Are You Destined To Become Overweight Or Obese?

There is a growing pile of evidence showing that obesity is not just a result of bad eating habits, but is a result of a variety of factors such as behavior, environmental factors and genetics. The interaction of these factors is more likely to explain why people gain weight over time rather than a result of just one cause such as poor diet or unhealthy lifestyle.

Claude Bouchard, who is chairman of genetics and nutrition at the Human Genomics Laboratory of Pennington Biomedical Research Center, in Baton Rouge, cites, for example, that while poor dietary habits and lack of physical activity are major factors driving the obesity epidemic, their effects are not the same in everyone.

He says that the body has a biology driver, in the form of pro-obesity genes, which may enhance the risk of behaviors in causing obesity. This is why some people can eat high-calorie foods and not seem to gain weight while others immediately see a significant change in their body measurements. One study that was published in the journal BMJ in 2014 involved more than 37,000 participants and examined the effects of having genetic risks and the frequency of their consumption of fried food. After analyzing the data, researchers found that compared to people with low genetic risk, eating fried food on most days of the week had a greater effect on body size for participants who had a higher genetic risk of obesity. However, some studies also show that a healthy lifestyle can counteract these genetic risks, as seen in people who carry the so-called "obesity genes", but do not become overweight. 

How Genes Influence Weight

There are several theories on how your genes may affect your weight.

Fat Distribution. The common belief is that fat distribution differs according to your gender suggests that men typically store fat in their abdomen while women have more fat in the thighs and hips. However, it has been observed that with age, both men and women lose muscle weight, but women tend to store more fat in the abdomen.

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Energy Metabolism. Another way your genes may affect your body weight is their effect on how you burn calories. Differences in energy metabolism or how people use calories can determine whether they store excess calories as fat or burn them more efficiently. In one study, UCLA researchers found that mice of different genetic strains which were fed the same normal diet for eight weeks, then fed a high-sugar, high-fat diet for the next eight weeks gained weight in different degrees. While some mice did not have a significant change in body-fat percentage, other mice increased their body fat percentages by up to 600 percent. The scientists explained that those differences may be attributed to genes associated with fat gain and obesity in the mice. They added that many of these genes overlap with those linked to obesity in man. The genetic differences were significant because they affected how some mice were naturally more active and more effective in burning calories while others were not.

Genetic Differences Can Determine Your Body Weight

There are more reasons why genes can influence a person’s tendency to gain weight. Let's examine them.

Basal Metabolic Rate

Your BMR or basal metabolic rate is a measure of how much energy you burn when you are at rest. The lower your BMR, the easier it is for you to gain weight. However, your BMR may vary slightly according to certain conditions. Eating a very low-calorie diet, for example, can decrease your BMR, while severe physical stress increases BMR.

Set Point

One theory suggests that the body tries to keep its weight within a specific range or set point, which is influenced by one’s genetic makeup. However, actual body weight is influenced by lifestyle and environmental factors. It is believed that the set point may adjust to a new level over time and may be affected by exercise, overeating, certain medicines, and medical conditions.

Body Signals

Your body gives you certain signals such as hunger, appetite, and fullness (satiety), which influence how much you eat, although you can ignore these for short periods of time. Environmental factors can also influence these signals. Hunger and satiety are normal sensations that make you either want to eat or to stop eating. These are controlled by interactions involving a region in the brain called the hypothalamus, your blood sugar levels, the production of certain hormones, and the stretch receptors in the stomach.

Research shows that individuals who carry genes called FTO (fast mass and obesity-associated gene) and BDNF (brain-derived neurotrophic factor gene) have a greater risk of obesity. These genes affect the part of the brain that controls eating and appetite and are linked with overeating. A large study involving more than 2,000 participants found that variations in the FTO gene were significantly associated with an increased tendency to eat more meals and snacks per day, with greater consumption of energy from fat and sweets. It also showed that individuals who had variations in the BDNF gene tend to consume more servings of dairy, meat, eggs, nuts and beans. They were also found to consume about 100 more calories daily, which could have a considerable influence on body weight.

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According to scientist Joseph Majzoub, MD, chief of the endocrinology division at the Boston Children’s Hospital, gene mutations that are known to cause obesity in humans account for less than five percent of obesity in our society, and are not totally responsible for the on-going epidemic. However, these mutations have led scientists to the discover mechanisms that may help explain energy balance in humans, which may someday lead to the development of drugs that can affect these pathways to prevent obesity, either by decreasing appetite or promoting burning of calories.