After studying the relationship between body mass index at the age of 25 and obesity later in life, researchers have found that people who are obese by 25 have a much higher risk of more severe obesity after the age of 35.

The researchers, who used data from the 1999-2010 US National Health and Nutrition Examination Survey (NHANES), will publish their findings in the June issue of the American Journal of Preventive Medicine.

According to the Centers for Disease Control and Prevention (CDC), obesity has risen over the past decades. The latest statistics for the US show that 35% of adults over the age of 20 are obese. The percentage of adolescents between 12 and 19 years old who are obese is 18.4%.

Conditions related to obesity include heart disease, stroke, type 2 diabetes and certain cancers, and the estimated annual medical cost of obesity in the US in 2008 was $147 billion.

The researchers - led by Jennifer B. Dowd, associate professor of Epidemiology and Biostatistics at City University of New York School of Public Health, Hunter College - found that while people who were obese by age 25 were more likely to be severely obese later in life, current weight was a better indicator of cardiovascular and metabolic risk, rather than duration of obesity.

Prof. Dowd says:


"The current findings suggest that the biological risks of longer-term obesity are primarily due to the risk of more severe obesity later in life among those obese early in life, rather than the impact of long-term obesity per se."

'Chance of severe obesity after 35 more pronounced for women'

In detail, the team found that 25-year-old men who were obese had a 23.1% probability of class III obesity after age 35. The researchers explain that class III obesity is defined as a body mass index (BMI) greater than 40.

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Individuals who are obese by age 25 are more likely to be severely obese by 35, compared with their normal-weight peers, putting them at risks for other chronic conditions.

This is compared with men of a normal weight at age 25, whose chance of severe obesity after age 35 was only 1.1%.

However, for women, the chance of severe obesity after age 35 was even more striking, with the likelihood rising to 46.9% for obese 25-year-olds, compared with 4.8% for normal-weight women of the same age.

In the wake of these compelling findings, the researchers note that there is a silver lining; they found that losing weight at any stage of life could reduce cardiovascular and metabolic risks, regardless of how long an individual has been obese or overweight.

"This is good news in some respects," says Prof. Dowd, "as overweight and obese young adults who can prevent additional weight gain can expect their biological risk factors to be no worse than those who reach the same level of BMI later in life."

Still, the team notes that because they are more likely to experience severe obesity levels, people in these risk groups are more prone to hypertension, inflammation, diabetes and other chronic conditions.

Fast facts about obesity in the US
  • Medical costs for obese individuals were $1,429 higher than those of a normal weight in 2008.
  • In 2012, higher prevalence of adult obesity was found in the Midwest and the South.
  • Lower prevalence was found in the Northeast and the West.

Anna Zajacova, assistant professor of Sociology at the University of Wyoming and study co-author, adds:

"Duration of obesity may still have important implications for mobility and musculoskeletal disease, research questions that should be investigated. Prevention of weight gain at all ages should thus be a clinical and public health priority."

Prof. Dowd says their study "adds to growing evidence that in terms of traditional cardiovascular, inflammatory and metabolic risk, obesity duration confers little additional risk beyond the current level of attained weight."

However, she cautions that "maintaining a stable level of obesity from a young age is not the norm, and being obese at age 25 years places individuals at risk of a much more severe level of obesity later in life compared to those who are normal weight at age 25 years."

Medical News Today recently reported on a study published in The Lancet, which suggested 37 million deaths could be prevented by reducing six risk factors, one of which was obesity.