Cavan Images/Getty Images
About 43% of the general population has a genetic predisposition to obesity, which does not guarantee obesity, but makes it harder to lose weight.
Most of the time, this predisposition is caused by an obesity-associated gene called FTO, and regular exercise and a healthy diet can reduce the risk of obesity for those with this gene.
There are also rare single gene defects that make it nearly impossible to lose weight, and these can genetically cause obesity.
Nearly 40% of adults in the US are obese, meaning that they have a body mass index greater than 30. High rates of obesity are often blamed on our unhealthy Western diet or sedentary lifestyle, but genetics also play an important role in how much we weigh. Here's look at how our genes affect whether or not we are likely to become obese.
A genetic predisposition to obesity
There are over 400 genes that have been linked to obesity or being overweight. Having one or more of these genes means you are more predisposed to obesity than people without these genes, but it doesn't necessarily mean that you will become obese.
One of the most common genes is the obesity-associated gene (FTO), which is found in up to 43% of the general population. These genes were helpful to us back when humans were hunter-gatherers, as they are believed to have helped our ancestors store fat and survive times when food was scarce.
Studies show that people with the FTO gene are 67% more likely to be obese, compared with people who did not inherit the gene. However, people with the FTO gene can lower their risk of obesity by 27% if they exercise regularly. If you follow a regimen of healthy diet and exercise, you should be able to maintain a healthy weight, though it may be more difficult.
Some signs that you may be genetically predisposed to obesity are:
You have trouble losing weight, even when you cut calories and increase exercise for many months.
You have been overweight for most of your lifetime.
Your parents or other relatives are very overweight.
Doctors can test for the FTO and other common obesity genes. However, knowing that it might be harder for you to shed pounds will not change the recommendation that doctors give everyone struggling to lose weight: burn more calories than you consume. Maintaining a healthy weight is especially important since obesity has been linked to several serious health conditions including type 2 diabetes, heart disease, and stroke.
Ultimately, unless you have a serious single gene defect, it's just a question of diet and exercise, says Sir Stephen O'Rahilly, MD, director of the MRC Metabolic Diseases Unit at the University of Cambridge. "But we need to understand that for those genetically predisposed it's a lot harder to implement those changes."
Single gene defects that cause obesity
The genes that make us more likely to gain weight are different from another type of condition known as monogenic obesity. Monogenic obesity is much rarer and occurs when you are born with a major defect in a single gene. For people with this type of gene defect, it is almost impossible to prevent extreme obesity without medication.
Some of these defects include:
Leptin Deficiency. Leptin is a hormone that helps regulate your weight by stopping your feeling of hunger once your stomach is full. For people without enough leptin, the feeling of hunger never stops.
Proopiomelanocortin (POMC) Deficiency. People with this condition are constantly hungry because their brain is unable to correctly interpret hunger and fullness signals.
MC4R Deficiency. This condition also interrupts brain signals for feeling full and tends to be more severe in children and improve with age. Around 2%-3% of obese people suffer from this genetic condition.
People with single gene defects will generally start to become obese in their first year of life, sometimes as early as 3 months old, says O'Rahilly. "Parents often notice extreme hunger and inability to be satisfied by normal size and frequency of meals. "
For some severe forms of genetic obesity, specific drug treatment is available, says O'Rahilly. "New drugs are being developed that attempt to bypass the defect in the brain chemistry that leads to the hunger and overeating."
Many of us carry genes that make us more likely to become obese, but this outcome is not set in stone. Losing weight can be more of a challenge for people predisposed to obesity, but exercise and diet can still be a huge help in lowering your risk.
Related stories about diet and nutrition:
Read the original article on Insider