Obesity in the absence of metabolic disease may not increase health risks.
I have many patients who feel that if their blood pressure, blood sugar, and cholesterol are normal that they do not need to worry about their weight. In medicine, this is referred to as metabolically healthy obesity. The problem up to this date is that the research is not very supportive of this concept. In fact, Research: Fat and metabolically health vs. lean and metabolically unhealthy and Overweight, Obesity, or Overfat both discuss this topic and the supporting research conflicts with this concept. Most prior studies have examined mortality risk for metabolically healthy obesity, defined as zero or one metabolic risk factors but not as zero risk factors and this might be a flaw in their research.
A new research study published in October of 2018 in Clinical Obesity looked at this very flaw. In the study, researchers sought to determine the independent mortality risk associated with obesity or elevated glucose, blood pressure or lipids in isolation or clustered together. The study looked at a sample that included 54,089 men and women from five cohort studies. In our study sample, 6% of individuals presented with obesity but no other metabolic abnormalities. General obesity and abdominal obesity in the absence of metabolic risk factors were not associated with mortality risk compared to lean individuals. Conversely, diabetes, hypertension and dyslipidaemia in isolation were significantly associated with mortality risk. However, when using traditional approaches, obesity is independently associated with mortality risk after statistical adjustment for the other metabolic risk factors.
The bottom line: Elevation of even a single metabolic risk factor is associated with increased mortality risk. Metabolically healthy obesity, when defined as zero or one risk factor, is also associated with increased mortality risk as compared to lean healthy individuals, but would you actually call that metabolically healthy? Obesity in the absence of metabolic abnormalities may not be associated with a higher risk for all-cause mortality compared to lean healthy individuals. More research is needed, but it is clear that the results depend on your definition of metabolically healthy. This research does not mean that weight loss is not recommended in those that are overweight.