Is our jeans size determined by our genes?

2011-07-28 00:00

CAN we lay all the blame for our weight on our genes?

Last time we began by asking the question: “Why do seemingly healthy people land up with dangerously high cholesterol levels, despite eating well and exercising regularly?”

We opened up a can of worms as this and many other similar questions have yet to be answered by scientific research. The reason that people respond differently to similar lifestyles is closely linked to our genetic make-up. Every individual who has ever been born, and ever will be, has a unique set of genes that cause unique characteristics and reactions within the body. This influences not only eye colour or mathematical ability, but also all the intricate workings of our cells.

If you are someone who always seems to be fighting with the bathroom scale and living in a constant battle of the bulge no matter how you change your behaviour, then today may give you a new way of facing the challenge.

I’m sure that most of us have heard at least one person lamenting the fact that they can’t seem to lose weight no matter what they try. The sceptics would say they just aren’t trying hard enough, but interestingly, science has started to prove otherwise.

Often the child of overweight parents becomes overweight and the reason is simply the environment, lifestyle (little physical activity) and food choices that are common in the home. However, in the 1960s and 1970s, researchers became increasingly interested in stories of identical twins who were raised in separate homes and different environments. It appears that even when twins (who have identical genes) were raised in different homes with different diets and lifestyles, their weight was similar. Other studies have shown that adopted children seem to have a weight closer to their biological parents than that of their adoptive parents. This put even more fuel on the fire of weight being genetically programmed in each one of us.

Over the last four decades, scientists have been furiously at work attempting to isolate the gene that seems to influence or dictate our weight. One gene was isolated in mice and proven to influence directly whether the mouse was obese or slim. (Mice have a remarkably similar genetic make-up to humans). This gene influenced a hormone called leptin, which is also present in humans. In human trials, however, the presence or absence of this gene did not directly influence obesity as it did in mice, and scientists are now delving more deeply into the mechanisms behind its action.

Unfortunately, the task of isolating “fat” genes has not been simple. Obesity is a complex issue, and literally hundreds of genes have been identified that regulate various aspects of weight — including appetite, taste preferences, formation of fat tissue, food metabolism and many others.

Obesity is not just a mild problem that concerns those who would like to look a little different. It is a serious health issue and a leading cause of many diseases in the developing world, including diabetes, hypertension, stroke, and heart disease. So we can’t simply sit back and blame our genetic make-up for our size and shape. Adjusting our diets and lifestyles still has hugely beneficial effects on our health.

To prove that you can still achieve results regardless of genetics, look at the study done in 2000 in Prague. Obese women were used in this study, and they were all identical twin pairs. These sets of twins were all placed on the same strict weight-loss diet. They were kept in hospital for one month and closely supervised so that there was no chance of them eating any additional food. The results were dramatic. Some lost six kilograms, while others lost up to 12 kgs. Although there were dramatic differences between individuals in terms of weight loss, the weight loss achieved by the twin pairs was remarkably similar. Each woman lost a similar amount of weight to her twin.

While the fact that someone may be able to lose double the weight that you can with the same effort is very frustrating news, don’t miss the good news here. All the women still lost a considerable amount of weight. Regardless of what your genes say about you, you can still achieve better health with a better lifestyle and nutrition choices. It may be necessary, however, to adjust your expectations for success and remember not to base them on others’ achievements.

• Sharon Hultzer is a consulting dietitian. She can be reached at

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