For the past 30 years, the prevalence of overweight and obesity has increased sharply for both adults and children. These increasing rates raise concern because of their implications for health. Being overweight or obese increases the risk of many health problems, including:

• High blood pressure
• High total cholesterol or triglycerides
• Coronary heart disease
• Stroke
• Osteoarthritis
• Gallbladder disease
• Sleep apnoea and respiratory problems
• Some cancers (endometrial, breast, and colon)
• Stroke

Definitions for Adults

For adults, overweight and obesity ranges are determined by using weight and height to calculate a number called the “body mass index” (BMI). BMI is used because, for most people, it correlates with their amount of body fat.

• A BMI of 25.0 - 29.9 is overweight
• A BMI of 30.0 - 39.9 is obese
• A BMI of 35.0 or higher with at least one other significant comorbidity ; or a BMI of 40.0 or higher is severely (or morbidly) obese

It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat. Other methods of estimating body fat and body fat distribution include:

• measurements of skinfold thickness
• waist circumference (which is a predictor of risk for obesity-related diseases)
• calculation of waist-to-hip circumference ratios
• techniques such as ultrasound, computed tomography, and magnetic resonance imaging (MRI)
   

Definitions for Children and Teens

For children and teens, BMI ranges above a normal weight have different labels (at risk of overweight or underweight). Additionally, BMI ranges for children and teens are defined so that they take into account normal differences in body fat between boys and girls and differences in body fat at various ages.
 

Causes Of Overweight & Obesity

Being overweight is generally caused by the intake of more calories by over eating, than are expended by the limited physical exercise and sedentay everyday living. Other factors which may contribute to this imbalance include:

• Genetic predisposition
• Hormonal imbalances (e.g. hypothyroidism)
• Metabolic disorders
• Eating disorders (such as binge eating)
• Alcoholism
• Psychotropic medications
• Smoking cessation and other stimulant withdrawal

Treatments For Overweight

A large number of people undergo some forms of treatment to attempt to reduce their weight, usually in an attempt to improve their health, to improve their lifestyle, and for cosmetic reasons. The generally recommended treatment for being overweight is a modified or controlled diet in conjunction with increased physical exercise.

Various dietary approaches have been proposed, some of which have been compared by trials, but in general, most of them that based on a low carbohydrate and low fat diet have similar benefits.

Reducing calorie intake by dieting may have short-term effects, but does not lead to long-term weight loss. 80 - 95% of those who has lost 10% or more of their body mass by dieting alone regain all that weight back within 2 to 5 years. The body has systems that maintain its homeostasis at certain set points, including body weight. For this reason, it is generally recommended that weight-loss diets should be done in combination with increased exercise and long-term planning and weight management.

While it is generally accepted that for significantly obese patients, losing weight can reduce health risks and improve quality of life, there is some evidence to suggest that for merely overweight patients, the health effects of attempting to lose weight may actually be more detrimental than simply remaining slightly overweight. Moreover, for all individuals, repeatedly losing weight and then gaining it back (weight cycling), is believed to do more harm than good and can be the cause of significant additional health problems. This is caused by the loss of more muscle than fat.

Treatments For Obesity

If the above goals are not achieved, pharmacotherapy can be offered. The patient needs to be informed of the possibility of side-effects and the long-term safety and efficacy data.

Drug therapy may consist of sibutramine, orlistat, phentermine, and diethylpropion. In patients with BMI > 40 who fail to achieve their weight loss goals, with or without medication, and who develop obesity-related complications, surgery may be indicated. The patient needs to be aware of the potential complications.

Mechanisms Of Anti-obesity Drugs

• Suppression of the appetite. Catecholamines and their derivatives, such as amphetamine-based drugs, are the main drugs used for this. Drugs blocking the cannabinoid receptors is recently launched.
• Increase of the body's metabolism.
• Interference with the body's ability to absorb fat or carbohydrate in food. For example, Orlistat blocks fat breakdown and thereby prevents fat absorption. The OTC fiber supplements glucomannan and guar gum have been used for the purpose of inhibiting digestion and lowering carbohydrate absorption.

Orlistat

Orlistat reduces intestinal fat absorption by inhibiting pancreatic lipase. It may cause frequent, oily bowel movements. Fat in the diet needs to be reduced to ameliate the symptoms.

Sibutramine

Sibutramine is an appetite suppressant, reducing the desire to eat. It may increase blood pressure and may cause dry mouth, constipation, headache, and insomnia.

Rimonabant

The discovery of cannabinoid receptors in the brain, liver and muscle has stimulated research in a new class of drugs, namely cannabinoid (CB1) receptor antagonists. These drugs not only causes weight loss, but prevent or reverse the metabolic effects of obesity, such as insulin resistance and hyperlipidemia, and may also decrease the tendency to abuse substances such as alcohol and tobacco.

This is more appropriate to use in people with co-existing high blood pressure and dibetes.

Others

The combination of phentermine and fenfluramine or dexfenfluramine, popularly referred to phen-fen, was used in producing significant weight loss by suppressing the appetite. However, fenfluramine and dexfenfluramine were pulled from the market due to the complication of heart valve damage.

Other weight loss drugs have also been associated with medical complications, such as fatal pulmonary hypertension due to Redux; and hemorrhagic stroke due to phenylpropanolamine. Many of these substances are related to amphetamine.

Products that work as a laxative or diuretic can drop the potassium level in blood, which may cause heart and muscle problems. Pyruvate, which is found in red apples, cheese, and red wine, may result in a small amount of weight loss, but its weight loss potential has not been scientifically established.

Underweight refers to a human who is considered to be under a healthy weight. The definition is usually made with reference to the body mass index (BMI), with a value under 18.5. It is important to note that the BMI is a statistical estimate, and some individuals classified as underweight may be perfectly healthy.

Causes

The most common cause of a person being underweight is primarily malnutrition caused by the unavailability of adequate food, which can be as high as 50% in some parts of the world.

In the presence of adequate food resources, being underweight can sometimes be the result of mental or physical disease. There are hundreds of possible medical causes for excessive weight loss. Some of the more prevalent include:

• Anorexia Nervosa
• Bulimia Nervosa
• Over-training (endurance sports)
• Hyperthyroidism
• Chronic liver and kidney disease
• Malabsortpion due to bowel diseases
• Cancer and the treatment
• Tuberculosis
• Diabetes
• Anxiety and depressive disorders
• Drug abuse
• HIV/AIDS

Problems Of Underweight

The most immediate problem with underweight is that it might be secondary to an underlying disease. Unexplained weight loss requires professional medical diagnosis.

Underweight can also be a primary causative condition. Severely underweight individuals may have poor physical stamina and a weak immune system, leaving them open to infection. People who are malnutrative underweight may also lack intake and absorption of other vital nutrients, especially essential amino acids, vitamins and minerals.

In women, being grossly underweight can result in absence of menstruation and possible complications during pregnancy. It can also cause anaemia and hair loss.

It is an established risk factor for impaired bone metabolism and may lead to osteoporosis, even for young people.

Treatments

If an individual is severely underweight to the point where problems with his or her health develop, it may be necessary for the person to make a concentrated effort to gain weight. The treatment for an underweight individual is to increase the nutritional energy intake so that more is consumed than is being used as work. It is usually suggested that weight training is also to be undertaken to increase muscle mass.

If weight loss results from a disease, resolving the illness and consuming adequate calories can bring many underweight individuals to a healthy body weight.

Anorexia nervosa and bulimia are eating disorders associated with a negative body image. Anorexia nervosa is a disorder in which people extremely limit their food intake. This results in dangerously quick weight loss, to the point of starvation. This disorder is most commonly found in adolescent females.

Bulimia is binge eating followed by self-induced vomiting. It's often associated with anorexia nervosa. Many people with bulimia do not lose a lot of weight.

These conditions require the help of psychological counselling and psychiatric intervention.