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Abdominal obesity, colloquially known as belly fat or clinically as central obesity, is the accumulation of abdominal fat resulting in an increase in waist size. There is a strong correlation between central obesity and cardiovascular disease.[1] It is important to note that abdominal obesity is not confined only to the elderly and obese subjects.[2] Visceral and central abdominal fat showed a strong association with type 2 diabetes. Both measures correlated well with each other and with waist circumference.[3] Visceral fat, also known as organ fat or intra-abdominal fat, is located inside the peritoneal cavity, packed in between internal organs and torso, 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 fat. 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 shaped " in which fat is deposited on the hips and buttocks. In recent years scientists have come to an important recognition that body fat, instead of body weight, is the key to evaluating obesity.
Causes The immediate cause of obesity is net energy imbalance the organism consumes more usable calories than it expends, wastes or discards through elimination. The fundamental cause of obesity is not well understood, but is presumably a combination of the organism's genes and environment. Some studies indicate central obesity is related to the excessive consumption of fructose.[4][5][6] Other environmental factors, such as maternal smoking, estrogenic compounds in the diet and endocrine-disrupting chemicals may be important also.[7] Obesity plays an important role in the impairment of lipid and carbohydrate metabolism shown in high-fat diets.[8] It has also been shown that the quality protein intake in a 24-hour period and the times achieving the essential amino acid threshold of approximately 10 g[9] is inversely related to percent central abdominal fat. Quality protein uptake is defined as the ratio of essential amino acids to daily dietary protein.[10] Visceral fat cells will release their metabolic by-products in the portal circulation, where the blood leads straight to the liver. Thus, the excess of triglycerides and fatty acids created by the visceral fat cells will go into the liver and accumulate there. In the liver, most of it will be stored as fat. This concept is known as 'lipotoxicity'.[11] Hypercortisolism, such as in Cushing's syndrome also leads to central obesity. Many prescription drugs, such as dexamethasone and other steroids, can also have side effects resulting in central obesity,[12] especially in the presence of elevated insulin levels. The prevalence of abdominal obesity is increasing in western populations, due to a combination of low physical activity and high-energy diets, and also in developing countries, where it is associated with the urbanization of populations.[13][14] Waist measurement is more prone to errors than measuring height and weight. It is recommended to use both standards. BMI will illustrate the best estimate of your total body fatness, while waist measurement gives an estimate of visceral fat and risk of obesity-related disease.[15] 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 (> in men and > in women) and the waist-hip ratio (>0.9 for men and >0.85 for women)[16] are both used as measures of central obesity. A differential diagnosis includes distinguishing central obesity from ascites and intestinal bloating. 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. In other words, excessive waist circumference appears to be more of a risk factor for metabolic syndrome than BMI.[17] Another measure of central obesity which has shown superiority to BMI in predicting cardiovascular disease risk is the Index of Central Obesity (waist-to-height ratio - WHtR), where a ratio of >=0.5 (i.e. a waist circumference at least half of the individual's height) is predictive of increased risk.[18] Another diagnosis of obesity is the analysis of intra abdominal fat having the most risk to one's personal health. The increased amount of fat in this region relates to the higher levels of plasma lipid and lipoproteins as per studies mentioned by Dr. Eric D. Poehlman(1998) review.[19] An increasing acceptance of the importance of central obesity within the medical profession as an indicator of health risk has led to new developments in obesity diagnosis such as the Body Volume Index, which measures central obesity by measuring a person's body shape and their weight distribution.the effect of abdominal adiposity does not just occur in those who are obese, but also affects people who are non-obese and it also contributes to insulin sensitivity Index of Central Obesity Index of Central Obesity (ICO) is the ratio of waist circumference and height first proposed by a Parikh et al. in 2007[20][21] as a better substitute to the widely-used waist circumference in defining metabolic syndrome.[22] The National Cholesterol Education Program Adult Treatment Panel III suggested cut off of and for males and females as a marker of central obesity.[23] The same was used in defining metabolic syndrome.[24] Misra et al. suggested that these cutoffs are not applicable among Indians and the cutoffs be lowered to and for males and females.[25] Various race specific cutoffs were suggested by different groups. The International Diabetes Federation defined central obesity based on these various race and gender specific cutoffs. The other limitation of waist circumference is that it can not be applied in children. Parikh et al. looked at the average heights of various races and suggested that by using ICO various race- and gender-specific cutoffs of waist circumference can be discarded.[22] An ICO cutoff of more than 0.5 is suggested as a criteria to define central obesity. Parikh et al. further tested a modified definition of metabolic syndrome in which waist circumference was replaced with ICO in the National Health and Nutrition Examination Survey (NHANES) database and found the modified definition to be more specific and sensitive.[22] This parameter has been used in the study of metabolic syndrome[26][27] and cardiovascular disease.[28] Body Volume Index BVI is based upon the principle that excess abdominal weight, measured by part volume as a percentage of total volume, constitutes a greater health risk. Recent validation has concluded that total and regional body volume estimates correlate positively and significantly with biomarkers of cardiovascular risk and BVI calculations correlate significantly with all biomarkers of cardio-vascular risk.[29] Health risks Central obesity is associated with a statistically higher risk of heart disease, hypertension, insulin resistance, and Diabetes Mellitus Type 2 (see below).With an increase in the waist to hip ratio and overall waist circumference the risk of death increases as well.[30] Belly fat is a symptom of metabolic syndrome, and is an indicator used in the diagnosis of that disorder.[31][32][33] It is now generally believed that intra-abdominal fat is the depot that conveys the biggest health risk.[34] Central obesity can be a feature of lipodystrophies, a group of diseases that 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[35] and is also common in patients with polycystic ovary syndrome (PCOS). Central obesity is associated with glucose intolerance and dyslipidemia.the effect of abdominal adiposity does not just occur in those who are obese but also affects people who are non-obese and it also contributes to insulin sensitivity. 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.[36][37] Increased adiposity (obesity) raises serum resistin levels,[38][39][40][41] which in turn directly correlate to insulin resistance.[42][43][44][45] Studies have also confirmed a direct correlation between resistin levels and T2DM.[38][46][47][48] 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.[49][50] Conversely, serum resistin levels have been found to decline with decreased adiposity following medical treatment.[51] Individuals with obesity are likely to develop weakened non-esterified fatty acid (NEFA), which can weaken the metabolism of the liver causing [52] high glucose production. An individual is at a higher risk of developing ischemic heart disease if they have hyperinsulinemia-dyslipidemia while being abdominal obese.[53] Relationship with Alzheimer's Disease A U.S. study reported in May 2010 Annals of Neurology examining over 700 adults found evidence to suggest higher volumes of visceral fat, regardless of overall weight, were associated with smaller brain volumes and increased risk of dementia.[54][55][56] Relationship with Pulmonary Function A study conducted found a relationship between abdominal obesity and lung function. It has been shown with increasing waist circumference there is a strong correlation with spirometry or breathing results. Also, abdominal obesity affects pulmonary function more in men than in women.[57] http://onlinelibrary.wiley.com/doi/10.1111/j.1475-097X.2011.01064.x/abstract Measurement Silhouettes and waist circumferences representing normal, overweight, and obese There are various ways of measuring abdominal obesity including: In those with a BMI under 35, intra-abdominal body fat is related to negative health outcomes independent of total body fat.[59] Intra-abdominal or visceral fat has a particularly strong correlation with cardiovascular disease.[16] Men are considered to be at high risk of abdominal obesity if their waist measurements are 40 inches or higher. On the other hand, women are considered to be at high risk, if their waist measurements are 35 inches or higher. BMI and waist measurements are known to determine any form of obesity occurring. However, waist measurements are not as accurate as BMI measurements. For this reason, it is recommended to use both methods of measurements.[60] Sex differences Female sex hormone causes fat to be stored in the buttocks, thighs, and hips in women. Men are more likely to have fat stored in the belly due to sex hormone differences. When women reach menopause and the estrogen produced by ovaries declines, fat migrates from their buttocks, hips and thighs to their waists;[61] later fat is stored in the belly.[62] Prevention and treatments A permanent routine of exercise, eating more healthfully and consuming the same number or fewer calories than one expends will prevent and help fight obesity.[63] Adjunctive therapies which may be prescribed by a physician are orlistat or sibutramine, although the latter has been associated with increased cardiovascular events and strokes and has been withdrawn from the market in the United States,[64] the UK,[65] the EU,[66] Australia,[67] Canada,[68] Hong Kong,[69] Thailand,[70] Egypt and Mexico. In the presence of diabetes mellitus type 2, the physician might instead prescribe metformin and thiazolidinediones (rosiglitazone or pioglitazone) as antidiabetic drugs rather than sulfonylurea derivatives. Thiazolidinediones may cause slight weight gain but decrease "pathologic" abdominal fat (visceral fat), and therefore may be prescribed for diabetics with central obesity.[71] Low-fat diets may not be an effective long-term intervention for obesity: as Bacon and Aphramor wrote, "The majority of individuals regain virtually all of the weight that was lost during treatment."[72] The Women's Health Initiative ("the largest and longest randomized, controlled dietary intervention clinical trial"[72]) found that long-term dietary intervention increased the waist circumference of both the intervention group and the control group, though the increase was smaller for the intervention group. The conclusion was that mean weight decreased significantly in the intervention group from baseline to year 1 by 2.2 kg (P<.001) and was 2.2 kg less than the control group change from baseline at year 1. This difference from baseline between control and intervention groups diminished over time, but a significant difference in weight was maintained through year 9, the end of the study.[73] 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, if any, on fat in that area of the body, or on the body's distribution of body fat. The same logic applies to sit-ups and belly fat. Sit-ups, crunches and other abdominal exercises are useful in building the abdominal muscles, but they have little effect, if any, on the adipose tissue located there.[74] Slang terms Excess abdominal fat on a male. 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 its 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.[75][76] Chronic alcoholism can lead to cirrhosis, symptoms of which include gynecomastia (enlarged breasts) and ascites (abdominal fluid). These symptoms can suggest the appearance of central obesity. "Love handles" and "spare tire" (or "spare tyre") are colloquial terms for deposits of fat around a person's midsection, especially visible on the sides over the abdominal external oblique muscle. Love handles are visible deposits on each side of the abdomen or lower back (that a hypothetical lover might grab to pull the subject into an embrace). A spare tire appears to encircle the abdomen (thus resembling an automobile tire). "Muffin top" is a term used for a person whose midsection spills over the waistline of his or her pants in a manner that resembles the top of a muffin spilling over its baking pan. "Pot belly" is another colloquial term used to describe a person who has an excessive amount of abdominal fat. See also - Bariatrics, the branch of medicine that deals with the causes, prevention, and treatment of obesity
- Sagittal Abdominal Diameter (SAD), a measure of Visceral Obesity
- Steatosis, also called fatty change, fatty degeneration or adipose degeneration
- Lipoatrophy, the term describing the localized loss of fat tissue
- Lipodystrophy, a medical condition characterized by abnormal or degenerative conditions of the body's adipose tissue.
- Gros Ventre
Further reading References ar: de:Stammfettsucht fr:Poign e d'amour ko: nl:Bierbuik no:Bukfett pl:Oty o brzuszna simple:Abdominal obesity fi:Keskivartalolihavuus sv:Bukfetma tl:Bilbil (taba) zh-yue: zh:
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