Why women put on weight after their teenage years
There is a gene in everyone’s body called the FTO gene. And this gene influences whether you put on weight, find it hard to resist food, and continue to eat, even when you feel full. It also increases your risk for heart disease and type 2 diabetes. This FTO gene is the most well-studied gene for obesity. There are hundreds of studies showing that this gene is linked to weight gain. These studies have been carried out on hundreds of thousands of people across many different countries and ethnicities, on women and on men, over many years. The results are always the same: the FTO gene influences weight gain as we get older.
It gets worse. The FTO gene also slows metabolism and reduces the ability to burn fat. Not only are you more likely to put on weight, it’s also harder to lose that weight.
But if we all have the FTO gene, why doesn’t everyone put on weight? This is because most genes have numerous variations called SNPs (pronounced “snip”). Each SNP has two forms called an “allele,” and this is represented by a letter. In the case of the FTO gene these letters are either “A” or “T,” and we inherit one letter from each parent. Therefore, your own FTO variation could be either A/A or T/T or A/T. To recap, everyone has an FTO gene, but their variation of this gene is different, and one of these variations means that you are more likely to put on weight. All you need to remember is that a variation in the FTO gene can cause weight gain and type 2 diabetes, and that some people have this variation, and some do not.
The early studies on the FTO gene focused upon Europeans, then they spread across the globe to study other populations such as the Chinese. The results were consistent: the FTO gene influences obesity. But the early studies on South Asia, meaning people of Bangladeshi, Indian, Pakistani, and Sri Lankan heritage, were inconsistent. Some showed weight gain due to the FTO gene, some did not. This was probably due to poorly designed studies, or a too small sample size, because from 2009 a good number of studies started to show that South Asians put on weight due to their FTO gene.
We want to focus a little on some of the FTO gene studies coming out of this region. For one thing, these studies affect over one billion people of South Asian heritage. For another, they reveal some unique findings, particularly one study conducted in Lahore, Pakistan.
The study in question was carried out in 2013 at the University of Health Sciences in Lahore. The researchers there recruited Pakistani females aged between 5 and 45. They confirmed, as we might expect, that a variation in the FTO gene increases the risk of obesity in Pakistani females. They also found that it increased the risk for all manner of things: larger waist size, larger hip size, high blood pressure, and blood glucose levels, as well as disturbing their metabolism. In fact, their risk of weight gain was 2.8 times more than other people. All these things put the women at a hugely increased risk for heart disease, kidney disease, and type 2 diabetes. This risk wasn’t limited to a small group of women. Around 30% of people carry this risk variant of the FTO gene. All of this is important, but not as intriguing as another finding that emerged out of this same study. The research team noticed that the gene didn’t do its damage until after the age of 18. In other words, the women in the study who carried the risk variant of the FTO gene were normal weight until the age of 18, then somehow, as adulthood entered, the gene was activated, and weight gain started to happen.
These risks from the FTO gene were not limited to Pakistani women. As the studies broadened out across the Indian subcontinent the findings were replicated among Punjabi Sikhs, north Indians, west Indians, and other regions of South Asia.
These studies also showed weight gain, but they also revealed another problem. Namely, the risk variant of the FTO gene was causing type 2 diabetes, even if the person was not overweight. This was new. In the European studies the link between the FTO gene and type 2 diabetes was thought to be due to obesity. Yet here was evidence that South Asians were getting type 2 diabetes due to their FTO gene, even if they weren’t overweight.
At this point some people might be thinking, what if I’ve got this variation of the FTO gene? After all, it does affect 30% of the population. Some people might also be thinking that this gene will cause them to get fat, get diabetes, have a large waist and big hips, get heart disease, then die young, and that there’s nothing that can be done. They would be wrong.
We need to back up a little. The FTO gene, like other genes, does not actually “cause” these things to happen. It is not inevitable or deterministic. It is not like a genetically inherited disease like cystic fibrosis, that little can be done about. Think about this. A number of your ancestors would have carried the risk variant of the FTO gene and they didn’t get fat. We know this because obesity is a recent trend in world history. What actually happens is that genes, such as the FTO gene, interact with our environment, lifestyle choices, and the food we eat. The problem is that we now live in a time where calorie-rich food is easily available. Junk food is readily available at all times of the day and night. Sugar is everywhere. We eat more meat than ever before. And we don’t move or exercise like we once did. It is certain food choices that interact with the FTO gene to “cause” weight gain and disease. So we need to know what variation of the gene we have, and what foods we should eat for that variation.
There are some good answers to this problem. Returning to the study on Pakistani women we find that the women with the risk variant of the FTO gene have altered blood leptin levels. Leptin is a hormone—the so-called “satiety” hormone. What we find in people with the risk variant of the FTO gene is that they have a decreased ability to sense that they are full, even if they have eaten energy rich food—like a whole packet of cookies or a whole tub of ice-cream. Put these people in an environment where there is lots of delicious food and they have a hard time saying “no.” This wasn’t the case in the past, because such food wasn’t easily available or even invented. People with the risk variant of the FTO gene are also more sensitive to saturated fat than other people; they need to eat less of it. They probably do better on a higher protein diet, because this helps with satiety, or feeling “full.” They also respond well to exercise interventions. In fact, exercise might explain why the women started to put on weight after the age of 18: children tend to be more active. These are just some of the interactions with the FTO gene that can make a person gain or lose weight.
Therefore, while the FTO gene is indeed the most well-studied gene for obesity across many different populations in the world, it doesn’t, by itself, cause weight gain. The different variations of this gene interact with different foods and lifestyles. Knowing which variation you have means that you can make the correct food choices. It may also explain why you used to be slender while growing up, but now a few extra pounds have appeared.