Obesity is considered a long-term complex disease. Many factors are involved in determining why some people are heavier than others and how much risk they have for developing other medical problems.
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 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 adverse effects of excessive weight and alleviate the serious physical, emotional and social consequences of the disease.
You gain weight when you consume more calories from food than your body uses through its normal functions (basal metabolic rate [BMR]) and physical activity. The unused calories are stored as fat. You become obese if you consistently consume excess calories over a long period of time. For example, eating an extra 100 calories per day can lead to a gain of about 10 lbs (4.5 kgs) in a year. Gaining 10 pounds a year eventually will result in a BMI of 30 or higher.
Your activity level is also important. Activity uses calories, which helps balance the calories you get through food. If you are inactive, it may be easier to gain weight.
However, calories alone do not explain weight gain and why some people gain (or lose) weight more easily than others. Other factors that play a major role in weight gain and obesity include:
Genetic or Hereditary Factors
Research has shown that in many cases a significant underlying cause of morbid obesity is genetic - you inherit the tendency to gain weight. 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 whom they have never met. Identical twins with the same genes show a much higher similarity of body weights 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 lifestyle and environment that has readily available inexpensive food high in fat and low in fruits and vegetables may lead to weight gain and obesity. 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 by nonoperative measures.
Metabolism
We used to think of weight gain or loss as only a function of calories ingested and then burnt. Take in more calories than you burn and gain weight; burn more calories than you ingest and 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. |
