A 2025 study published in Nutrition Journal examined how animal and plant-based proteins affect energy metabolism after meals. In a controlled cross-over design, 48 overweight and obese men consumed two breakfasts with identical calories and macronutrient composition — differing only in protein source. Researchers then tracked metabolic responses for 5.5 hours, measuring energy expenditure and substrate oxidation.
The results showed that animal protein led to a faster and higher increase in postprandial energy expenditure compared to plant protein. In simple terms, the body spent more energy processing animal protein. Carbohydrate oxidation followed a sharper rise-and-fall pattern, and amino acid availability peaked earlier. Plant protein, by contrast, produced a slower, more stable metabolic response.
However, the difference was not dramatic. Both protein sources increased thermogenesis, just through different metabolic pathways. This highlights an important point often missed in nutrition debates: TEF is only one part of the picture. What matters just as much is the nutrient package that comes with protein in real food.
Protein never arrives alone. It comes with fats, carbohydrates, fiber, and other compounds — some beneficial, others commonly overconsumed. These accompanying nutrients can influence energy balance, insulin response, appetite, and overall metabolic health more than the relatively small TEF difference between protein sources. Choosing protein wisely therefore means looking beyond its origin and considering the full context of the food.
📎 Reference
Dehnavi Z. et al. (2025).
How animal and plant-based proteins affect energy metabolism during the postprandial phase in overweight and obese men: a cross-over design study.
Nutrition Journal.