BMI: A Reliable Measure of Obesity? New Study Says Yes
BUCHAREST — May 16, 2024 — Johns Hopkins University researchers recently published a study in JAMA indicating that the widely used body mass index (BMI) is a fairly accurate measure of obesity. The research examined data from the National Health and Nutrition Examination Survey, finding a strong correlation between BMI and excess body fat. Further analysis will likely be needed to continue the BMI’s position in obesity evaluation.
bmi: a reliable measure of obesity? new study says yes
body mass index (bmi) might be a more accurate measurement than commonly thought, according to new research.a recent study indicates that most people with a bmi signifying obesity also have significant excess body fat.
the study: bmi vs. body fat
- scientists at johns hopkins university conducted the study, published in jama this month.
- researchers analyzed data from the national health and nutrition examination survey (nhanes), a survey of americans’ dieting and lifestyle habits run by the centers for disease control and prevention (cdc).
- the study examined nhanes data from 2017-2018, including participants who underwent body fat and waist circumference measurements in addition to bmi checks.
key findings
the research team discovered that:
- more than 98% of individuals classified as obese by bmi also met the criteria for obesity based on waist circumference or body fat percentage.
- this suggests that bmi remains a valuable tool for assessing obesity at the population level.
although certain patient populations (eg, athletes) may warrant further evaluation, our results suggest that these individuals make up a very small portion of the population.johns hopkins university researchers
defining obesity
obesity is commonly defined in several ways:
a call for change?
the findings come amid calls for a shift in how obesity is diagnosed. earlier this year, a group of experts advocated for doctors to:
- use two measurements of body size (one of which can include bmi) or a direct measurement of body fat.
- group obesity into preclinical and clinical categories, based on whether it is causing related health problems.
some researchers and advocates in the body positivity and fat acceptance movement have long pushed for phasing out bmi, supported by groups like the american heart association and world obesity federation.
the debate continues
despite the push for alternative measures, the study suggests bmi remains relevant. direct body fat tests require specialized equipment and can be costly. the researchers argue that many people might not benefit from these additional tests.
for nearly all u.s. adults with elevated bmi, there may be limited utility to confirming excess adiposity.johns hopkins university researchers
currently, about 40% of adults in the u.s. are considered obese based on bmi criteria. [3] this rate might potentially be declining due to newer weight loss medications.
faq: understanding bmi
- what is bmi?
- bmi (body mass index) is a measure of body fat based on height and weight. [1], [2]
- how is bmi calculated?
- bmi is calculated using a formula that takes your weight (in kilograms) and divides it by your height (in meters squared), or using pounds and inches with a conversion factor. [1],[2]
- what are the bmi categories?
- bmi categories include underweight, normal weight, overweight, and obese. [1]
- is bmi always accurate?
- while bmi is a useful tool, it has limitations and may not be accurate for everyone, such as athletes. the study suggests it is indeed generally accurate for most of the population.
- what are the obesity classes?
- obesity is classified into three classes based on bmi ranges, each associated with different health risks. [3]
