Obesity and Genetics
Posted: Jan. 1, 2005
Obesity is characterized by an excessively high amount of body fat or adipose tissue. This condition is common, but the condition varies from individual to individual.
At one end of the spectrum, a healthy weight can be attained by cutting down on certain foods, taking smaller portions, and embarking on a regimen of regular exercise. For individuals in this population, a moderate change in diet and exercise are the proper interventions because they work.
At the other end of the spectrum, there is another population of overweight people who do not respond as well to these interventions. Everyone knows someone who tries diligently to lose weight but who experiences limited success or loses weight only to gain it back over time. In fact, more than 80% of those who lose weight will gradually regain it unless a weight maintenance program is implemented over the long-term.
What is different about these people compared to those who either stay thin or lose weight readily and keep it off with relatively minor lifestyle changes? One difference may be genetic risk factors that affect energy metabolism and result in an inborn susceptibility to gain weight.
Genetics as a risk factor for obesity
Although rare obesity syndromes caused by mutations in single genes have been described, by far the greatest proportion of obesity in humans is not due to mutations in single genes.
Genetic predisposition may not be health destiny, but studies indicate that inherited genetic variation is an important risk factor for obesity. Evidence from twin, adoption and family studies strongly suggests that biological relatives exhibit similarities in maintenance of body weight. Genetic factors also are beginning to be implicated in the degree of effectiveness of diet and physical activity interventions for weight reduction.
These genetic risk factors tend to be familial, but are not inherited in a simple manner; they may reflect many genetic variations, and each variation may contribute a small amount of risk and may interact with environmental elements to produce the clinical condition of obesity.
You can’t change your genes, but you can change your behavior
Does this mean that those with a susceptible genotype are destined to a life of futile efforts to achieve a healthy weight? This need not be the case. We can’t change our genes, but we can change our behavior.
Small victories in weight loss — often as little as 10% of total body mass — can result in positive effects on health and well-being, even if an ideal weight remains elusive. Also, the positive effects of regular physical activity include lower blood pressure and increased cardiorespiratory fitness even in people who are significantly overweight.
In the longer term, understanding the genetic variations that influence energy metabolism may help us to understand the underlying biological factors that affect weight gain and energy expenditure. Also, to recognize that obesity may be due to a metabolic condition rather than a flaw in character is important both for the people who are affected and for society as a whole.
The public health messages to prevent overweight emphasize a nutritious diet and daily physical activity. Many who follow this advice from the outset are able to maintain a healthy weight, even with a genetic susceptibility to gain weight.
However, these lifestyle interventions have a range of effectiveness, especially if obesity is already present. For people who are already overweight, the public health interventions aimed at the general population are not a complete solution. Insights from genetics and molecular biology in controlling appetite and activity may provide more effective therapies for treatment.
Source: Center for Disease Control and Prevention
Causes of Morbid Obesity
The reasons for obesity are multiple and complex. Despite conventional wisdom, it is not simply 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.
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 effects of excessive weight and alleviate the serious physical, emotional and social consequences of the disease.
The underlying causes of severe obesity are not known. 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.
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.
(Original Air Date: 04/27/06) Morbid obesity changes the dynamic of two entire families … and tears them apart. DeeDee weighs over 700 pounds and hasn't left her house in more than a year. She has become a burden to her friends and family by constantly demanding their help and company. Is DeeDee ready to get real and make a change, or will she continue to blame her weight gain on other circumstances? Also, her children explain why they resent their mother and feel hostage to her demands. Then, MaLynn is only 14 years old, but she already weighs 419 pounds, and her obesity is causing problems in school. Her mother, Shari, admits she can't say no to her daughter when it comes to food. Dr. Phil shows MaLynn how she can easily lose 86 pounds, and he gets this mother-daughter team to work together to save their relationship and their lives. Talk about the show here.
