Use waist-to-height ratio along with BMI to assess obesity for children
Key takeaways:
- Most children aged 9 and 15 years with BMI in overweight range had a normal fat level.
- High and excess fat according to waist-to-height ratio was tied to higher odds for prediabetes and diabetes.
Waist-to-height ratio should be used in conjunction with BMI to assess overweight and obesity in children and adolescents, a researcher reported in a study published in Obesity and Endocrinology.
As Healio previously reported, a report from a Lancet Diabetes & Endocrinology Commission recommended the use of body fat measures instead of BMI to determine whether a person has obesity. A new study written by Andrew Agbaje, MD, MPH, PhD, FACC, FAHA, FESC, FNYAM, associate professor of clinical epidemiology and child health at the University of Eastern Finland, builds on that commission’s recommendations by proposing the use of waist-to-height ratio for assessing overweight and obesity among children and adolescents as well as introducing new terms to describe excess adiposity.
“Considering that obesity is a disease of excess fat rather than weight, the use of the term overweight and obesity reinforces the BMI limitation and subsequent stigma,” Agbaje told Healio. “Therefore, we proposed a new nomenclature based on waist-to-height ratio assessment of adiposity that can be used by health care professionals. The previous BMI overweight category can be replaced with waist-to-height ratio high fat (adiposopathy grade 1) and waist-to-height ratio excess fat (adiposopathy grade 2).”
Agbaje assessed BMI and waist-to-height ratio for 7,600 children in the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort in the U.K. Data were collected at age 9, 15 and 24 years. BMI standard deviation scores were used to diagnose underweight, overweight and obesity at age 9 and 15 years.
Four categories were created to define body fat according to waist-to-height ratio. Very low body fat was defined as a waist-to-height ratio of less than 0.4, normal body fat was labeled as a waist-to-height ratio of 0.4 to less than 0.5 for males or 0.4 to less than 0.51 for females, high body fat was defined as a waist-to-height ratio of 0.5 to less than 0.53 for males and 0.51 to less than 0.54 for females, and excess body fat was considered a waist-to-height ratio of at least 0.53 for males and at least 0.54 for females.
Discordance between BMI, fat measure
At age 9 years, 1,431 children had overweight according to BMI. Of those with overweight, 25% had high fat, 11% had excess fat and 64% had normal fat as measured by waist-to-height ratio. Of 517 children who were defined as having high fat according to waist-to-height ratio, 69.8% had overweight and 24% had obesity according to BMI.
There were 720 participants at age 15 years with overweight according to BMI. Of that group, 56.7% had normal fat according to waist-to-height ratio, 22.6% had high fat and 20.3% had excess fat. Of 311 adolescents with high fat in waist-to-height ratio, 52.4% had overweight according to BMI, 13.2% had obesity and 34.4% had normal BMI.
Of the study group, 814 had overweight according to BMI at age 24 years. Of those young adults, 48% had normal fat, 24.6% had high fat and 27.4% had excess fat according to waist-to-height ratio. There were 312 adults aged 24 years with high fat according to waist-to-height ratio, of whom 71.5% had a BMI in the overweight range, 17.3% had a normal BMI and 11.2% had obesity according to BMI.
“Children need at least four times more muscle mass than fat mass to adequately prevent the risk of premature cardiac and metabolic diseases,” Agbaje said. “However, BMI cannot distinguish between muscle and fat, and varies across age, sex and ethnicity; hence, a poor tool in diagnosing excess adiposity in children. Our result confirms that a heavy muscular child is not necessarily a child with high or excess fat.”
Fat measure tied to diabetes odds
The waist-to-height ratio cut points were validated using data from the 2021-2023 cycle of the National Health and Nutrition Examination Survey. Participants with high fat were more likely to develop prediabetes with a fasting glucose of 100 mg/dL or higher than those with normal fat (OR = 2.36; 95% CI, 1.1-5.1). People with excess fat were more likely to develop prediabetes as defined by an HbA1c of 5.7% or higher (OR = 1.5; 95% CI, 1.21-1.84) or diabetes with a fasting plasma glucose of 126 mg/dL or greater (OR = 6.08; 95% CI, 2.84-13.01) than those with normal fat.
Agbaje added more research is needed to examine how the waist-to-height ratio cut points detailed in the study are tied to other cardiometabolic diseases.
For more information:
Andrew Agbaje, MD, MPH, PhD, FACC, FAHA, FESC, FNYAM, can be reached at andrew.agbaje@uef.fi.
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