Obesity: It’s in Our Genes, But Not Out of Our Control
By Allison Janson Hazell, Genetic Counsellor
Most of the messaging we hear about weight management is focused on diet and exercise, so people are usually shocked to learn that up to 70 per cent of obesity can be attributed to genetic factors. Research has shown that our genes may play a role in areas of the brain that are involved in appetite, satiety, energy expenditure, and behaviour. From a genetic perspective, obesity can be broken down into three distinct categories: monogenic obesity, syndromic obesity and common polygenic obesity.
Monogenic obesity
This refers to a very rare form of obesity in which an individual has a single gene mutation causing them to gain weight. In the late 1990’s researchers discovered that the LEP gene (named after its protein product Leptin) on chromosome 7 was involved in appetite and satiety. It has been found that people who carried mutations in the leptin gene are more likely to be binge eaters, are less likely to feel full and as a consequence tended to be morbidly obese at a young age.
Syndromic obesity
There are a handful of genetic syndromes that have obesity as one of the many features of the condition. These genetic conditions are usually associated with significant cognitive and developmental delays. Prader Willi Syndrome (PWS) is one example of syndromic obesity. In addition to distinct congenital issues, individuals with PWS live in a state of constant hunger, often resulting in extreme food-seeking behaviour. This can result in severe obesity and all of the health problems that come along with it. Click here to learn more about PWS.
Common ‘Polygenic’ Obesity
This is the type of obesity that is being called an epidemic and is threatening public health globally. Certainly, a collective increase in diets high in sugar and fat coupled with more sedentary lifestyles are to blame for the population-wide increase in BMI. However, on an individual level there are very specific biological issues at play.
Currently, there are more than 20 genetic factors that have been found to be associated with common obesity — thus the term ‘polygenic’ or ‘many genes.’ These genetic factors contribute to overall weight management and can help to explain why some people, even though they generally eat well and exercise routinely, have difficulty maintaining a healthy weight.
The most significant obesity-related gene that has been identified to date is called FTO. Studies show that individuals who carry 2 copies of a FTO risk marker are more likely to be obese, while individuals without any copy of the risk marker are more likely to be slim, regardless of how many calories they consume or how little they exercise. In January 2011 the Globe and Mail ran an article entitled ‘Skinny Genes’ on this very subject, which is certainly worth the read.
So, if you struggle with weight management, it is likely that there are at least some underlying genetic factors at play. However, this doesn’t mean that you should simply throw in the (gym) towel and grab a cheeseburger instead. These genetic factors are modifiable — meaning that for the most part we can overcome our genetic predisposition to weight gain through a healthy diet and regular exercise. It may mean, however, that you need to spend extra hours at the gym to ward off obesity and maintain your healthy weight.
We’ve learned a lot about the genetics of obesity in the past ten years. But we do still have a lot to learn. There are likely new genetic markers that will be identified, and over time we will learn more about how these risk markers interact with one another and environmental influences. And, hopefully as we gain better understanding we will be better able to tailor treatment and personalize preventative efforts. For now we can at least offer up a scientific explanation: if you feel like you are working harder than your friends, only to achieve the same modest results, chances are your intuition is correct. However, we encourage you to look at this as a challenge rather than a barrier. In achieving your healthy weight you will know that you had to work that much harder for it, and you certainly will reap the health benefits of your work.
Obesity (including the FTO gene) is one of 28 health conditions included on Medcan’s Personal Genome Testing panel.
To book an appointment with a Medcan Genetic councellor contact our bookings team at (416) 350-5900 or email to bookings@medcan.com.