 This study found that self-reported physical activity and weight are reliable measures when compared to objectively measured data. However, certain demographic groups such as males, college-educated individuals, and those who are older, heavier, and less happy tend to over or underestimate their levels of physical activity and weight. Additionally, self-reported physical activity and weight were correlated with actual measurements, suggesting that they could be used as valid alternatives to more expensive and time-consuming methods of measuring these variables. This article was authored by James Buskewicz, Chelsea Rose, Shilpi Gupta, and others.