Understanding obesity

Although exact mechanisms of this disease are still being discovered, there are several factors involved including:

  • Genetics
  • Metabolic
  • Neuroendocrine
  • Environmental factors

The reasons for obesity are multiple and complex. It is not simply a result of overeating. Studies have demonstrated that once the problem is established, efforts such as dieting and exercise have a limited ability to provide effective long-term relief.

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

Contributing factors

There are many factors that contribute to the development of obesity including genetic, hereditary, environmental, metabolic and eating disorders, but the underlying causes of severe obesity are not known. 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 genes play an important role in the tendency to gain excess weight.

Adopted children

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, whom they have never met.

Identical twins

Identical twins, with the same genes, show a much higher similarity of body weights than do fraternal twins, who have different genes.

The Pima Paradox

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.

Genes relating to weight

A number of genes directly relate to weight. Just as some genes determine eye color or height, others affect the appetite, the ability to feel full or satisfied, metabolism, fat-storing ability, and even 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 suffering from morbid obesity, anything less than a total change in environment usually results in failure to reach and maintain a healthy body weight.


We used to think of weight gain or loss as only a function of calories ingested and then burned. Take in more calories than you burn, gain weight; burn more calories than you ingest, lose weight. 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. You then gain back any weight you lost.

Eating disorders and medical conditions

It’s important to understand that 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 should be treated with medication and counseling instead of surgery.

Health threats of morbid obesity

Morbid obesity brings with it an increased risk for a shorter life expectancy. For individuals whose weight exceeds twice their ideal body weight (that's about two to six percent of the U.S. population), the risk of an early death is doubled compared to non-obese individuals.

The risk of death from diabetes or heart attack is five to seven times greater. Even beyond the issue of obesity-related health conditions, weight gain alone can lead to a condition known as "end-stage" obesity where, for the most part, no treatment options are available. Yet an early death is not the only potential consequence. Social, psychological and economic effects of morbid obesity, however unfair, are real and can be especially devastating.

Last reviewed: 
June 2018

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