Thermic-effect-of-food

Certain dietary components genuinely increase energy expenditure through the thermic effect of food and thermogenic mechanisms. This article quantifies the evidence for protein, caffeine, capsaicin, green tea EGCG, and other dietary components on metabolic rate — with realistic effect size estimates.

Foods that genuinely affect metabolic rate do so through two mechanisms: thermic effect (the energy cost of digestion) and thermogenesis (heat production that increases energy expenditure). Protein has by far the largest thermic effect of any macronutrient. Other foods — capsaicin, caffeine, catechins — have small, transient effects that do not translate to meaningful weight loss without a calorie deficit.

The thermic effect of food (TEF) — energy expended in digestion, absorption, and processing — varies substantially between macronutrients and food types. High-protein and high-fibre foods have the highest metabolic costs. This article reviews TEF evidence and practical dietary implications.