Is Weight Gain Genetic?

Why is it that your friend eats a lot and yet still have that sexy, slim body? You, on the other hand, drool over that thin slice of cake, but you find yourself gaining two pounds even if you didn’t eat it. Is weight gain genetic? Makes you wonder.

“It’s so unfair,” you cry while standing on a weighing scale.

Is this you?

Well, you’re not alone. There are many people in the world who are struggling to lose weight but still manage to pile on the pounds even if they go on a diet or exercise.

If you are one of these people, it is possible that your problem of overweight and obesity is due to genetics.

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Is Weight Gain Genetic?


The State of Overweight/Obesity Today

The World Health Organization (WHO) defines overweight and obesity as “abnormal or excessive fat accumulation that may impair health.” Overweight and obesity in adults is classified according to Body Mass Index (BMI), which is the weight of a person in kilograms divided by the square of his/her height in meters (kg/m2).

In a report by the Institute for Health Metrics and Evaluation (IHME), it is estimated that nearly 30 percent of the world’s population – or 2.1 billion people – are obese or overweight. It is estimated that one-fifth of adults all over the world will be obese by 2025.

In the most recent US obesity data acquired by, adult obesity rates exceed 20 percent in all 50 states. But there is some good news. The same site also reported that the national childhood obesity rate has “leveled off” and the increase in adult obesity is starting to slow down. Still, much work needs to be done because the obese and overweight rates for both adults and children remain very high.

Why is overweight and obesity such a huge concern? This is because having excess weight makes you prone to develop serious diseases, which include the following:

You may be thinking “Where do genes fit in the obesity picture?”

Numerous studies have been done on genetics and its role in obesity. Let’s take a look at just a few of these studies to answer: Is weight gain genetic?

Is Weight Gain Genetic? Blame It on the Cavemen!

Is weight gain genetic?

Scientists have a theory called “The Thrifty Genotype Hypothesis”. They believe that humans still possess the “energy-thrifty genes” of their cavemen ancestors. These genes cause them to store fat when food is scarce. In this time of abundant food, this genetic mechanism is being challenged.

This hypothesis may have been proven in an August 2015 study on mice published in the New England Journal of Medicine. Scientists discovered a “genetic switch” which represses fat-producing cells. This repressing action leads to the creation of more energy-storing white fat than energy-burning beige fat. When the scientists disrupted this switch, the mice lost more than 50 percent of their body fat, even if they were fed a high-fat diet and they exercised just as much as the other mice.

Monogenic Obesity: “Rare Obesity” Caused by Single Gene Mutations

There are very rare forms of obesity that develop as a result of mutations in single genes. These genes end up influencing the person’s food intake, appetite control, and energy equilibrium.

Examples of these rare obesity syndromes are Prader-Willi, Bardet-Biedl, MOMO or Ayazi, and Cohen Syndromes.

“Common Obesity”: Mutations in Multiple Genes

Is weight gain genetic?

“Common Obesity” – or the overweight and obesity that we see today – are believed to be caused by mutations in not just one, but multiple genes. These gene mutations make a person susceptible to environmental factors that cause obesity to develop.

Studies focusing on the effects of genes and the environment were done on adopted children and adopted twins.

In a 1986 study done on 540 adult Danish adoptees, researchers found that their weights were similar to their biological parents. No such weight correlation was found between these adoptees and their adoptive parents.

In a 1990 study done on sets of identical and fraternal twins that are reared together and apart, researchers found that the children’s weights are similar and that the childhood environment did not have a significant impact on their weight. The researchers concluded that 70 percent of the weight variation is due to genetics.

However, this study was contradicted by a 2015 research paper published by London’s Centre for Economic Performance. In their study, they found that children adopted by overweight parents have a 21 percent chance of becoming overweight themselves than if they were taken in by parents with healthy weights. In addition, they also found that there is a 27 percent chance that biological children of overweight parents will also become overweight (a much lower figure compared to the 70 percent value concluded in the above study on twins.

Identifying the Obesity Genes

Researchers have long been looking for gene variations that may cause certain diseases. In 2007, researchers identified the first obesity-related gene variant. It is called the “Fat Mass and Obesity Associated” (FTO) gene located in Chromosome 16.

In the years that followed, over 30 more genes located on 12 chromosomes were also found to contribute to severe child and adult obesity. But FTO remains the primary culprit. These gene variant is prevalent among Europeans (40 percent) and Southeast Asians (42 percent). Only 5 percent of Africans carry FTO. In another study, an estimated 10 to 30 percent of European adults are obese. There is 1.5 percent chance of African-American adults becoming obese like their Caucasian counterparts.

What these studies show is that while the obesity gene may increase one’s risk of becoming obese, many people do not become fat because of other factors. I hope this helps you answer the question: Is weight gain genetic?

Let’s Not Forget Hormones

Hormones play a big role in maintaining body health. They regulate key body processes including appetite and digestion. The main hormone responsible for appetite suppression is leptin.

There is a genetic condition known as Congenital Leptin Deficiency. Children with this condition are prone to develop obesity at a very early age because they couldn’t control their appetite. In a 2015 study on two severely obese children with this disease, treatment with leptin resulted in a marked improvement in their eating behavior and weight loss.

What Can You Do?

Even if you have the genetic predisposition for overweight and obesity, GENES ARE NOT YOUR DESTINY. In their study published in Pediatrics on March 1998, Hill and Trowbridge stated, “Despite obesity having strong genetic determinants, the genetic composition of the population does not change rapidly. Therefore, the large increase in obesity must reflect major changes in non-genetic factors”.

These non-genetic factors include the following:

  1. Eating a healthy diet that largely consists of vegetables, fruits, whole grains, lean proteins, and healthy fats.
  2. Stop eating sugary, fatty, salty and processed foods. Fried foods have been found to have a negative interaction with obesity genes. This will increase weight gain risk.
  3. Exercise regularly. In a 2008 study, it was found that genetically predisposed people who live an inactive lifestyle are at greater risk for obesity than their counterparts who don’t have the gene. The same study also noted that people with the gene who exercise regularly share similar BMIs with people without the gene.


While a strong link has been found between obesity and genetics, you can lower your risk by eating healthy, exercising regularly and living a healthy lifestyle. I hope this helps you answer the question: Is weight gain genetic?

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