Study analysis · British Journal of Nutrition · 2010
Higher whey protein in a drink led to eating up to 1,283 kJ less at the next meal — about 31% lower relative — but people didn’t report feeling any less hungry.
In healthy-weight adults, a 400 mL whey-protein drink was followed by eating less at a meal 90 minutes later, with more protein linked to less eaten, but no differences in subjective appetite ratings.
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 is a randomised controlled trial, which is one of the best ways to test if something causes an effect. Because people were randomly assigned to different protein drinks, we can be fairly confident that the protein itself changed how much they ate at the next meal, not other differences between people. But it only looked at one meal in healthy-weight adults, so we can't say it helps with weight loss over time.
What’s the bottom line?
Scientists gave healthy-weight people a 400 ml drink with different amounts of whey protein, then let them eat as much as they wanted 90 minutes later. They also used a flavoured-water control drink.
How strong is this study?
The study was well-designed because it randomly assigned people to different drinks and used a control drink, which helps make the comparison fair. However, we only have the summary, not the full details, so we don't know if people could tell which drink they got or how many people were in the study, which makes it harder to be completely sure about the results.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
44 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample sizeno sample size reported
- 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 541 / 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. While the study uses a randomised crossover design, which can support causal inference, the abstract-only nature limits verification of key methodological details (blinding, allocation concealment, sample size, statistical analysis). The findings are limited to acute, single-meal energy intake in healthy-weight adults, so causation cannot be extended to long-term weight outcomes or other populations.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding information is provided in the abstract, so potential conflicts cannot be evaluated.
The text is limited to an abstract; no declaration sections are available. This prevents assessment of COI, funding sources, or author affiliations.
Key takeaways
- 01
In Study 1, after flavoured water people ate 4136 kJ.
- 02
After 12.5% protein they ate 3520 kJ, after 25% protein 3384 kJ, and after 50% protein 2853 kJ.
- 03
In Study 2, after flavoured water people ate 4801 kJ, after 10% protein 4205 kJ, after 20% protein 3988 kJ, and after 40% protein 3801 kJ.
- 04
Higher protein meant less eaten later.
- 05
Appetite ratings did not differ.
- 06
Compared with flavoured water, the highest-protein preloads meant people ate roughly 1283 kJ less (Study 1, 50% protein) and 1000 kJ less (Study 2, 40% protein) at the next meal.
- 07
That is about 31% and 21% lower relative to the control meal, but it is a single-meal effect; the study did not show whether this changes daily energy balance, weight, or health.
Practical takeaways
For now, treat this as an acute experimental finding rather than a weight-loss recommendation: a higher-whey-protein liquid preload was followed by lower next-meal energy intake in healthy-weight adults.
Abstract only; full methodology, sample size, and blinding are not available. No long-term weight or health outcomes were reported. Subjective appetite ratings did not differ, and the effect is from a single meal 90 minutes later.
low confidenceWhy this study matters
More whey protein, less eaten later — a dose-response pattern
In Study 1 (1675 kJ preload), energy intake after control was 4136 kJ, versus 3520 kJ after 12.5% protein, 3384 kJ after 25% protein, and 2853 kJ after 50% protein (all P<0.05 vs control). In Study 2 (1047 kJ preload), intake was 4801 kJ after control, versus 4205 kJ after 10% protein, 3988 kJ after 20% protein, and 3801 kJ after 40% protein (P<0.05). Absolute reductions vs control ranged from 616 to 1283 kJ in Study 1 and 596 to 1000 kJ in Study 2; relative reductions were about 15–31% and 12–21%, respectively.
It suggests a simple lever — protein content of a drink — may affect how much you eat at your next meal. But the effect is from a single meal and doesn’t prove weight loss.
You can eat less without feeling less hungry
Despite significant differences in actual energy intake between preloads, the abstract reports no differences in subjective appetite ratings between preloads in either study. Appetite ratings were collected before and after the preload and after the test meal.
Most people assume eating less happens because you feel fuller. Here, the behaviour changed but the conscious experience of appetite did not — a dissociation worth discussing.
The finding replicated across two different preload sizes
Two separate randomised crossover studies used 400 mL liquid preloads followed by an ad libitum test meal 90 minutes later. Study 1 used a 1675 kJ preload; Study 2 used a 1047 kJ preload. Both showed a dose-response effect of whey protein content on subsequent energy intake.
Replication across two studies with different preload energy levels strengthens the signal, even though the abstract lacks full methodology details.
What the abstract does not tell us
The abstract does not specify sample size, blinding, or long-term outcomes. Participants were healthy-weight men and women (BMI 19.0–25.0 kg/m², age 19.4–40.4 years). The study measured acute energy intake at a single meal, not daily energy balance, weight, or health outcomes.
It is a useful reminder that a compelling acute effect does not automatically translate into a practical long-term strategy.
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
Scientists gave healthy-weight people a 400 ml drink with different amounts of whey protein, then let them eat as much as they wanted 90 minutes later. They also used a flavoured-water control drink.
Research results
In Study 1, after flavoured water people ate 4136 kJ. After 12.5% protein they ate 3520 kJ, after 25% protein 3384 kJ, and after 50% protein 2853 kJ. In Study 2, after flavoured water people ate 4801 kJ, after 10% protein 4205 kJ, after 20% protein 3988 kJ, and after 40% protein 3801 kJ. Higher protein meant less eaten later. Appetite ratings did not differ.
What this means - more context
Compared with flavoured water, the highest-protein preloads meant people ate roughly 1283 kJ less (Study 1, 50% protein) and 1000 kJ less (Study 2, 40% protein) at the next meal. That is about 31% and 21% lower relative to the control meal, but it is a single-meal effect; the study did not show whether this changes daily energy balance, weight, or health.
To investigate whether different amounts of whey protein in a liquid preload affect appetite and subsequent ad libitum energy intake in healthy-weight adults.
In two randomised crossover studies, higher whey protein content in 400 mL liquid preloads was followed by lower ad libitum energy intake 90 min later. Study 1 (1675 kJ preload): control 4136 kJ vs 12.5% protein 3520 kJ, 25% protein 3384 kJ, 50% protein 2853 kJ (P<0.05). Study 2 (1047 kJ preload): control 4801 kJ vs 10% protein 4205 kJ, 20% protein 3988 kJ, 40% protein 3801 kJ (P<0.05). Absolute reductions vs control: 50% protein in Study 1 was 1283 kJ lower (~31% lower relative); 40% protein in Study 2 was 1000 kJ lower (~21% lower relative). No differences in subjective appetite ratings.
Methods Used
Two separate randomised crossover studies. Healthy-weight men and women (BMI 19.0–25.0 kg/m², age 19.4–40.4 years) consumed one of four 400 mL liquid preloads followed by an ad libitum test meal 90 min later. Study 1 preloads: 1675 kJ with 12.5%, 25%, or 50% energy from protein; Study 2: 1047 kJ with 10%, 20%, or 40% energy from protein. Flavoured water was control in both. Appetite ratings were collected before/after preload and after meal. Sample size and blinding not specified in abstract.
Main Finding
Dose-response effect of preload protein content on subsequent meal energy intake: higher whey protein preloads were followed by lower ad libitum energy intake. Absolute reductions vs flavoured-water control ranged from 616 kJ (12.5% protein, Study 1) to 1283 kJ (50% protein, Study 1) and from 596 kJ (10% protein, Study 2) to 1000 kJ (40% protein, Study 2). Relative reductions were about 15–31% in Study 1 and about 12–21% in Study 2. No detectable differences in subjective appetite ratings. Long-term energy balance/weight outcomes not reported.
Confidence Level
Limited - based on abstract only, full methodology not available; randomised crossover design is appropriate for acute feeding effects, but sample size, blinding, and long-term outcomes are not specified.
Study Flags
Red Flags
- •Full text not available - methodology details cannot be verified
- •Sample size not specified in abstract
- •Blinding not specified; acute feeding study with no long-term weight or health outcomes
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Practical Takeaways
For now, treat this as an acute experimental finding rather than a weight-loss recommendation: a higher-whey-protein liquid preload was followed by lower next-meal energy intake in healthy-weight adults.
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 541 / 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 is a randomised controlled trial, which is one of the best ways to test if something causes an effect. Because people were randomly assigned to different protein drinks, we can be fairly confident that the protein itself changed how much they ate at the next meal, not other differences between people. But it only looked at one meal in healthy-weight adults, so we can't say it helps with weight loss over time.
Strengths
- Randomised crossover design
- Controlled with flavoured water preload
- Dose-response assessment of protein content
Weaknesses
- Full methodology not available - based on abstract only
- Blinding status unknown
- Sample size not reported
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists gave healthy-weight people a 400 ml drink with different amounts of whey protein, then let them eat as much as they wanted 90 minutes later. They also used a flavoured-water control drink.
Research results
In Study 1, after flavoured water people ate 4136 kJ. After 12.5% protein they ate 3520 kJ, after 25% protein 3384 kJ, and after 50% protein 2853 kJ. In Study 2, after flavoured water people ate 4801 kJ, after 10% protein 4205 kJ, after 20% protein 3988 kJ, and after 40% protein 3801 kJ. Higher protein meant less eaten later. Appetite ratings did not differ.
What this means - more context
Compared with flavoured water, the highest-protein preloads meant people ate roughly 1283 kJ less (Study 1, 50% protein) and 1000 kJ less (Study 2, 40% protein) at the next meal. That is about 31% and 21% lower relative to the control meal, but it is a single-meal effect; the study did not show whether this changes daily energy balance, weight, or health.
To investigate whether different amounts of whey protein in a liquid preload affect appetite and subsequent ad libitum energy intake in healthy-weight adults.
In two randomised crossover studies, higher whey protein content in 400 mL liquid preloads was followed by lower ad libitum energy intake 90 min later. Study 1 (1675 kJ preload): control 4136 kJ vs 12.5% protein 3520 kJ, 25% protein 3384 kJ, 50% protein 2853 kJ (P<0.05). Study 2 (1047 kJ preload): control 4801 kJ vs 10% protein 4205 kJ, 20% protein 3988 kJ, 40% protein 3801 kJ (P<0.05). Absolute reductions vs control: 50% protein in Study 1 was 1283 kJ lower (~31% lower relative); 40% protein in Study 2 was 1000 kJ lower (~21% lower relative). No differences in subjective appetite ratings.
Methods Used
Two separate randomised crossover studies. Healthy-weight men and women (BMI 19.0–25.0 kg/m², age 19.4–40.4 years) consumed one of four 400 mL liquid preloads followed by an ad libitum test meal 90 min later. Study 1 preloads: 1675 kJ with 12.5%, 25%, or 50% energy from protein; Study 2: 1047 kJ with 10%, 20%, or 40% energy from protein. Flavoured water was control in both. Appetite ratings were collected before/after preload and after meal. Sample size and blinding not specified in abstract.
Main Finding
Dose-response effect of preload protein content on subsequent meal energy intake: higher whey protein preloads were followed by lower ad libitum energy intake. Absolute reductions vs flavoured-water control ranged from 616 kJ (12.5% protein, Study 1) to 1283 kJ (50% protein, Study 1) and from 596 kJ (10% protein, Study 2) to 1000 kJ (40% protein, Study 2). Relative reductions were about 15–31% in Study 1 and about 12–21% in Study 2. No detectable differences in subjective appetite ratings. Long-term energy balance/weight outcomes not reported.
Confidence Level
Limited - based on abstract only, full methodology not available; randomised crossover design is appropriate for acute feeding effects, but sample size, blinding, and long-term outcomes are not specified.
Study Flags
Red Flags
- •Full text not available - methodology details cannot be verified
- •Sample size not specified in abstract
- •Blinding not specified; acute feeding study with no long-term weight or health outcomes
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Practical Takeaways
For now, treat this as an acute experimental finding rather than a weight-loss recommendation: a higher-whey-protein liquid preload was followed by lower next-meal energy intake in healthy-weight adults.
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 541 / 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 is a randomised controlled trial, which is one of the best ways to test if something causes an effect. Because people were randomly assigned to different protein drinks, we can be fairly confident that the protein itself changed how much they ate at the next meal, not other differences between people. But it only looked at one meal in healthy-weight adults, so we can't say it helps with weight loss over time.
Strengths
- Randomised crossover design
- Controlled with flavoured water preload
- Dose-response assessment of protein content
Weaknesses
- Full methodology not available - based on abstract only
- Blinding status unknown
- Sample size not reported
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study was well-designed because it randomly assigned people to different drinks and used a control drink, which helps make the comparison fair. However, we only have the summary, not the full details, so we don't know if people could tell which drink they got or how many people were in the study, which makes it harder to be completely sure about the results.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
44 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample sizeno sample size reported
- 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 541 / 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. While the study uses a randomised crossover design, which can support causal inference, the abstract-only nature limits verification of key methodological details (blinding, allocation concealment, sample size, statistical analysis). The findings are limited to acute, single-meal energy intake in healthy-weight adults, so causation cannot be extended to long-term weight outcomes or other populations.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding information is provided in the abstract, so potential conflicts cannot be evaluated.
The text is limited to an abstract; no declaration sections are available. This prevents assessment of COI, funding sources, or author affiliations.
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
5 researchersIf this is your work, this is how we attribute it on Fit Body Science. Nerys M. Astbury is listed as the lead author.