Metabolically Healthy Obesity Increases Risk of Diabetes

People with metabolically healthy obesity may not remain free of metabolic diseases in the long term.

Metabolically healthy obesity (MHO) is a medical condition in which obesity does not produce medical conditions. It stratifies patients with obesity according to their respective metabolic status. Some people with obesity are free of metabolic diseases (such as diabetes, high blood pressure, triglyceridemia) which often accompany this condition. This is what is known as “metabolically healthy obesity.”

Regardless of a diagnosis of nonalcoholic fatty liver disease (NAFLD), adults with MHO are more likely to develop diabetes compared to those who are metabolically healthy normal weight (MH-NW). This study was conducted to investigate the association between MHO and diabetes in a cohort of the middle-aged and elderly Chinese population, and whether the presence of NAFLD had an impact on the association.

The study included 17,801 participants (7,980 males and 9,821 females with a mean age of 63 years) excluding those that had diabetes at baseline, those with BMI less than 18.5, excessive alcohol consumption or liver diseases. The median follow-up time was 4.6 years. Based on their BMI and metabolic status, participants were divided into six phenotypes:

(1)  metabolically healthy normal weight (MH-NW), (2) metabolically healthy overweight ( MH-OW), (3) metabolically healthy obese (MHO), (4) metabolically unhealthy normal weight ( MU-NW), (5) metabolically unhealthy overweight ( MU-OW), (6) metabolically unhealthy obese (MUO).

The researchers observed 1,453 cases of diabetes where the incidence of diabetes was higher in patients with overweight ( HR= 2.11,95% CI 1.84-2.42) and obesity ( HR= 3.20, 95% CI 2.72-3.75) compared to patients who had normal weight. Metabolically unhealthy patients had a higher incidence of diabetes compared to MH individuals ( HR= 3.23, 95% CI 2.83-3.71). These results remained significant even after adjusting for NAFLD. MH-NW without NAFLD had the lowest incidence of diabetes while MH-OW and MHO had a higher incidence of diabetes regardless of the presence of NAFLD.

This study had a prospective design and a relatively large sample size compared to previous studies. A modest statistical power was used to assess the association between MHO and diabetes incidence. However, the analyses were restricted to middle-aged and elderly Chinese population which makes the generalization to other age groups and ethnicities questionable. In addition to that, HbA1c levels and 2-hour glucose tolerance tests were not performed at baseline, which might misclassify undiagnosed diabetes.

To conclude, this study reveals the importance of weight management in the middle-aged and elderly population to help avoid metabolic diseases such as diabetes in this age population. The findings of this study support that MHO was associated with an increased incidence of diabetes regardless of the presence of NAFLD.

Practice Pearls:

• Out of 17,801 participants, 1,453 cases of diabetes were identified where the incidence was higher in patients with overweight or obesity, compared to individuals with normal weight.
• This study had a large sample size compared to previous studies and good statistical power to assess the association. 
• Individuals with overweight and obesity must be encouraged to lose weight and counseled to live a healthy lifestyle to help minimize the risk of metabolic diseases such as diabetes.  

Wei Y, et al. Diabetes Metab Res Rev. 2019;doi:10.1002/dmrr.3202.

Nadeen Ayad, BCPS, PharmD Candidate, Skaggs School of Pharmacy, University of Colorado