The concept of metabolically healthy obesity (MHO) – or ‘fat but fit’- has been challenged by the link between adiposity and a range of health conditions.
Estimates suggest a different prevalence of MHO in men and women, with women living with obesity more likely to have MHO (7-28%) than men (2-19%). At the other end of the spectrum, around half of people living with obesity have at least 2 complications. For a given total body fat mass, people with MHO have lower liver fat mass (than expected for the BMI and total fat mass).
Professor Matthias Blüher, from Germany’s University of Leipzig, Munich, who will be giving a keynote address on the subject at this year’s Annual Meeting of the European Association for the Study of Diabetes, explained that how MHO was defined impacted whether it could really be described as healthy.
“Some 15-20% of people living with obesity have none of the metabolic complications we associate with the condition, namely abnormal blood sugar control and blood fats, high blood pressure, type 2 diabetes and other signs of cardiovascular disease,” Professor Blüher said.
“Yet when people with obesity have fat stored viscerally, or internally around organs such as in the liver, the data show that these people are much more likely to develop type 2 diabetes than those who store fat more evenly around their body.
“It is how the adipose tissue behaves in people with obesity, rather than their body-mass index, that will determine whether their obesity can be described as MHO.”
People with adipocytes of normal size are less likely to display the complications of obesity, whereas individuals with enlarged adipocytes and inflamed adipose tissue are more likely to exhibit traits such as insulin resistance that lead to metabolic complications.
“In people with adipose tissue dysfunction, this can lead to damaged tissue, fibrosis, secretion of proinflammatory and adipogenic molecules that subsequently contribute to end-organ damage. As an example, adipokines (fat released hormones) may act directly on cells of the vascular system and lead to atherosclerosis,” Professor Blüher said.
“In addition, metabolites such as fatty acids may impair the function of liver or insulin-producing cells in the pancreas, and several studies show that compared with people of normal weight with no metabolic comorbidities, people living with obesity and no metabolic comorbidities have a 50% increased risk of coronary heart disease.”
A diagnosis of MHO has frequently led to a low priority for obesity treatment, however, Professor Blüher pointed out that timely and personalised treatment of obesity should still be recommended to individuals with MHO to prevent future cardiometabolic complications.
“There is still a residual increased risk for those people living with obesity, even with what we would typically call MHO,” Professor Blüher said.
“Even in the absence of other cardiometabolic risk factors, increased fat mass and adipose tissue dysfunction contribute to a higher risk of type 2 diabetes and cardiovascular diseases – weight management and recommendations for weight loss are still important for people living with MHO.”