Masood N. Khan M.D., F.A.C.P.

What is metabolically healthy obesity? This term has come into common usage nowadays.

Yes there is such thing as ‘metabolically healthy obesity’. It is defined as overweight condition with a BMI (Body Mass Index – an index of weight and height) of 30 or above but without any major risk factors for heart disease for example, high blood pressure, diabetes and high cholesterol level etc. By another criterion healthy obesity should also be free of abdominal obesity based on waist circumference. Increase in waist circumference is an important component of metabolic syndrome a condition that increases the risk for heart disease.

However, Dr. Yoosoo Chang of Kangbuk Samsung Hospital, Seoul, South Korea and his colleagues evaluated 14,828 individuals aged 30 to 59 years who were metabolically healthy according to above definition. Examinations were regularly conducted on these individuals between 2010 and 2012. As a part of these examinations they measured deposition of calcium within coronary arteries which supply blood to the heart muscle. The deposition of calcium in the arteries of the heart is considered to be a strong indicator of diseased arteries with obstructing plaques within them that lead to heart attacks.

Dr. Chang and colleagues found that the calcium deposit within the coronary arteries was higher among metabolically healthy obese participants compared with metabolically healthy normal-weight participants. Further analysis revealed that adjustment for metabolic risk factors especially LDL(bad cholesterol) levels between the two groups eliminated the significance of between increased heart disease and obesity. To understand this concept of adjustment in comparing, imagine there are 50 individuals who are obese and healthy and you are comparing them with 50 individuals who are healthy but not obese. In comparing them you found increased calcium deposit in the obese group and this fact did put them at increased risk of heart disease. But if you go into further details in comparing, to see how many individuals among obese have low cholesterol level and match them with those who are not obese but having the same low cholesterol level, the calcium deposit among obese individuals does not seem to increase the risk of heart disease as compared to their counterparts in the other group. Yet without detailed comparison, on an average, increased deposit of calcium in the coronary arteries among healthy obese individuals provides strong support to the notion that metabolically healthy obesity is not a harmless condition.

An independent analysis of the above study by Dr Caroline Kramer at Mount Sinai Samuel Lunenfield-Tanenbaum Research Institute at Toronto came to similar conclusions that compared to normalweight healthy individuals obese but healthy individuals are at increased risk of adverse longterm heart related outcomes even in the absence of metabolic abnormalities, suggesting that there is no healthy pattern of increased weight.

Dr. Bjorn Morkedal MD, PhD from Norwegian University at Trondheim, Norway and his colleagues recently published a study in Journal of American College of Cardiology, that investigated the relationship between metabolically healthy obesity with acute heart attack and heart failure. According to their research obese adults have an elevated risk for heart failure regardless of how healthy they are otherwise.

1. Chang Y. J Am Coll Cardiol2014: doi: 10.1016/ j. jacc. 2014.03.042
2. Kramer CK. Ann Intern Med. 2013; 159:758-769
3. Morkedal B. J Am Coll Cardiol 2014; 63:1071-1078
4. Stefan N. Lancet Diabetes Endocrinol. 2013; 2:152-162