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As a nation, we are gaining weight faster than ever before in our history and obesity is now officially classed as an epidemic. How can this be happening? Is it ‘all in our genes’, or are our modern diet and environment to blame? The truth is complex but one thing is clear: being aware of the theories can help you to find your own practical solution.
Why do some people put on weight easily while others seem to eat what they like and stay slim? We don’t fully understand but the evidence has a positive message: in health and fitness, nearly all of us have the power to take our destiny into our own hands.
It’s worth getting babies into healthy eating habits as early as possible: overweight children are more likely to stay that way into adult life.
The energy equation
There is no getting away from it: we gain weight when we eat more calories than we expend, and vice versa. This ‘energy equation’ is a basic law of physics and it is important not to lose sight of it, especially if you are weighing up some of the commercial weight-loss plans on offer. Any diet that promises that you can slim without changing your diet or activity level in anyway is one to strike off your list!
However, the simple truth of the energy equation hides a multitude of complex factors that can affect, on the one side, how and why we eat, and on the other, how efficiently our bodies burn fuel. These factors include our genetic make-up; our age; our metabolism; our environment; our state of general health; and our emotional response to food.
Very often you will read about a new scientific breakthrough that appears to lay the blame for our weight problems solely at the door of one of these factors: ‘it’s all in our genes’ or ‘how hormones make you fat’. In reality, however, it is unlikely that any single discovery will ever give us all the answers or provide a complete solution. And in a way this is good news because it means that we have more control than we might think over the many factors that affect our weight, and there is a lot that we can do to improve our chances of staying in good shape throughout our lives.
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Getting heavier?
There is now evidence that our environment can seriously damage our size. In 1955, fewer cars and more housework meant that the average woman could expend up to 800 calories a day more in activity than she does today. According to a recent survey, the average woman now weighs 65 kg (10 st 3.5 lb) and measures 38-34-40.5, but in 1951 she weighed 62 kg (9 st 10 lb) and she measured 37–27.5–39.
Family matters
A child with two obese parents has a 70 per cent chance of becoming obese, compared to 20 per cent for a child of two slim parents. That alone suggests strongly that our weight is predetermined by what we inherit from our parents. But how far is that inheritance down to genes, and how much is due to the family’s lifestyle? And if the link is genetic, which side of the energy equation are the inherited genes affecting?
Much of the current research into the link between genes and weight concerns the behaviour of individual genes and how they affect our appetite or the way we turn food into energy. There have been some exciting developments: for instance, it has been shown that in very rare cases, severe obesity is caused by a genetic mutation that causes the failure of a hormone called leptin, which regulates appetite in the brain. Children born without leptin will eat uncontrollably, but their appetite and weight will return to normal once they receive leptin injections.
Our caveman inheritance
Eventually, research into leptin deficiency and some other specific gene mutations may lead to effective treatments for what scientists now call ‘common obesity’. However, whereas only a very few people are unlucky enough to have faulty genes, none of us can escape the genetic pattern that has been handed down to us over millions of years.
Our earliest human ancestors evolved in an environment where food supplies were scarce and sporadic. Our strongest food preferences and cravings – for sweet, fatty and salty foods – are a reminder of the times when sources of glucose, essential fats and minerals were hard to come by. Energy conservation in time of famine was vital, so those human beings who had ‘thrifty genes’ –who were most able to convert food to fat and store it effectively – were the most likely to survive, breed and pass on those genes.
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Body shapes
Basic body shape is inherited and can only be modified, not completely changed, by diet and exercise. Typical body shapes are as follows:
Old genes, new environment
Unfortunately, the genetic make-up that suited us so well for survival in prehistoric times is very unhelpful today in our modern environment. Instead of eating fatty, sweet or salty foods only rarely, we now have access to them 24 hours a day, seven days a week, if we want. When we do eat excess fat and sugar, our ‘thrifty genes’ ensure that we store it very efficiently as fat. And instead of foraging and hunting to find our food, we only have to drive to the supermarket, pick up the phone or log on to the internet.