Large Figure in a Landscape

Normal Weight Obesity: Unhealthy at Any Size

It’s tough to get people to let go of weight and body size as the defining feature of obesity. But indeed, weight does not define obesity. Nor does BMI. What defines obesity is abnormal or excess fat (adipose) tissue that harms health. Most often, this occurs when someone’s weight is high. Not always, though. In fact, Nadeeja Wijayatunga and Emily Dhurandhar tell us in an excellent new review that about 30 million Americans have normal weight obesity. People with this condition have a high fat mass, but a BMI below 25. They have obesity – despite their weight status – and also a higher risk for other cardiometabolic diseases and death.

Definitions Vary

Body composition is the key measure for diagnosing normal weight obesity. It’s all about a high percentage of body fat – not body weight. But people disagree about how much body fat is too much. For women, the most common cutoff is 30 percent body fat. But the American Association of Clinical Endocrinologists (AACE) puts it at 35 percent for women. Others set it as high as 44 percent. Likewise, the numbers vary for men. AACE sets it at 25 percent. Some definitions put it as low as 22 percent or as high as 33 percent.

Wijayatunga and Dhurandhar summarize the wide variety of definitions in their review.

Health Effects and Interventions

Normal weight obesity results from the interaction of genes, environment, and behavior patterns. This is not so different from the factors contributing to broader patterns of obesity. Inflammation, oxidative stress, and metabolic abnormalities are key features of the pathology of this condition. This adds up to three times more risk for cardiometabolic disease, including high cholesterol, high blood pressure, and diabetes.

Much less is known about effective treatments for this condition. The limited research to date is all about lifestyle interventions – diet and exercise.

Invisible and Poorly Understood

This is a relatively common condition that’s rarely diagnosed. We need a clear consensus for diagnosis, a better understanding of the etiology, and more rigorous studies of interventions and outcomes. Because for now, normal weight obesity is progressing silently in 30 million Americans. Attention to the problem only comes after the complications emerge – diabetes, heart disease, or liver disease.

Better understanding and better approaches to preventive care are possible, but only if we can let go of preconceived notions that obesity is all about body weight.

Click here for the review by Wijayatunga and Dhurandhar. For further perspective on the problems with an excessive focus on BMI, click here.

Large Figure in a Landscape, painting by Georges Seurat / WikiArt

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May 19, 2021