Genetics within you can be a cause of obesity and can influence your weight management. (Image source:

I have little self-control when it comes to Big Mac, McNuggets, and french fries at McDonald’s restaurant. Its mesmerizing taste and smell make me forget all about the excess calories I am about to ingest until I step on a scale, which serves as a stern reminder of the awful reality in weight management. Like most people, I have to hit the gym in order to shed the extra pound so that I can prevent weight gain and avoid adding myself to the increasing number of 500 million obese adults globally. However, you must have come across a friend whom you are incredibly jealous of because this person can eat foods that are notorious for high calories, such as burgers, potato chips, and sweets, yet he or she does not seem to gain weight as readily as you do. Unfortunately, other than pouting and expressing your jealousy, there is not much you can do to change the situation because of the genetic difference we are born with.

Part of weight gain is genetics

The cause of obesity is multifactorial. It includes factors such as environment, emotion and lifestyle but your individualized genes contribute significantly to the overall weight management. Scientists have tested this genetic theory of weight gain by conducting a 100 day over-feeding study with 12 pairs of genetically identical twins . Under this controlled environment, the twins showed tremendous similarity in the amount of weight gained and areas of fat distribution, which suggests a genetic component in weight gain. In the simplest term, weight management is determined by the body’s balance between energy-in and energy-out. Energy-in is categorized as the amount of energy (calories) a person gets from food or drinks while energy-out represents the amount of energy the body uses up during things like breathing, food digestion, and exercises. When this teeter-totter system favors energy-in (i.e. eating too much), weight gain occurs. On the contrary, when energy-out is emphasized (i.e. increased physical activity), weight lost is achieved. So if genetics is a factor in weight management, how does it control this teeter-totter to determine a person weight profile?

I can’t stop eating

When you wake up in the morning, you feel a sense of hunger that makes you look for breakfast. After you finish an all-you-can-eat buffet, your feel extremely full and can’t eat another spoon of food even if you try. This sensation of appetite control is accurately controlled by our nervous system in the brain. One of the key hormones that regulates appetite is called leptin. This hormone is released after a meal in order to relay information to the brain that subsequently provides the feeling of satiety and appetite control. However, for patients who are born with the rare genetic mutation in leptin, the satiety feeling fails to be delivered from the brain . This causes overeating and severe weight gain. Alarmingly, the inability of the body to respond to leptin is also a common trait in people who are chronically overweight. This decrease in appetite control and the unfavorable tip in the energy-in side of the weight equation contribute greatly to the cause of obesity.

I gain weight so fast

On the other side of the weight equation is energy-out. Energy-out is determined by how fast the body can store and use up the ingested calories. Variations in genes such as lipoprotein lipase and PPAR gamma that control fat metabolism and fat storage can affect greatly an individual’s path to weight management . For your friend who eats everything on your guilty pleasure list without much weight gain, he or she most likely has a higher rate of energy burning compared to normal people. Indeed, when obese patients with a history of failure in weight management are genetically screened for variations in genes responsible for energy-out and individualized diet is created to match their genetic profiles, 73% of the participants maintained their weight loss after 300 days3. Clearly, genetics and the type of food our body is born to metabolize preferentially will affect a person’s weight management plan. As a result, a matching diet reflecting our genetic energy-out profile can significantly improve the success of person’s weight management. For example, Bodykey offers genetic testing to match an individual’s metabolic profile to personally tailored diets to achieve sustained weight loss.

Genetic contribution to energy-in and energy-out explains part of the reasons why everyone gains weight at a different rate. The advancement in genetic testing and the growth in field of personalized treatment will provide a tremendous opportunity in the future to execute individualized diet plan to battle people’s frustrating struggle in weight management.

What’s next?

Want to know more about other causes of obesity? Check out this interesting blog about intestinal bacteria’s role in obesity.

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  1. The response to long-term overfeeding in identical twins. N Engl J Med. 1990 May 24;322(21):1477-82.
  2. Congenital leptin deficiency is associated with severe early-onset obesity in humans. Nature. 1997 Jun 26;387(6636):903-8.
  3. Improved weight management using genetic information to personalize a calorie controlled diet. Nutr J. 2007 Oct 18;6:29.
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