Recently, a patient in his 40s, a busy banker and father of two little ones, showed up at my clinic, completely stressed out. The day before, he finally took the blood test he had been putting off ("who has time for that?"), and the results kept him up at night.
Even before stepping into my office, he pulled out his phone from his shirt pocket and thrust the screen at me, filled with concern. The red numbers staring back at him, thankfully, didn't reveal any serious health issues: they were relatively mild disruptions in fasting sugar levels, "good cholesterol" and free blood fats.
However, the scientific reassurance didn't quite calm the emotional storm he was in. "Honestly, I just don't understand how this could be," he said in frustration, "my weight is completely normal!"
Welcome to our new medical game show: "The Fat in the Mask." Contestants: men and women aged 18 and over, with a normal BMI (between 18.5 and 24.9 kg/m², or about 18.5 to 24.9 lbs/ft²), but with a high body fat percentage (more than 35-30% in women and more than 25-20% in men, depending on age - see table below).
In the world of medicine, attention toward this puzzling population is growing, and the accepted term to describe them is NWO - Normal Weight Obesity. The problematic use of BMI as the sole index for defining obesity has been discussed before, and the enigmatic phenomenon of "skinny fat" people is a prime example of this.
The term NWO was first coined about 20 years ago by an Italian obesity researcher named Antonio De Lorenzo, referring to people who suffer from obesity where their weight, and thus their BMI, is normal.
Since then, numerous studies have been conducted, but they are not sufficient concerning this issue. The studies mainly examined the prevalence of the phenomenon in different populations (leading: East Asia) and its connection to common risk factors for cardiovascular diseases, like metabolic syndrome, lipid disorders, hypertension and more.
Today, it's a done deal: people with normal weight are not necessarily lean, and at least about 20% of them suffer from hidden obesity that could one day complicate them with cardiovascular diseases.
The pathophysiological basis of the NWO phenomenon is similar to that explaining "regular" obesity. The excess fat accumulated in various tissues, especially that surrounding the internal abdominal organs ("visceral fat"), acts like an endocrine gland and releases various substances into the bloodstream that encourage the development of chronic inflammation.
This fact is manifested, among other things, by an increase in the level of the inflammatory marker CRP among many people suffering from obesity (this can be checked with a simple blood test at a clinic).
Furthermore, chronic inflammation, over time, leads to growing insulin resistance in all its target tissues: the liver, muscle and fat. Resistance to this hormone is the main cause of the development of pre-diabetes and later, in about a third of the cases, also type II diabetes, packed with a plethora of complications.
So, who among those with normal weight might develop NWO sooner or later? Firstly, age is a significant risk factor, although young people are certainly exposed to the development of the disease. Secondly, it is known that women are at increased risk. Those who do not engage in regular and sufficient physical activity are also at risk of obesity at normal weight. This includes those who like to declare loudly, "I am always thin, so I don't need to exercise."
An unhealthy and unbalanced diet, especially regular and excessive alcohol consumption, is also considered a significant risk factor for NWO. As for smoking, findings are inconclusive.
The question arises: How are community doctors supposed to identify and catch those "misleading" individuals, completely normal in their weight and figure, but suffering from obesity? Firstly, according to the risk factors mentioned above: every patient should be questioned about physical activity, diet and especially alcohol consumption.
Secondly, regular screening tests should be performed according to the accepted protocol, such as measuring blood pressure, blood fats and fasting sugar level or glycosylated hemoglobin (HbA1C). Even a relatively slight deviation from the norm of these test results, without any deviation in waist circumference – like in the case of the patient from the beginning of the article, might lead to the diagnosis of metabolic syndrome: a combination of various signs in the physical examination and laboratory, whose presence indicates an increased risk of developing type II diabetes and cardiovascular diseases.
Every patient with a normal BMI on one hand and with metabolic syndrome on the other should be considered an immediate suspect for NWO. As such, they should be sent promptly to a clinical dietitian, where the body fat percentages are usually checked - by a special electronic scale relying on electrical conductivity, or by a caliper used to measure skinfolds.
The DEXA examination, based on X-ray radiation, is considered the most reliable method for assessing body fat percentage. In practice, due to its unavailability and relatively high cost, its use is relatively rare. Only after determining body fat percentages can we know if the patient suffers from obesity at normal weight - classified, in its milder form, as excess fat, and in its more severe form - as obesity.
And what is currently accepted as treatment for obesity at normal weight? As is known, the criteria for prescribing the medications accepted in the country and the world for treating obesity, whether older and less effective like Razin or Xenical, or newer and more effective like Wigovy, are based solely on BMI and not on body fat percentages.
For illustration, a super-muscular patient with a BMI higher than 30 and normal fat percentages could theoretically meet the threshold for medicinal treatment for obesity, while a patient with a normal BMI and high fat percentages (i.e., a person who suffers from obesity at normal weight) would not be able to receive the drug.
Hence, in cases of obesity at normal weight, the treating doctors have to settle - at least at this stage - for another type of prescription, no less important than the medicinal one. This refers to a prescription for a healthy lifestyle, emphasizing the encouragement of voluntary physical activity (at least 150 minutes a week of aerobic activity like walking or cycling at moderate to high intensity), along with adherence to a balanced and personalized diet.
These are exactly the guidelines the banker from the first paragraph received from me, who has meanwhile already visited a dietitian for the first time in his life and even signed up to a gym near his home. In about six months, he is expected to repeat the blood test that worried him so much, and hopefully, the desired improvement in his body fat percentages will bring with it a brighter health horizon.