Beth Bradford
Aug 15, 2023
Your BMI might be healthy, but you could still be at a cardiometabolic risk.
Despite the ubiquitous use of Body Mass Index (BMI) as an indicator of health, a 2023 study in Frontiers in Nutrition has highlighted its limitations, bringing the concept of Normal Weight Obesity (NWO) to the fore. Traditional measures like BMI, a simple ratio of weight to height, may fail to identify a hidden epidemic of obesity among those with a normal weight range.
In a comprehensive cross-sectional study spanning six years (2015 to 2021), researchers recruited 3,001 adults aged between 20 and 95 years who visited a nutrition clinic in Israel. The study aimed to determine the prevalence of NWO and its relationship with cardiometabolic risk.
NWO was defined as having a normal BMI between 18.5 and 24.9 but with an excess body fat percentage—25% or more for men and 35% or more for women. The novel aspect here is the focus on body composition rather than weight alone, recognizing that fat distribution and muscle mass play critical roles in health outcomes.
Is there such a thing as skinny fat?
The results revealed that a significant proportion of the population might be "skinny fat," a term used to describe individuals who appear slim but have high levels of body fat relative to muscle. Among those with a normal BMI, 26% of men and 38% of women had excess body fat, classifying them as NWO.
More alarmingly, individuals with NWO exhibited higher levels of triglycerides, LDL cholesterol, and total cholesterol compared to their lean counterparts. This indicates a heightened cardiometabolic risk, as these are markers associated with heart disease and diabetes.
This research underscores the critical importance of assessing body composition, not just weight, in determining health risks. It spotlights the limitations of using BMI alone, which can provide a false sense of security for those with normal weight but poor body composition.
The use of dual-energy X-ray absorptiometry (DXA) scans in this study to measure body composition is noteworthy. Unlike many prior investigations that used bioelectrical impedance (BIA) for the same purpose, DXA is considered a gold standard in the field, adding to the study's reliability.
However, as with all studies, it has its limitations. Being a cross-sectional investigation, it lacks the ability to track changes in body composition and cardiometabolic parameters over time. The exclusive use of a single research center may also limit the generalizability of the findings to other population groups.
Despite these limitations, the study provides valuable insights into the hidden epidemic of NWO. It suggests a need for a paradigm shift in obesity identification and management, moving beyond just weight and BMI towards a more nuanced understanding of body composition.
In conclusion, the findings of this study are a wake-up call for both the medical community and the general public. They highlight the need for more comprehensive health assessments, including body composition analysis, to identify and manage obesity and its associated health risks effectively. In doing so, we might be better equipped to tackle the silent, insidious epidemic of normal weight obesity.