Central Obesity

Visceral fat
Visceral fat, also known as organ fat or intra-abdominal fat, is located inside the peritoneal cavity, packed in between internal organs, as opposed to subcutaneous fat which is found underneath the skin, and intramuscular fat which is found interspersed in skeletal muscle. Visceral fat is composed of several adipose depots including mesenteric, epididymal white adipose tissue (EWAT) and perirenal depots.
An excess of visceral fat is known as central obesity, the "pot belly" or "beer belly" effect, in which the abdomen protrudes excessively. This body type is also known as "apple" shaped, as opposed to "pear" shape, in which fat is deposited on the hips and buttocks.

Diagnosis
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 cohort of 15,000 people participating in the National Health and Nutrition Examination Survey (NHANES III), waist circumference explained obesity-related health risk better than the body mass index (or BMI) when metabolic syndrome was taken as an outcome measure and this difference was statistically significant.[2]
A differential diagnosis includes distinguishing central obesity from ascites and intestinal bloating.

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[6] and is also common in patients with polycystic ovary syndrome (PCOS). Central obesity is associated with glucose intolerance and dyslipidemia.

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]

Causes
The immediate cause of obesity is net energy imbalance--the organism consumes more usable calories than it expends, wastes, or discards via elimination. The fundamental cause of obesity is not well understood, but is presumably a combination of the organism's genes and environment. The specific cause of central distribution of fat is also not well understood.
In humans, central obesity is correlated with overeating and a sedentary lifestyle. Hypercortisolism, such as in Cushings syndrome also leads to central obesity. Many prescription drugs can also have side effects resulting in 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.[23]

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.[24] In order to burn fat, one must take part in aerobic exercises.

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.[25]. "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