Created the calorie measurement system used on every nutrition label
Wilbur Olin Atwater built the first human respiration calorimeter in the United States — a sealed chamber that could precisely measure heat production and oxygen consumption. Through thousands of experiments, he determined the "Atwater factors": proteins and carbohydrates provide 4 calories per gram, fats provide 9 calories per gram. These numbers, still printed on every nutrition label today, were derived by burning food in a "bomb calorimeter" and adjusting for digestibility. He also led the first comprehensive study of American eating habits and established the USDA's food composition database.
Methods and Results of Investigations on the Chemistry and Economy of Food
1895
Created the 4-4-9 calorie system used worldwide; established food composition databases