, Janakievski F, Desilva K, Clifton PM. Effect of glycomacropeptide fractions on cholecystokinin and food intake. British Journal of Nutrition. 2010;104(2):286–290. https://doi.org/10.1017/S0007114510000280
6. Chungchunlam SMS, Henare SJ, Ganesh S, Moughan PJ. Effect of whey protein and glycomacropeptide on measures of satiety in normal-weight adult women. Appetite. 2014;78:172–178. https://doi.org/10.1016/j.appet.2014.03.027