This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: MPET2008CH6B- 1 - OBESITY Obesity is an important health problem. It is increased by a sedentary life style, a better income and the increased use of processed foods. Not only because of the high prevalence (33% in the USA) but also because of the reduction in life expectancy and the complications such as diabetes, hypertension, hypertriglyceridemia, low HDL cholesterol and cardiovascular diseases, obesity should be taken seriously. The mechanisms causing these complications are complex and hardly dissected. Recently, one discovered a protein, resistin, that is made by fat cells (adipocytes) and causes insulin resistance. This could form the link between obesity and diabetes type II. Obese persons also have an enhanced triglyceridemia, resulting in vascular disease. Obesity is defined by several measures and ratios that are a rather crude measure for the relative fat content. The most important is the BMI=Body Mass Index. This is calculated by dividing the body weight (in kg) by the square of the body length (in m) (e.g. 75 kg, 1.8 m: BMI= 23). Recent directives of the WHO give following criteria: BMI Classificiation < 18.5 underweight 18.5-24.9 normal 25-29.9 overweight grade I (overweight) 30-39.9 overweight grade II (obesity) >40 overweight grade III (severe obesity) Central obesity (abdomen) has a higher risk than distributed obesity, but there are no generally accepted thresholds for waist circumference. The generation of obesity is complex and simple: complex due to many mechanisms playing a role in food intake, food digestion and energy MPET2008CH6B- 2 - consumption, simple because of the central mechanism: one becomes obese when the energy intake is chronically higher than the energy consumption. The extra calories are stored in the fat tissue as triglycerides. Both sides of the energy balance are regulated very tightly by neuronal and hormonal factors. Normally the body weight is finely tuned and stable over years. When the food consumption decreases also the energy consumption is decreased and inverse. Seemingly, an internal control mechanism, the lipostat or set point regulates this. The set point is largely genetically determined. Recently, one gained more insight about the molecular nature of this control. The central mechanisms of this regulation are located in the hypothalamus. Food uptake and fat mass give signals that after integration in the hypothalamus will result in other signals resulting in a feeling of satiety with a reduced food intake, a lowering in insulin levels and a stimulation of the parasympaticus accompanied by an increased energy expenditure. A number of these factors were identified by the use of natural mutant obese inbred strains....
View Full Document
- Spring '10