Monday, July 06, 2009
Earlier this year I discussed the notion of metabolically healthy obese individuals - that is, individuals who are clinically obese (body mass index >30kg/m2) and yet who appear to have perfect metabolic health (normal blood glucose, blood lipids, blood pressure, and cytokine profile).
While countless epidemiological studies have shown that as you move from a normal weight (BMI = 18.5-24.9 kg/m2) towards overweight (BMI = 25-29.9kg/m2) and obesity (BMI ≥ 30kg/m2) the risk of many diseases increases exponentially, it is also true that approximately 25% of obese individuals are metabolically healthy despite their excess weight.
Knowing the above, the question then becomes: should every obese person be instructed to lose weight for health reasons?
According to a recent study by Karelis and colleagues from Quebec, otherwise healthy obese people who lose weight via dieting may actually WORSEN their metabolic profile.
In the study, a sample of obese women were divided into either metabolically healthy (20 women) or metabolically at-risk (24 women) based on their level of insulin sensitivity (a marker of diabetes risk - the more insulin sensitive, the better) as measured using the euglycemic-hyperinsulinemic clamp procedure. These women then underwent 6 months of a medically supervised dietary weight loss program consisting of approximately 500-800 kcal reduction in daily food intake.
After the intervention all women lost a significant amount of body weight (approximately 6-7%).
More interestingly, however, while the metabolically at-risk obese women showed a 26% increase in their level of insulin sensitivity, the insulin sensitivity of the metabolically healthy obese women actually deteriorated by 13%!
This finding is very unexpected, and as of yet has not been corroborated by another study. Nevertheless, it does raise the very intriguing possibility that weight-loss among otherwise healthy obese women is not only unnecessary but, in fact, counter-productive.
This finding falls in line with a recommendation paper by Drs. Arya Sharma and Robert Kushner published in the International Journal of Obesity earlier this year. In that paper the authors proposed a novel obesity classification system which not only assesses weight, but also health complications of excess weight. Germane to the above discussion, Sharma and Kushner recommend that among obese individuals who have “no apparent obesity-related risk-factors” the goal of patient management should be to simply avoid further weight gain, or maintain current weight, rather than to induce weight loss. (To read Dr. Sharma’s full discussion of the new classification system please visit his blog here.)
In essence, the idea that healthy obese individuals may not have much to benefit health-wise from weight loss is not that surprising – they are healthy to begin with! However, whether weight-loss may actually be ill-advised for healthy obese individuals needs to be investigated by future studies which look at health outcomes other than insulin sensitivity. For example, it remains unknown whether exercise-induced weight loss among healthy obese individuals could also result in metabolic detriment (doubtful). Also, we have currently no idea if the above finding also holds true among men.
More on this topic in the near future.
Karelis, A., Messier, V., Brochu, M., & Rabasa-Lhoret, R. (2008). Metabolically healthy but obese women: effect of an energy-restricted diet Diabetologia, 51 (9), 1752-1754 DOI: 10.1007/s00125-008-1038-4
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