Fat But Fit: Is Healthy Obesity Fact or Fiction?

“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,” explains Professor Matthias Blüher, University of Leipzig, Leipzig and Helmholtz Center Munich, Germany.

Estimates suggest that the prevalence of MHO is different among men and women, with obese women being more likely to have MHO (7-28%) than men (2-19%).  However, around half of the people with obesity have at least 2 complications which doesn’t qualify as MHO.

The session will discuss how adipose tissue behaves in those with obesity rather than their BMI, which determines whether or not they are MHO. In those with adipocytes that are of normal size, those people are less likely to present with complications that are associated with obesity, whereas those with enlarged adipocytes and inflamed adipose tissue are more likely to exhibit traits such as insulin resistance that lead to metabolic complications. The way we store fat is likely key to whether or not obesity can be described as MHO.

“When people with obesity have fat stored viscerally, or internally around their 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,” says Prof Blüher.

Those with adipose tissue dysfunction are more likely to have damaged tissues, fibrosis, and secretion of proinflammatory and adipogenic molecules that subsequently contribute to end organ damage. Adipokine may act directly on cells of the vascular system and lead to atherosclerosis, for example. To add to this, fatty acids or other metabolites may also impair the function of liver or insulin-producing cells in the pancreas. 

The most important question is whether or not MHO can genuinely be described as healthy. Several studies show that compared to those of normal weight with no metabolic comorbidities, those with obesity with no metabolic comorbidities still face a 50% increased risk of coronary heart disease, which suggests that in actuality MHO is not healthy. 

“So there is still a residual increased risk for those people living with obesity, even with what we would call metabolically healthy obesity,” says Prof Blüher.

Prof Blüher concluded that there are some with obesity without cardio-metabolic complications at a certain point in time, and in the past, a diagnosis of MHO led to low-priority treatment. However, the concept of MHO has been challenged with recent data that suggests the term metabolically healthy obesity is misleading:

“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. Therefore, weight management and recommendations for weight loss are still important for people living with metabolically healthy obesity.”