Do Genes Play a Role in Obesity? The Answer is More Complex
Obesity is an epidemic in the United States. Those most affected by the obesity epidemic are populations living in an environment that promotes a poor diet and physical inactivity/sedentary lifestyle. Environment alone does not predict nor cause obesity, though.
Scientists have looked to genes as a possible cause of obesity, as well. However, genetic changes in human populations occur very slowly. In terms of obesity, this type of genetic change would occur too slowly to be solely responsible for the obesity epidemic.
When looking only at environment or only at genetics as a potential cause, these factors show that neither alone can be responsible for obesity:
- Differences in weight and related health conditions are seen within families.
- Body fat distribution is not the same from person to person in an environment, nor are the associated health problems.
- Differences are observed within groups in an environment, such as people with the same racial or ethnic background.
Given the variation in how people’s bodies react to the same environment suggests that genes and environment both may play a role in the development of obesity.
Definition of Obesity (CDC) for Adults*
- Underweight = a body mass index (BMI) less than 18.5
- Normal/healthy weight = BMI of 18.5 to <25
- Overweight = BMI of 25.0 to <30
- Obese = BMI of 30.0 or higher
*Measuring BMI in children is conducted using different factors
Morbid Obesity (National Institutes of Health [NIH])
- Being 100 pounds or more above your ideal body weight
- BMI of 40 or higher
- BMI of 35 or higher plus one or more comorbid condition (for example, diabetes)
Morbid obesity is defined by having trouble performing basic physical functions such as breathing or walking. Long-term consequences of morbid obesity include a shorter life expectancy, serious weight-related conditions such as type 2 diabetes and heart disease, and a lower quality of life with fewer economic and social opportunities than those who are not morbidly obese.
The Role of Genes in Influencing Obesity
Research shows that a large part of the variation in weight among adults is indirectly due to genetic factors. Although a link exists, no direct link shows a specific gene is responsible for obesity and that the gene is hereditary.
There are variations in many genes that may be contributing to obesity through an increased feeling of hunger and eating. The genetics of metabolism have also been extensively studied. A person with obesity may have a metabolism that has a harder time converting dietary fats to energy, or their metabolism might produce an increased tendency to store excess body fat.
Environment + Genetics
One hypothesis that is often cited in research is that in today’s environment, food is plentiful year-round, but there may be “thrifty” genes in humans. Thrifty genes had an original purpose of fat storage for when availability of food was unpredictable. According to this hypothesis, the same genes that helped our ancestors survive sporadic famines are now working in an environment of plentiful food. The thrifty genes have not yet adapted to the current environment and continue to prepare the body for times of famine.
Other hypotheses have been proposed including the role of bacteria in our digestive system; and, exposures to epigenetic changes early in life. Epigenetic changes are factors that change our DNA, such as certain lifestyle factors, including diet, physical activity, tobacco smoking, alcohol consumption, environmental pollutants and psychological stress.
Explaining obesity in terms of genes plus environmental factors can help encourage people who are working to achieve a healthy weight. They cannot control their genes, but they can control their environment to a large extent.
How Family History Can Help Identify Risk Factors
Family health histories help identify people who may be at high risk for developing obesity-related diseases, such as diabetes, cardiovascular diseases, and some forms of cancer. Family health history provides physicians information about the effects of shared genetics as well as the environment among close relatives.
Though families can’t change the genes they inherited, with guidance and assistance they can change aspects of their environment to promote healthy eating habits and regular physical activity. An added benefit is that these environmental changes benefit the health of all family members and possibly future generations.
Genes that Influence the Development of Obesity
More than 50 genes have been discovered that have a strong association with obesity. People with obesity often have multiple genes that predispose them to extra weight gain. One of these genes is called the fat mass and obesity-associated gene (FTO). People who have this gene may have trouble limiting the number of calories they consume. This gene in combination with other obesity-related genes can cause these symptoms:
- Increased hunger
- Increased intake of calories and reduced control when eating
- Not feeling “full”
- Increased tendency to not be physically active
- Increased tendency to store body fat instead of burn it
Should I Be Tested for Obesity Genes?
ALA does not offer genetic testing. However, testing for genetic links to obesity is not usually helpful because the outcome is irrelevant in terms of treatment. The treatments for obesity in adults are the same whether the FTO gene is present or not.
If you have been tested and you know you have genes that are shown to predispose some people to obesity, this does not mean you will develop obesity. Genes are only one factor in developing obesity. You may or may not have an increased appetite and reduced metabolism, but a consistent treatment plan incorporating a healthy diet, physical activity and cognitive behavioral therapy can help prevent obesity and promote a healthy lifestyle.
Research has shown that bariatric surgery is the most effective long-term weight-loss treatment for people suffering from obesity. There are many health benefits of bariatric surgery and different types of weight-loss surgery options to fit your individual needs. Request an appointment and one of our surgeons will discuss your options and answer our questions. Our ALA team will be with you every step of the way on your weight-loss journey.