September 15, 2021
Individuals aged 18-24 years are at the highest risk of weight gain and developing overweight or obesity over the next 10 years compared with all other adults, and should be a target for obesity prevention policies, say UK researchers.
The research, published online September 2 in The Lancet Diabetes and Endocrinology, showed that factors more traditionally associated with obesity — such as socioeconomic status and ethnicity — play less of a role than age.
"Our results show clearly that age is the most important sociodemographic factor for BMI change," said lead author Michail Katsoulis, PhD, Institute of Health Informatics, University College London, UK, in a press release.
Co-senior author Claudia Langenberg, PhD, agreed, adding young people "go through big life changes. They may start work, go to university, or leave home for the first time," and the habits formed during these years "may stick through adulthood."
Current obesity prevention guidelines are mainly directed at individuals who already have obesity, the researchers say in their article.
"As the evidence presented in our study suggests, the opportunity to modify weight gain is greatest in individuals who are young and do not yet have obesity," they observe.
"If we are serious about preventing obesity, then we should develop interventions that can be targeted and are relevant for young adults," added Langenberg of the MRC Epidemiology Unit, University of Cambridge, UK, and Berlin Institute of Health, Germany.
Risks for Higher BMI Substantially Greater in the Youngest Adults
The researchers gathered data on more than 2 million adults aged 18-74 years registered with general practitioners in England. Participants had BMI and weight measurements recorded between January 1, 1998, and June 30, 2016, with at least 1 year of follow-up. Overall, 58% were women, 76% were White, 9% had prevalent cardiovascular disease, and 4% had prevalent cancer.
Changes in BMI were assessed at 1 year, 5 years, and 10 years.
At 10 years, adults aged 18-24 years had the highest risk of transitioning from normal weight to overweight or obesity compared with adults aged 65-74 years, at a greatest absolute risk of 37% versus 24% and an odds ratio of 4.22.
Moreover, the results showed that adults aged 18-24 years who were already overweight or obese had a greater risk of transitioning to a higher BMI category during follow-up versus the oldest participants.
They had an absolute risk of 42% versus 18% of transitioning from overweight to class 1 and 2 obesity, at an odds ratio of 4.60, and an absolute risk of transitioning from class 1 and 2 obesity to class 3 obesity of 22% versus 5%, at an odds ratio of 5.87.
Online Risk Calculator and YouTube Video Help Explain Findings
While factors other than age were associated with transitioning to a higher BMI category, the association was less pronounced.
For example, the odds ratio of transitioning from normal weight to overweight or obesity in the most socially deprived versus the least deprived areas was 1.23 in men and 1.12 in women. The odds ratio for making the same transition in Black versus White individuals was 1.13.
The findings allowed the researchers to develop a series of nomograms to determine an individual's absolute risk of transitioning to a higher BMI category over 10 years based on their baseline BMI category, age, sex, and Index of Multiple Deprivation quintile.
"We show that, within each stratum, the risks for transitioning to higher BMI categories were substantially higher in the youngest adult age group than in older age groups," the team writes.
From this, they developed an open access online risk calculator to help individuals calculate their risk of weight change over the next 1, 5, and 10 years. The calculator takes into account current weight, height, age, sex, ethnicity, and socioeconomic area characteristics.
They have also posted a video on YouTube to help explain their findings.
COVID and Obesity Pandemics Collide
Co-senior author Harry Hemingway, MD, PhD, also of University College London, believes that focusing on this young age group is especially critical now because of the COVID-19 pandemic.
"Calculating personal risk of transitioning to a higher weight category is important" as COVID-19 "collides with the obesity pandemic," he said, noting that "people are exercising less and finding it harder to eat healthy diets during lockdowns."
"Health systems like the NHS [National Health Service] need to identify new ways to prevent obesity and its consequences," he continued.
"This study demonstrates that NHS data collected over time in primary care holds an important key to unlocking new insights for public health action."
The study was funded by the British Heart Foundation, Health Data Research UK, the UK Medical Research Council, and the National Institute for Health Research. The authors have reported no relevant financial relationships.