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Eric Ravussin is a world-renowned expert on obesity, metabolism, and aging whose pioneering research has shaped much of what we understand today about energy balance and caloric restriction. In this episode, Eric shares insights from his cutting-edge work on energy expenditure—a critical factor in understanding how our bodies regulate weight and appetite. He discusses methods for measuring energy output, energy balance, food intake, and appetite regulation, and explores key studies on macronutrient manipulation. Eric then delves into the CALERIE study on caloric restriction, highlighting insights related to biomarkers of both primary and secondary aging. The conversation also covers the potential of GLP-1 agonists to replicate these effects and looks ahead to how AI and technology could transform metabolic research in the coming years.

We discuss:

• Eric’s background and current work metabolism and measuring energy expenditure [3:00];

• The science behind metabolic chambers for measuring energy expenditure, and the complexities of indirect and direct calorimetry [8:00];

• The body's regulatory systems for maintaining energy balance and the primary influence of energy intake on body weight [18:30];

• The epidemic of obesity and a discussion of resting metabolic rate [24:45];

• The impact of exercise, appetite, gut hormones, and eating patterns on weight regulation [28:45];

• Experiments looking at how macronutrient composition affects energy expenditure [38:45];

• The challenges of studying diet in real-life settings, the potential of personalized nutrition, and how public health policy could play a role in guiding nutritional habits [51:00];

• The importance of protein in the diet, the limitations of dietary data collection, and how AI could potentially transform nutrition science [1:08:15];

• How Eric’s interest in caloric restriction (CR) began with Biosphere 2, metabolic efficiency's role in aging, and goals of the CALERIE study [1:15:15];

• The CALERIE study: exploring the real-world impact of caloric restriction [1:28:00];

• Notable findings from the CALERIE study after two years: sustained weight loss, participant retention, and more [1:40:00];