Beyond body mass index: Study indicates health is about more than weight

Is it possible to be both obese and healthy? It’s true that obesity has long been associated with cardiovascular disease, Type 2 diabetes and several forms of cancer, but a lingering question is the degree to which obesity itself actually contributes to poor health. For every study suggesting that as body mass index (BMI) increases, the risk of chronic disease and early death also increases, there are others demonstrating that people can be healthy — or unhealthy — at almost any body weight.

For example, a study published in July in the Lancet examined data from more than 10 million people from four continents and found that BMI outside the normal range — both underweight and overweight — was associated with an increased risk of poor health and early death. However, a similar study of more than 300,000 Korean adults, also published in July, concluded that something called “metabolic health” was more important than BMI when it comes to estimating future health risk.

Metabolic health — a term that used to be found mostly in medical research but is coming into more general use — means not only that you don’t have cardiovascular disease or Type 2 diabetes but also that you don’t have the precursors of these diseases — increased levels of blood sugar, blood pressure or cholesterol.

Although it’s possible that genetics play a role in staving off these conditions at higher weights, how we live matters, too. Metabolically healthy obesity is more common among younger women who eat a healthy diet, are physically active and have a higher socioeconomic status. That’s probably because women are more likely to seek out preventive health care, and lower socioeconomic status affects the availability of resources that support a healthy lifestyle, including healthy food, walkable neighbourhoods and access to health care.

What’s clear is that health is not a given; it’s something that’s ours to be lost or gained based on the sum of our daily actions. A healthful diet, regular physical activity and avoiding tobacco use are important for protecting health and preventing disease, regardless of body weight.

As for whether weight loss improves health, that depends. For healthy obese individuals who have normal blood pressure, blood sugar and cholesterol levels, losing weight has not been shown to improve those metrics any further, and in some cases it actually contributes to unhealthy physical and psychological effects, including further weight gain. One unfortunate finding of long-term research studies is that as many as half to two-thirds of healthy obese individuals eventually become unhealthy. While it’s not clear why this happens, increasing age and decreasing physical activity are likely factors.

What’s clear is that health is not a given; it’s something that’s ours to be lost or gained ...