A recent study adds one more reason to be concerned about obesity in adolescents and young adults. 

A research letter, published online in JAMA Pediatrics in August, found that large portions of obesity-related conditions (ORCs) — such as prediabetes — in US adolescents and young adults may be due to obesity and to a lesser degree being overweight. 

The study found that, in adolescents, 6 of 7 of the measured ORCs had statistically significant population attributable fractions (PAFs) due to obesity; and among young adults, 8 of 9 of the measured ORCs had statistically significant PAFs due to obesity. 

PAF is a measure of the proportion of adverse health outcomes in a population that are due to a certain risk factor. 

Among cases of prediabetes, hypertension, and dyslipidemia, 20%-35% of adolescent cases and 40% of adult cases are attributable to obesity.

“So that just gives you a highlight of that — a large portion of these chronic diseases in this very young population can be attributable to obesity,” Ashwin Chetty, first author of the study and a third year medical student at Yale University, New Haven, Connecticut, told Medscape Medical News. “And that underscores the importance of being able to treat and prevent obesity in this population.”

“It definitely falls in line with other literature suggesting that if you adequately, successfully and durably treat obesity or excess adiposity, you could expect that it’s likely that …many of these other chronic conditions and diseases will improve,” said Aaron Kelly, PhD, co-director of the Center for Pediatric Obesity Medicine at University of Minnesota Medical School, Minneapolis. Some of the diseases will get better and some “will actually remit,” said Kelly who was not affiliated with the study. 

To conduct the cross-sectional study, the researchers used pooled data from the 2013-2023 National Health and Nutrition Examination Survey (NHANES) focusing on adolescents and young adults designated as obese or overweight according to their BMI. Researchers computed the prevalence of ORCs by BMI and age. 

The conditions studied were prediabetes, type 2 diabetes, hypertension, dyslipidemia, asthma, obstructive sleep apnea (only for young adults), liver steatosis, stress urinary incontinence (only for young adults), and kidney hyperfiltration.

The study sample included 4199 teenagers and 3200 young adults representing 25,171,549 teenagers and 30,957,997 young adults nationwide. Based on these survey populations, 18.7% of adolescents had overweight and 22.3% had obesity, and 25.8% of young adults had overweight and 29.7% had obesity.

Researchers used logistic regression to analyze the adjusted relative risk of having each obesity-related condition in those who had obesity or overweight compared to those with normal BMI, controlling for age, sex, NHANES cycle, insurance status, and self-reported regular healthcare. They also calculated PAFs due to obese vs overweight status.

Among teenagers, 6 of the 7 measured ORCs had statistically significant PAFs resulting from obesity, ranging from 10.2% (95% CI, 5.0%-14.1%) for asthma to 49.6% (95% CI, 48.3%-50.5%) for liver steatosis. Among young adults, 8 of 9 of the measured ORCs had statistically significant PAFs resulting from obesity, ranging from 10.4% (95% CI, 0.7%-17.1%) for asthma to 78.9% (95% CI, 47.2%-83.0%) for type 2 diabetes.

Researchers concluded that ORCs during youth raise the risk of more severe disease in the future and that treating and preventing obesity may reduce ORCs and their associated costs. 

“These PAFs can inform estimates of the potential impact of expanding access to behavioral, surgical, and pharmacotherapeutic interventions, including glucagon-like peptide 1 receptor agonists, on reducing ORCs in US youth,” authors wrote in the study. 

One caveat: “The relationships don’t seem to be as strong with overweight,” Kelly said.

“I mean, and that’s not super surprising because … when someone’s just in the overweight category, you typically don’t have the high levels of excess adiposity that you have in obesity and severe obesity,” Kelly said.

Why the Study?

Earlier this year The Lancet Diabetes & Endocrinology Commission published a report on the “Definition and diagnostic criteria of clinical obesity” in The Lancet Diabetes & Endocrinology. 

It created this new definition of obesity and identified obesity related conditions, Chetty said of the piece.

“And part of their definition of clinical obesity was the presence of these obesity related conditions. So, there is this understanding — and even now some people are incorporating these conditions into the definition of obesity itself. But what was unclear to me and to the people I was working with is not everyone with obesity has these conditions,” Chetty said.

Not everyone with obesity develops these conditions but a large portion do, Chetty added. So, when it comes to making policy and estimating the potential impact of public health interventions on preventing and treating obesity, it’s important to know how much obesity contributes to developing these conditions, Chetty continued. 

“So, this project was really an attempt to quantify how much obesity may contribute to these conditions,” Chetty said. 

“And these types of estimates can help inform policy discussion. It can help inform modeling for the impact of potential interventions and what their effect might be on preventing or treating some of these obesity related conditions,” Chetty added.

This is one paper among many that suggests that obesity can “wreak havoc on human health,” Kelly said. The study shows that even in adolescents and young adults “that a lot of the manifestations of cardiometabolic problems that pediatricians are seeing — or healthcare providers of young adults are seeing — can be attributable to obesity,” Kelly said.

Prevention is extremely important, Chetty said. “And one way to show its importance is to generate evidence about … how it may reduce complications down the line, and I think this study is one step or one contribution to that ongoing conversation.” 

Kelly advocates a treat obesity first approach which means that if an adult, adolescent, or child has obesity, it’s likely their high blood pressure, their liver problems, etc are caused by that, he said.

“So, you could use a blood pressure medication. You could use a statin, whatever, or a reasonable approach. With the treat obesity first sort of approach would be ‘let’s engage in an effective obesity treatment before we start tackling these other things,’” Kelly said.

But Chetty acknowledged that while a substantial proportion of these conditions are attributable to obesity, “a pretty substantial portion of these… conditions [are] not attributable to obesity.”

The study also highlights the point that people have been bringing up for a while that obesity in and of itself cannot completely address the rise in some of these chronic conditions in adolescents and young adults, Chetty said. 

“Many of these conditions are also caused by other factors that we aren’t able to identify in this study,” Chetty said. 

Study Limits

Notable limitations to the study are its sample size and cross-sectional nature, Chetty said.

“The way NHANES works is through survey weighting. So, our sample size for some of these conditions can be quite small,” Chetty said. 

The number of participants evaluated for type 2 diabetes, for example, was 4193 for adolescents and 3195 for young adults. “Those numbers represent the number of participants who had sufficient data available for us to determine whether or not they had type 2 diabetes,” Chetty said in an email. “However, only a fraction of those participants actually had type 2 diabetes.” In fact, in the sample, 12 adolescents had type 2 diabetes, and 16 young adults had it.

“So, in this population, we only had a handful of people who had type two diabetes… And while we were able to use the statistical methods … to make that representative of the US population, if you look at the confidence intervals for some of our estimates, some of those confidence intervals are quite large,” Chetty said.

“And what that says is that the actual number for our population attributable fractions should be taken with a grain of salt for some of these condition,” Chetty continued. “So, for example, type 2 diabetes and adolescents, we had a population attributable fraction of 3.2%. But the 95% confidence interval ranges from 0.4% to 28%. Ultimately, that means there’s a lot of uncertainty around the population attributable fraction we calculated for that. And that’s primarily a result of a small sample size.” 

Other confidence intervals such as that for liver steatosis are narrower, Chetty said. “We’ve more certainty in what that number is.”

Another limitation to the study is that it is cross-sectional, and so causation cannot be established.

“We don’t know whether they developed obesity and then developed hypertension” for example, Chetty said. “Some of these people might have had hypertension and later on developed obesity in which case their obesity just couldn’t have caused their hypertension, so we don’t have longitudinal information on these people.”

The study’s cross section design means “we can’t say it’s causative,” Kelly said. “But I do think that it adds to the literature in a meaningful way.”

Chetty reports personal fees from Close Concerns, which puts out a paid information service for digital health and technology companies. 

Kelly engages in unpaid consulting and educational activities and has served as an unpaid investigator for Novo Nordisk. He also engages in unpaid consulting activities and serves as an unpaid investigator for Boehringer Ingelheim, Eli Lilly, and Vivus. He receives donated drug/placebo from Novo Nordisk and Vivus for National Institute of Diabetes and Digestive and Kidney Diseases-funded clinical trials.