Metabolically Healthy Obesity: What every registered dietitian needs to know

As dietitians already know, obesity continues to be a major healthcare crisis, and learning more about the care of individuals with obesity will be a huge part of practice for years to come. Metabolically healthy obesity (MHO) has been studied since the 1980s, yet this knowledge has not significantly changed clinical practice. When looking at the research about MHO, what limitations exist, and the implications we can draw, a new role for registered dietitians emerges.

What is MHO?

MHO is simply defined as the presence of obesity (a BMI greater than or equal to 30 kg/m²) without the metabolic conditions that usually accompany obesity.¹ Currently, there is no standard definition for MHO. However, many research studies characterize MHO by measuring waist circumference, and by classifying blood pressure, triglycerides, and HDL cholesterol within normal limits.¹ 

Individuals with MHO also showcase some level of physical fitness.¹ It is estimated that the prevalence of MHO among individuals with obesity ranges from six to 75 percent, depending on the definition of MHO used in the study.²

What are the limitations surrounding MHO?

Because there is no standard definition for MHO at this time, the ability to draw widely-accepted conclusions from research is limited. In addition, this condition is not yet a true medical diagnosis due to the lack of consensus in categorizing it. Researchers also have difficulty capturing the true prevalence and long-term health effects. Usually we hear the mantra, “more research is needed” at the end of a study, but when it comes to MHO, we really need a standard definition before continuing with more research.

How does MHO occur?

By looking at what MHO individuals have in common, research indicates preserved insulin sensitivity, low visceral and ectopic fat accumulation, normal adipose tissue function, normal adipokine secretion patterns, and high levels of physical fitness are possible causes of preserved metabolic health.¹ Genetic, environmental, and behavioral factors can lead to expansion of fat mass in the body.

If adipocyte storage is exceeded, lipids can accumulate ectopically in visceral fat deposits, which is associated with development of metabolically unhealthy co-morbidities. For those with MHO, the adipose tissue can expand, decreasing the amount of fat stored viscerally and leading to preserved insulin sensitivity, which reduces the risk of developing the metabolically unhealthy co-morbidities.³

What can dietitians do about MHO?

The key factors impacting a person’s transition from being metabolically healthy to metabolically unhealthy include following a healthy diet and high level of physical activity along with a stable or reduced BMI, waist circumference, and waist-to-hip ratio.³ Registered dietitians are the best experts to educate individuals about these lifestyle interventions to prevent or reverse metabolically unhealthy obesity.

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References

Jung CH, Lee WJ, Song KH. Metabolically healthy obesity: friend or foe? Korean J Intern Med 2017;32:611-621.

Rey-Lopez JP, Rezende LF, Pastor-Valero M, Tess BH. The prevalence of metabolically healthy obesity; a systematic review and critical evaluation of the definitions used. Obes Rev 2014; 15:781-790.

Schroder H, Ramos R, Baena-Diez JM, et al. Determinants of the transition from a cardiometabolic normal to abnormal overweight/obese phenotype in a Spanish population. Eur J Nutr 2014; 53:1345-1353.

Dennett, C. Metabolically healthy obesity—an oxymoron or medical reality? Today’s Dietitian 2017;19(1):30.