“Don’t judge a book by its cover.” In metaphorical sense, it means to not form a quick judgment based on a first impression alone, be it a book or person. Likewise, one’s outward appearance does not reflect their health and well-being. One stark example that embodies this idea is the concept of normal-weight obesity.
More often than not, obesity is associated with being overweight. The World Health Organization defines obesity as the excess accumulation of fat and is measured by BMI (body mass index). BMI is calculated based on the ratio of a person’s height and weight to estimate the amount of body fat present. A BMI past 25 is considered overweight and beyond 30 is considered obese. However, obesity is not just about being overweight. Even those who appear skinny can fall into the category of obesity despite their healthy BMI. This is known as “normal weight” obesity (NWO), a condition characterized by a high body fat percentage despite normal weight.
BMI is interpreted using four weight categories: underweight, normal, overweight, obesity. However, it does not take into account obesity can occur at normal body weights.
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Shockingly, normal weight obesity affects 30 million Americans and is more commonly found in the elderly aged 60 and above. While NWO individuals have normal BMI, their body fat distribution is abnormal with higher amounts of visceral fat (fat stored in the belly that wraps around the abdominal organs) and lower fat in the lower limbs. Just as in the case with overweight obesity, NWO is associated with higher risk of cardiometabolic diseases such as heart attack, diabetes, and chronic kidney disease. This may possibly be due to elevated circulating fatty acids in the abdominal area, which contribute to increased inflammation and insulin resistance.
NWO is caused by a combination of lifestyle choices and dietary habits. Among normal weight adolescents, researchers found that individuals were less physically active and consumed fewer vegetables compared to lean young adults. In addition, consuming high-fat meals in crucial growth stages may induce normal weight obesity in children, which gradually progresses into overweight obesity during adulthood. This emphasizes the importance of maintaining balanced meals and engaging in regular exercise from early life through adulthood.
Despite the high prevalence of NWO, it often falls under the radar in health-related, and deserves greater attention due to the health risks associated with excessive fat accumulation. The problem lies in the use of BMI and its lack of sensitvity to identify individuals at cardiometabolic risk, causing NWO cases to be frequently overlooked during routine health check-ups. Hence, an alternative screening tool beyond BMI is urgently needed to identify these at-risk individuals.
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