Study analysis · Appetite · 2009
The milk protein trick that cuts lunch calories by 10% without trying
A specific part of whey protein called GMP helped people eat about 10% less at lunch, regardless of how much protein they had for breakfast.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study is like a taste test where people got two different breakfasts and then ate lunch. It found that when people had the breakfast with a special part of milk protein, they ate a little less at lunch. But we can't say that this special protein part makes people eat less forever because the study only looked at one meal and had a small number of people.
What’s the bottom line?
Researchers tested if a component of whey protein (glycomacropeptide, or GMP) helps people eat less at lunch after breakfast.
How strong is this study?
This study was well-done because it was random and each person tried both breakfasts, so we can compare them fairly. But it was only a small study with 25 people, and the researchers knew what each person was eating, which might have affected results a little. So we trust the results but need more studies to be sure.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
58 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=25)+2.4/20
- Follow-upno follow-up reported
100 / 100
23 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Single-blind design (potential for bias), small sample size (n=25), short-term outcome (single meal), and crossover design with possible period effects, though randomization and washout mitigate some concerns. Causal inference is limited to the specific intervention and population studied.
Minor COI
Minor conflicts that may slightly influence the study
No conflicts of interest are declared, but the authors are affiliated with Top Institute Food and Nutrition, which may have industry ties.
Conflict Details
Top Institute Food and Nutrition: Affiliation with an institute that partners with industry
The text does not include a conflict of interest or funding statement. The study uses whey products from specific companies (Volactive, DMV International) for the custards, but no financial relationship with these companies is disclosed.
Key takeaways
- 01
People who ate breakfast containing GMP ate about 330 kilojoules less at lunch compared to those who ate breakfast without GMP.
- 02
That amount equals roughly a small cookie or a piece of fruit - might help with weight control if sustained.
Surprising findings
- Higher protein (25%) did not increase satiety or reduce food intake compared to normal protein (10%). In fact, subjective satiety was higher after the lower-protein breakfast.This contradicts decades of research showing protein is the most satiating macronutrient. It suggests there's a ceiling effect or that other factors override hormonal signals.
- Whey without GMP caused a larger insulin spike than complete whey, yet complete whey reduced food intake more.Insulin is often touted as an appetite-suppressing hormone, but here the protein that raised insulin more (whey without GMP) was less effective at reducing intake, indicating insulin is not the key player.
Practical takeaways
Choose whey protein that retains its natural GMP fraction (often labeled as 'complete' or 'native' whey) if you want potential appetite control benefits.
The study was small (n=25), single-blind, and used a specific timing (3 hours after breakfast). Effects may not translate to everyday snacking or other protein sources.
Medium confidenceDon't assume more protein always means less hunger. A moderate-protein breakfast (10% En% protein) may be as effective as a high-protein one (25%) for controlling lunch intake.
This applies to whey protein in a custard breakfast; other protein types (casein, soy) or whole foods may behave differently.
Medium confidenceWhy this study matters
GMP: The Hidden Appetite Controller in Whey
In a randomized crossover trial, 25 healthy adults ate breakfast with either complete whey or whey without GMP. Later, at a pre-determined lunch (180 minutes after breakfast when ghrelin differences were maximal), those who had GMP consumed 2877 kJ vs 3208 kJ – a 10% reduction (p<0.05). This effect occurred whether the breakfast had 10% or 25% protein energy.
It suggests that the type of protein matters more than the amount for appetite control, giving people a simple way to eat less without feeling deprived.
Protein Paradox: More Protein, Less Satiety
Surprisingly, increasing whey protein from 10% to 25% of breakfast energy did not reduce lunch intake or boost satiety. In fact, subjective satiety ratings were higher after the lower-protein breakfast. Despite larger increases in insulin and GLP-1 and greater ghrelin suppression, these hormonal changes did not translate into eating less.
This contradicts the common belief that more protein automatically means better appetite control, revealing a disconnect between hormone signals and actual eating behavior.
Insulin Mystery: More Insulin Without GMP, But More Food Intake With It
Whey without GMP caused a larger insulin spike than complete whey, yet complete whey reduced food intake more. This suggests that insulin is not the primary driver of GMP's appetite-suppressing effect. Instead, specific amino acids like serine, threonine, alanine, alpha-aminobutyric acid, and isoleucine were elevated after GMP-containing breakfasts and may play a key role.
Highlights that appetite control is complex – simply boosting insulin (as some diets suggest) may not work; the composition of protein matters.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers tested if a component of whey protein (glycomacropeptide, or GMP) helps people eat less at lunch after breakfast.
Research results
People who ate breakfast containing GMP ate about 330 kilojoules less at lunch compared to those who ate breakfast without GMP.
What this means - more context
That amount equals roughly a small cookie or a piece of fruit - might help with weight control if sustained.
To compare effects of whey vs whey without GMP in high (25%) vs normal (10%) protein breakfast on energy intake and satiety.
GMP reduced subsequent lunch energy intake by ~10% (331 kJ) independent of protein content. Higher protein increased insulin, GLP-1, and suppressed ghrelin but did not increase satiety or reduce intake.
Methods Used
25 healthy adults (mean BMI 23.9, age 22) in a randomized single-blind crossover trial; breakfasts with whey or whey without GMP at 10% or 25% energy from protein; ad libitum lunch at 180 min based on ghrelin differences.
Main Finding
Lunch energy intake was lower after whey vs whey without GMP (2877 vs 3208 kJ, p<0.05); no effect of protein concentration on intake.
Confidence Level
Moderate: small sample, but crossover design, power calculation, and consistent findings across conditions.
Study Flags
Red Flags
- •Small sample size (n=25)
- •Single-blind design (subjects not blind to taste?)
- •Timing of lunch based on ghrelin differences may not reflect real-world eating patterns
Surprising Findings
Higher protein (25%) did not increase satiety or reduce food intake compared to normal protein (10%). In fact, subjective satiety was higher after the lower-protein breakfast.
This contradicts decades of research showing protein is the most satiating macronutrient. It suggests there's a ceiling effect or that other factors override hormonal signals.
Practical Takeaways
Choose whey protein that retains its natural GMP fraction (often labeled as 'complete' or 'native' whey) if you want potential appetite control benefits.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study is like a taste test where people got two different breakfasts and then ate lunch. It found that when people had the breakfast with a special part of milk protein, they ate a little less at lunch. But we can't say that this special protein part makes people eat less forever because the study only looked at one meal and had a small number of people.
Minor conflicts detected — such as academic funding or advisory roles. These are common and have a small score impact.
Strengths
- Randomized crossover design (each subject serves as own control), reducing inter-individual variability.
- Controlled standardised breakfasts with matched energy density and taste.
- Objective measurement of energy intake at lunch.
Weaknesses
- Small sample size (n=25), potentially underpowered for some outcomes.
- Single-blind design (participants may have been aware of treatment? Actually participants were blinded, but researchers knew), possible performance bias.
- No washout period length reported between sessions? It says at least 1 week, likely adequate.
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers tested if a component of whey protein (glycomacropeptide, or GMP) helps people eat less at lunch after breakfast.
Research results
People who ate breakfast containing GMP ate about 330 kilojoules less at lunch compared to those who ate breakfast without GMP.
What this means - more context
That amount equals roughly a small cookie or a piece of fruit - might help with weight control if sustained.
To compare effects of whey vs whey without GMP in high (25%) vs normal (10%) protein breakfast on energy intake and satiety.
GMP reduced subsequent lunch energy intake by ~10% (331 kJ) independent of protein content. Higher protein increased insulin, GLP-1, and suppressed ghrelin but did not increase satiety or reduce intake.
Methods Used
25 healthy adults (mean BMI 23.9, age 22) in a randomized single-blind crossover trial; breakfasts with whey or whey without GMP at 10% or 25% energy from protein; ad libitum lunch at 180 min based on ghrelin differences.
Main Finding
Lunch energy intake was lower after whey vs whey without GMP (2877 vs 3208 kJ, p<0.05); no effect of protein concentration on intake.
Confidence Level
Moderate: small sample, but crossover design, power calculation, and consistent findings across conditions.
Study Flags
Red Flags
- •Small sample size (n=25)
- •Single-blind design (subjects not blind to taste?)
- •Timing of lunch based on ghrelin differences may not reflect real-world eating patterns
Surprising Findings
Higher protein (25%) did not increase satiety or reduce food intake compared to normal protein (10%). In fact, subjective satiety was higher after the lower-protein breakfast.
This contradicts decades of research showing protein is the most satiating macronutrient. It suggests there's a ceiling effect or that other factors override hormonal signals.
Practical Takeaways
Choose whey protein that retains its natural GMP fraction (often labeled as 'complete' or 'native' whey) if you want potential appetite control benefits.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study is like a taste test where people got two different breakfasts and then ate lunch. It found that when people had the breakfast with a special part of milk protein, they ate a little less at lunch. But we can't say that this special protein part makes people eat less forever because the study only looked at one meal and had a small number of people.
Minor conflicts detected — such as academic funding or advisory roles. These are common and have a small score impact.
Strengths
- Randomized crossover design (each subject serves as own control), reducing inter-individual variability.
- Controlled standardised breakfasts with matched energy density and taste.
- Objective measurement of energy intake at lunch.
Weaknesses
- Small sample size (n=25), potentially underpowered for some outcomes.
- Single-blind design (participants may have been aware of treatment? Actually participants were blinded, but researchers knew), possible performance bias.
- No washout period length reported between sessions? It says at least 1 week, likely adequate.
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
This study was well-done because it was random and each person tried both breakfasts, so we can compare them fairly. But it was only a small study with 25 people, and the researchers knew what each person was eating, which might have affected results a little. So we trust the results but need more studies to be sure.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
58 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=25)+2.4/20
- Follow-upno follow-up reported
100 / 100
23 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 546 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Single-blind design (potential for bias), small sample size (n=25), short-term outcome (single meal), and crossover design with possible period effects, though randomization and washout mitigate some concerns. Causal inference is limited to the specific intervention and population studied.
Minor COI
Minor conflicts that may slightly influence the study
No conflicts of interest are declared, but the authors are affiliated with Top Institute Food and Nutrition, which may have industry ties.
Conflict Details
Top Institute Food and Nutrition: Affiliation with an institute that partners with industry
The text does not include a conflict of interest or funding statement. The study uses whey products from specific companies (Volactive, DMV International) for the custards, but no financial relationship with these companies is disclosed.
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
8 researchersIf this is your work, this is how we attribute it on Fit Body Science. Margriet A. B. Veldhorst is listed as the lead author.