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Genetic Factors of Obesity

Obesity and Heart Disease

Evidence shows that genetics can play a role in obesity, but genes don’t tell the whole story. People with a genetic propensity to being overweight can live their entire lives at a healthy weight, and people with no family history or genetic predisposition to being overweight can continually struggle with weight loss

Three general subgroups of obesity are related to the genes – monogenic, syndromic, and polygenic. Monogenic obesity is severe class 3 obesity that occurs without developmental delays. Syndromic obesity is obesity that occurs along with developmental abnormalities, such as Down Syndrome. Polygenic obesity, also known as common obesity, is the type of obesity that can affect anyone. Currently, about 20 genetic mutations have been identified that can result in monogenic obesity. Syndromic obesity is also linked to genetics. For example, a genetic syndrome, Prader-Willi syndrome (PWS) is caused by an abnormality in the chromosomes. People with this syndrome tend to become obese at an early age because of central nervous system dysfunction that leads to an abnormally increased appetite (hyperphagia). 

However, despite the possibility of genetic abnormalities causing obesity, it’s quite rare. Genetic factors play only a small part in your propensity to gain weight and become obese. However, obesity does tend to run in families. This is often due to environment. People who live together and eat together often learn the same eating habits and engage in similar lifestyles.

The role of genes in establishing metabolism

You probably know people who seem to be able to eat whatever they want and never gain weight. While no one can really eat countless calories without gaining weight, metabolic rate does vary from person to person, and the faster your metabolic rate is, the more you can eat without putting on the pounds. The opposite is also true. If your metabolic rate is slower than average, it may feel like you just have to look at food to gain weight. That’s obviously an exaggeration, but it is true that two people who are the same height, weight, body shape and size, age, and gender can burn calories at different rates. 

Your genes may play a role in your metabolic rate. The technical term for this is your basal metabolic rate (BMR). Your BMR is your resting metabolic rate, in other words the amount of energy (calories) your body burns while you’re at rest. This rate is partially determined by your genes, but other factors can influence your BMR as well. Muscle mass is one of those factors. The larger percentage of muscle you have in your body, the faster your BMR will be. On average, men have more muscle mass than women, so a man who’s 5’7” and 160 pounds is likely have a faster BMR than a woman of the same height and weight. That’s a generalization, but it helps illustrate the role muscle mass has on BMR. 

Ultimately (unless you have rare genetic or health conditions), it’s your environment and your lifestyle choices that have the greatest effect on your weight. Even people with a slower metabolism can maintain a healthy weight, and people with a fast metabolism can be overweight. So while there is a genetic component to BMR, it’s not as strong a predictor of obesity as environment and lifestyle.

The thyroid

Your thyroid gland plays an important role in your metabolism. And there are genetic thyroid disorders that can speed up or slow down your BMR. If your thyroid gland is underactive (hypothyroidism), your metabolism will be slower, and if your thyroid gland is overactive (hyperthyroidism), your metabolism will be faster. 

If you’ve been diagnosed with hypothyroidism, you should work with your doctor to increase the thyroid hormones circulating in your blood. In addition to making it difficult for you to lose weight, low levels of thyroid hormones can have several uncomfortable and even dangerous effects. The most common treatment for an underactive thyroid gland is thyroid hormone replacement. If you have a prescription for thyroid hormones, take them every day as directed. Once your hormone levels increase to normal, your metabolism should bounce back as well. 

The role of the genes in establishing appetite

As we mentioned earlier, there are some genetic syndromes that, among other things, tend to increase appetite. Prader-Willi syndrome is one of those syndromes. People with PWS have a dysfunction of their central nervous system that increases their appetite. This is a rare condition that shows there can be a link between genetics and appetite.

There is additional evidence of a link between certain genes and appetite. One study at UCLA College of Medicine found that people who tended to binge on carbohydrates had the same genetic marker as some people who are chemically dependent upon alcohol. A study of sweet sensitivity showed a link between a genetic variation and a tendency to have taste receptors that are sensitive to sweetness. Other studies have shown a family history of obesity, but the evidence doesn’t show whether this link is due to genes, the environment, or both. 

While there is evidence that your genes could affect your appetite or hunger, evidence is stronger that lifestyle has more of an effect than heredity. In fact, your DNA is always changing. And some parts of your DNA blueprint are changeable. It can evolve in response to your environment, your emotions, your food and beverage intake, and more. The science behind this theory is called epigenetics. Experts in epigenetics say that you can have an effect on changing your epigenetic code through your lifestyle choices and your attitudes. Evidence shows that you can affect the expression of your genes by your actions. Studies are underway to see how people can use nutrition to switch genes on or off, effectively changing whether your genes influence your life. The science of epigenetics is in its infancy, and this is a very basic explanation of a complex topic. But the bottom line is that while your genes can play a role in your weight, your lifestyle and environment tend to be much more influential. 

By making healthy choices, like eating a balanced diet full of nutrients and exercising regularly, you can reduce your risk of obesity and the conditions associated with obesity and overcome any genetic tendency toward being overweight. 

If you have been exercising and dieting, and you’re still unable to achieve your weight loss goals, you may want to consider a medical weight loss program. Call 800-633-7377 to request an appointment with a Beaumont medical weight loss expert