The fat epidemic

Health Page
By Dr Walter Chin
Stabroek News
April 8, 2001

Obesity (a condition in which there is too much body fat) is now one of the most common disorders in the Caribbean, with the incidence rising rapidly. According to surveys since 1971, 7-21 per cent of Caribbean men and 22-48 per cent of Caribbean women were obese. Obesity is associated with an increase in mortality and is a known risk factor for chronic diseases including heart disease, diabetes, high blood pressure, stroke, and some forms of cancer. Obesity is thus a key public health problem.

Everyone needs a certain amount of body fat for stored energy, heat insulation, shock absorption, and other functions. As a rule, women have more fat than men. It is generally agreed that men with more than 25 per cent body fat and women with more than 30 per cent body fat are obese.

The precise measurement of a person's body fat, however, is not easy. The most widely used measurement is the body mass index, otherwise known as the BMI.

The body mass index uses a formula which takes into account a person's height and weight.

The BMI is equivalent to a person's weight in kilograms divided by the height in metres squared; the desirable range is between 20- 24.9.

In general, a person age 35 or older is obese if he or she has a BMI of 27 or more. For people aged 34 or younger, a BMI of 25 or more indicates obesity. A BMI of more than 30 is usually considered a sign of moderate to severe obesity.

There is concern not only with how much fat a person has, but also with how the fat is distributed on the body. Women typically store fat in their hips and buttocks, giving their figures a "pear" shape.

Men, on the other hand usually store their fat around their bellies, giving them more of an "apple" shape. Sometimes, however, men are pear-shaped and some women are apple-shaped, especially after the menopause.

The distribution of fat is considered to be important as people whose fat is concentrated mostly in the abdomen are more likely to develop many of the health problems associated with obesity.

Obesity can only result from a person's calorie/energy intake exceeding the total energy expenditure. What causes this imbalance is unclear. Whether this means that the disorder is primarily a problem of food intake and appetite control, or a consequence of reductions or defects in one or more components of energy expenditure has been the subject of much debate. There is a lot of evidence to suggest that there are several causes of obesity.

It is now clear that there is an underlying genetic basis for obesity.

Although obesity is not a simple genetic disorder, it tends to run in families.

However, family members share not only genes, but also diet and lifestyle habits that may contribute to obesity. There is, thus, a distinct behavioural contribution to obesity, relating not only to the quantity and nature of the food consumed, but also to the level of physical activity.

The environment also plays a significant part in the development of obesity. Environment includes life-style behaviours such as what a person eats and how active that person is.

Many persons tend to consume high fat diets, putting taste ahead of healthy choices when choosing meals. And most people do not get enough exercise.

Psychological factors also influence eating habits. Many people eat in response to emotions such as boredom, anxiety, sadness, or anger.

Some illnesses can cause obesity. These include hypothyroidism, Cushing's syndrome, and depression. Certain drugs, such as steroids and some antidepressants, may also cause excessive weight gain.

Obesity is not just a cosmetic problem. It is also a health hazard. A person who is moderately to severely overweight is twice as likely to die prematurely as a person of average weight. This effect is seen after 10 to 30 years of being obese. Obesity is linked to several serious conditions, including diabetes, heart disease, high blood pressure, and stroke. It is also associated with higher rates of certain types of cancer. Obese men are more likely to die from cancer of the colon, rectum, and prostate. Obese women are more likely to die from cancer of the gallbladder, breast, uterus, cervix, and ovaries.

Other diseases and health problems linked to obesity include: gallbladder disease and gallstones; and osteoarthritis, a disease in which the joints deteriorate, possibly as a result of the excess weight they have to carry. The more obese a person is, the more likely that person is to have health problems.

The most important components in managing obesity are a diet that is limited in calories and increased physical activity. Both components are also crucial to the maintenance of weight once weight loss has occurred.

It is not necessary to achieve ideal weight to derive health benefits from obesity treatment. Instead the goal of treatment should be to reach and maintain a healthier weight.

As far as diets are concerned, studies indicate that replacing foods high in fats and sugars with low-fat complex carbohydrates (fruits, vegetables, and grains) is effective in reducing and maintaining weight loss. Some fat is essential in a diet, but this should be derived from oils (such as olive, corn, canola) and fish.

All healthy diets should also be high in fibre (found in grains, seeds, peas and beans, fruits and vegetables), which helps to promote weight loss. In relation to physical activity, it is recommended that individuals should exercise for 30-40 minutes at least four times a week.

There are two main types of medications used in treating obesity - medications that decrease appetite and medications that inhibit absorption of nutrients from the intestines. Medications that decrease appetite include fenfluramine, dexfenfluramine, and phentermine, while orlistat is an example of a medication that inhibits absorption of fat.

The feeling of hunger and fullness (satiety) are regulated by brain chemicals called neurotransmitters.

Anti-obesity medications that suppress appetite do so by increasing the level of these neurotransmitters (including serotonin, noradrenaline, and dopamine) at the junction between nerve endings in the brain. Fenfluramine and dexfenfluramine suppress appetite mainly by increasing release of serotonin by the cells.

However, both of these medications have been withdrawn from use because they have been associated with damage to the heart valves of some patients.

Orlistat is a new class of anti-obesity drug which acts by inhibiting the action of lipase which breaks down fat in the intestines. By so doing, orlistat prevents the intestinal absorption of fat by some 30 per cent.

Long term decrease in fat absorption can cause deficiency of fat soluble vitamins (such as vitamins A,D, E, and K), so that patients on this drug should receive adequate vitamin supplementation.

A relatively new drug, sibutramine, has been approved for the treatment of obesity. Sibutramine suppresses appetite by increasing the amount of serotonin and noradrenaline at the nerve junctions. It does this by preventing the re-uptake of these neurotransmitters in the brain, allowing them to act at higher concentrations on the nerve cells.

At present, there is no "magic cure" for obesity. The best and safest way to lose fat and keep it off is through a life-long process of proper diet and regular exercise. Medications should just be considered as useful adjuncts to these.