Study finds high-protein breakfasts boost fullness but do not change how much you eat later - Video

A new study from Newcastle University explores whether plant-based proteins can rival animal-based proteins in curbing hunger after breakfast. With growing concerns about sustainability and ethics, this research, published in European Journal of Nutrition, addresses whether plant and animal proteins differ in their ability to suppress appetite and influence subsequent calorie intake.

Protein is essential for health, but environmental and ethical concerns have increased interest in plant-based alternatives. Protein impacts digestion, metabolism, and appetite by stimulating satiety hormones like PYY and GLP-1, while suppressing ghrelin. Studies show varied results: some find certain plant proteins more satiating; others favor whey. Liquids generally suppress appetite less than solids, but the influence of protein source on this difference remains unclear.

The research involved 18 healthy adults in a randomized crossover design. Participants consumed three breakfast types on separate occasions: a plant-based high-protein drink (30 g protein, 7.8 g fiber), an animal-based high-protein meal (30 g protein, 4.5 g fiber), and a low-protein, high-carb meal. After fasting overnight and avoiding caffeine and exercise, they consumed the breakfasts under controlled lab conditions. Appetite was assessed using visual analog scales for four hours, and blood samples were collected to measure satiety hormones peptide YY (PYY) and glucagon-like peptide-1 (GLP-1). Finally, participants ate an ad libitum lunch to test how breakfast affected later food intake.

Results showed both high-protein breakfasts significantly boosted PYY and GLP-1 levels compared to the low-protein meal, with no meaningful difference between plant- and animal-based proteins. Subjective appetite decreased more after the plant-based drink, though differences were modest. Importantly, calorie intake at lunch did not differ across breakfast types or age groups. Hormone levels correlated weakly and non-significantly with energy intake.

The study concludes that plant-based protein drinks can match animal-based meals in stimulating satiety hormones and reducing appetite, offering a practical, sustainable breakfast option. However, these hormonal and appetite differences did not translate into decreased food intake later. Limitations include the small older adult sample and lack of testing different meal forms. Future research should examine long-term adherence and real-world effects.

This work supports plant proteins as effective alternatives to animal sources for appetite control, aligning sustainability with nutrition goals without compromising satiety.

REFERENCE: Watson, A.W., Brooks, A., Moore, L. et al. The effect of consuming different dietary protein sources at breakfast upon self rated satiety, peptide YY, glucagon like peptide-1, and subsequent food intake in young and older adults. Eur J Nutr 64, 315 (2025). https://doi.org/10.1007/s00394-025-03839-y