What Is Obesity?

Obesity word illustration surrounded by question marks.Obesity results from the excessive accumulation of fat that exceeds the body's skeletal and physical standards. According to the National Institutes of Health (NIH), an increase of 20 percent or more above your ideal body weight is the point at which excess weight becomes a health risk.

Today 97 million Americans, more than one-third of the adult population, are overweight or obese. An estimated 5 to 10 million of those are considered morbidly obese.

What is morbid obesity?

Obesity becomes "morbid" when it reaches the point of significantly increasing the risk of one or more obesity-related health conditions or serious diseases (also called co-morbidities) that result either in significant physical disability or death. Sometimes the term "clinically severe obesity" is used interchangeably.

Morbid obesity is typically defined as being 100 lbs. or more over ideal body weight or having a Body Mass Index (BMI) of 40 or higher.

According to the National Institutes of Health Consensus Report, morbid obesity is a serious disease and must be treated as such. It is a chronic disease, meaning that its symptoms build slowly over an extended period of time.

Causes of obesity

The reasons for obesity are complex. Despite conventional wisdom, it is not just a result of overeating. Research has shown that in many cases a significant underlying cause of morbid obesity is genetic. Studies have demonstrated that once the problem is established, efforts such as dieting and exercise programs have a limited ability to provide effective long-term relief.

Until the disease is better understood, the control of excess weight is something patients must work at their entire lives. That is why it is very important to understand that all current medical interventions, including weight-loss surgery, should not be considered medical cures. Rather they are attempts to reduce the effects of excessive weight and alleviate the serious physical, emotional and social consequences of the disease.

There are many factors that contribute to the development of obesity including genetic, hereditary, environmental, metabolic and eating disorders. There are also certain medical conditions that may result in obesity like intake of steroids and hypothyroidism.

Genetic factors

Numerous scientific studies have established that your genes play an important role in your tendency to gain excess weight.

  • The body weight of adopted children shows no correlation with the body weight of their adoptive parents, who feed them and teach them how to eat. Their weight does have an 80 percent correlation with their genetic parents.
  • Identical twins, who share the same genes, show a much higher similarity of body weight than do fraternal twins, who have different genes.
  • Certain groups of people, such as the Pima Indian tribe in Arizona, have a very high incidence of severe obesity. They also have significantly higher rates of diabetes and heart disease than other ethnic groups.
  • We probably have a number of genes directly related to weight. Just as some genes determine eye color or height, others affect our appetite, our ability to feel full or satisfied, our metabolism, our fat-storing ability and even our natural activity levels.

Environmental factors

Environmental and genetic factors are obviously closely intertwined. If you have a genetic predisposition toward obesity, then the modern American lifestyle and environment may make controlling weight more difficult. Fast food, long days sitting at a desk and suburban neighborhoods that require cars all magnify hereditary factors such as metabolism and efficient fat storage. For those with morbid obesity, failure to change their environment usually results in failure to reach and maintain a healthy body weight.


We used to think of weight gain or loss as a function of calories ingested and burned. But now we know the equation isn't that simple. Obesity researchers now talk about a theory called the "set point," a sort of thermostat in the brain that makes people resistant to either weight gain or loss. If you try to override the set point by drastically cutting your calorie intake, your brain responds by lowering metabolism and slowing activity, making it harder to achieve and maintain weight loss.

Eating disorders and medical conditions

weight-loss surgery is not a cure for eating disorders. And there are medical conditions, such as hypothyroidism, that can also cause weight gain. That's why it's important that you work with your doctor to make sure you do not have a condition that is best treated with medication and counseling.

Obesity-related health conditions

Obesity-related health conditions, aka co-morbidities, are health conditions that, whether alone or in combination, can significantly reduce your life expectancy. They include:

  • Type 2 Diabetes
  • High blood pressure/heart disease
  • Osteoarthritis of weight-bearing joints
  • Sleep apnea/respiratory problems
  • Gastroesophageal reflux/heartburn
  • Depression
  • Infertility/menstrual irregularities
  • Urinary stress incontinence