A landmark study from leading U.S. researchers reveals a stark surge in ‘extremely severe’ obesity among American children over the past decade and a half, igniting alarm among health experts worldwide. Drawing on nationally representative health data, the study, published in JAMA Network Open, found the proportion of kids with the most extreme forms of obesity more than tripled between 2008 and 2023—a trend that poses urgent questions for public health both in the United States and in countries like Thailand where childhood obesity is a rising concern (Gizmodo).
This latest research, led by academics from the University of California San Diego, is the first to specifically examine the prevalence and health consequences of what the team dubbed ‘Class 4’ and ‘Class 5’ obesity among young people. According to the study, 1.13% of U.S. children in 2023 fell into these new, ultra-high BMI categories—more than triple the percentage (0.32%) seen just fifteen years earlier. Given the estimated 73 million Americans under age 18, this figure translates to about 825,000 children now living with ‘extremely severe obesity’, medically defined as a body mass index (BMI) between 160% and 180% of the 95th percentile for age and sex (Class 4), or exceeding 180% of the 95th percentile (Class 5).
The spike is not only a statistical anomaly; it is already upending pediatric care. Children with these extreme BMI levels, the researchers report, are developing conditions traditionally seen only in adults, including fatty liver disease, type 2 diabetes, and advanced metabolic syndrome—all before even graduating from high school. As a leading pediatrician at the University of California San Diego explained, “[these children] are developing adult-type complications—fatty liver scarring, type 2 diabetes, metabolic syndrome—years before graduation. These conditions track into adulthood and shorten life expectancy… Treating them strains families, clinics, and the health care system.” (Gizmodo)
The study relied on data from the CDC’s National Health and Nutrition Examination Survey (NHANES), widely considered the gold standard for nationwide public health tracking in the U.S. Researchers combed through records from 2008 to 2023, analyzing changes in obesity and its most extreme forms. Notably, the risk of life-altering complications scaled dramatically with BMI severity: those with extremely severe obesity were seven times more likely to have fatty liver, eight times more likely to have severe insulin resistance, and ten times more likely to develop advanced liver scarring compared to peers with milder obesity.
Contributing factors range from changing dietary patterns—including greater access to ultra-processed foods and sugary beverages—to decreased physical activity, covid-era lifestyle shifts, and even genetic vulnerabilities. According to the lead researcher, “Because these pressures overlap, weight gain is not merely a personal choice issue but a complex, environment-driven problem.” This insight resonates acutely in Thailand, where rapid urbanization, changing family diets, and pandemic disruptions have driven a steady increase in childhood overweight and obesity, particularly in Bangkok and other urban centers (NHSO Thailand).
Researchers in the U.S. are now calling for more precise definitions to capture the added health risks faced by these children, whose needs may be obscured by existing BMI benchmarks. The American Academy of Pediatrics currently classifies severe obesity as a BMI 140% or more above the 95th percentile. But the study authors urge adoption of new categories—Class 4 and 5 obesity—and tailored interventions. They argue that failure to recognize the distinct vulnerabilities of this group risks under-treating those with the greatest health burdens.
This nuanced understanding has direct implications for Thailand, where health officials already struggle to contain a rise in childhood obesity. According to the National Health and Examination Survey (NHES) of Thailand, obesity among Thai children aged 6-14 reached 13.5% in the last decade, a figure that has continued to climb since the covid-19 pandemic with the proliferation of sedentary lifestyles and consumption of high-calorie foods (Thai NHES). As in the U.S., Thai children with higher grades of obesity are at sharply increased risk for diabetes, hypertension, and psychological distress—trends now being documented by pediatricians at Thailand’s major hospitals.
To combat this threat, the U.S. study points to successful interventions including clearer food labeling, healthier school meal standards, policies targeting junk food marketing to youth, and expanded access to community exercise facilities. Perhaps most transformative are the new weight-loss medications, such as semaglutide (known commercially as Ozempic and Wegovy), which show promise in achieving dramatic reductions in BMI. However, as noted by the UCSD study team, these drugs are expensive and, in many countries, largely inaccessible for children most in need. “Given the limited availability of novel, highly effective weight-loss medications such as semaglutide, I strongly believe that patients—especially pediatric patients—with classes 4 and 5 obesity, who carry by far the highest health risks, should be prioritized for access to these treatments,” the study’s lead author explained. He also argued for the creation of clinical trials specifically focused on children with extremely severe obesity.
In the context of Thailand’s public health system, this challenge is even more pronounced. Although the Thai Universal Health Coverage (UHC) scheme aims to provide broad access to essential medicines, the high cost and tight regulatory restrictions around new anti-obesity drugs put them out of reach for most families. Furthermore, the medical community in Thailand still faces stigma in addressing childhood obesity, compounded by low awareness among parents and limited school-based interventions outside a small number of international schools (The Lancet Regional Health – Western Pacific).
Historically, obesity in Thai children was relatively rare, with traditional diets high in vegetables and fish acting as a bulwark against chronic disease. But phenomena such as urban migration, increased exposure to Western fast food, and reduced open play spaces have shifted the landscape. Public health campaigns like the “ลดหวาน มัน เค็ม” (“Reduce Sugar, Fat, Salt”) initiative have gained traction, but persistent gaps remain—especially for teens in city environments and low-income families lacking safe exercise options.
Many local experts believe that swift policy, clinical, and community action must be taken to counteract these trends before Thailand faces its own epidemic of ‘extremely severe’ obesity. Pediatricians at government hospitals are reporting steadily increasing cases of advanced fatty liver and metabolic syndrome in children as young as ten. Without intervention, these children are at elevated risk of lifelong illness, decreased productivity, and higher national healthcare costs. Educational officials are also concerned about weight-based discrimination and bullying, which can impair mental wellbeing and school performance.
Internationally, the new American findings serve as a cautionary tale: once childhood BMI extremes take root, they become stubbornly difficult to reverse. Adolescent obesity strongly predicts adult obesity, creating intergenerational cycles of disease. For Thailand, this underscores the urgency of front-loading prevention efforts—expanding physical education hours in Thai schools, ensuring fruits and vegetables are affordable, cracking down on targeted junk food ads, and, where necessary, bringing evidence-based pharmacological and surgical treatments into the standard of care.
Looking ahead, experts stress that combating ‘extremely severe’ obesity in kids will require a multi-sectoral approach, enlisting not just doctors but also educators, community leaders, and policymakers. The lead researcher of the U.S. study concludes, “Children living with extremely severe obesity need greater access to obesity treatment, which can include family-oriented lifestyle programs, medications, and, for some cases, bariatric surgery.” Thai clinicians echo this call, noting that early screening and intervention could save countless lives and reduce burdens on the healthcare system in the decades ahead.
For Thai readers, the message is clear: childhood obesity is not simply a matter of willpower or personal responsibility. It is a complex, systemic problem shaped by urban infrastructure, food marketing, school environments, and the evolving Thai lifestyle. Families are urged to engage with their family doctor or pediatrician if concerned about their child’s growth trajectory and to take advantage of community exercise resources and health education campaigns. For policymakers, investing in healthy children is an investment in Thailand’s future prosperity—an issue demanding urgent action before a U.S.-style crisis takes hold.
For more in-depth information and suggested interventions, readers can consult reports by the World Health Organization, Thailand’s National Health Security Office, or visit the JAMA Network Open publication for full study details.