Central obesity

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Central obesity
Classification and external resources
ICD-10 E66
ICD-9 278
Central obesity, or "belly fat"
Central obesity, or "belly fat"

Central obesity, the "apple-shaped" obesity commonly referred to as belly fat, is the accumulation of visceral fat (fat deposited between the internal organs in the torso) resulting in an increase in waist size. There is a strong correlation between central obesity and cardiovascular disease.[1]

While central obesity can be obvious just by looking at the naked body (see the picture), the severity of central obesity is determined by taking waist and hip measurements. The absolute waist circumference (>102 centimetres (40 in) in men and >88 centimetres (35 in) in women) and the waist-hip ratio (>0.9 for men and >0.85 for women)[1] are both used as measures of central obesity. In the scientific experiment known as the National Health and Nutrition Examination Survey (NHANES III), which included almost 15,000 people, waist circumference explained obesity-related health risk significantly better than the body mass index (or BMI) when metabolic syndrome was taken as an outcome measure.[2]

Contents

[edit] Health risks

Central obesity is associated with a statistically higher risk of heart disease, hypertension, insulin resistance, and diabetes mellitus type 2 (see below). Belly fat is a symptom of metabolic syndrome, and is an indicator used in the diagnosis of that disorder.[3][4][5]

Central obesity can be a feature of lipodystrophies, a group of diseases which is either inherited, or due to secondary causes (often protease inhibitors, a group of medications against AIDS). Central obesity is a symptom of Cushing's syndrome (which may cause it)[6]. Central obesity is also common in patients with polycystic ovary syndrome (PCOS).

[edit] Relationship with diabetes

There are numerous theories as to the exact cause and mechanism in type 2 diabetes. Central obesity is known to predispose individuals for insulin resistance. Abdominal fat is especially active hormonally, secreting a group of hormones called adipokines that may possibly impair glucose tolerance.

Insulin resistance is a major feature of diabetes mellitus type 2 (T2DM), and central obesity is correlated with both insulin resistance and T2DM itself.[7][8] Increased adiposity (obesity) raises serum resistin levels[9][10][11][12], which in turn directly correlate to insulin resistance[13][14][15][16]. Studies have also confirmed a direct correlation between resistin levels and T2DM.[9][17][18][19]. And it is waistline adipose tissue (central obesity) which seems to be the foremost type of fat deposits contributing to rising levels of serum resistin.[20][21] Conversely, serum resistin levels have been found to decline with decreased adiposity following medical treatment.[22]

[edit] Causes

The main causes of central obesity are overeating and a sedentary lifestyle. Hypercortisolism, such as in Cushings syndrome also leads to central obesity.

[edit] Prevention and treatments

Performing adequate aerobic exercise and eating a healthy diet prevent central obesity, and losing weight via these methods is the main way to reverse the condition.

Adjunctive therapies which may be prescribed by a physician are orlistat or sibutramine. In the presence of diabetes mellitus type 2, the physician might instead prescribe metformin and thiazolidinediones (rosiglitazone or pioglitazone) as anti-diabetic drugs rather than sulfonylurea derivatives. Thiazolidinediones may cause slight weight gain but decrease "pathologic" abdominal fat, and therefore may be prescribed for diabetics with central obesity.[23]

[edit] Sit ups myth

There is a common misconception that spot exercise (that is, exercising a specific muscle or location of the body) most effectively burns fat at the desired location. But this is not the case. Spot exercise is good for building specific muscles, but it has little effect on fat in that area of the body, or on the body's distribution of body fat. The same thing applies to sit ups and belly fat. Sit ups and other abdominal exercises are great for building the abdominal muscles, but they have little effect on the adipose tissue located there.[24]

[edit] Slang terms

There are some slang terms used to refer to central obesity, and to people who have it. There is little scientific evidence that beer drinkers are more prone to abdominal obesity, despite it being known colloquially as "beer belly" or "beer gut". "Love handles" is a colloquial term for a layer of fat that is deposited around a person's midsection, especially visible on the sides over the abdominal external oblique muscle. "Muffin top" is a generally pejorative term used for a person whose flabby midsection spills over the waistline of his or her pants in a manner that resembles the top of a muffin spilling over its paper casing. Another slang term, "spare tire" is also used as a descriptor of the "ring" of fat surrounding one's midsection.

[edit] See also

[edit] References

  1. ^ a b Yusuf S, Hawken S, Ounpuu S, Dans T, Avezum A, Lanas F, McQueen M, Budaj A, Pais P, Varigos J, Lisheng L, INTERHEART Study Investigators. (2004). "Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study.". Lancet 364: 937-52. PMID 15364185. 
  2. ^ Janssen I, Katzmarzyk PT, Ross R (2004). "Waist circumference and not body mass index explains obesity-related health risk". Am. J. Clin. Nutr. 79 (3): 379–84. PMID 14985210. 
  3. ^ Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). JAMA 2001;285:2486-97. PMID 11368702.
  4. ^ Grundy SM, Brewer HB, Cleeman JI, Smith SC, Lenfant D, for the Conference Participants. Definition of metabolic syndrome: report of the National, Heart, Lung, and Blood Institute/American Heart Association conference on scientific issues related to definition. Circulation. 2004;109:433-438.
  5. ^ American Heart Association's description of Syndrome X
  6. ^ Bujalska IJ, Kumar S, Stewart PM (1997). "Does central obesity reflect "Cushing's disease of the omentum"?". Lancet 349 (9060): 1210–3. doi:10.1016/S0140-6736(96)11222-8. PMID 9130942. 
  7. ^ Duman BS, Turkoglu C, Gunay D, Cagatay P, Demiroglu C, Buyukdevrim AS. The interrelationship between insulin secretion and action in type 2 diabetes mellitus with different degrees of obesity: evidence supporting central obesity. Diabetes Butr Metab. 16(4): 243-250, 2003.
  8. ^ Gabriely, I., Ma, X. H., Yang, X. M., Atzmon G, Rajala MW, berg AH, Sherer P, Rossetti L, Barzilai N. Removal of visceral fat prevents insulin resistance and glucose intolerance of aging: an adipokine-mediated process? Diabetes. 51: 2951–2958, 2002.
  9. ^ a b Asensio, C., Cettour-Rose, P., Theander-Carrillo, C., Rohner-Jeanrenaud, F. and Muzzin, P. Changes in glycemia by leptin administration or high-fat feeding in rodent models of obesity/type 2 diabetes suggest a link between resistin expression and control of glucose homeostasis. Endocrinology. 145: 2206–2213, 2004.
  10. ^ Degawa-Yamauchi MBJE, Juliar BE, Watson W, Kerr K, Jones RM, Zhu Q & Considine RV. Serum resistin (FIZZ3) protein is increased in obese humans. Journal of Clinical Endocrinology and Metabolism. 88: 5452–5455, 2003.
  11. ^ Lee, J. H., Bullen, Jr, J. W., Stoyneva, V. L. and Mantzoros, C. S. Circulating resistin in lean, obese and insulin-resistant mouse models: lack of association with insulinemia and glycemia. Am. J. Physiol. Endocrinol. Metab. 288: E625–E632, 2005.
  12. ^ Vendrell J, Broch M, Vilarrasa N, Molina A, Gomez JM, Gutierrez C, Simon I, Soler J & Richart C. Resistin, adiponectin, ghrelin, leptin, and proinflammatory cytokines: relationships in obesity. Obesity Research. 12: 962–971, 2004.
  13. ^ Hirosumi J, Tuncman G, Chang L, Gorgun CZ, Uysal KT, Maeda K, Karin M, Hotamisligil GS. A central role for JNK in obesity and insulin resistance. Nature. 420: 333-336, 2002. [1]
  14. ^ Rajala, M. W., Qi, Y., Patel, H. R., Takahashi N, Banerjee R, Pajvani UB, Sinha MK, Gingerich RL, Scherer PE, Ahima RS. Regulation of resistin expression and circulating levels in obesity, diabetes, and fasting. Diabetes. 53: 1671–1679, 2004.
  15. ^ Silha JV, Krsek M, Skrha JV, Sucharda P, Nyomba BL and Murphy LJ. Plasma resistin, adiponectin and leptin levels in lean and obese subjects: correlations with insulin resistance. Eur. J. Endocrinol. 149: 331-335, 2003.
  16. ^ Smith, S. R., Bai, F., Charbonneau, C., Janderova, L. and Argyropoulos, G. A promoter genotype and oxidative stress potentially link resistin to human insulin resistance. Diabetes 52, 1611–1618, 2003.
  17. ^ Fujinami, A., Obayashi, H., Ohta, K, Ichimura T, Nishimura M, Matsui H, Kawahara Y, Yamazaki M, Ogata M, Hasegawa G, Nakamura N, Yoshikawa T, Nakano K, Ohta M. Enzyme-linked immunosorbent assay for circulating human resistin: resistin concentrations in normal subjects and patients with type 2 diabetes. Clin. Chim. Acta. 339: 57–63, 2004.
  18. ^ McTernan, P. G., Fisher, F. M., Valsamakis, G, Chetty R, Harte A, McTernan CL, Clark PM, Smith SA, Barnett AH, Kumar S. Resistin and type 2 diabetes: regulation of resistin expression by insulin and rosiglitazone and the effects of recombinant resistin on lipid and glucose metabolism in human differentiated adipocytes. J. Clin. Endocrinol. Metab. 88: 6098–6106, 2003.
  19. ^ Steppan CM, Bailey ST, Bhat S, Brown EJ, Banerjee RR, Wright CM, Patel HR, Ahima RS, Lazar MA. The hormone resistin links obesity to diabetes. Nature. 409:307-312, 2001.
  20. ^ McTernan, C. L., McTernan, P. G., Harte, A. L., Levick, P. L., Barnett, A. H. and Kumar, S. Resistin, central obesity, and type 2 diabetes. Lancet. 359: 46–47, 2002.
  21. ^ McTernan, P. G., McTernan, C. L., Chetty, R, Jenner K, Fisher FM, Lauer MN, Crocker J, Barnett AH, Kumar S. Increased resistin gene and protein expression in human abdominal adipose tissue. J. Clin. Endocrinol. Metab. 87: 2407, 2002.
  22. ^ Valsamakis, G., McTernan, P. G., Chetty, R, Al Daghri N, Field A, Hanif W, Barnett AH, Kumar S. Modest weight loss and reduction in waist circumference after medical treatment are associated with favourable changes in serum adipocytokines. Metab. Clin. Exp. 53:430–434, 2004.
  23. ^ Fonseca V (2003). "Effect of thiazolidinediones on body weight in patients with diabetes mellitus". Am. J. Med. 115 Suppl 8A: 42S–48S. doi:10.1016/j.amjmed.2003.09.005. PMID 14678865. 
  24. ^ Michael Jensen, M.D. (2007-01-19). Belly fat in men: What you need to know. Mayoclinic.com. Retrieved on 2008-04-07. “Sit-ups will make your abdominal muscles stronger, sure. And, you may look thinner by building your abdominal muscles because you can hold in your belly fat better. But strengthening your stomach muscles alone will not specifically reduce belly fat.”