ABSTRACT: Obesity is one of the greatest health challenges of the 21st century, currently affecting nearly one third of US citizens. Obesity was rare in the US as little as 120 years ago, and it remains uncommon in cultures that have not adopted an industrial diet and lifestyle. How did we get where we are today? Learn why cultures as different as the carbohydrate-eating Pima and the fat-eating Inuit remain lean eating a traditional diet, yet rapidly become obese after the introduction of Western industrial food. Unravel the paradox of why low-carbohydrate and low-fat diets can both cause sustained weight loss. Come explore the biology of obesity with me; learn why the industrial diet causes fat gain, and what we can do about it.