Some obese individuals are “metabolically healthy,” Australian researchers reveal

While excess weight is usually associated with a host of other health problems, some obese individuals intriguingly remain free from type 2 diabetes and other metabolic disorders, according to an Australian study.

Researchers from Garvan Institute of Medical Research have shed new light on the key characteristics of metabolically healthy obese are and how they differ from other people with obesity. Their findings could provide a clearer understanding of type 2 diabetes causes, which could lead to better and more targeted treatments, the team shared.

"While it has been known that some obese individuals seem to stay metabolically healthy, there has been no consensus about how to define the condition,” said Associate Professor Jerry Greenfield, the study’s lead author and of a clinical research lab at the Garvan Institute of Medical Research. As a result, it has not been easy to understand what underpins these individuals’ apparent protection from disease, he added.

“Our own approach is to define metabolically healthy obesity in clearly measurable terms. We examine whether or not obese individuals also have a key complication of excess body fat: a resistance to the hormone insulin, which regulates the level of sugar in the blood after a meal,” Greenfield stated.

Obese individuals, who are not insulin-resistant, but instead remain sensitive to insulin, can be thought of as being metabolically healthy, Greenfield pointed out.

To explore insulin resistance in obesity in greater detail, Greenfield and his colleagues involved 64 obese individuals for the study. Using a gold standard technique, the team measured how each participant’s blood glucose levels responded to insulin over several hours.

They found that some participants were sensitive to insulin at muscle but were resistant at liver, while others had the opposite profile – sensitive to insulin at the liver but resistant at muscle. The researchers also observed that obese individuals who are sensitive to insulin in muscle only or liver only are metabolically healthier in many respects than the group that is insulin-resistant at both sites. This unique sensitivity to insulin serves as the metabolic protection for obese individuals, the team found.

“Not only do they have lower blood pressure, but they also have less deep abdominal fat and less fat within the liver. In fact, judging by these criteria, the metabolic health of these people is similar to that of individuals who are insulin-sensitive at both muscle and liver,” said Dr Dorit Samocha-Bonet, who co-led the study.

“The demonstration that insulin sensitivity in the liver and muscle may occur independently in humans potentially paves the way for earlier detection and individualised treatment of people at risk of developing metabolic disease,” noted Greenfield.

While it is early days, the team says they are taking the first steps towards a personalised and targeted approach to the treatment of obesity and type 2 diabetes.

Almost two in three Australian adults are overweight or obese, according to the Australian Institute of Health and Welfare. In addition to type 2 diabetes and insulin resistance, most of these obese individuals also develop high blood pressure and an abnormal blood lipid profile.

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