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Nutrition:
"Overweight and Obesity: A Growing Concern"

It has been recognized that both deficient and excessive body fat increase health risks among individuals. Excessive body fat is associated with increased risks of disease. The health risks of over-fatness are so many that it has been referred to as a disease: obesity. Apart from diabetes and hypertension, other risks include high blood lipids, cardiovascular diseases, sleep apnea, osteoarthritis, abdominal hernias, some cancers, varicose veins, gout, gallbladder disease, arthritis, respiratory problems, liver malfunction, complications in pregnancy and surgery, flat feet, and even a high accident rate.

How much fat is too much fat? Research results vary, but what is implied is excess weight is composed of fat and not muscle. Visceral fat (fat that collects within the central abdominal are of the body) may be especially dangerous with regard to risks of diabetes, stroke, hypertension, and coronary artery disease. Some people are prone to develop the “apple” shape of central obesity while others develop more of a “pear” (fat around the hips and thighs). Men of all ages and women past menopause are more likely to be “apples” while women in reproductive age are more likely to be “pears”.

Why are some people fat while others are thin? Why do some people stay at the same weight over time? Both internal and external factors operate together, and in different combinations in different people.

Causes of obesity : Within the body

1. Genetic inheritance
The probability of becoming obese is higher if both parents are obese than if only one parent is obese. Recent findings discovered a gene in humans, the ob (obese) gene. A protein hormone, leptin, made by ob gene in fat cells, has been isolated and was found to have responding sites in the human brain. Leptin in mice was found to suppress appetite and to speed up metabolism. When leptin were injected to genetically obese mice their weights remained within normal. However, this is not the case in humans, since fat people feel hungry and stay fat despite high levels of leptin possibly because obese people may be unresponsive to leptin.

2. Set point theory
This is the theory that the body tends to maintain a certain weight by means of its own internal controls. Hence, most people who lose weight on reducing diets later quickly regain all the lost weight.

3. Enzyme theory
Strong evidence also links fat storage with elevated storage with elevated concentrations of the enzyme that enables fat cells to store triglycerides. This ; brown fat enzyme, lipoprotein lipase (LPL) increase in levels as cells become enlarged with fat, the more LPL, the more easily fat cells store lipid, and more likely the body will remain obese.

4. Fat cell theory
Another cause of obesity may be the development of excess fat cells during childhood. The number of fat cells increases during the growing years and then levels off during adulthood. Fat cell number increases more rapidly in obese children. A fat cell can expand eight to tenfold in size and once it reaches a certain size, it may also divide. Fat cells of obese people also contain more LPL so they are likely to reach a large size more quickly.

5. The theory of thermogenesis
Regular white fat cells store energy in fat’s chemical bonds and have a slow metabolic rate; brown fat cells break those bonds and actively release their stored energy as heat. Brown fat is more abundant and more active in lean animals than in fat ones. New evidence suggests that both brown and white fat cells of obese people may burn off less energy than normal.

Causes of obesity: Outside the body

1. External Cue Theory
People overeat as a response to stimuli in their surroundings – foremost among hem, the availability of a multitude of delectable foods. One food constituent stands out in being perceived as palatable – fat.

2. Exercise.
Overweight people may engage in less exercise and it is believed that physical activity can help regulate the appetite.

”Obesity is no longer a purely medical issue – obesity has become a societal and public health problem”. (Drewnowski, A. and Specter, SE. Amer. J. Clin. Nutr. 79: 2004)

Reference : Sizer, F. and Whitney, E. Nutrition: Concepts and Controversies, 7th ed. Wadsworth Publishing Company, 1997.

Lucila B. Rabuco, PhD

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