|Year : 2018 | Volume
| Issue : 3 | Page : 301-302
Lean metabolic syndrome: An emerging concept
Department of Endocrinology, KPC Medical College, Jadavpur, Kolkata, West Bengal, India
|Date of Web Publication||16-Jul-2018|
36 Block H, New Alipore, Kolkata - 700 053, West Bengal
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sanyal D. Lean metabolic syndrome: An emerging concept. Indian J Endocr Metab 2018;22:301-2
The prevalence of metabolic syndrome (MetS) in India is reported to be up to 29.7%, quite high as compared to other south-east Asian countries. The concept of MS was to identify a clustering of cardiovascular (CV) risk factors which predisposed subjects to risk of developing cardiovascular disease (CVD) and type 2 diabetes (T2DM), so that early effective preventive measures can be implemented. The original accepted criteria for the MetS were based on risk prediction in the non-Asian Indian populations. Therefore, there is a continuous debate regarding the optimum definition which is most sensitive and universally applicability in different populations like Asians. National Cholesterol Education Program Adult Treatment Panel III recommends that three of five clinical and/or biochemical abnormalities should be present to satisfy labeling of MetS, whereas the International Diabetes Federation (IDF) definition requires abdominal obesity as an obligatory criterion and presence of at least two other abnormal criteria. The recent data by Mukhopadhyay et al. in the original article “Lean metabolic syndrome: A concept or a reality?” suggests that even the current IDF Asian Indian cut-offs of waist circumference (WC) may not be sensitive for predicting the risk of metabolic disorders in all segments of our population.
The criteria for selection of cut-off points of WC for diagnosis of abdominal obesity are based on data derived from white Caucasians. However, sensitivity and specificity of these cut-off points were low in some Caucasian population when correlated with individual CV risk factors. Misra et al. analyzed WC cutoff points in Asian Indians using multiple CV risk factors and body mass index (BMI) as reference points. WC level 1 cut-off points: 72 cm in women (sensitivity: 68.7%, specificity: 71.8%) and 78 cm in men (sensitivity: 74.3%, specificity: 68.0%) were observed to be optimum for identifying those with presence of at least one CV risk factor and BMI levels of 21–23 kg/m 2. The currently IDF-recommended WC cutoff points of ≥90 cm in men and ≥80 cm in women or level 2 identified greater number of CV risk factors and those with a BMI ≥25 kg/m 2. Vikram et al. reported that among non-obese (BMI <25 kg/m 2) individuals with WC in the range of 70–80 cm, men had significantly high odds for hypertriglyceridemia (3.2), and women had high odds for hypertension (2.5) and hypertriglyceridemia (2.5).
Convergence of CV risk factors could be ascribed to a large extent by peculiarity in body composition of the Asian Indians with higher percentage of body fat and abdominal adiposity at lower WC levels as compared to counterpart Caucasians. Both intra-abdominal and subcutaneous adipose tissue account for CV risk associated with abdominal obesity. The heterogeneity in total mass and composition of skeletal muscles, subcutaneous, and intra-abdominal adipose tissue and bone in different ethnic groups is a major hindrance in setting uniformly applicable criteria for WC for identification of abdominal obesity. Less skeletal muscle mass and pelvic skeleton dimensions are seen in Asians, particularly those who have suffered childhood malnutrition, and may affect WC. Thus, lower WC in Indians does not preclude the occurrence of IR as the so-called appearing “trim-looking Asian Indian” has higher proportion of visceral fat content as compared to the subcutaneous fat.
The high prevalence of T2DM in our country may be one of the plausible factors for lean MetS as demonstrated by Perseghin et al. where lean off-springs of T2DM parents have higher degree of insulin resistance, one of the strongest predisposing predictors of MetS. Asian Indians have significantly lower glucose disposal rates during the insulin clamp, higher procoagulant tendency, and dyslipidemia at lower BMI and WC as compared to Caucasians. Earlier in the BMI-dominated era, Molero-Conejo et al. had reported that even with a BMI as low as 21 kg/m 2, an unhealthy diet and low physical activity are responsible for high insulin levels and dyslipidemia in lean but metabolically altered adolescents. So a WC cut-off of 72 cm in women and 78 cm (Action level 1) in men may be optimum in India for universally identifying those with presence of CV risk and diabetes. Any person with WC above these levels should avoid gaining weight and maintain physical activity to avoid acquiring any further CV risk factor. Subjects with WC above 90 cm in men and 80 cm in women (Action level 2) should seek medical help so that obesity-related risk factors could be investigated and managed.
Although various international bodies have recognized central adiposity as a component of MetS, the time has come to inspect the metabolic profile of individuals with WC below the current cut-offs. It may be a common belief that lean individuals with slender waist are metabolically healthy and subsequently screening of MetS is unnecessary. But recent studies suggest that metabolic disorders are highly prevalent in lean and trim individuals. Emerging literature also propose that an abnormal metabolic profile, rather than elevated WC, is linked with higher risk of diabetes and CVD., This also provokes us to consider the measurement of alternative anthropometric markers of MS such as neck circumference and wrist circumference in the so-called “lean MetS” cohort as identified by Mukhopadhyay et al. In conclusion, we need to shift our focus from an obligatory central obesity centric prismatic viewpoint, to a broader all encompassing, comprehensive multifactorial strategy to screen for MetS in presence of any risk factor. Finally, screening is superfluous unless we extend lifestyle and therapeutic management to all sections of high-risk population to prevent the growing menace of diabetes and CVD.
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