Study reveals how different types of obesity are linked to cancer

Both metabolically healthy and unhealthy “forms” of obesity are linked to an increased risk of various types of cancer, a new study warns.

Cases of obesity with metabolic complications, commonly called “metabolically unhealthy obesity”, as well as reports of “healthy” forms of the condition that do not pose metabolic harm on the body, were assessed by researchers, including those from Lund University in Sweden.

The findings, to be presented this week in the European Congress on Obesity in Dublin, highlighted that the type of metabolism in obesity patients is important when assessing their cancer risk.

There are no universally agreed definitions for a metabolically healthy person, but previous studies suggest that in those with such a metabolism status, the body is able to respond to food in an agile and beneficial way, reducing the risk of conditions like type 2 diabetes, heart disease and fatty liver disease.

And in some people with obesity, having a healthy metabolism has been shown to protect them from many of the adverse effects of excess body fat.

In their new study published in the Journal of the National Cancer Institute, however, researchers found that while metabolically unhealthy obesity is more strongly linked to cancer, both forms of the high body fat condition are related to an increased risk of different cancer types.

They analysed how body mass index, along with the metabolic health status of over 797,000 European individuals, was linked to obsesity-related cancer risk.

Researchers developed a metabolic score comprising blood pressure, plasma glucose and triglycerides fats to define metabolically healthy and unhealthy status.

The participants were then grouped into six categories – metabolically unhealthy obesity, metabolically healthy obesity, metabolically unhealthy overweight, metabolically healthy overweight, metabolically unhealthy normal weight and metabolically healthy normal weight.

Scientists found metabolically unhealthy obesity was associated with an increased risk of colon, rectal, pancreas, endometrial, liver, gallbladder and renal cancer, compared to metabolically healthy normal weight.

The highest risk estimates, according to researchers, were for endometrial, liver and renal cancer with 2.5-3 times increased risk.

Metabolically unhealthy women with obesity were found to have a 21 per cent increased risk of colon cancer, a three-fold increased risk of endometrial cancer and a 2.5-fold increased risk of kidney cancer, compared to metabolically healthy women of normal weight.

Women with obesity who were metabolically healthy had a 2.4 times increased risk of endometrial cancer and an 80 per cent increased risk of kidney cancer, scientists said.

In men, metabolically unhealthy individuals with obesity had a 2.6 times increased relative risk of kidney cancer, an 85 per cent increased risk of colon cancer and a 32 per cent increased risk of both pancreatic and rectal cancer.

Among men, researchers said obesity with metabolic complications increased the risk of these obesity-related cancers more than expected from the sum of either risk factor individually.

“This has important public health implications, suggesting that a significant number of cancer cases could potentially be prevented by targeting the co-existence of metabolic problems and obesity, in particular for obesity-related cancers among men,” scientists noted.

“In general, being metabolically unhealthy further increased the obesity-related cancer risk, suggesting that both obesity and metabolic conditions are useful targets for prevention for obesity-related cancers,” they concluded.