A condition in which an adult is severely overweight, usually due to overeating and too little exercise
- More common with increasing age
- Slightly more common in females
- Sometimes runs in families
- Overeating and a sedentary lifestyle are risk factors
Whether a person is a healthy weight, underweight, or overweight is assessed by using a measure called the body mass index (BMI). This provides an indication of the degree of fatness, although it is not a direct measure of body fat. A person’s BMI is calculated by dividing his or her weight (in kilograms) by his or her height (in metres) squared. For most healthy adults under 60, a BMI over 30 is classed as obese (see Are you a healthy weight? and Controlling your weight). For children, the definition of obesity is different (see Obesity in children). About 1 in 4 adults in the UK is obese and the condition has become increasingly common in recent years, in children as well as adults.
Obesity can have an adverse effect on virtually any part of the body and can therefore lead to a wide variety of health problems. For example, back pain, painful hips and knees, and shortness of breath are common problems. It increases the risk of some serious disorders, such as coronary artery disease, stroke, high blood pressure (see Hypertension), type 2 diabetes mellitus, and certain cancers. Obesity may also lead to psychological problems, including depression.
What are the causes?
Obesity occurs when food taken into the body provides more energy than is used. The main causes are overeating and a sedentary lifestyle. Obesity may run in families as a result of learned eating habits in addition to inherited factors. In rare cases, it may be a symptom of a hormonal disorder, such as hypothyroidism. Some drugs, particularly corticosteroids, can lead to obesity. Occasionally, obesity may be due to an underlying psychological problem.
Are there complications?
Obesity increases the risk of various long-term problems. For example, obese people are more likely to have high blood cholesterol levels (see Hypercholesterolaemia). High cholesterol in turn increases the risk of atherosclerosis, in which fatty deposits build up on the inner linings of the arteries. Atherosclerosis may contribute to high blood pressure, coronary artery disease, and strokes. Arterial thrombosis and embolism, which is blockage of a blood vessel by a blood clot, occurs more frequently in obese people. Obese adults are at greater risk of gallstones and are more likely to develop type 2 diabetes. Certain cancers, such as breast cancer, cancer of the uterus, and colon cancer (see Colorectal cancer) are also more common in obese people.
What might be done?
Your doctor will probably measure your weight and height (to calculate your body mass index) and discuss your diet with you (see A healthy diet) as well as how much exercise you take (see Exercise and health). Tests may be performed to measure blood sugar levels (to look for diabetes) and cholesterol levels. Rarely, you may have blood tests to check for a hormonal disorder.
Obesity is most commonly treated by a weight-reduction diet and increased exercise. Calorie intake per day is usually reduced to 500–1,000 calories less than the average requirement for a person of your age, sex, and height (see Controlling your weight). This type of eating plan is designed to produce slow, sustainable weight loss. The diet may be formulated by your doctor or a dietitian, although you may also choose to join a self-help group. Moderate, regular exercise is essential in losing weight. Changes in diet and lifestyle need to be maintained throughout life. Support from your family, doctor, and a self-help group should help you to follow your weight-loss plan successfully.
Drugs to aid weight loss are available but are usually recommended only for people who are obese and who have not succeeded in losing weight through diet and exercise alone. These drugs may cause adverse side effects and should not be used long term; they should always be used in conjunction with diet and exercise. Orlistat (Xenical), available over the counter or on prescription, inhibits fat absorption from the digestive tract. It may cause headaches, flatulence, the feeling of an urgent need to defecate, and an oily rectal discharge. Bulking agents, such as methyl cellulose, are also available over the counter. They make you feel full but may cause bloating and flatulence.
Rarely, surgery is used to treat obesity but usually only as a last resort because of the risk of serious complications. Various surgical procedures may be used, including gastric banding and bypass surgery. Gastric banding involves putting a band around the stomach to create an upper and lower stomach pouch. The upper pouch is small, so that you feel full after eating only a small amount. The food then passes slowly into the lower stomach pouch and is digested as normal. Bypass surgery involves joining the stomach directly to the lower part of the small intestine, thereby bypassing the upper small intestine. Part of the stomach may also be removed to reduce its capacity. Bypass surgery reduces the amount of nutrients that are absorbed from food. Because of this, there is a risk of malabsorption and malnutrition.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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