Central obesity

DiseaseDisorder infobox
Name = Central obesity
ICD10 = E66
ICD9 = ICD9|278

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.cite journal | author=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. | title=Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study.|journal=Lancet | year=2004 | pages=937–52 | volume=364 | pmid=15364185 | doi=10.1016/S0140-6736(04)17018-9]

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 (>convert|102|cm|in in men and >convert|88|cm|in in women) and the waist-hip ratio (>0.9 for men and >0.85 for women) 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. [cite journal |author=Janssen I, Katzmarzyk PT, Ross R |title=Waist circumference and not body mass index explains obesity-related health risk |journal=Am. J. Clin. Nutr. |volume=79 |issue=3 |pages=379–84 |year=2004 |pmid=14985210 |url=http://www.ajcn.org/cgi/content/abstract/79/3/379 |doi=10.1185/030079906X159489]

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. [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.] [http://circ.ahajournals.org/cgi/reprint/109/3/433.pdf 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.] [ [http://www.americanheart.org/presenter.jhtml?identifier=4756 American Heart Association's description of Syndrome X] ]

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) [cite journal |author=Bujalska IJ, Kumar S, Stewart PM |title=Does central obesity reflect "Cushing's disease of the omentum"? |journal=Lancet |volume=349 |issue=9060 |pages=1210–3 |year=1997 |pmid=9130942 |doi=10.1016/S0140-6736(96)11222-8] . Central obesity is also common in patients with polycystic ovary syndrome (PCOS).

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. [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.] [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.] Increased adiposity (obesity) raises serum resistin levelsAsensio, 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.] [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.] [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.] [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.] , which in turn directly correlate to insulin resistance [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. [http://www.hsph.harvard.edu/GSH-LAB/tnf-ins.html] ] [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.] [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.] [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.] . Studies have also confirmed a direct correlation between resistin levels and T2DM. [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.] [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.] [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.] . 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. [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.] [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.] Conversely, serum resistin levels have been found to "decline" with decreased adiposity following medical treatment. [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.]

Causes

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

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. [cite journal |author=Fonseca V |title=Effect of thiazolidinediones on body weight in patients with diabetes mellitus |journal=Am. J. Med. |volume=115 Suppl 8A |issue= |pages=42S–48S |year=2003 |pmid=14678865 |doi=10.1016/j.amjmed.2003.09.005]

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 beneficial 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 useful in building the abdominal muscles, but they have little effect on the adipose tissue located there. [cite web In order to burn fat, one must take part in aerobic exercises.
url= http://www.mayoclinic.com/health/belly-fat/MC00054
title= Belly fat in men: What you need to know
accessdate= 2008-04-07
author= Michael Jensen, M.D.
date= 2007-01-19
publisher= Mayoclinic.com
quote= Sit-ups will make your abdominal muscles stronger, sure. And, you maylook thinner by building your abdominal muscles because you can hold inyour belly fat better. But strengthening your stomach muscles alonewill not specifically reduce belly fat.]

Slang terms

Several colloquial terms used to refer to central obesity, and to people who have it, refer to beer drinking. However, there is little scientific evidence that beer drinkers are more prone to abdominal obesity, despite it being known colloquially as "beer belly", "beer gut", or "beer pot". One of the few studies conducted on the subject did not find that beer drinkers are more prone to abdominal obesity than nondrinkers or drinkers of wine or spirits. [Bobak M, Skodova Z, Marmot M. "Beer and obesity: a cross-sectional study". Eur J Clin Nutr 2003;57:1250–3. This study is also mentioned in [http://news.bbc.co.uk/2/hi/health/3175488.stm "Why the beer belly may be a myth"] , "BBC", 12 October, 2003] .

"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 pejorative term used for a person whose midsection spills over the waistline of his or her trousers in a manner that resembles the top of a muffin spilling over its baking pan.

See also

* Bariatrics
* Exercise
* General fitness training
* Healthy diet
* Intentional weight loss
* Physical fitness
* Obesity

References