Does eating a protein-heavy diet cause you to lose weight faster? Taking to Instagram longevity expert Peter Attia revealed the truth. He explained that weight loss ultimately comes down to the difference between energy in and energy out and one component of the energy out aspect of the process is the energy required to digest and metabolise food, termed the “thermic effect of food” or diet included thermogenesis. Protein is actually the least efficient source of energy and more than 25 per cent of the energy in protein is spent just metabolising it. Citing a meta analysis of 52 randomized trials, Attia explained that when our calorie intake is constant, diets with high protein does lead to increase of DIT as well as energy expenditure in comparison to protein deficit diet. But how much is fat loss related to increase of DIT? DIT contributes to just 5-15 per cent of energy expenditure. However, this isn’t to say that protein has no effect on weight loss as high protein intake has been proved to accelerate fat loss. However, this is more due to the fact that high protein diets lead to greater satiation leading to less overeating rather than a great increase in energy expenditure. However, protein is mandatory for one’s long-term health as it is necessary for musco-skeletal development which in turn is connected to longevity. Peter Attia is a Canadian-American physician, researcher, and writer widely recognized for his contributions to the field of longevity medicine and preventive health. Attia is an alumnus of Stanford University School of Medicine. He is also the author of Outlive: The Science and Art of Longevity, a critically acclaimed book that explores scientific approaches to increasing lifespan through lifestyle changes, preventive care, and modern medical insights. The book was a commercial success, and was voted as #1 New York Times best seller.