How We Got the Science of Weight Loss Wrong - with Giles Yeo

The speaker, Jose, a geneticist from the University of Cambridge, introduces himself and sets the stage for a talk on why calories may not count as expected in terms of weight management. He explains his focus on the interaction between genetics, the environment, and food, and how societal perceptions of calories may not align with biological reality. He also mentions the launch of his book, 'Why Calories Don't Count,' and prepares the audience for a detailed discussion with time allocated for questions.

Jose delves into the concept of a calorie, distinguishing between the small 'calorie' (a unit of heat) and the larger 'Calorie' (used to measure food energy). He explains the difference between the total calories in food and the usable calories our bodies actually extract, introducing the term 'caloric availability.' He uses examples of sugar and sweet corn to illustrate how food processing and structure affect the calories we absorb. Jose also touches on the historical methods, like the bomb calorimeter, used to measure food calories.

The speaker discusses the work of Wilbur Atwater, who developed the Atwater factors (9 calories per gram of fat, 4 calories per gram of carbohydrate, and 4 calories per gram of protein) in the late 1800s. These factors, still used today, were derived through extensive calorimetry and by measuring the heat of combustion in food. Jose points out that these factors do not account for the caloric availability of protein and fiber, which can differ significantly from the calculated values.

Jose explains how protein and fiber influence our perception of fullness and caloric absorption. Protein makes us feel fuller due to its complex digestion process and the hormones released during digestion. Similarly, fiber, both soluble and insoluble, contributes to satiety and reduces the effective caloric content of food. He emphasizes that the longer it takes for food to digest, the fuller we feel, and the fewer calories we absorb, which is why protein and fiber-rich foods are beneficial for weight management.

The speaker discusses the process of metabolism, highlighting how our bodies convert food into energy through the creation and use of ATP (adenosine triphosphate). He explains that the energy from food is stored in ATP molecules and released as needed, which is a more controlled process than burning calories as heat. Jose also points out that protein requires additional energy to remove nitrogen, which is excreted as urea, making it less calorically available than carbohydrates and fats.

Jose explores how different diets create a caloric deficit, leading to weight loss. He categorizes effective diets into three types: caloric restriction, high-protein, and high-fiber diets. He explains that while high-protein diets are popular and effective, they work because they inherently reduce carbohydrate intake, leading to a lower caloric availability. He also critiques the paleo and gluten-free diets, arguing that their effectiveness is due to their high-protein and high-fiber content rather than their adherence to a specific dietary philosophy.

The speaker shares his personal experience with a plant-based diet, which led to weight loss due to the high fiber content and lower caloric density of plant-based foods. He argues that the effectiveness of vegan and plant-based diets is due to their high fiber and protein content, which naturally reduces calorie intake. Jose also discusses the alkaline diet, noting that while it may be effective for weight loss, its principles are flawed and its benefits are likely due to the high fiber content of alkaline foods.

Jose addresses the socioeconomic divide in the consumption of ultra-processed foods, which are cheap, long-lasting, and often lower in protein and fiber. He notes that these foods are more prevalent among lower-income populations and contribute to health issues. The speaker emphasizes the need to improve the nutritional quality of ultra-processed foods and to promote healthier eating habits across all socioeconomic classes. He concludes by advocating for a balanced approach to diet and health, rather than fear-based restrictions on food.