Dr Nick Fuller

The science behind why diets don’t work

The science behind why diets don't work
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For decades we have been told that it’s all our fault; that the reason many of us don’t manage to lose weight is a lack of willpower.

But there’s a bigger cause behind our failure to shift the pounds and it’s certainly not due to floundering commitment. It’s down to a part of the brain called the hypothalamus. In fact, there are several well-researched biological pathways that protect our body from weight loss and ensure our weight rebounds each and every time we attempt to slim down. Research shows that in order to lose weight and make it stick, you must eat well and exercise for a month – then have a month off.

Ever since obesity became a problem in the 1980s we have been led to believe that the best way to lose weight is by continuously cutting the calories. Indeed, it has been in the interests of a multi-billion dollar dieting industry to suggest that this is the case. But evidence shows that diets are actually making us fatter.  Initially weight loss may occur but, as many serial dieters will recognise, a plateau tends to kick in around three to six months and dieters, however committed, will start to regain the lost weight. Consequently, 95 per cent of people fail in their attempts to get into better shape because of the biological protections left over from our time on earth as hunter gatherers.

When a stress is imposed on the body, it starts to work differently – to defend its level of fatness and go back to its starting point – otherwise known as our ‘set point’. It’s not possible to lose weight without your body fighting your efforts to do so.

There are, however, ways to trick your body into avoiding a return to its set point. The first is to eat more, not less. 95 per cent of the population fail to meet basic nutrient requirements; they fall well below the two portions of fruit and five portions of vegetables each day. The modern-day environment means we are reaching for far too many processed foods and wrong information has led to a fear of certain foods – for example, carbs, fruit and dairy. Consequently, many of us are actually deficient in various vitamins and minerals, despite our enormous calorie intake.

One of the key components of successful weight loss lies in increasing our food intake from wholesome, nutritious foods. We can all cut certain foods for a period of time – typically one to three months – but cravings for high fat and high sugar foods will come back with vengeance. Research utilising brain imaging has confirmed this: there is a heightened activity of the limbic (reward) system in the brain following weight loss, which drives an increased desire for those foods which had been cut from the diet. The key is to change the type of food we are eating over time so that these cravings subside.

The second way to avoid weight gain is to use diet breaks. The hypothalamus, whilst regulating our weight day-to-day, works against us when we try and shed the kilos. This evolutionary response served our ancestors well when food was scarce; but now our propensity for weight gain overrides any sustained loss we might bring about through a diet.

We all know that a large weight change is possible through dietary restriction. But, eventually, the weight will come creeping back. Our metabolism will drop, our appetite may increase. Both these side effects kick into place when a stress is imposed on the body.

The answer to sustainable long-term weight loss does not lie in continuous restrictive eating; this strategy can actually bolster our fat reserves rather than reduce them. One way to prevent these biological protections kicking into place is to follow an Interval Weight Loss approach which requires imposing ‘diet breaks’ along the way. The diet should be paused every second month as part of a month-on, month-off plan.

These diet breaks have to go hand in hand with a more active lifestyle. According to the WHO, one in four people are too sedentary, failing to meet the basic guideline of 30 minutes of daily exercise. Chronic inactivity is physiologically abnormal and the human body fails to function properly to maintain health with insufficient amounts – historically ‘normal’ amounts – of exercise.

Too many of us have an all or nothing attitude to exercise that means we end up not moving at all. But even a small amount of daily exercise minimises the amount of weight you lose from muscle stores and instead allows your body to target fat. It also plays a vital role in weight maintenance as research has proven it as a key predictor of keeping the weight off.

Written byDr Nick Fuller

Dr Nick Fuller is Commercial and Industry Research Leader at the University of Sydney and author of Interval Weight Loss

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