Obesity: Genes, environment and addiction
- Published: 18 April 2010
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Science is in its infancy with regard to learning the causes of obesity. Genes, environmental pressures and food addiction all play a part, writes Judy Shepps Battle.
"I am so confused. Every time I watch TV or read the newspaper, I hear some new cause of obesity. Is it inherited? Is it caused by too many fast-food ads and too many opportunities to be sedentary? Or is it the result of brain chemistry that causes food addiction?
"I mean, we have been working with a really great nutritionist and exercise person to create a healthier lifestyle for our entire family. We all have lost some weight and feel better but it scares me that our actions won't cure our 14-year-old son, that maybe Bobby just inherited a tendency to be overweight from my wife and me and is stuck with it. And frankly, I don't even understand how someone could be 'addicted' to food."
Mr. S. was visibly agitated as he spoke to fellow members of the support group for parents of overweight kids. He held in his hand a national magazine, the cover of which posed the question "The Weight Debate: Is Obesity Really a Disease?" The magazine had some great information in it, but nothing definitive about an exact cause or guaranteed treatment for weight problems.
Scientists have known for a long time that children of significantly overweight parents have a greater risk of developing weight disorders than peers from non-obese parents.
The unanswered question involves the parental pattern of obesity. Is it environmental -- did their parents (the child's grandparents) teach eating patterns that resulted in being overweight? – or is excess poundage the result of a genetic propensity for obesity that goes back generations?
While there is no clear answer to this question, scientists are actively working to locate genes and gene neighborhoods that are associated with obesity. The first discovery -- a gene for leptin, a weight-regulating hormone -- was found more than a decade ago.
Since that time more than 300 obesity-related genes have been located. Some genes relate to how the body burns up calories and others affect the brain chemistry that controls appetite and feelings of satiation. Still other genes relate to where fat is deposited on our bodies.
Current thought is that a person's most comfortable weight range -- the “set point” -- indeed may be genetically determined. This is not to say, however, that an individual cannot lose weight and weigh less than this range, or gain weight and be heavier than his or her set point.
Further evidence of the role of genes comes from studies of adoptive children whose weight tends to be more like their biological parents than their adoptive ones. Also, identical twins who are raised apart tend to look physically similar as adults, no matter how conducive -- or non-conducive -- to overeating their environment has been.
The good news is that even though a person can't change genetic makeup, he or she can make environmental changes in level of activity and eating habits.
Environmental causes of obesity largely have to do with external stimuli, such as media advertising, and the lifestyle choices made in response to these cues.
How often do we choose to cook at home instead of ordering a pizza or driving through the Golden Arches? How much regular exercise do we elect to have, rather than being a couch potato and watching television or surfing the Web? Do we take the dog for a long walk at night, or put him in the backyard on a trolley-run and return to reading the newspaper?
It isn't easy to opt for healthy alternatives. Advertisements for "empty calorie" foods appear in all media, with most beamed directly at children. For example, Saturday morning cartoons -- traditionally saturated with ads for sugary cereal, salty snacks, and junk food -- feature a disproportionate number of commercials for “fast foods.”
In addition, portions of food at restaurants, movies, and even sporting events have become super-sized. Under such circumstances, it is hard to remember that a child's portion generally is about the size of a child's fist. And it is not necessary for an adult to consume an entire bucket of popcorn that has been topped with a butter-substitute.
Finally, adequate exercise, which a child might get in a school physical education program, is often compromised by budget cuts and by non-active programming (such as driver's education) taking place during class time.
The Surgeon General of the United States recommends that adults -- parents and educators -- encourage all children to be physically active for at least 60 minutes a day, not only in team or individual sports, but by choosing to take the stairs instead of an elevator, riding their bikes, and just getting out and playing with friends.
Genes and environment are two important factors in causing obesity. But there is one more; it’s the influence that Mr. S. has trouble understanding: food addiction.
Food Addiction and Obesity
It is difficult to understand why people who overeat just don't stop when they are full or why they have such difficulty eating smaller portions. The fact is that many people -- children and adults -- are unable to control the amount and/or type of food they eat because they are under a compulsion to consume too much.
Many of these people suffer from food addiction. An addict is a person who knows an activity is not good for him or her yet is compelled to do it anyway.
For a food addict, this means a vicious cycle of compulsive overeating, feeling lethargic and snacking to try to regain energy, watching the number on the scale increase, feeling awful about self, swearing to start "eating right," and killing these painful feelings of shame and low self-esteem with more compulsive overeating.
Fortunately, scientists are learning that food addiction is not a failure of will power but a function of individual brain chemistry.
For example, a brain-imaging study conducted by the Brookhaven National Laboratory suggests that many overweight people find food more palatable than those of normal weight because they have fewer brain receptors for dopamine - a neurotransmitter that signals feelings of satisfaction and pleasure. The implication is that obese people may be self-medicating good feelings by eating, much like a drug addict does with drugs.
The medical profession tends to treat overweight patients of all ages in the same way: by providing a diet plan, a referral to a nutritional specialist, and/or prescribing medication. For the food addict, an appropriate food plan also must be established that does not contain "trigger chemicals." For many, these "triggers" include sugar, flour, caffeine, and eating a high volume in one sitting.
In addition, emotional support must be obtained that goes beyond family and friends. Some find peer recovery systems, such as twelve-step groups, helpful; others turn for guidance to a counselor trained in addictions. It is always helpful when family treatment supplements individual counseling.
Science is in its infancy with regard to learning the causes of obesity. In the interim, the greatest tool is learning healthy eating behaviors and partaking in regular physical activity as a family. Become educated about how the body metabolizes foods and find out if "trigger foods" are a problem for you or members of your family.
And, like Mr. S., if the statements you read about obesity confuse you, ask for help. Don't hesitate to consult your family doctor or nutritionist for answers on this important subject.