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Obesity Paradox

Obesity Paradox

  • Although prospective studies have shown a strong relationship between body mass index (BMI) and incidence of heart attack  and related mortality, obese patients have a better survival when they develop a heart attack or undergo coronary  procedures such as angioplasty, stent or bypass surgery.1 This phenomenon has been commonly referred to as the “obesity paradox.1, 2
  • For more than two decades, a plethora of studies have clearly shown that the distribution of body fat, especially excess abdominal fat accumulation (which can be readily estimated by the measurement of waist girth), is predictive of both prevalent and incident CAD and diabetes—this relationship being largely independent from the contribution of total body fat.3
  • A recent meta-analysis of all studies on the subject has confirmed that an elevated BMI was indeed associated with a 36% lower mortality in coronary artery disease (CAD) patients. However, abdominal obesity was associated with 70% higher mortality in people with and without high BMI. 4 Both high waist circumference (WC) and high waist-hip ratio (WHR) were used as an index of abdominal obesity.4
  • Thus, central obesity is directly associated with higher mortality in individuals with CAD, whereas the opposite is observed with BMI.4 Abdominal obesity is associated with higher incidence of CAD even in apparently healthy people without high BMI.5-7
  • In patients with asymptomatic CAD, excess visceral adipose tissue/liver fat deposition is clearly associated with diabetogenic and atherogenic metabolic abnormalities. 8 3, 9 In clinical practice these people can be readily identified by finding the hypertriglyceridemic waist (WC>90 cm and triglycerides > 175 mg/dl or 2 mmol/L).10, 11
  • People with central obesity have higher mortality even when the BMI is normal and therefore WC should be recorded and pursued in every individual in addition to BMI for better risk stratification and therapeutic considerations.4

Table 108 A. Correlation between body mass index (BMI)

 and waist circumference (WC) in Europid men3

BMI (kg/m2) WC (cm) Health Risk
20 80 Below average
23 86 Threshold of high risk
25 92 High risk
30 100 Very high risk
  •  In men a BMI of 20, 23, 25 and 30  correspond to a WC of 80 cm, 86 cm, 92 cm and 100 cm; respectively.3 Those with disproportionately large WC usually have less muscle mass and a poor cardiorespiratory fitness. They also have an excess of visceral adipose tissue and ectopic fat deposition in liver, pancreas, epicardium and myocardium.8
  • For Indians high risk status is characterized best by WC than BMI, although BMI should not be ignored. The BMI cutpoint for obesity is 5 units lower and the WC cutpoint is 12 units lower than Europid men.12
  • Recent studies have confirmed that an elevated BMI was indeed associated with a 36% lower mortality in CAD patients. However, abdominal obesity was associated with 70% higher mortality in people with and without high BMI. Both high waist circumference (WC) and high waist-hip ratio (WHR) were used as an index of abdominal obesity.4
  • It is suggested that WC and WHR are more reliable than BMI in stratifying mortality risk in CAD patients, and WC and/or WHR should be documented in individuals with CAD and normal BMI for better risk stratification and therapeutic considerations.4 
  • It appears that BMI is now to anthropometry, what total cholesterol is to lipidology13  and there is no obesity paradox and only a BMI paradox.3

Sources

1. Romero-Corral A, Montori VM, Somers VK, et al. Association of bodyweight with total mortality and with cardiovascular events in coronary artery disease: a systematic review of cohort studies. Lancet. Aug 19 2006;368(9536):666-678.

2. Lavie CJ, Milani RV, Ventura HO. Obesity and cardiovascular disease: risk factor, paradox, and impact of weight loss. J Am Coll Cardiol. May 26 2009;53(21):1925-1932.

3. Despres J P. Excess visceral adipose tissue/ectopic fat the missing link in the obesity paradox? J Am Coll Cardiol. May 10 2011;57(19):1887-1889.

4. Coutinho T, Goel K, Correa de Sa D, et al. Central obesity and survival in subjects with coronary artery disease: a systematic review of the literature and collaborative analysis with individual subject data. J Am Coll Cardiol. May 10 2011;57(19):1877-1886.

5. de Koning L, Merchant AT, Pogue J, Anand SS. Waist circumference and waist-to-hip ratio as predictors of cardiovascular events: meta-regression analysis of prospective studies. Eur Heart J. Apr 2007;28(7):850-856.

6. Lee CM, Huxley RR, Wildman RP, Woodward M. Indices of abdominal obesity are better discriminators of cardiovascular risk factors than BMI: a meta-analysis. J Clin Epidemiol. Jul 2008;61(7):646-653.

7. Yusuf S, Hawken S, Ounpuu S, et al. Obesity and the risk of myocardial infarction in 27,000 participants from 52 countries: a case-control study. Lancet. Nov 5 2005;366(9497):1640-1649.

8. Despres J P, Lemieux I, Bergeron J, et al. Abdominal obesity and the metabolic syndrome: contribution to global cardiometabolic risk. Arterioscler Thromb Vasc Biol. Jun 2008;28(6):1039-1049.

9. Despres JP, Moorjani S, Lupien PJ, Tremblay A, Nadeau A, Bouchard C. Regional distribution of body fat, plasma lipoproteins, and cardiovascular disease. Arteriosclerosis. 1990;10(4):497-511.

10. Lemieux I, Pascot A, Couillard C, et al. Hypertriglyceridemic waist: A marker of the atherogenic metabolic triad (hyperinsulinemia; hyperapolipoprotein B; small, dense LDL) in men? Circulation. 2000;102(2):179-184.

11. Lemieux I, Poirier P, Bergeron J, et al. Hypertriglyceridemic waist: a useful screening phenotype in preventive cardiology? Can J Cardiol. Oct 2007;23 Suppl B:23B-31B.

12. Enas  EA, Singh V, Gupta R, Patel R, et al. Recommendations of the Second Indo-US Health Summit for the prevention and control of cardiovascular disease among Asian Indians. Indian heart journal. 2009;61:265-74.

13. Poirier P. Adiposity and cardiovascular disease: are we using the right definition of obesity? Eur Heart J. Sep 2007;28(17):2047-2048.

 

 

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