Katsoulis M, Lai AG, Diaz-Ordaz K, et al. - For individual- and population- level prevention of obesity as well as its long-term consequences for health and health care, a radical shift in policy is needed to focus on people at the highest risk of weight gain (ie, young adults aged 18–24 years).

• This longitudinal, population-based cohort study used electronic health records data from 400 primary care practices in England.

• A total of 2,092,260 eligible persons with more than 9 million BMI measurements were included.

• Young adult age was identified as the strongest risk factor for weight gain at 1, 5, and 10 years of follow-up.

• At 10 years, the highest odds ratio (4·22) and greatest absolute risk of transitioning from normal weight to overweight or obesity was observed in adults in the youngest age group (18–24 years) vs the oldest age group (65–74 years).

• Consistently less strong association with these transitions was shown by other demographic factors.

• An open access online risk calculator is afforded, and high-resolution obesity risk charts over a 1-year, 5-year, and 10-year follow-up period are presented.