Individuals aged 18-24 years are at greatest risk of becoming overweight or obese over the following decade, a longitudinal, large-scale, population-based cohort study has found.

Data were obtained from 400 primary care practices in England, between January 1998 and June 2016 via the Clinical Practice Research Datalink. Clinically recorded measures of height, weight and BMI for more than two million patients, 58% women, aged 18-74 years were analysed.

Individuals were grouped according to age at first BMI measurement: 18-24, 25-34, 35-44, 45-54, 55-64 and 65-74 years. Data on smoking, chronic disease and physical activity were also recorded.

These data were compared with cross-sectional comparators from UK and US health surveys to ensure that they were representative.

Changes in BMI over one, five and ten years were assessed. One pair of measurements from individuals taken during time windows of six months to two years, four years to six years, and eight years to 12 years, were obtained.

Absolute risk and odds ratios (OR) of transitioning between BMI categories were calculated.

The association of sociodemographic factors with BMI transitions was also estimated, adjusting for baseline BMI, family history of cardiovascular disease, use of diuretics, and prevalent chronic conditions.

Compared with adults in the oldest age group (65-74 years), adults in the youngest age group (18-24 years) had the highest risk at ten years of transitioning:

From the normal weight BMI category to overweight or obesity

• OR 4·22 (95% CI: 3·86-4·62)

• Absolute risk (37% vs 24%)

From overweight to class 1 or 2 obesity

• OR 4·60 (95% CI: 4·06-5·22)

• Absolute risk (42% vs 18%)

From class 1 and 2 obesity to class 3 obesity

• OR 5·87 (95% CI: 5·23-6·59)

• Absolute risk (22% vs 5%)

The following sociodemographic factors showed weaker associations with transitioning to a higher BMI:

• OR 1·23 (95% CI: 1·18-1·27) for those living in the most compared with the least deprived areas

• OR 1·12 (95% CI: 1·08-1·16) for men compared with women

• OR 1·13 (95% CI: 1·04-1·24) for black compared with white individuals

The study authors conclude:

‘Young adulthood offers an important, and currently neglected, opportunity for both population-level prevention of the onset of obesity and the identification of individuals at high risk of weight gain for targeted interventions.’ This is the first study to track patients over long periods identifying which individuals are at increased risk of obesity. Obesity is a risk factor for a range of conditions, and prevention measures offer enormous benefits. The findings reinforce the need to target this group of patients to address overweight.

Dr Peter Saul