[align=center]Obesity
DefinitionObesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death.
DescriptionObesity traditionally has been defined as a weight at least 20% above the weight corresponding to the lowest death rate for individuals of a specific height, gender, and age (ideal weight). Twenty to forty percent over ideal weight is considered mildly obese; 40–100% over ideal weight is considered moderately obese; and 100% over ideal weight is considered severely, or morbidly, obese. More recent guidelines for obesity use a measurment called BMI (body mass index) which is the individual's weight multiplied by 703 and then divided by twice the height in inches. BMI of 25.9–29 is considered overweight; BMI over 30 is considered obese. Measurements and comparisons of waist and hip circumference can also provide some information regarding risk factors associated with weight. The higher the ratio, the greater the chance for weight-associated complications. Calipers can be used to measure skin-fold thickness to determine whether tissue is muscle (lean) or adipose tissue (fat).
What cause obesity?
1- Genetic Genetics play a true causative role in relatively few cases of obesity .
A genetic disorder characterized by excessive a ppetite , massive obesity , short stature , and often mental retardation.
The following paragraphs describe some recent research involoving proteins that might help explain energy regulation and obesity development
for example
LeptinLeptin is a hormone produced by adipose cells and also in the placenta
that is directly linked to appetite and body fatness
(coded for by ob gene)
Leptin controls weight by signaling the brain to eat less when body fat stores are too high. If, for some reason the body cannot produce enough leptin, or leptin cannot signal the brain to eat less, this control is lost, and obesity occurs.
Ghrelin is a hormone found primarily in the stomach, though it exists in other areas of the body as well. Over the past several years, ghrelin levels in the human body have garnered a great deal of attention, as a link was found between the hormone and control of hunger. While researching ghrelin levels, scientists found that the hormone increases feelings of hunger when it is increased in the body. In addition, high levels of ghrelin have been found to suppress the amount of fat used by the adipose tissue. This implies that those with high levels of ghrelin in their bodies will not only feel hungrier than those with low levels, but may burn fat more slowly as well.
Overeating. Overeating leads to weight gain, especially if the diet is high in fat. Foods high in fat or sugar (e.g., fast food, fried food and sweets,) have high energy density (foods that have a lot of calories in small amount of food). Epidemiology studies have shown that diets high in fat contribute to weight gain.
A diet high in simple carbohydrates. The role of carbohydrates in weight gain is not clear. Carbohydrates increase blood glucose levels, which in turn stimulate insulin release by the pancreas, and insulin promotes the growth of fat tissue and can cause weight gain. Some scientists believe that simple carbohydrates (sugars, fructose, desserts, soft drinks, beer, wine, etc.) contribute to weight gain because they are more rapidly absorbed into the blood stream than complex carbohydrates (pasta, brown rice, grains, vegetables, raw fruits, etc.) and thus cause a more pronounced insulin release after meals than complex carbohydrates. This higher insulin release, some scientists believe, contribute to weight gain.
Frequency of eating. The relationship between frequency of eating (how often you eat) and weight is somewhat controversial. There are many reports of overweight people eating less often than people with normal weight. Scientists have observed that people who eat small meals four or five times daily, have lower cholesterol levels and lower and/or more stable blood sugar levels than people who eat less frequently (two or three) large meals daily. One possible explanation is that small frequent meals produce stable insulin levels, whereas large meals cause large spikes of insulin after meals.
Slow metabolism. Women have less muscle than men. Muscle burns more calories than other tissue (which includes fat). As a result, women have a slower metabolism than men, and hence, have a tendency to put on more weight than men, and weight loss is more difficult for women. As we age, we tend to lose muscle and our metabolism slows, therefore, we tend to gain weight as we get older particularly if we do not reduce our daily caloric intake.
Physical inactivity. Sedentary people burn fewer calories than people who are active. The National Health and Examination Survey (NHANES) showed that physical inactivity was strongly correlated with weight gain in both sexes.
Medications. Medications associated with weight gain include certain antidepressants (medications used in treating depression), anti-convulsants (medications used in controlling seizures such as carbamazepine and valproate), diabetes medications (medications used in lowering blood sugar such as insulin, sulfonylureas and thiazolidinediones), certain hormones such as oral contraceptives and most corticosteroids such as Prednisone. Weight gain may also be seen with some high blood pressure medications and antihistamines.
Psychological factors. For some people, emotions influence eating habits. Many people eat excessively in response to emotions such as boredom, sadness, stress or anger. While most overweight people have no more psychological disturbances than normal weight people, about 30 percent of the people who seek treatment for serious weight problems have difficulties with binge eating.
Diseases such as hypothyroidism, insulin resistance, polycystic ovary syndrome and Cushing's syndrome are also contributors to obesity.[/align]
المواضيع المتشابهه
Obesity
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