By Michael J. Critelli | MakeUsWell Newsletter, 

One of our beta users for our food intelligence product asked a question about visceral fat. To be honest, I did not understand the importance of this biometric health indicator, which, in itself, is a symptom of a problem with our primary care system. 

For decades, the way most of us have thought about body fat has been remarkably simple: weigh yourself, calculate your BMI, and try not to gain too much weight.

But those numbers can miss something important: Where fat is stored may matter almost as much as how much of it we carry.

Visceral fat is the fat that accumulates deep inside the abdomen around organs such as the liver and intestines. It is different from the subcutaneous fat we can pinch under the skin. Visceral fat is metabolically active and is strongly associated with insulin resistance, type 2 diabetes, high blood pressure, fatty liver disease and cardiovascular disease.

That means two people of the same height and weight, and therefore the same BMI, can have very different metabolic risk.

Yet we do surprisingly little to measure it.

The most accurate ways to quantify visceral fat are CT and MRI scans. Some DEXA scanners can also estimate it. But these technologies are too expensive or impractical to become part of every routine physical, and CT exposes patients to radiation. Consumer “smart” scales that report visceral fat generally estimate it indirectly and should not be mistaken for a precise medical measurement.

Fortunately, there is a much simpler tool: a tape measure.

Waist circumference is not a perfect measure of visceral fat, but it is a useful proxy for abdominal adiposity and provides information that BMI alone does not. A major international consensus statement published in Nature Reviews Endocrinology recommended that waist circumference be treated almost like a “vital sign” in clinical practice. Yet many physicians still record weight and BMI while never measuring a patient’s waist.

This strikes me as a missed opportunity.

We have become accustomed to tracking blood pressure, LDL cholesterol, blood glucose and A1C because changes in those numbers can reveal risk before disease becomes obvious. Why shouldn’t we also pay greater attention to a physical measurement that can help identify metabolic risk?

The National Institute of Diabetes and Digestive and Kidney Diseases notes that abdominal fat can increase health risk even in people who are not overweight. That is particularly important as we age. A person can maintain approximately the same weight while losing muscle and accumulating more abdominal fat. The scale says nothing has changed. Metabolically, quite a lot may have changed.

There is also a problem with the way we talk about improving health. We usually tell people to “lose weight.” But weight loss is not necessarily the best objective.

A better objective may be to reduce harmful visceral fat while preserving, or ideally increasing, muscle.

Exercise provides a good example. Someone who begins walking briskly, doing resistance training and improving diet may lose abdominal fat while gaining or maintaining muscle. The scale may barely move. Yet waist circumference, insulin sensitivity, strength and cardiovascular fitness may all improve substantially. Research summarized in the international consensus statement indicates that exercise and dietary interventions can reduce waist circumference even without corresponding changes in BMI.

This suggests a simple change in how we manage our health.

Measure your waist periodically, under consistent conditions, and follow the trend just as you would follow your weight or blood pressure. Physicians could incorporate waist circumference into routine examinations and interpret it alongside BMI, blood pressure, glucose, lipids and other risk factors. 

I have inadvertently paid some attention to this biometric indicator without realizing it by tracking how well or badly I fit into clothes. Recently, as I was trying on dress pants and jackets, I experienced the troublesome experience of having tighter fits, while not having gained a lot of weight. Obviously, this is a symptom of a fat accumulation issue.

We should not turn visceral fat into another number to obsess over. Nor should we assume that every person needs an expensive body-composition scan. But we should stop pretending that the bathroom scale tells us everything we need to know.

The larger lesson is one I return to repeatedly in MakeUsWell: better health decisions often begin with asking whether we are measuring the right things.

When it comes to body fat, we may have been looking at the wrong number.