Obesity is defined as an excess of body fat. Being overweight is different from being obese. Overweight refers to excess body weight compared to normal standards. The excess weight may come from muscle, bone, fat, and/or body water. Obesity refers specifically to having an abnormally high proportion of body fat. Healthcare practitioners use a number of methods to determine if an individual is overweight or obese. Body mass index, or BMI, is the measurement used to assess whether a person is overweight or obese. BMI is calculated using a mathematical formula that takes into account both a person's height and weight. A person is considered overweight if they have a BMI of between 25 and 29.9. A BMI of more than 30 is generally considered a sign of moderate to severe obesity.

Obesity is associated with many serious preventable diseases including heart disease, diabetes, high blood pressure, stroke, gallbladder disease, osteoarthritis, and respiratory disorders. The risk of developing these diseases is even higher when weight is concentrated near the waist. According to the National Institutes of Health, 60% of American adults are overweight and 25% are considered obese. For both men and women, the prevalence of obesity increases with age, but this problem is growing in children and adolescents—approximately 25% of American children are overweight or obese, and the numbers are rising.

Most practitioners use the following BMI ranges as indications that a person is overweight or obese:

• BMI 25 to 29.9 (overweight)
• BMI 30 to 39.9 (moderately obese)
• BMI 40 or above (extremely obese)

A high waist to hip ratio (indicating that fat is centered around the waist—also known as central obesity) increases the risk for developing serious, even life-threatening conditions associated with obesity. Physicians consider a very high waist circumference to be greater than 102 cm for men and greater than 88 cm for women.

Conditions that may accompany obesity include:

• High cholesterol (including high triglyceride levels)
• Diabetes
• High blood pressure
• Sleep apnea (episodes when a person stops breathing while asleep)
• Osteoarthritis
• Gallstones
• Stress incontinence (inability to control urine; small amounts of urine are released when a person laughs, coughs, or moves abruptly)

While there is no single underlying cause of obesity, the bottom line is that excessive weight reflects an imbalance between energy input and energy output. Both genetic and behavioral factors play a role in the development of excessive weight. For example, an individual's total number of fat cells (which may predispose an individual to weight gain) is determined genetically, but behavioral factors, such as a high-calorie, high-fat diet and lack of physical activity, must be present in order for weight gain to occur.

Other causes of obesity include:

• Rare congenital disorders (conditions present at birth), such as Prader-Willi syndrome and Laurence-Moon-Biedl syndrome
• Hormonal disorders such as Cushing's Syndrome and polycystic ovary syndrome
• Insulinoma (tumors of the pancreas)
• Hypothyroidism (diminished production of hormones from the thyroid gland)
• Brain injury (or lesion) from trauma or surgery
• Certain prescription medicines, including steroids, tricyclic antidepressants, anti-epilepsy drugs, or drugs used for high blood pressure

The following factors may increase an individual's risk for becoming obese:

• Being older than 18 years of age in an industrialized country, especially the United States
• Having family members who are overweight or obese
• Lack of physical activity
• Overeating
• Consuming a high-fat diet
• Taking certain prescription medications that may increase the risk for obesity (see Causes section)
• Having a hormone disorder, such as Cushing's syndrome or hypothyroidism (underactive thyroid)
• Being emotionally stressed (from the death of a loved one, for example), which may cause a person to overeat
• Being born with rare disorders associated with obesity (as mentioned in the Causes section)

The best way to prevent obesity and maintain a normal weight is to eat a healthy diet and exercise often. Maintaining daily records of both fat and calorie intake as well as exercise habits is an excellent way to get started in this endeavor.

Organizations such as the American Diabetes Association, the American Heart Association, and the American Dietetic Association have developed guidelines that promote weight loss and assure appropriate, balanced nutrition. These guidelines recommend that no more than 30% of a person's total calorie intake should come from fats. Overall, diets should be comprised of a wide variety of foods in order to provide a balanced intake of essential nutrients.

In addition to overeating, a sedentary lifestyle is a key factor in weight gain. Studies show that exercise—from moderate to rigorous—helps prevent obesity. While most proponents of exercise regimens (including those advocated by the Centers for Disease Control and Prevention) recommend at least 30 minutes of moderately intense aerobic activity (such as a brisk walk) at least 5 days a week, all physical activity is of value—from taking the stairs to cleaning the house or working in the garden. Strength training is also important for maintaining lean body mass.

The obesity guidelines put forth by the National Heart, Lung, and Blood Institute propose that healthcare practitioners use body mass index (BMI) to assess whether or not an individual is overweight or obese. To determine BMI, weight in kilograms is divided by height in meters, squared. As mentioned in the Signs and Symptoms section, the following BMI ranges are most often used as indications that a person is overweight or obese:

• BMI 25 to 29.9 (overweight)
• BMI 30 to 39.9 (moderately obese)
• BMI 40 or above (extremely obese)

After assessing BMI, blood pressure and percentage of body fat may be measured, and blood tests performed to evaluate cholesterol levels and determine how well the thyroid is functioning.

The primary goal in treating obesity is to reduce overall body weight and maintain the lower weight. This usually involves a combination of diet, exercise, and other lifestyle modifications, but the specific method of treatment depends on the severity of obesity. Factors such as general health and motivation to lose weight are also important considerations. Medications may be prescribed in addition to an exercise program and a low-calorie diet. Some herbs and supplements such as 5-HTP, fiber, and green tea may aid in weight loss and help alleviate the complications of obesity. Acupuncture may also have beneficial effects on weight loss, as can Ayurvedic medicines. Mind/body medicine, including psychotherapy, hypnosis, and meditation, may reduce the stress that so often leads to overeating. In severe cases, gastrointestinal surgery may be considered.

Increased physical activity and a diet that is limited in calories are the most important components of a weight loss program. Both components are also crucial to maintenance once the weight has been lost. The key to losing and keeping off weight is to set realistic weight loss goals that are achievable through eating in moderation, appropriate food selection, and consistent physical activity.

Increasing physical activity may help a person lose weight, primarily in the first 6 months, as well as maintain a desirable weight in the long-term. Exercise not only contributes to weight loss, it also decreases abdominal fat and increases cardiorespiratory fitness, which can reduce complications associated with overweight and obesity such as high blood pressure, diabetes, and heart disease.

It is important for people who are not used to exercising to begin with a gentle regimen that increases in intensity over time. The long-term goal is to participate in a moderately intense exercise routine for at least 30 minutes, 5 to 7 days a week. Ideally, an exercise program should combine aerobic activity such as walking, running, or swimming with a program of strength training, such as lifting light weights.

In addition to diet and exercise programs, social support from friends and family and practicing stress-reduction techniques (such as progressive muscle relaxation and meditation) may prevent overeating. It is also important to obtain appropriate professional guidance for any dietary and exercise regimen (especially early on) as it will ensure that weight is lost safely and in a controlled manner.

Although a variety of medications are available to help promote weight loss, no drugs cure obesity. Weight loss medications should therefore not be used in isolation—rather, they should be used in addition to diet, exercise, and other lifestyle modifications. Many are available by prescription only and some have serious side effects. For these reasons, weight loss medications should only be used under the direction and supervision of a physician.

Over-the-counter Medications

The following are medications that are available without a prescription. However, the evidence (obtained from medical studies) regarding the effectiveness of these drugs is not very convincing.

• Benzocaine gum—alters taste and numbs the mouth
• Ephedrine plus caffeine—boosts metabolism; ephedra can cause dangerous side effects, including heart attacks and stroke; should not be taken by people with heart disease, high blood pressure, thyroid disease, diabetes or an enlarged prostate

The Food and Drug Administration (FDA) is currently taking steps to remove phenylpropanolamine (PPA), a common ingredient in many over-the-counter weight loss medications, from drug products and has requested that drug companies discontinue marketing products containing PPA.Although PPA suppresses appetite, studies have shown that it increases the risk of hemorrhagic stroke (bleeding into the brain or into tissue surrounding the brain) in women.

Prescription Medications

• Sibutramine—boosts metabolism, enhances energy level, and promotes a feeling of fullness; studies have found it to be effective for weight loss, but side effects include dry mouth and insomnia; cannot be taken by people with a history of stroke, seizures, or heart, liver, or kidney diseases
• Orlistat—reduces the absorption of fat from foods, causing weight loss and lowered cholesterol; also reduces absorption of essential fat-soluble vitamins A,D, E, and K; should not be used by people with a history of kidney stones
• Phentermine—suppresses appetite; serious potential side effects include pulmonary hypertension and heart valve defects (these conditions are much more likely to occur when used in combination with fenfluramine, also known as fen-phen; fortunately, medications containing fenfluramine have been removed from the market); phentermine should not be used with SSRI and MAOI antidepressant medications
• Amphetamine derivatives (benzphetamine, diethylpropion, phendimetrazine, and mazindol)—elevate mood and reduce weight moderately over the short term (3 to 12 weeks); can cause addiction, agitation, and insomnia, consequently the use of these medications is not recommended

Surgery may be necessary for individuals who are extremely obese (those who have a BMI of 40 or higher). Physicians carefully select individuals for surgery, and appropriate behavioral and social support are required before the surgical procedure. Some options include:

• Roux-en Y procedure—reduces the size of the stomach, creating a feeling of fullness (satiety); vomiting is the most common side effect
• Gastric banding—passes an adjustable silicone band around the stomach, which creates feeling of satiety; gastric bands can be removed if necessary
• Liposuction—removes fat deposits from specific body areas; weight gain is more likely in other areas of the body after the procedure

Diet

Diet plans are enormously popular today. They range from traditional low-fat, high-carbohydrate diets to the more controversial high-protein, high-fat, low-carbohydrate diets. The truth is, no specific diet works for everyone, and no diet works without the other essential components of weight loss—exercise and stress management.

In general, studies have shown that diets limiting fat intake are safe and effective for weight loss. However, because obesity rates have risen in the United States despite lowering levels of fat in American foods, some experts have questioned whether or not low-fat diets are the preferred method for reducing weight. Studies have consistently shown, however, that low-fat diets combined with low-calorie intakes are the safest, most effective method of weight loss for overweight or obese individuals, and the best way for them to keep the pounds off for good. Although high protein diets (more popular in recent years) have also shown promise in helping overweight individuals reduce cholesterol and blood sugar levels as well as weight, it is not known if this diet is safe and effective for weight loss over the long term. Some experts suggest that increased levels of physical activity are necessary for weight loss when eating a diet high in protein. Before attempting any diet—low-fat or high-protein—it is important to consult a healthcare practitioner for help in determining an appropriate weight loss program.

Supplements

The following supplements have been suggested as treatments for obesity. Studies this far have been small or of poor methodological quality, but with further research, some of these supplements may prove to be beneficial weight loss aids. Before using these supplements, be sure to discuss their safety and appropriateness with a healthcare provider.

5-Hydroxytryptophan (5-HTP)

5-HTP, a supplement made from the seeds of the African plant Griffonia simplicifolia, may help reduce binge eating associated with obesity and dieting. 5-HTP is thought to reduce hunger cravings by boosting serotonin levels in the central nervous system. (Serotonin levels drop during dieting, often causing carbohydrate cravings and possible binge eating.) People who are taking antidepressant medications (SSRIs or MAOIs) must avoid 5-HTP.

Calcium 

Both animal and human studies have found that dietary calcium intake (from low-fat dairy products) may be associated with a decrease in body weight. For example, in a study of overweight women, daily intake of 1000 mg of calcium was associated with a loss of 8 kilograms (17.6 pounds) in weight, and 5 kilogram (11 pound) in body fat. Unfortunately, these effects cannot be specifically attributed to calcium since dairy sources of calcium contain other nutrients that may have been involved in the weight loss. Whether or not calcium supplements would achieve the same effect has yet to be proven.

Fiber

Preliminary evidence suggests that dietary fiber may help lower insulin levels (insulin controls the amount of sugar in the blood). In addition, one study of nearly 3,000 young adults suggests that high levels of insulin in the bloodstream (associated with low-fiber diets) may contribute to excessive weight gain for several reasons, including increased appetite.

Vitamin C

Studies suggest that obese individuals may have lower vitamin C levels than nonobese individuals. Researchers speculate that insufficient amounts of vitamin C may contribute to weight gain by decreasing metabolic rates and energy expenditures.

Fish Oil

Studies suggest that eating fish rich in omega-3 fatty acids (such as salmon, mackerel, and herring) seems to improve glucose-insulin metabolism and cholesterol levels in obese people both with and without high blood pressure. These effects were most pronounced when daily servings of fatty fish were incorporated into a weight-loss program that included physical activity and a low-fat diet. These studies also suggest that people who follow a weight loss program achieve better control over their blood sugar and cholesterol levels when fish is a staple in the diet. Fatty, coldwater fish should be consumed at least two to three times per week to obtain adequate amounts of omega-3 fatty acids.

Conjugated Linoleic acid (CLA)

Preliminary human and animal studies suggest that CLA can help control weight in obese individuals by reducing body fat and enhancing lean body mass. More studies are needed, however, to determine whether CLA is a safe and effective treatment for obesity. Until such time, use of this supplement is not recommended.

Zinc

Studies have revealed that zinc may increase lean body mass and decrease or keep fat mass stable. The reason for this may be that zinc increases levels of leptin, a molecule that stimulates energy expenditure and decreases appetite.

Chitosan

Derived from the shells of crustaceans, chitosan is promoted as a remedy for obesity in the United States and other countries. While some studies have found that chitosan (in addition to a low-calorie diet) significantly reduces weight in obese people, it is unclear whether the supplement itself, the low-calorie diet, or a combination of both led to the weight loss. More studies are needed to determine if chitosan is a safe and effective treatment for obesity.

Dehydroepiandrosterone (DHEA)

DHEA has only recently begun to be studied in humans as a treatment for obesity, and the results have been conflicting. While animal studies have found DHEA to be effective in reducing body weight, studies of nonobese men and women showed that DHEA produced no change in total body weight, but measures of total body fat and LDL ("bad") cholesterol did improve. These differences may be due to the fact that higher dosages were used in the animal studies than in the human studies (such high doses would cause intolerable side effects in people). Further studies (particularly with obese individuals) are needed to determine whether DHEA effectively reduces body weight in obese people. Until the safety and effectiveness of DHEA is fully tested, it is best not to use this supplement for weight loss.

Chromium

Although some studies suggest that chromium may regulate lean body mass and reduce body fat, its effects are small compared to those of exercise and a well-balanced diet. Chromium does appear to improve blood sugar (also a risk factor for heart disease), particularly in those with diabetes and glucose intolerance.

Vitamin D

Studies suggest that obese people tend to have lower levels of vitamin D than people who are not obese, and that supplementation may correct that deficiency.

Other Supplements

Although the following supplements have been promoted as weight loss supplements, few studies support their use:

Pyruvate

Pyruvate has been promoted as a weight loss and cholesterol-lowering supplement, but there is no substantive body of research to support these claims.

L-Carnitine

Although L-carnitine has been marketed as a weight loss supplement, a recent study of moderately overweight women found that L-carnitine did not significantly alter body weight, body fat, or lean body mass. Based on the results of this one small study, claims that L-carnitine helps to reduce weight appear to be unfounded.

Ephedra (Ephedra sinensis)

Supplements containing ephedra, also known as ma huang, have been widely touted as energy boosters and weight loss stimulants. In fact, studies have shown that ephedrine (derived from ephedra), when used in combination with caffeine, may be helpful in treating obesity. However, serious adverse effects ranging from extremely high blood pressure to fatal heart attacks, stroke, and seizures have been reported, causing the Food and Drug Administration (FDA) to propose limits on the dose and duration of its usage. Many healthcare practitioners recommend that ephedra not be used to treat obesity or for any other reason because of these dangerous side effects.

Psyllium (Plantaginis ovatae)

Studies and clinical reports suggest that psyllium, a soluble fiber, may increase the sensation of fullness (satiety) and reduce hunger cravings. For these reasons, incorporating psyllium and other sources of fiber into the diet may aid weight loss.

Green tea (Camellia sinensis) 

Studies suggest that green tea extract may boost metabolism and help burn fat, but there have been no specific studies of this herb in obese individuals. Some researchers speculate that substances in green tea known as polyphenols are responsible for the herb's fat-burning effect.

Hydroxycitric acid

Obtained from plants native to India (including Garcinia cambogia and Garcinia indica), hydroxycitric acid has been incorporated into many commercial weight-loss supplements. Although animal studies have found that hydroxycitric acid reduced food intake and prevented weight gain, studies of G. cambogia in humans have produced less promising results. More research is needed before conclusions can be drawn about using hydroxycitric acid, or the plants which produce the substance, for weight loss.

Oolong tea (Thea sinensis)

In traditional cultures, oolong tea has been used to prevent obesity and lower cholesterol. One animal study found that oolong tea prevented weight gain in rats fed a high-fat diet. This study suggests that the traditional use of oolong tea may have validity. Further research in animals and people would be helpful.

Capsaicin (Capsicum frutescens)

Preliminary evidence indicates that capsaicin (the substance that makes chili peppers taste hot) may help the body burn fat, particularly when eating a high-fat diet. Further research is needed to confirm these early findings, however.

There have been few studies examining the effectiveness of specific homeopathic remedies. Despite encouraging advertisements, there is no single or combination homeopathic remedy that will help all people lose weight. However, individualized homeopathic therapy can be designed to aid weight loss by addressing metabolism, digestion, and elimination. Before prescribing a remedy, homeopaths take into account a person's constitutional type. In homeopathic terms, a person's constitution is his or her physical, emotional, and intellectual makeup. An experienced homeopath assesses all of these factors when determining the most appropriate remedy for an individual.

Many studies have found both acupuncture and acupressure to have beneficial effects on weight. Acupuncture is believed to promote weight loss by stimulating points on the body that boost serotonin levels. (Elevated serotonin levels are thought to suppress appetite.) Although most studies that have investigated the effects of acupuncture on weight loss have been poorly designed, one well-designed study found that people who received electrical acupuncture of the ear (auricular acupuncture) experienced a reduction in appetite.

Cognitive Behavioral Therapy

Besides changing diet and exercise habits, successful weight loss often requires additional behavioral practices to keep the weight off in the long term. These practices include setting reasonable weekly or monthly goals—how much exercise or how much weight loss is desired, for instance—and establishing rewards for successes in ways other than with food. Working with both a dietician and a behavioral specialist can help an obese individual put these practices into play and achieve his or her ultimate goals.

Monitoring progress with a daily record of food and calorie intake, servings of fruits and vegetables, the amount of water consumed, total fat intake, and exercise sessions will also aid in weight loss.

It also helps to eliminate or reduce the stress that leads to overeating by practicing relaxation exercises, such as yoga, meditation, or tai chi. Avoiding restaurants that serve heavy, fat-laden food and "cues" that trigger the desire to eat, will also help prevent weight gain.

Finally, it is hard to lose weight without support. To remain focused on goals and to receive encouragement when needed, it is important to seek the advice of experienced professionals with a proven track record of successfully helping others lose weight. Joining a support group may also be of value.

Hypnosis

Although studies on hypnosis as a treatment for obesity are not conclusive, most research suggests that hypnotherapy (when used in combination with cognitive behavioral therapy, exercise, and a low-fat diet) may help overweight or obese individuals lose weight.

Guggal (Commiphora mukal) is a common ingredient found in several Ayurvedic medicines used to treat obesity. Studies have shown that overweight individuals who receive these guggal-containing Ayurvedic remedies lose a significant amount of weight compared to those who do not receive such medicines. These Ayurvedic remedies also caused substantial decreases in cholesterol. Minor side effects associated with guggal-containing preparations include mild diarrhea and nausea. Further studies are needed to determine whether guggal is a safe and effective treatment for obesity.

Pregnant women should not take any herbal remedies or over-the-counter or prescription medications for weight loss.

Obese women who become pregnant are at an increased risk for the following:

• Gestational diabetes—a diabetic condition that appears during pregnancy and usually goes away after the birth of the baby
• High blood pressure
• Preeclampsia—a potentially fatal condition causing high blood pressure, fluid retention, and protein in the urine; may cause abdominal pain and vomiting
• Abnormally large infants resulting in difficult deliveries
• Caesarean sections as well as complications associated with Caesarean sections
• Fetal distress—a condition in which the baby does not receive enough oxygen

People who are overweight or obese increase their risk for developing the following conditions:

• Type 2 diabetes
• High blood pressure
• Coronary artery disease
• High cholesterol
• High levels of triglycerides (fat) in the blood
• Heart failure
• Respiratory problems (such as sleep apnea)
• Circulatory problems (such as varicose veins)
• Gallblader disease
• Breast cancer (after menopause) and endometrial cancer
• Prostate cancer
• Colorectal cancer
• Arthritis
• Skin problems (such as warts)

In general, eating and exercise habits are hard to change. Many people are able to lose at least 20 pounds with diet and exercise plans, but only about 10 to 20 percent of these people can maintain that weight loss for a long period of time. Losing just 15 to 20 pounds has a significant payoff, however—it can reduce the risk of serious complications, such as diabetes and heart failure, by 10 to 25 percent.

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