The reality is that the relationship between obesity and genes is similar to the relationship between obesity and medication or illness: genes create a basic situation, but they don’t oblige anyone to be fat.
Things that really can be explained by genetics are appetite, preferences for certain flavours (such as sweet or fatty), and the natural urge to be physically active.
Several studies (for example a German study carried out by Haupt et al., 2009) have shown that carriers of so-called obesity genes consume on average 125 to 280 kcal per day more and have no differences in their metabolic rates.
To say that some children have a genetic propensity towards obesity means only that they have an inherently larger appetite than naturally slim children, who feel hungry less often.
But the deciding factor in whether children have a tendency towards being fat is the set of conditions created by their parents and the rest of their environment (school cafeteria meals, etc.), which can serve to either encourage or discourage obesity.
Living in a household where high- calorie food is constantly available won’t necessarily make children fat if their genetics mean they have a naturally small appetite. These children will simply have no desire to eat all the food they are offered.
Children with naturally large appetites, by contrast, will pounce on the proffered fare. By the same token, those children will be unable to overeat in households where there are not a lot of high-calorie foods. It is also possible to counterbalance a genetic predisposition through par- enting — although it can also be reinforced through parenting.
When a natu- rally thin child experiences being comforted or rewarded with food, she will eventually start comfort eating of her own accord. The only difference between her and a child with a genetically determined large appetite is that the latter al- ready has a desire to eat the chocolate and does not require any behavioural reinforcement to enjoy sweet and/or fatty foods.
A child with a larger appetite who is additionally comforted with food will descend ever deeper into the downward spiral of obesity. So it’s best to take countermeasures early. But even if such measures were never taken in our childhoods, we are not lost causes as adults.
Studies have shown that food preferences can still be influenced in adulthood and are not an inescapable fate. In one study, the brains of both obese subjects and subjects of normal weight were scanned to record their reactions to food.
The reward centres in the brains of the obese subjects showed a strong reaction to food that is high in fat (fast food, sweets). The test was repeated after the subjects had followed a dietary plan containing healthy, low-calorie foods for several months. The reward centres in the obese subjects’ brains reacted more strongly to healthy and low-calorie foods in the second test.
Alcohol addiction serves as a good example to explain the way people’s genes can affect them. Everyone understands that there is no such thing as a genetic alcoholic — that is, someone who is an alcoholic without ever having drunk alcohol to excess.
No one can be an alcoholic without ever having touched a drop. Despite this, alcoholism can be said to be about 50 per cent genetically determined. Herz (1997) writes that part of this genetic determination is to do with the various ways dopamine can be regulated in the brain and in certain en- zymes in the body, which affect the way alcohol is processed.
What this ulti- mately means is that alcohol has a considerably stronger effect on some people than others, and those people therefore have a greater risk of becoming ad- dicted.
A genetic inclination towards being overweight is similar: genes do not have direct influence, they don’t make people fat or addicted to alcohol, they just create the conditions which influence risky behaviour.
New research is now emerging that could change our understanding of genes completely. It indicates that our lifestyle can activate or deactivate certain genes, and even that a mother’s lifestyle can influence whether she passes on certain genes to her children or not (Watters, 2006). In the end, our genes just set out the path we will follow if we don’t actively strive to change its direction (and the change of direction, in turn, might influ- ence the effects our genes have on us).
Unfortunately, nature and nurture often go hand in hand since parents have the same genetic makeup as their offspring. Human beings also tend to seek out environments which correspond to their natural inclinations.
This means that working against our genetic predispo- sitions requires conscious effort, a kind of swimming against the tide, so to speak. However, studies have shown that those efforts are only temporary,