Yesterday, we introduced the fascinating and seemingly paradoxical concept of metabolically-healthy obesity. Today is part 2 of our 5-part series, in which we discuss evidence regarding the prospective risk of disease among the so-called metabolically-healthy obese.
The cross-sectional research certainly supports the existence of a sub-population of metabolically-health obese individuals; approximately 1 in 3 obese individuals has a healthy metabolic profile. But what about the chances of developing chronic diseases such as diabetes or cardiovascular disease – two common ailments tied to carrying excess weight?
Today, we look at two separate studies investigating this question.
In the first study, 2902 men and women were subdivided into different groups based on their weight (normal, overweight, and obese) and metabolic status (presence or absence of metabolic syndrome or insulin resistance). While this subdivision is a tad confusing, keep in mind that people with excess weight but lacking the presence of the metabolic syndrome or insulin resistance would be considered to fit the definition of the metabolically-healthy obese.
These individuals were prospectively followed for up to 11 years to see who would develop type-2 diabetes or cardiovascular disease.
And what say the results?
Over the follow-up period, 141 subjects (~5% of population) developed type-2 diabetes, and 252 experienced their first cardiovascular event (~9% of population).
In terms of risk for developing cardiovascular disease, overweight or obese subjects without the metabolic syndrome or insulin resistance, that is, metabolically healthy obese, were at NO higher risk in comparison to their equally healthy, but normal weight individuals.
Similar story in terms of type-2 diabetes risk; overweight or obese subjects without metabolic syndrome and overweight, insulin-sensitive subjects were not at increased risk for diabetes in comparison to healthy, normal weight individuals.
The authors of this study provide the following conclusion [emphasis added]:
“[…] in the absence of metabolic abnormalities, obesity itself did not increase risk for cardiovascular disease and was a relatively weak risk factor for incident diabetes.”
A similar conclusion was reached by Canadian researchers following a group of 1824 healthy men for a duration of 13 years.
Again, the subjects in this study were divided into 3 categories of body weight (normal weight, overweight, and obesity) and also on the presence of the metabolic syndrome.
During the follow-up period, 284 of the men developed cardiovascular disease.
Once again, the obese men who despite their excess weight had a relatively healthy metabolic profile (metabolically healthy obese) did not show any greater risk for developing cardiovascular disease in comparison to healthy, lean men.
The authors of this study, concluded the following:
“The results of this prospective population-based study indicate that the risk of ischemic heart disease associated with a high body mass index depended entirely on whether features of insulin resistance syndrome were simultaneously present.”
So, not only may 1 in 3 obese individuals have a healthy metabolic profile, but, in fact, their future risk of developing diabetes and cardiovascular disease may be equal to that of healthy, lean individuals.
But is there more to health than the level of triglycerides in one’s blood, or their risk of diabetes or cardiovascular disease? And if we consider other, potentially more telling outcomes – such as mortality – will metabolically-healthy obese individuals still be considered healthy?
Find out tomorrow in part 3 of the series.
Make sure to read Part 1 of this series: Metabolically-Healthy Obesity: an Oxymoron?
References and Further Reading:
Meigs, J. (2006). Body Mass Index, Metabolic Syndrome, and Risk of Type 2 Diabetes or Cardiovascular Disease Journal of Clinical Endocrinology & Metabolism, 91 (8), 2906-2912 DOI: 10.1210/jc.2006-0594
St-Pierre, A. (2005). Insulin resistance syndrome, body mass index and the risk of ischemic heart disease Canadian Medical Association Journal, 172 (10), 1301-1305 DOI: 10.1503/cmaj.1040834