Obesity

د. حسين محمد جمعه

اختصاصي الامراض الباطنة
البورد العربي
كلية طب الموصل
2011

Obesity

What Is Obesity?
Obesity is an excess proportion of total body fat.
A person is considered obese when his or her weight is 20% or more above normal weight. The most common measure of obesity is the body mass index or BMI. A person is considered overweight if his or her BMI is between 25 and 29.9; a person is considered obese if his or her BMI is over 30.
"Morbid obesity" means that a person is either 50%-100% over normal weight, more than 100 pounds over normal weight, has a BMI of 40 or higher, or is sufficiently overweight to severely interfere with health or normal function.

What Causes Obesity?

Obesity occurs when a person consumes more calories than he or she burns. For many people this boils down to eating too much and exercising too little.
But there are other factors that also play a role in obesity. These may include:


Age. As you get older, your body's ability to metabolize food slows down and you do not require as many calories to maintain your weight. This is why people note that they eat the same and do the same activities as they did when they were 20 years old, but at age 40, gain weight.

Gender. Women tend to be more overweight than men. Men have a higher resting metabolic rate (meaning they burn more energy at rest) than women, so men require more calories to maintain their body weight. Additionally, when women become postmenopausal, their metabolic rate decreases. That is partly why many women gain weight after menopause.

Genetics. Obesity (and thinness) tends to run in families. In a study of adults who were adopted as children, researchers found that participating adult weights were closer to their biological parents' weights than their adoptive parents'. The environment provided by the adoptive family apparently had less influence on the development of obesity than the person's genetic makeup.

In fact, if your biological mother is heavy as an adult, there is approximately a 75% chance that you will be heavy. If your biological mother is thin, there is also a 75% chance that you will be thin. Nevertheless, people who feel that their genes have doomed them to a lifetime of obesity should take heart. Many people genetically predisposed to obesity do not become obese or are able to lose weight and keep it off.

Environmental factors. Although genes are an important factor in many cases of obesity, a person's environment also plays a significant role. Environmental factors include lifestyle behaviors such as what a person eats and how active he or she is.
Physical activity. Active individuals require more calories than less active ones to maintain their weight. Additionally, physical activity tends to decrease appetite in obese individuals while increasing the body's ability to preferentially metabolize fat as an energy source. Much of the increase in obesity in the last 20 years is thought to have resulted from the decreased level of daily physical activity.

Psychological factors. Psychological factors also influence eating habits and obesity. Many people eat in response to negative emotions such as boredom, sadness, or anger. People who have difficulty with weight management may be facing more emotional and psychological issues; about 30% of people who seek treatment for serious weight problems have difficulties with binge eating. During a binge-eating episode, people eat large amounts of food while feeling they can't control how much they are eating.

Illness. Although not as common as many believe, there are some illnesses that can cause obesity. These include hormone problems such as hypothyroidism (poorly acting thyroid slows metabolism), depression, and some rare diseases of the brain that can lead to overeating.
Medication. Certain drugs, such as steroids and some antidepressants, may cause excessive weight gain

Emotional Aspects of Obesity

One of the most painful aspects of obesity may be the emotional suffering it causes. American society places great emphasis on physical appearance, often equating attractiveness with slimness or muscularity. In addition, many people wrongly stereotype obese people as gluttonous, lazy, or both. However, more and more evidence contradicts this assumption. Obese people often face prejudice or discrimination at work, at school, while looking for a job, and in social situations. Feelings of rejection, shame, or depression are common.

When to Seek Help for Obesity

You should call your doctor if you are having emotional or psychological issues related to your obesity, need help losing weight, or if you fall into either of the following categories.
If your BMI is 30 or greater, you're considered obese. You should talk to your doctor about losing weight since you are at high risk of having health problems.


If you have an "apple shape" -- a so-called, "potbelly" or "spare tire" -- you carry more fat in and around your abdominal organs. Fat deposited primarily around your middle increases your risk of many of the serious conditions associated with obesity. Women's waist measurement should fall below 35 inches. Men's should be less than 40 inches. If you have a large waist circumference, talk to your doctor about how you can lose weight.

Obesity facts

Obesity means having excess body fat. For adults 35 and older, having a BMI greater than 30 is considered obese.
Obesity is not just a cosmetic consideration. It is a chronic medical disease that can lead to diabetes, high blood pressure, heart disease, gallstones, and other chronic illnesses.

Obesity is difficult to treat and has a high relapse rate. Greater than 95% of those who lose weight regain the weight within five years.
Even though medications and diets can help, the treatment of obesity cannot be a short-term "fix" but has to be a life-long commitment to proper diet habits, increased physical activity, and regular exercise.

The goal of treatment should be to achieve and maintain a "healthier weight", not necessarily an ideal weight.
Even a modest weight loss of 5% to 10% of initial weight and the long-term maintenance of that weight loss can bring significant health benefits by lowering blood pressure and lowering the risks of diabetes and heart disease.
Chances of long-term successful weight loss are enhanced if the doctor works with a team of professionals including dietitians, psychologists, and exercise professionals.

What are the health risks associated with obesity?

Obesity is not just a cosmetic consideration; it is a dire health dilemma directly harmful to one's health. In the United States, roughly 300,000 deaths per year are directly related to obesity, and more than 80% of these deaths are in patients with a BMI over 30. For patients with a BMI over 40, life expectancy is reduces significantly (as much as 20 years for men and 5 years for women ). Obesity also increases the risk of developing a number of chronic diseases.

Insulin Resistance. Insulin is necessary for the transport of blood glucose (sugar) into the cells of muscle and fat (which is then used for energy). By transporting glucose into cells, insulin keeps the blood glucose levels in the normal range. Insulin resistance (IR) is the condition whereby the effectiveness of insulin in transporting glucose (sugar) into cells is diminished. Fat cells are more insulin resistant than muscle cells; therefore,one important cause of insulin resistance is obesity.

The pancreas initially responds to insulin resistance by producing more insulin. As long as the pancreas can produce enough insulin to overcome this resistance, blood glucose levels remain normal. This insulin resistance state (characterized by normal blood glucose levels and high insulin levels) can last for years. Once the pancreas can no longer keep up with producing high levels of insulin, blood glucose levels begin to rise, resulting in type 2 diabetes, thus insulin resistance is a pre-diabetes condition.

In fact scientists now believe that the atherosclerosis associated with diabetes likely develops during this insulin resistance period.
Type 2 diabetes is associated with central obesity; a person with central obesity has excess fat around his/her waist, so that the body is shaped like an apple.


Hypertension is common among obese adults. A Norwegian study showed that weight gain tended to increase blood pressure in women more significantly than in men. The risk of developing high blood pressure is also higher in obese people who are apple shaped (central obesity) than in people who are pear shaped (fat distribution mainly in hips and thighs).

Heart attack. A prospective study found that the risk of developing coronary artery disease increased three to four times in women who had a BMI greater than 29. A Finnish study showed that for every one kilogram (2.2 pounds) increase in body weight, the risk of death from coronary artery disease increased by one percent. In patients who have already had a heart attack, obesity is associated with an increased likelihood of a second heart attack.

Cancer. While not conclusively proven, some observational studies have linked obesity to cancer of the colon in men and women, cancer of the rectum and prostate in men, and cancer of the gallbladder and uterus in women. Obesity may also be associated with breast cancer, particularly in postmenopausal women. Fat tissue is important in the production of estrogen, and prolonged exposure to high levels of estrogen increases the risk of breast cancer.
Gallstones
Gout and gouty arthritis
Osteoarthritis (degenerative arthritis) of the knees, hips, and the lower back
Sleep apnea

What Causes Obesity?

The balance between calorie intake and energy expenditure determines a person's weight. If a person eats more calories than he or she burns (metabolizes), the person gains weight (the body will store the excess energy as fat). If a person eats fewer calories than he or she metabolizes, he or she will lose weight. Therefore the most common causes of obesity are overeating and physical inactivity. At present, we know that there are many factors that contribute to obesity, some of which have a genetic component:

Genetics. A person is more likely to develop obesity if one or both parents are obese. Genetics also affect hormones involved in fat regulation. For example, one genetic cause of obesity is leptin deficiency. Leptin is a hormone produced in fat cells, and also in the placenta. 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. The role of leptin replacement as a treatment for obesity is currently being explored.

Overeating. Overeating leads to weight gain, especially if the diet is high in fat. Foods high in fat or sugar (for example, fast food, fried food, and sweets) have high energy density (foods that have a lot of calories in a small amount of food). Epidemiologic 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, contributes 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 (metabolizes) 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 Nutrition Examination Survey (NHANES) showed that physical inactivity was strongly correlated with weight gain in both sexes.

Medications.

certain antidepressants ,anti-convulsants such as carbamazepine ,valproate, 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.

What are other factors associated with obesity?

Ethnicity. Ethnicity factors may influence the age of onset and the rapidity of weight gain. African American women and Hispanic women tend to experience weight gain earlier in life than Caucasians and Asians. Hispanic men tend to develop obesity earlier than African American and Caucasian men.

Childhood weight. A person's weight during childhood, the teenage years, and early adulthood may also influence the development of adult obesity. For example:
Being mildly overweight in the early 20's was linked to a substantial incidence of obesity by age 35.
Being overweight during older childhood is highly predictive of adult obesity, especially if a parent is also obese.
Being overweight during the teenage years is even a greater predictor of adult obesity.

Hormones. Women tend to gain weight especially during certain events such as pregnancy, menopause, and in some cases with the use of oral contraceptives. However, with the availability of the newer low dose estrogen pills, weight gain has not been as great a risk.


How is body fat measured?
Measuring a person's body fat percentage is not easy, and is often inaccurate if the methods are not monitored carefully. The following methods require special equipment, trained personnel, can be costly, and some are only available in certain research facilities:

Underwater weighing (hydrostatic weighing): This method weighs a person underwater and then calculates lean body mass (muscle) and body fat. This method is one of the most accurate ones; however, it is generally done in special research facilities, and the equipment is costly.

BOD POD: The BOD POD is a computerized, egg-shaped chamber. Using the same whole-body measurement principle as hydrostatic weighing, the BOD POD measures a subject's mass and volume, from which their whole-body density is determined. Using this data, body fat and lean muscle mass can then be calculated.

DEXA: Dual-energy X-ray absorptiometry (DEXA) is used to measure bone density. It uses X-rays to determine not only the percentage of body fat, but also where, and how much fat is located in the body.
The following two methods are simple and straightforward:

Skin calipers: This method measures the skinfold thickness of the layer of fat just under the skin in several parts of the body with calipers (a metal tool similar to forceps); the results are then used to calculate the percentage of body fat.

Bioelectric impedance analysis (BIA): This is another seemingly simple method. There are two methods of the BIA. One involves standing on a special scale with footpads. A harmless amount of electrical current is sent through the body, and then percentage of body fat is calculated.
The other type of BIA, involves electrodes t placed on a wrist and an ankle, and on the back of the right hand and on the top of the foot.

The change in voltage between the electrodes is measured. The person's body fat percentage is then calculated from the results of the BIA.
Health clubs and weight loss centers often use the skin caliper or bioelectric impedance analysis method; however, these can yield inaccurate results if an inexperienced person performs them or they are used on someone with significant obesity.

What about weight-for-height tables?

Measuring a person's body fat percentage can be difficult, so other methods are often relied upon to diagnose obesity. Two widely used methods are weight-for-height tables and body mass index (BMI). While both measurements have their limitations, they are reasonable indicators that someone may have a weight problem.
The calculations are easy, and no special equipment is required.


Most people are familiar with weight-for-height tables. Doctors and nurses (and many others) have used these tables for decades to determine if someone is overweight.
The tables usually have a range of acceptable weights for a person of a given height.

One small problem with using weight-for-height tables is that doctors disagree over which is the best table to use. Several versions are available. Many have different weight ranges, and some tables account for a person's frame size, age and sex, while other tables do not.
A significant limitation of all weight-for-height tables is that they do not distinguish between excess fat and muscle. A very muscular person may be classified as obese, according to the tables, when he or she in fact is not.

What is the body mass index (BMI)?

The body mass index (BMI) is a now the measurement of choice for many physicians and researchers studying obesity.
The BMI uses a mathematical formula that accounts for both a person's weight and height. The BMI equals a person's weight in kilograms divided by height in meters squared (BMI=kg/m2).

The BMI measurement, however, poses some of the same problems as the weight-for-height tables. Not everyone agrees on the cutoff points for "healthy" versus "unhealthy" BMI ranges. BMI also does not provide information on a person's percentage of body fat. However, like the weight-for-height table, BMI is a useful general guideline and is a good estimator of body fat for most adults 19 and 70 years of age. However, it may not be an accurate measurement of body fat for body builders, certain athletes, and pregnant women.

It is important to understand what "healthy weight" means. Healthy weight is defined as a body mass index (BMI) equal to or greater than 19 and less than 25 among all people aged 20 or over. Generally, obesity is defined as a body mass index (BMI) equal to or greater than 30, which approximates 30 pounds of excess weight. Excess weight also places people at risk of developing serious health problems.
The World Health Organization uses a classification system using the BMI to define overweight and obesity

BMI (kg/m2)

Obesity Class
Men 102cm (40 in) or lessWomen 88cm (35 in) or less
Men > 102cm (40 in)Women > 88cm (35 in)
Underweight
< 18.5


Normal weight
18.5 - 24.9

Overweight

25.0 - 29.9

Increased

High
Obesity
30.0 - 34.9
I
High
Very High
Obesity
35.0 - 39.9
II
Very High
Very High
Extreme Obesity
40.0 +
III
Extremely High
Extremely High* Disease risk for type 2 diabetes, hypertension, and CVD.


• * Disease risk for type 2 diabetes, hypertension, and CVD.

Does it matter where body fat is located? (Is it worse to be an 'apple' or a 'pear'?)

Concern is directed not only at how much fat a person has but also where that fat is located on the body. The pattern of body fat distribution tends to differ in men and women.

Women typically collect fat in their hips and buttocks, giving their figures a "pear" shape. Men, on the other hand, usually collect fat around the belly, giving them more of an "apple" shape. (This is not a hard and fast rule; some men are pear-shaped and some women become apple-shaped, particularly after menopause).

Apple-shaped people whose fat is concentrated mostly in the abdomen are more likely to develop many of the health problems associated with obesity. They are at increased health risk because of their fat distribution. While obesity of any kind is a health risk, it is better to be a pear than an apple.
In order to sort the types of fruit, doctors have developed a simple way to determine whether someone is an apple or a pear. The measurement is called waist-to-hip ratio.
To find out a person's waist-to-hip ratio:
Measure the waist at its narrowest point, and then measure the hips at the widest point.
.

Divide the waist measurement by the hip measurement.

For example, a woman with a 35-inch waist and 46-inch hips would have a waist-to-hip ratio of 0.76 (35 divided by 46 = 0.76)
Women with waist-to-hip ratios of more than 0.8 and men with waist-to-hip ratios of more than 1.0 are "apples."

Another rough way of estimating the amount of a person's abdominal fat is by measuring the waist circumference. Men with a waist circumference of 40 inches or greater and women with a waist circumference of 35 inches or greater are considered to have increased health risks related to obesity.

What can be done about obesity?

All too often, obesity prompts a strenuous diet in the hopes of reaching the "ideal body weight." Some amount of weight loss may be accomplished, but the lost weight usually quickly returns. More than 95% of the people who lose weight regain the weight within five years. It is clear that a more effective, long-lasting treatment for obesity must be found.


We need to learn more about the causes of obesity, and then we need to change the ways we treat it. When obesity is accepted as a chronic disease, it will be treated like other chronic diseases such as diabetes and high blood pressure. The treatment of obesity cannot be a short-term "fix," but has to be an ongoing life-long process.

Obesity treatment must acknowledge that even modest weight loss can be beneficial. For example, a modest weight loss of 5% to 10% of the initial weight, and long-term maintenance of that weight loss can bring significant health gains, including:

Lowered blood pressure

Reduced blood levels of cholesterol
Reduced risk of type 2 (adult-onset) diabetes. In the Nurses Health Study, women who lost 5 kilograms (11 pounds) of weight reduced their risk of diabetes by 50% or more.
Decreased chance of stroke
Decreased complications of heart disease
Decreased overall mortality

It is not necessary to achieve an "ideal weight" to derive health benefits from obesity treatment. Instead, the goal of treatment should be to reach and hold to a "healthier weight." The emphasis of treatment should be to commit to the process of life-long healthy living including eating more wisely and increasing physical activity.
In sum, the goal in dealing with obesity is to achieve and maintain a "healthier weight."