Is obesity a chronic illness, or a risk factor for a host of illnesses?
That debate has been going on for decades.
Now, a blue-ribbon panel has weighed in with a new definition and diagnostic criteria that answers the question by saying, essentially: It depends. In a paper published by The Lancet medical journal’s Diabetes & Endocrinology Commission, a group of international experts has stated forcefully that obesity is more than just a high body mass index (BMI).
BMI, which is a calculated measure of a person’s body weight in kilograms, divided by their height in metres squared, has the advantage of providing a quick and easy metric. A BMI of 18 to 25 is considered normal, while a number more than 25 is overweight, more than 30 is obese, and more than 40 is morbidly obese. (For example, a person measuring 1.75 metres and weighing 100 kilograms would have a BMI of 32.7, and they would be categorized as obese.)
While BMI is handy, it can be misleading. A stocky, muscular person could have a high BMI but little body fat, while a thin person could have a low BMI, but with all their body fat accumulated around the waist.
BMI is also a bit too black and white; the new Lancet report stresses that obesity is a spectrum, with health consequences increasing with body fat.
The commission stresses that “excess adiposity” (accumulation of body fat) is what really matters, especially if it is around the waist, where it can cause damage to vital organs.
Obesity can cause many serious medical conditions – 18 conditions in adults and 13 in children, according to the new report – most notably the three biggest killers: cardiovascular disease, diabetes and cancer.
There are a number of ways to measure adiposity that are more telling than BMI. A simple one is waist circumference. A measure in excess of 102 centimetres for men and 88 centimetres for women is considered problematic. And remember, waist circumference should be measured just above the belly button; it’s not your pants size.)
Another measure is waist-to-hip ratio, which is considered a better predictor of health problems than BMI. To calculate, divide waist size by hip size; if the ratio is 0.9 or more for a man, or 0.85 for a woman, they are classified as having abdominal obesity.
There are also hi-tech tools that measure fat more directly, such as dual energy X-ray absorptiometry (DEXA), bioelectrical impedance analysis (BIA), and magnetic resonance imaging (MRI.) But diagnostic tools should be cheap and easy so, with obesity, the focus should be on waist size. The best tool remains the tape measure.
The Lancet commission that came up with the new definition said there is a need to distinguish between “clinical obesity,” a chronic, systemic disease state directly caused by excess body fat, and “preclinical obesity,” a condition of excess adiposity without current organ dysfunction or limitations in daily activities but with increased future health risk.
In not as many words, they are saying that more effort should be put into identifying and treating those who are truly obese, and not so much into those who are overweight but otherwise healthy.
One of the main critiques of the new approach is that it does not put enough emphasis on prevention. Still, the distinction between people whose excess body fat is causing them health problems and those who are not (yet), is an important one, especially at a time when new weight-loss drugs, such as Wegovy and Zepbound, are making waves and in high demand.
Many people taking the new class of fat-busting GLP-1 (glucagon-like peptide-1) drugs have had dramatic results, with average weight loss in the 15- to 20-per-cent range.
But these drugs are expensive, so insurers, both private and public, are trying to ensure coverage for those who will benefit most – meaning those with clinical obesity, not preclinical obesity.
Obesity is not a trivial issue, either from a health or economic perspective.
The World Health Organization says one billion people worldwide are living with obesity – one in eight people on the planet. The World Obesity Federation estimates the economic impact of obesity will top US$4-trillion by 2035.
In Canada alone, about nine million adults are considered obese, and economic costs are estimated at $27.6-billion annually.
The new definition of obesity could, if nothing else, focus some attention on the breadth and depth of the challenge.
That’s welcome news, because the cost of inaction is staggering.