It’s the 21st century and we as human beings are expanding – and not just by bulldozing our way into virgin rainforests and previously unpopulated wildernesses, but also in our waistlines. The past two decades have seen the dawn of what’s been described as the age of obesity and inactivity, which threatens to reverse the steady increase in life expectancy seen over the last few centuries of human history.
Since the age of the first cave-dwellers, the average human lifespan has increased from about 30 to almost 70 with improvements in nutrition, hygiene and healthcare. But all of this hard work is about to be undone as the ill effects of being overweight (such as high blood pressure, heart disease, type II diabetes and numerous other chronic conditions) take their toll. Which begs the question: why are we getting so fat?
BLAME YOUR BRAIN
Of course the simple answer is because we’re eating too much and exercising too little, but there seems to be more to it than that. Scientists have found that obesity may, at least in part, be caused by structural and functional changes in the brain, which make us want to eat and eat despite our best intentions. These brain effects also make it more difficult to burn fat, which means it’s stored as extra baggage instead.
Under normal circumstances, our appetite is controlled by a complex set of nervous system and hormonal networks that connect the digestive tract to the brain – that’s how we know when we’re hungry, but also when we’ve had enough and should stop eating. This regulatory mechanism becomes disrupted, though, when we keep loading our plates with food that’s high in sugar and fat, particularly the saturated variety (which is found in animal products including cream, cheese and butter, as well as commercially prepared cakes, cookies and other snacks). And so we keep on eating long past the point necessary for survival.
THE EATING INSTINCT
While you may see this override in your brain as the bane of your existence, thwarting all weight-loss attempts, our berry-picking, deer-hunting ancestors would have benefited from eating as much energy-dense food as possible in times when resources were limited. And because eating is an instinctual behaviour vital to our survival, we’re wired to seek and consume palatable food at just about any cost. To overcome potential obstacles to getting said food (for example, facing the dangers of antlers and horns when hunting), the food itself comes with its own reward – the pleasure and satisfaction derived from eating. The problem is that we tend to get the most pleasure out of eating food that’s high in calories from fat and sugar, because such high-energy options would have benefited our starving hunter-gatherer forefathers. So that’s the kind of food most of us crave, with obese people being top of the list. Studies have shown that obese people tend to crave and enjoy sugary and fatty food more than people of normal weight, especially if this food is easily available. And that it most certainly is, with a fast-food joint around every corner and supermarket aisles bulging with tempting treats – all of which makes it very easy to overindulge in unhealthy options.
OBESITY – IT’S WORSE THAN YOU THINK
- According to the World Health Organization, half a billion people worldwide (12% of the total population) are obese, an incidence that’s doubled between 1980 and 2008.
- Obesity is generally defined as a body mass index (BMI – your weight in kilos divided by the square of your height in meters) above 30, but recent findings suggest that this measurement isn’t accurate enough and that the extent of the problem is therefore being underestimated.
- The study showed that while only 26% of participants met BMI criteria for obesity, 64% were classified as obese by measuring body fat percentage (more than 25% for men and more than 30% for women).
- Using BMI only, a quarter of men and almost half of all participating women were misclassified as being non-obese, which implies that the worldwide obesity epidemic is even worse than we thought. Older women were especially likely to be misclassified, probably due to the greater loss of muscle mass in aging women compared with men.
- The researchers suggest that BMI cut-offs of 24 for women and 28 for men would provide more accurate estimates of obesity incidence. They also recommend that other classification methods (such as body fat percentage and certain hormone levels) be used when available to improve the characterisation of obesity and its management.
REWIRING YOUR CIRCUITS
While it’s not entirely clear how the changes in the food reward system in obese people come about, researchers suggest that genetic predisposition and continuous exposure to unhealthy food options play a role. What’s more, early life nutrition (including before birth) has been shown to influence the risk of becoming obese in adulthood by affecting the brain circuits involved in eating control. To stop obesity in its tracks, make sure that your children eat their veggies and only rarely have unhealthy treats, and stick to a healthy diet during pregnancy.
If you’re already tipping the scales, replacing unhealthy fat with the polyunsaturated kind (which is found in oily fish, vegetable oils, nuts and seeds) has been shown to help correct the brain connections that control appetite and limit food intake. So be sure to make this good fat a part of your healthy eating plan.
And there’s just no way of getting around exercise – physical activity not only awakens long-dormant muscles, but also increases your metabolism and improves the nervous system and hormonal networks that keep telling you to eat. Getting enough sleep and reducing your stress levels may also be of benefit, as stress and a lack of sleep have been shown to negatively affect various pathways involved in metabolism and appetite control.
Also see Weight Loss
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