The major factors responsible for the obesity epidemic are an increased energy intake combined with reduced physical activity. The authors of the study wanted to determine the relative contributions of increased energy intake and reduced physical activity to the U.S. obesity epidemic. Using data from the National Health and Nutrition Examination Surveys (NHANES) for mean weights and the U.S. food supply for the per capita energy supply estimate, they predicted the changes in weight from the changes in estimated energy intakes in U.S. children and adults between the 1970s and 2000s. Body weight increases predicted from the equations were compared with weight increases measured in representative U.S. surveys over the same period. The predicted changes in weights derived from the equations suggest that increase in estimated energy intake is sufficient, by itself, to explain the increase in weight in the U.S. population. These data reinforce the fact that population approaches to reduce obesity should focus on energy intake.