Obesity and genes
On a global scale, obesity has reached epidemic proportions with approximately 1.5 billion adults reaching the overweight or obese categories. A few studies indicate that number may reach 3 billion by 2030. Obesity is often believed to be a result of eating more calories than we are burning. Why is it that some people gain more weight than others?
An often heard witty line is “ Obesity does not run in the family. The problem is that no one runs in the family.”
Well, looking at this scientifically, sometimes Obesity DOES run in the family and that’s the reason some people gain weight more easily than others or even struggle to shed off extra kilos. There is growing evidence that some of the weight gain that burdens modern humans is actually predetermined.
With the ever-growing obesity outbreak and the multitude of lifestyle diseases associated with it, scientists began understanding the role of genetics apart from factors like lifestyle and environment. Scientific studies published on twins in the 1970s and availability of genetic testing after the completion of Human Genome Project accelerated an interest in this field. Research has revealed a strong influence of genetics in determining a person’s BMI(body mass index) and his/ her tendency towards obesity.
Genetic obesity can be classified as Monogenic(occurring due to mutation in a single gene) and Polygenic(occurring due to genetic mutations in many genes). Till date, 11 different genes are known to cause monogenetic obesity which is very rare. So far, only 200 cases have been reported worldwide. For most individuals with a genetic predisposition to obesity, it’s many genes that may be mutated(polygenic). The strongest risk factor for childhood and adolescent obesity is parental obesity, which is doubled if both parents are obese. Maternal weight gain in pregnancy is positively correlated with the child’s BMi in adulthood. Twin studies, in comparison to family and adoption studies reveal that 60-90% of BMI variance within a population can be attributed to genetic effects.
A study that included 775 adult bariatric patients and 3197 control patients found that participants with a specific risky variant of the FTO gene had an almost 1.7 times greater likelihood of being extremely obese than those without the mutation. A risky variant of this gene leads to fat is being stored instead of being burnt, by impairing satiety and increasing appetite. Almost 1/5th population of obese people have this genetic mutation. This mutated gene has its impact from childhood and may increase risk of metabolic syndrome, PCOS & diabetes.
Another gene, the APOA2, with a risky variant can result in a higher BMI. The APOA2 gene directs the body to produce a specific protein called apoliprotein A 2 , which plays an important role in lipid metabolism, specially with regard to saturated fats. 1 in 7 obese people have the risk variant of this gene.
New research from the Research Triangle suggests that variants in a gene called Ankyrin-B, carried by millions of Americans could cause people to put on pounds with no fault of their own. The study, which was conducted in mice, shows that the gene variation causes fat cells to suck up glucose faster than normal, more than doubling their size. A slow metabolism or high-fat diet along with this gene variant makes obesity inevitable.
It is believed this gene might have helped our ancestors store energy in times of famine. In current times, where food is plentiful, ankyrin-B variants could be fueling the obesity epidemic.
Studies on children have also shown a genetic influence on obesity. A Genetic testing done on 1,509 children with extreme obesity and 5,380 normal-weight children found that mutations in four genes (LEPR, PRKCH, PACS1, and RMST) were associated with extreme obesity, and mutations in these genes raised the likelihood of severe early-onset obesity by almost 50%.
With all these statistics, it’s easy to feel disheartened. Don’t think of throwing up your hands in despair with – “What can I do? It’s all in my genes.” The good news is that you can overcome this genetic propensity toward obesity every single day. Being aware of genetic risk through genetic testing can help one make better-informed dietary & lifestyle decisions and changes that will help them achieve optimum health. Remember, gene expressions are like buttons that can be switched off or on.
That’s what researches in the field of epigenetics are discovering.
A healthy lifestyle and eating pattern can turn off the disease gene and turn on the longevity gene. It’s a matter of perspective that we become encouraged or depressed with the fact that our lifestyle can affect our gene expression. Positively or negatively depends on us ultimately. You are not at the mercy of your genes, but you can control them to large extent with your lifestyle.
