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Obesity is a modern-day pandemic affecting over one billion adults around the world. Do we blame it on lifestyle, or put it down
to genes?

In New Zealand obesity is a rapidly growing problem, and along with it comes an alarming increase in obesity-related diseases such as heart disease, stroke, high blood pressure, Type II diabetes and some forms of cancer. Over half-a-million adult New Zealanders are considered obese, with a further 900,000 overweight. 
Scientists are locked in debate over the cause of this pandemic.
The central question, “Do our genes make us fat, or is it our diet and lifestyle choices?”
Gene theorists argue that the obese are born with a genetic make-up that predisposes them to easy weight gain. Commonly, obese parents produce obese children. At first glance one could take this as evidence to support the gene theory of obesity. However, children growing up in “obese” homes not only share their parents genetic legacy, they also most likely share the same dietary and exercise patterns.
Children grow up making the same food and exercise choices modelled by their parents. If takeaways, snack foods and hours of television are the parental norm, most often this becomes the norm for the children too. 
Scientists studying Body Mass Index values in twins and other family members estimate that genes contribute to 40% of obesity variance. Already we know of 200 different genes and gene markers that can contribute to obesity.

BUT DON'T FORGET LIFESTYLE...
Proponents of the “nurture” theory argue that genes cannot possibly be the main or only cause of obesity, as the obesity epidemic is a phenomenon of the past 20–30 years, and our genes have changed little during that time. Identical twins share identical genes but often end up at different weights as adults, suggesting that something other than genes determines our weight. 
It is looking increasingly likely that obesity is the result of a complex interplay between our genes and our environment.
In truth, we have “old” genes reminiscent of the days when we roamed the plains killing our food. These same genes now exist in a totally different world in which a high-fat, high-calorie takeaway is only a moment away, and lounging on the sofa has become the activity of choice for many. 

SWITCHING GENES ON AND OFF  
The new and exciting field of epigenetics can cast some light on the “nature or nurture” debate.
We now know that our genetic potential is not simply a result of the DNA we are born with. Sitting upon our DNA are beacons or “tags” which are able to switch a particular gene on or off, changing the way that our DNA expresses itself. An individual may carry a gene which may predispose them to weight gain... but only if the gene is turned on by the environment.
What switches a gene on? The list is long and ever-growing. The maternal diet during pregnancy can influence the subsequent weight of the offspring throughout the course of its entire life. Even the diet consumed by your grandmother has the potential to affect how your genes express themselves!
A developing foetus whose mother severely overeats or undereats during pregnancy, will face an increased risk of obesity in childhood and adult life. The extreme nutritional environment it is exposed to during its foetal development appears to “switch on” its genes in ways which will predispose obesity later in life.
Other proven epigenetic triggers include stress, diet after birth, and even in-utero exposure to cigarette smoke. In-utero exposure to environmental toxins such as pesticide sprays and plastics which disrupt human hormones, also appear to increase the risk of adult obesity. FHD

BEATING OBESITY
  • Exercise regularly with both aerobic and resistance activity to burn calories and build lean muscle mass, which helps stimulate your metabolism.
  • Reduce energy content of your diet by choosing “wholefoods” and avoiding processed foods which tend to be energy dense, but with little nutritional content and ability to satisfy the appetite.
  • Avoid soft drinks and foods containing high sugar content.
  • Consume a high-fibre diet with at least 5 servings of fruits and vegetables daily. Choose wholegrains in place of refined cereal and flour.
  • Avoid carbohydrates with a high glycaemic index (often processed and refined carbs with added sugars) – these cause blood sugar fluctuations and uncontrollable hunger.
  • Eat a healthy, nutrient-dense diet during pregnancy for the future healthy weight of your child.

By Lynda Wharton


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