The Study
A randomized cross-over trial to determine the effect of a protein vs. carbohydrate preload on energy balance in ad libitum settings
This study gave people protein shakes or sugar shakes before meals and saw what happened over 5 days. It found that protein shakes made people burn a bit more calories after eating, and they ate more protein overall—but didn’t make them eat less food or lose weight. So we know protein changes what you eat and how your body uses energy, but we don’t know if it helps you lose weight over time.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Scientists gave people protein shakes before meals for 5 days and compared them to sugar shakes to see if protein made people feel fuller or eat less.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 588 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Even though protein is supposed to make you feel full, this study shows that in real-life eating, adding protein shakes doesn't help people eat less or lose weight in the short term.
- 2People ate the same amount of food with protein shakes as with sugar shakes.
- 3Protein made their bodies burn 3–5% more calories right after eating, but they didn't lose weight or eat less overall.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Nutrition Journal
Year
2019
Authors
Madeline Gibson, J. Dawson, N. Wijayatunga, Bridget Ironuma, Idah Chatindiara, F. Ovalle, D. Allison, E. Dhurandhar
Related Content
Claims (6)
When healthy adults with a normal body weight consume egg white protein shakes before meals, the proportion of their daily calories coming from protein rises to about 25.8%, and their total calorie intake does not decrease.
In healthy adults, eating egg white protein before a meal causes a small increase in short-term calorie burning compared to eating the same number of calories from carbohydrates, but this does not result in any measurable change in total energy balance over five days.
Eating protein or carbohydrate snacks before meals does not change how many calories people consume in a day, how many calories they burn, or their overall energy balance over five days when eating freely.
When healthy adults consume protein-based meals before eating, their feelings of fullness are not higher than when they consume the same number of calories from carbohydrates over five days.
When healthy adults eat a high-protein snack before a meal, they do not eat less protein later to compensate. This suggests the body does not adjust protein intake based on prior supply during normal eating.
Eating a diet high in protein leads to greater feelings of fullness and lower hunger afterward than eating a diet high in carbohydrates.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.