Whey Protein Reduces Hunger But Doesn't Change GLP-1, Insulin Sensitivity, or Body Composition
A 12-week trial in 73 obese adults found whey protein reduced subjective hunger and increased peptide YY response, but did not improve GLP-1, insulin sensitivity, body composition, or blood pressure.
Quick Facts
What This Study Found
Whey protein for 12 weeks reduced subjective hunger (p=0.02) and increased postprandial peptide YY response (with low fiber), but had no effect on insulin sensitivity, GLP-1, body composition, 24-hour blood pressure, or energy expenditure versus maltodextrin control.
Key Numbers
73 randomized; 60 g/day WP; 12 weeks; hunger p=0.02; PYY increased with WP+LoFi; no effects on GLP-1, GLP-2, GIP, insulin sensitivity, body composition, BP, or energy expenditure
How They Did This
12-week, double-blind, randomized, controlled, parallel study. 73 subjects with abdominal obesity. 4 groups: whey protein hydrolysate (60g/day) or maltodextrin + high-fiber (30g/day) or low-fiber (10g/day). Assessed: insulin sensitivity, gut hormones (GLP-1, GLP-2, GIP, PYY), body composition, blood pressure, energy expenditure.
Why This Research Matters
Whey protein is widely promoted for weight management, but this rigorous trial shows its benefits may be limited to appetite reduction without meaningful metabolic improvements — important context for consumers spending money on protein supplements.
The Bigger Picture
This study tempers expectations about whey protein as a metabolic fix. While appetite-suppressing effects (via peptide YY) are real, they don't automatically translate to weight loss or metabolic improvement — highlighting the complexity of obesity treatment beyond simple hunger control.
What This Study Doesn't Tell Us
Relatively small study (73 subjects, 65 completed). 12-week duration may be insufficient for body composition changes. 60g/day whey protein is a high dose. Maltodextrin control may have metabolic effects of its own. Population-specific (abdominal obesity).
Questions This Raises
- ?Would longer whey protein supplementation eventually produce body composition changes?
- ?Does the hunger reduction from whey protein lead to reduced calorie intake and weight loss over time?
- ?Would whey protein combined with exercise produce different metabolic results?
Trust & Context
- Key Stat:
- Hunger reduced, metabolism unchanged Whey protein lowered subjective hunger (p=0.02) and boosted PYY, but produced no measurable changes in insulin sensitivity, body composition, or metabolic rate over 12 weeks
- Evidence Grade:
- Moderate evidence: double-blind RCT design, but relatively small sample (73) and short duration (12 weeks) limit power to detect modest metabolic changes.
- Study Age:
- Published 2021. The appetite-hormone effects of dietary protein continue to be studied, with growing interest in how protein quality affects GLP-1 and PYY responses.
- Original Title:
- Effects of whey protein and dietary fiber intake on insulin sensitivity, body composition, energy expenditure, blood pressure, and appetite in subjects with abdominal obesity.
- Published In:
- European journal of clinical nutrition, 75(4), 611-619 (2021)
- Authors:
- Fuglsang-Nielsen, Rasmus, Rakvaag, Elin, Langdahl, Bente, Knudsen, Knud Erik Bach, Hartmann, Bolette, Holst, Jens Juul, Hermansen, Kjeld, Gregersen, Søren
- Database ID:
- RPEP-05393
Evidence Hierarchy
Frequently Asked Questions
Does whey protein help with weight loss?
This study found whey protein reduces feelings of hunger and increases the appetite-suppressing hormone peptide YY, but these effects didn't translate to measurable weight loss, body composition changes, or metabolic improvements over 12 weeks.
Does whey protein affect GLP-1 levels?
In this trial, whey protein did not significantly change GLP-1 levels compared to the control group. The main hormonal effect was an increase in peptide YY, a different appetite-regulating hormone, when whey was combined with low dietary fiber.
Read More on RethinkPeptides
Cite This Study
https://rethinkpeptides.com/research/RPEP-05393APA
Fuglsang-Nielsen, Rasmus; Rakvaag, Elin; Langdahl, Bente; Knudsen, Knud Erik Bach; Hartmann, Bolette; Holst, Jens Juul; Hermansen, Kjeld; Gregersen, Søren. (2021). Effects of whey protein and dietary fiber intake on insulin sensitivity, body composition, energy expenditure, blood pressure, and appetite in subjects with abdominal obesity.. European journal of clinical nutrition, 75(4), 611-619. https://doi.org/10.1038/s41430-020-00759-4
MLA
Fuglsang-Nielsen, Rasmus, et al. "Effects of whey protein and dietary fiber intake on insulin sensitivity, body composition, energy expenditure, blood pressure, and appetite in subjects with abdominal obesity.." European journal of clinical nutrition, 2021. https://doi.org/10.1038/s41430-020-00759-4
RethinkPeptides
RethinkPeptides Research Database. "Effects of whey protein and dietary fiber intake on insulin ..." RPEP-05393. Retrieved from https://rethinkpeptides.com/research/fuglsang-nielsen-2021-effects-of-whey-protein
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.