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21 August 2018

To what extent are your genes responsible for your weight?

Do you believe you are doomed to a life of obesity because of your genes? Dietitian Monique Piderit unpacks the effects that DNA can have on your weight.

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"Obesity runs in my family" is a phrase commonly uttered by people who find it difficult to manage their weight. But is there any truth to the theory that our genes predispose us to being overweight? Possibly, but the answer is not so straightforward.

Scientists are starting to understand how genes not only influence our outward appearance, such as eye colour and height, but also how we function from the inside – and if this affects our ability to maintain a healthy weight.

Your genetic makeup

At conception our mothers contribute half our genes and our fathers the other half. Genes are at the centre of our genetic makeup. They consist of sequences of DNA and RNA (threads of nucleic acids) that contain all the instructions needed for the body cells to function. In 2003, the revolutionary Human Genome Project mapped every gene in the human body. There are around 22 300 genes, each with variations (such as those for hair colour), and all our genes together are known as our genome.

So are your parents to blame? 

Soaring rates of obesity in South Africa parallel those seen around the world. According to the South Africa Demographic and Health Survey (SADHS, 2017), two-thirds (68%) of women, and just under one third of men (31%) in South Africa are overweight/obese. Being overweight is a concern as it increases a person’s risk for other chronic diseases like heart disease and type 2 diabetes and can lead to an overall poorer quality of life.

There is some evidence that obesity has a genetic basis. The risk of a child being obese is 10 times higher if both the parents are obese, and up to four times higher in the case of one parent being obese. There is also research to show that variations in single genes may be associated with excess weight. For example, variations in a gene called FTO have been associated with obesity. FTO also increases risk of type 2 diabetes and heart disease through the gene’s effect on body fat.

People with a gene called ADRB2 also find it more challenging to lose weight, as a variation of this gene sees a higher propensity to store dietary fat as body fat. Other gene variations possibly implicated in weight are ADRB3, FABP2 and PPARG.

overweight parents and child watching tv

You are more than your genes

Scientists are, however, cautious not to overemphasise the role of genes as the basis for the rapid rise in overweight and obesity. While genes may play a role, it is difficult to tease out what part of this is a true genetic association and what part is due other factors that cluster in families.

Beyond inheriting a direct genetic predisposition to be overweight, we may also indirectly inherit other habits around food from our parents that may have affected their weight, such as eating large portions, not making time to be active, drinking sugary drinks, eating too often, and indulging in too many snacks high in sugar and fat.

We therefore emphasise that the causes of obesity are multifactorial and multidimensional. While there might be a genetic link to obesity, it is only a small piece of a the larger, very complex weight management puzzle. In South Africa, it is possible to test our genes to understand what type of diet genetically best suits us for weight loss. These results can help guide us on our journey to long-term and successful weight loss.

But simply knowing what our genes may predispose us to is not enough – we still need to take actionable steps to improving our weight and overall health. Speak to a registered dietitian who can help you implement the necessary key dietary changes and behaviours in conjunction with your personalised genetic results.

Image credit: iStock 

 
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