Damon Gameau spends sixty days eating only foods considered healthy, including low-fat yogurt, muesli bars, and fruit juice, to test what happens when sugar comes from supposedly wholesome sources rather than candy. He keeps his calories in a normal range and tracks his body with regular blood work and scans, and the changes arrive fast: mood swings, weight gain around his midsection, and a liver doctors compare to a heavy drinker's. Gameau frames the experiment around his own impending fatherhood, wanting evidence rather than conflicting headlines before deciding what to feed his family. The film travels to an Aboriginal community in Australia grappling with diet-related disease, to American towns built around soda and processed food, and brings in doctors, nutrition researchers, and food industry insiders to explain how sugar gets hidden in products marketed as health food. Animated sequences break down how fructose behaves differently in the liver than other sugars. It plays as both a personal case study and an argument that the real culprit is not fat but the sugar added to replace it.