Waist Measures Reveal Hidden Obesity Risk in One in Six Young People Worldwide

Nearly one in three adolescents and young adults across 70 countries carries excess body fat that standard body mass index screening can miss, according to a multi-country cross-sectional study published in eClinicalMedicine. Using nationally representative survey data from 60,634 people aged 15 to 29 years, researchers found that 33.7 percent met criteria for confirmed excess adiposity when BMI and waist-based measures were considered together. The most striking finding concerned a hidden group: 15.7 percent of participants had waist-confirmed adiposity despite not meeting BMI criteria for obesity, and these young people already showed elevated cardiometabolic risk markers, including higher blood pressure, blood glucose, and cholesterol levels.

The study drew on the World Health Organization’s STEPwise approach to noncommunicable disease risk factor surveillance, a standardised household survey framework administered in countries across all six WHO regions between 2010 and 2023. Africa contributed the largest share of participants at 51.1 percent, followed by the Western Pacific at 14.8 percent, the Eastern Mediterranean at 10 percent, South-East Asia at 9.0 percent, Europe at 8.2 percent, and the Americas at 6.9 percent. The median participant was 24 years old, and males made up just over half of the sample. Within each surveyed household, one eligible member was randomly selected through an electronic data-collection application, and sub-national surveys restricted to specific provinces or cities were excluded to preserve national representativeness.

The analytical framework followed recommendations from the Lancet Diabetes & Endocrinology Commission, which in 2025 proposed moving beyond BMI-only assessment of obesity. Participants were classified as having confirmed excess adiposity if they met any of three criteria: an elevated BMI combined with at least one elevated waist-based measure, elevated values for both waist circumference and waist-to-height ratio, or an extreme BMI alone. The researchers applied sex, age, and ethnicity-specific cutoffs to account for variations in body composition. For adolescents aged 15 to 17 years, obesity-range BMI was defined using body mass index-for-age z-scores of plus two standard deviations or more, while for adults aged 18 to 29 years the threshold was set at 27.5 kilograms per square metre in Asian participants and 30.0 in non-Asian participants. Waist circumference cutoffs were similarly adjusted, with lower thresholds for Asian males at 90 centimetres compared with 94 centimetres for non-Asian males, and 80 centimetres for females in both groups.

The rationale for adding waist measurements rests on a well-documented weakness of BMI: it cannot distinguish fat from muscle or indicate where visceral fat is stored. People with normal BMI but excess abdominal fat, a pattern sometimes called normal-weight obesity, are routinely overlooked, while others with high BMI but healthier fat distribution may be wrongly flagged. Previous research has underscored the scale of this problem. In a United States study of more than 300,000 adults, obesity prevalence rose from 42.9 percent to 68.6 percent when waist-based measures were incorporated. An earlier multi-country study by the same research team found that more than one in five adults with normal BMI had abdominal obesity, a phenotype associated with elevated cardiometabolic risk.

The geographic patterns revealed by the new analysis were stark. Country-level prevalence of confirmed excess adiposity ranged from 6.6 percent in Ethiopia to 77.2 percent in Tonga and 77.1 percent in the Cook Islands. At the regional level, the Eastern Mediterranean recorded the highest pooled prevalence at 48.2 percent, closely followed by the Western Pacific at 47.7 percent, while Africa at 21.2 percent and South-East Asia at 19.1 percent showed the lowest figures. Economic gradients were equally pronounced: prevalence climbed from 21.6 percent in low-income countries to 51.7 percent in high-income countries. The authors attribute these contrasts to differing stages of the nutrition transition, noting that high-income settings face widespread ultra-processed foods and sedentary behaviour, while many low- and middle-income countries are experiencing a rapid rise in adolescent and young adult adiposity driven by energy-dense diets and declining physical activity.

Beyond prevalence, the study examined who was most affected. Excess adiposity was strongly associated with older age, female sex, higher country income, and physical inactivity. Compared with adolescents aged 15 to 17 years, the odds of excess adiposity nearly doubled among those aged 18 to 24 years and were almost four times higher among those aged 25 to 29 years. Females had substantially higher odds than males globally, with the strongest association observed in Africa, where the odds were more than nine times higher for females. Confirmed excess adiposity was two- to three-fold more prevalent in females than males across all age groups, and the absolute sex difference widened from adolescence into young adulthood. Physical inactivity, present in 16.9 percent of the sample, was associated with a modest but consistent increase in odds, with stronger effects in South-East Asia and the Western Pacific.

The cardiometabolic findings carry the greatest clinical weight. Among participants with waist-confirmed adiposity but no BMI-defined obesity, the odds of having at least one cardiometabolic risk marker were 1.92 times those of participants with no evidence of adiposity, and the odds of having two or more risk markers were 3.93 times higher. The risk markers assessed were hypertension, defined as systolic blood pressure of 140 millimetres of mercury or more, diastolic blood pressure of 90 or more, or current antihypertensive medication; diabetes, defined as fasting blood glucose of 7 millimoles per litre or more or glucose-lowering medication use; and high total cholesterol, defined as 5.0 millimoles per litre or more or lipid-lowering medication use. For participants with both BMI and waist criteria met, or very-high BMI alone, the associations were stronger still, with odds of 3.08 for any risk marker and 6.89 for multiple risk markers. Overall, confirmed excess adiposity was associated with 2.15 times the odds of any risk marker and 4.09 times the odds of multiple risk markers.

These associations matter because cardiometabolic risk factors that emerge during childhood and adolescence can persist into adulthood and contribute to later cardiovascular morbidity and mortality. Previous studies have shown that visceral fat gained in late adolescence and early adulthood predicts later hypertension, dyslipidaemia, type 2 diabetes, and metabolic syndrome, even among individuals with normal BMI. Adolescence and young adulthood therefore represent critical windows for prevention, when risk trajectories established during these periods may influence cardiovascular health across the life course. The authors argue that incorporating low-cost waist-based measures alongside BMI surveillance could help identify young people at higher cardiometabolic risk earlier, supporting more targeted prevention before risk accumulates.

The study has important limitations that shape how the findings should be interpreted. The cross-sectional design precludes causal inference, meaning the data show associations between excess adiposity and cardiometabolic markers but cannot establish that adiposity causes the elevated risk. WHO STEPS surveys lack direct measures of body fat such as dual-energy X-ray absorptiometry, computed tomography, or magnetic resonance imaging, so waist circumference and waist-to-height ratio remain indirect indicators of central adiposity. The surveys also do not comprehensively assess organ dysfunction, symptoms, functional limitation, or clinical history, which means the study estimated anthropometrically confirmed excess adiposity rather than diagnosing clinical or preclinical obesity under the Lancet Commission framework. Biochemical markers were not consistently available across all countries, point-of-care devices may differ from laboratory methods, and several variables including physical activity, diet, and medication use were self-reported and subject to recall or social desirability bias.

Further constraints include the composition of the sample itself. Participants aged 15 to 17 years accounted for only 4.5 percent of the total and were not represented in the European or American regions, limiting generalisability for that age group. WHO STEPS does not cover all countries, including some high-income nations, which may restrict applicability to higher-resource settings. Some regional estimates relied on small subgroups, such as participants with no formal schooling in the Region of the Americas, where only 75 people fell into that category. Despite adjustment for major confounders, unmeasured factors including genetic, early-life, and environmental influences may have contributed to the observed associations. Even so, the authors conclude that BMI alone is insufficient for assessing excess adiposity and cardiometabolic risk in young populations, and that adding simple waist-based measures to existing surveillance could strengthen early identification of those most likely to benefit from prevention.

Subject of Research: Prevalence of anthropometrically confirmed excess adiposity and its association with early cardiometabolic risk markers among adolescents and young adults across 70 countries

Article Title: Excess adiposity and early cardiometabolic risk markers among adolescents and young adults in 70 countries: a multi-country cross-sectional study

Article References: Aychiluhm, S. B., Isaac, V., Ross, A. G., Thapa, S., & Ahmed, K. Y. (2026). Excess adiposity and early cardiometabolic risk markers among adolescents and young adults in 70 countries: a multi-country cross-sectional study. eClinicalMedicine, 101, Article 104282. https://doi.org/10.1016/j.eclinm.2026.104282

Image Credits: AI Generated

DOI: 10.1016/j.eclinm.2026.104282

Keywords: excess adiposity, adolescent health, young adults, BMI limitations, waist circumference, cardiometabolic risk, obesity surveillance, WHO STEPS, hypertension, diabetes, high cholesterol, global health