To date, 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 ≥ 30 kg/m2) the risk of many diseases increases exponentially.
Does this imply that every individual carrying excess weight is guaranteed to develop diabetes, cardiovascular disease, cancer, or some other disease?
Although this belief prevails, the cumulative research suggests the answer to the above question is a resounding “NO!”
It all started in 1965. Two researchers, Albrink and Meigs, were performing a general investigation into the health of factory workers, and noted a rather counter-intuitive result: that “many obese men had normal triglycerides.”
Subsequently, in 1982, Ethan Sims first included the designation of “healthy obese” subtype in his classification of obesity, thereby first identifying a unique subset of obese individuals that appear to be at least partially protected from the development of the metabolic disturbances generally attributed to obesity.
Today it is believed that approximately 25-30% of obese individuals remain metabolically healthy (normal blood glucose, blood lipids, blood pressure, and cytokine profile) despite their excess weight. However, despite awareness of the metabolically-health obese phenotype for close to 30 years, there currently exist no established criteria by which to define these individuals. Not surprisingly, there is significant variation in the predicted prevalence of these individuals within the total obese population.
The defining characteristics of the metabolically healthy obese phenotype, in contrast to obese individuals with metabolic risk, include limited abdominal, particularly visceral fat accumulation, an earlier onset of obesity (<20 years) and high levels of physical activity. Additionally, black obese individuals have a greater tendency of being metabolically-healthy in contrast to white obese.
Japanese sumo wrestlers are often used as a popular example of metabolically healthy obese. They are morbidly obese and yet due to their high level of activity have very little visceral fat accumulation, tons of muscle mass, and a healthy metabolic profile – until they stop training, that is. Once they stop training, their fitness drops significantly, they accumulate excess fat in deleterious locations, and their metabolic profiles deteriorate. Football linemen are also a popular example of metabolically healthy obese, when they are training.
As a important caveat, there are countless other health issues brought on by carrying excess weight that are not always metabolic (i.e. joint problems due to excess load, skin infections, etc.). Thus, it is often argued that despite being metabolically-healthy these individuals may still be far from optimal health.
Nevertheless, it is important to note that excess weight alone doesn’t absolutely guarantee the presence of metabolic disease.
There is certainly truth to the notion that there is more to health than the number on one’s bathroom scale.
Join us tomorrow for part 2 of the series when we discuss the risk of diabetes and cardiovascular disease among these obese, but metabolically healthy individuals.
References and Further Reading:
Albrink, M., & Meigs, J. (1965). THE RELATIONSHIP BETWEEN SERUM TRIGLYCERIDES AND SKINFOLD THICKNESS IN OBESE SUBJECTS Annals of the New York Academy of Sciences, 131 (1 Adipose Tissu), 673-683 DOI: 10.1111/j.1749-6632.1965.tb34830.x
Sims, E. (2001). Are there persons who are obese, but metabolically healthy? Metabolism, 50 (12), 1499-1504 DOI: 10.1053/meta.2001.27213
Karelis, A. (2004). Metabolic and Body Composition Factors in Subgroups of Obesity: What Do We Know? Journal of Clinical Endocrinology & Metabolism, 89 (6), 2569-2575 DOI: 10.1210/jc.2004-0165