ABSTRACT There is controversy regarding the differential metabolic effects of proteins from plant and animal sources. Existing literature focuses on a limited range of plant proteins consumed just before, or as part of, a mixed meal, resulting in limited insight into the differential effects of plant proteins when ingested alone. This study compared the acute effects of a mixed plant‐based protein supplement and whey, when ingested in a fasted state and in the absence of other nutrients, on postprandial metabolism, appetite, and subsequent energy intake. Fifteen healthy adults completed three study visits in a randomized single blind crossover study design. Participants consumed 20 g protein from whey or a plant‐based protein supplement (blend of pea, brown rice, pumpkin seeds) mixed in water, or an equal volume of water as control. Plasma ketones, non‐esterified fatty acids (NEFA), glucose, insulin, and glucagon‐like peptide 1 (GLP‐1) were measured over 3 h postprandial, alongside resting energy expenditure (REE), respiratory exchange ratio (RER), and perceived appetite. Intake from an ad libitum lunch meal was used to assess subsequent energy consumption. There was a transient reduction in postprandial ketones and NEFA, and elevation of insulin and GLP‐1 following protein ingestion. Compared to plant protein, whey resulted in lower NEFA at T30 ( p = 0.037) and higher insulin concentrations at T30 ( p < 0.001) and T60 ( p = 0.010). REE, RER, subjective appetite ratings and subsequent energy intake were not different between the two proteins, relative to the control. The results from this study indicate that whey and a plant protein blend supplement have comparable metabolic effects.
Petkova et al. (2026) studied this question.