Study analysis · European Journal of Nutrition · 2025
Your plant-based protein shake is just as filling as eggs and toast—here’s why that breaks the mold.
A plant-based protein shake and an egg-and-toast breakfast made people feel just as full, but neither made them eat less at lunch.
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 tested what happens right after people eat different kinds of breakfasts — like a plant-based shake vs. eggs on toast — and measured how full they felt and what hormones changed. It doesn't prove that one breakfast makes you eat less all day, just what happens in the few hours after eating.
What’s the bottom line?
Scientists tested if a plant-based protein drink and a solid egg-and-toast breakfast made people feel equally full after eating them for breakfast.
How strong is this study?
The study did a good job making sure everyone ate the same meals in a fair order, but we don't know if the people knew what they were eating — which could make them feel fuller just because they expected it. Also, only 18 people took part, so we can't be sure it works for everyone.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
58 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=18)+1.7/20
- Follow-up+10/10
100 / 100
54 / 100
- P-values+15/15
- Effect size+20/20
- 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 562 / 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. Randomization was confirmed, but blinding was unknown, which introduces potential performance and detection bias. However, the study design still allows for causal inference with moderate confidence due to random assignment and control of conditions.
COI Unknown
Could not determine conflict of interest status
No conflicts of interest or funding information are explicitly provided in the text. The study uses a commercially available plant-based protein drink (Huel) as one test condition, but author affiliations and funding sources are not disclosed.
The text lacks sections on competing interests, funding, and author affiliations. The study appears to be conducted at Newcastle University with ethical approval from the university's ethics committee. The use of a commercial product (Huel) may raise potential conflicts, but without author disclosures, no specific conflicts can be identified.
Key takeaways
- 01
Both meals raised fullness hormones by the same amount and made people feel equally less hungry.
- 02
But neither made people eat less at lunch.
- 03
Even though the body responded with fullness signals, people still ate the same amount of food at lunch — meaning these signals didn’t change actual eating behavior in the short term.
Surprising findings
- Higher GLP-1 and PYY levels were positively correlated with higher lunch intake—not lower.This directly contradicts the textbook belief that these hormones suppress appetite and reduce food intake. The study found people with higher hormone spikes actually ate more, not less.
- A plant-based liquid meal suppressed appetite as well as a solid animal-based meal.Liquid meals are typically considered less satiating than solid foods—this study found no difference, even though one was a shake and the other a full plate.
Practical takeaways
Swap your carb-heavy breakfast for a 30g plant-based protein shake—it’s just as filling as eggs and toast, and takes 2 minutes to make.
It didn’t reduce lunch intake, so it won’t automatically help with weight loss. Also, taste and long-term adherence weren’t tested.
high confidenceIf you’re over 65 and struggling to eat enough protein, try a plant-based shake—it worked just as well as animal protein for older adults in this study.
Only 6 older adults were studied—larger trials are needed, and this doesn’t prove long-term benefits.
medium confidenceWhy this study matters
Plant vs. Animal Protein: Tie Game
A 30g plant-based protein drink and a 30g animal-based breakfast (eggs, salmon, toast) triggered identical spikes in satiety hormones GLP-1 and PYY (p < 0.004) and equally suppressed hunger (p = 0.899), despite one being a liquid and the other solid.
Most people think animal protein is more satiating—this study flips that assumption, showing plant protein can match it exactly when protein content is matched, which matters for vegans, athletes, and eco-conscious eaters.
Hormones Don’t Control Eating—Here’s the Shock
Despite significant increases in GLP-1 and PYY (fullness hormones), participants ate the exact same amount of pasta at lunch regardless of whether they had the plant shake, animal meal, or low-protein carb breakfast (p = 0.220).
We’ve been told ‘hormones = control appetite,’ but this shows your body can ignore those signals—meaning fullness doesn’t always mean less eating.
Older Adults Respond Just Like Teens
Even though the older adult subgroup was small (n=6), their hormone responses and appetite suppression to 30g protein were statistically identical to young adults (p > 0.39 for age interactions), challenging the idea that aging blunts protein’s satiety effect.
Seniors often struggle to eat enough protein—this suggests plant-based shakes could be just as effective for them as traditional meals, without needing to chew or cook.
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 tested if a plant-based protein drink and a solid egg-and-toast breakfast made people feel equally full after eating them for breakfast.
Research results
Both meals raised fullness hormones by the same amount and made people feel equally less hungry. But neither made people eat less at lunch.
What this means - more context
Even though the body responded with fullness signals, people still ate the same amount of food at lunch — meaning these signals didn’t change actual eating behavior in the short term.
This study investigates whether a 30-gram plant-based protein drink and a 30-gram animal-based protein breakfast produce equivalent acute effects on satiety hormones, subjective appetite, and subsequent energy intake in healthy young and older adults.
A plant-based protein drink and an animal-based protein breakfast, both providing 30g protein, elicited identical increases in GLP-1 and PYY hormones and similar suppression of subjective appetite compared to a low-protein breakfast. No difference in subsequent ad libitum energy intake was observed between any conditions, and age did not influence responses.
Methods Used
Eighteen healthy adults (12 young, 6 older) completed a within-subject, counterbalanced, crossover trial with three breakfast conditions: plant-based liquid protein drink (HPDp), animal-based solid breakfast (HPBa), and low-protein high-carb breakfast (HCLPB). Satiety hormones (GLP-1, PYY), subjective appetite (VAS), and ad libitum lunch intake were measured over 4 hours.
Main Finding
A 30g plant-based protein drink and 30g animal-based protein breakfast produced equivalent increases in GLP-1 and PYY (both p < 0.004) and comparable suppression of subjective appetite (p = 0.899), despite differences in food form (liquid vs. solid). Neither significantly reduced subsequent energy intake (p = 0.220).
Confidence Level
High. Randomized crossover design with controlled conditions, validated hormone assays, and sufficient power (n=18) to detect large effects. Limitations include small older adult subgroup and lack of plant-based solid or animal-based liquid controls.
Study Flags
Red Flags
- •Small sample size (n=18), especially for older adults (n=6)
- •No control for plant-based solid or animal-based liquid meals to isolate form vs. source effects
- •No long-term or real-world adherence data
Surprising Findings
Higher GLP-1 and PYY levels were positively correlated with higher lunch intake—not lower.
This directly contradicts the textbook belief that these hormones suppress appetite and reduce food intake. The study found people with higher hormone spikes actually ate more, not less.
Practical Takeaways
Swap your carb-heavy breakfast for a 30g plant-based protein shake—it’s just as filling as eggs and toast, and takes 2 minutes to make.
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 562 / 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 tested what happens right after people eat different kinds of breakfasts — like a plant-based shake vs. eggs on toast — and measured how full they felt and what hormones changed. It doesn't prove that one breakfast makes you eat less all day, just what happens in the few hours after eating.
Strengths
- Randomized, counterbalanced, within-subject crossover design reduces individual variability
- Controlled meal composition and timing
- Use of validated measures (VAS for appetite, ELISA for hormones)
Weaknesses
- Blinding status unknown — risk of performance and detection bias
- Very small sample size, especially for older adults (n=6)
- No control for dietary intake prior to study days beyond standardized evening meal
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists tested if a plant-based protein drink and a solid egg-and-toast breakfast made people feel equally full after eating them for breakfast.
Research results
Both meals raised fullness hormones by the same amount and made people feel equally less hungry. But neither made people eat less at lunch.
What this means - more context
Even though the body responded with fullness signals, people still ate the same amount of food at lunch — meaning these signals didn’t change actual eating behavior in the short term.
This study investigates whether a 30-gram plant-based protein drink and a 30-gram animal-based protein breakfast produce equivalent acute effects on satiety hormones, subjective appetite, and subsequent energy intake in healthy young and older adults.
A plant-based protein drink and an animal-based protein breakfast, both providing 30g protein, elicited identical increases in GLP-1 and PYY hormones and similar suppression of subjective appetite compared to a low-protein breakfast. No difference in subsequent ad libitum energy intake was observed between any conditions, and age did not influence responses.
Methods Used
Eighteen healthy adults (12 young, 6 older) completed a within-subject, counterbalanced, crossover trial with three breakfast conditions: plant-based liquid protein drink (HPDp), animal-based solid breakfast (HPBa), and low-protein high-carb breakfast (HCLPB). Satiety hormones (GLP-1, PYY), subjective appetite (VAS), and ad libitum lunch intake were measured over 4 hours.
Main Finding
A 30g plant-based protein drink and 30g animal-based protein breakfast produced equivalent increases in GLP-1 and PYY (both p < 0.004) and comparable suppression of subjective appetite (p = 0.899), despite differences in food form (liquid vs. solid). Neither significantly reduced subsequent energy intake (p = 0.220).
Confidence Level
High. Randomized crossover design with controlled conditions, validated hormone assays, and sufficient power (n=18) to detect large effects. Limitations include small older adult subgroup and lack of plant-based solid or animal-based liquid controls.
Study Flags
Red Flags
- •Small sample size (n=18), especially for older adults (n=6)
- •No control for plant-based solid or animal-based liquid meals to isolate form vs. source effects
- •No long-term or real-world adherence data
Surprising Findings
Higher GLP-1 and PYY levels were positively correlated with higher lunch intake—not lower.
This directly contradicts the textbook belief that these hormones suppress appetite and reduce food intake. The study found people with higher hormone spikes actually ate more, not less.
Practical Takeaways
Swap your carb-heavy breakfast for a 30g plant-based protein shake—it’s just as filling as eggs and toast, and takes 2 minutes to make.
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 562 / 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 tested what happens right after people eat different kinds of breakfasts — like a plant-based shake vs. eggs on toast — and measured how full they felt and what hormones changed. It doesn't prove that one breakfast makes you eat less all day, just what happens in the few hours after eating.
Strengths
- Randomized, counterbalanced, within-subject crossover design reduces individual variability
- Controlled meal composition and timing
- Use of validated measures (VAS for appetite, ELISA for hormones)
Weaknesses
- Blinding status unknown — risk of performance and detection bias
- Very small sample size, especially for older adults (n=6)
- No control for dietary intake prior to study days beyond standardized evening meal
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study did a good job making sure everyone ate the same meals in a fair order, but we don't know if the people knew what they were eating — which could make them feel fuller just because they expected it. Also, only 18 people took part, so we can't be sure it works for everyone.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
58 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=18)+1.7/20
- Follow-up+10/10
100 / 100
54 / 100
- P-values+15/15
- Effect size+20/20
- 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 562 / 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. Randomization was confirmed, but blinding was unknown, which introduces potential performance and detection bias. However, the study design still allows for causal inference with moderate confidence due to random assignment and control of conditions.
COI Unknown
Could not determine conflict of interest status
No conflicts of interest or funding information are explicitly provided in the text. The study uses a commercially available plant-based protein drink (Huel) as one test condition, but author affiliations and funding sources are not disclosed.
The text lacks sections on competing interests, funding, and author affiliations. The study appears to be conducted at Newcastle University with ethical approval from the university's ethics committee. The use of a commercial product (Huel) may raise potential conflicts, but without author disclosures, no specific conflicts can be identified.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
1 video from Physionic cite this study, drawing 1 claim from it.
- Conflicting evidence
Evidence points in both directions — no clear conclusion yet.
Evidence
Authored by
4 researchersIf this is your work, this is how we attribute it on Fit Body Science. Anthony Watson is listed as the lead author.