Why diets don't work

Posted on: 23 September 2011 by Alexander Hay

The process of fighting the flab continues to mystify as nutritionists in America question whether diet advice is any use at all. Dieters of all ages may wish to look away at this point while the numbers crunch and metabolisms keep flubbing their lines...

Scales of injusticeOverweight and over 50? Weight is a complicated issue. While the overweight are seen as one of the last groups it's OK to to be cruel to, mainly because of a 'moral' assumption that they are guilty of gluttony, this is plainly not making anyone thinner.

In fact, diets aren't making people thin either, despite the vast fortune and vaster still amounts of time and effort put into them.

Why? It seems we don't understand the process of weight loss, which isn't the simple in/out transaction many would have us believe:

...The British Dietetics Association, the NHS and the American Dietetic Association all say losing weight at this rate [1lb or 0.45kg a week] is "about right" and that if you stick at it for 12 months, for example, you will shed about 52 lb (26kg).

But US researchers from the National Institutes for Health say this is a gross overestimation because the calculation used is flawed.

They say it takes much longer to lose the weight - around three years to be precise, according to their work published in The Lancet.

For example, a year of dieting will result in only half of the amount of weight loss that experts currently predict...

Veterans of the dieting scene may have noticed this many times. The weight loss, such as it is, slows and even plateaus. Why does the same diet, followed with equal vigour, fail some while others succeed?

...Dr [Kevin] Hall says the error occurs because the "500 calorie-cut a day" sum fails to take account of how metabolism changes as we diet.

The mathematic equation relies on the assumption that one pound of fat contains 3,500 calories, so to lose one pound a week a person should consume approximately 3,500 fewer calories a week, or 500 fewer calories a day.

But in fact, weight loss is not this steady...

In other words, something as complicated and diverse as the human body doesn't view calories and food consumption as an accountancy exercise, despite what some doctors and dieticians advise. The truth is, as befits something as intricate as a living organism, more complex:

...Using knowledge about how the human body responds to changes of diet and physical activity, Dr Hall's team have created a computer program that they say gives a more realistic and reliable prediction of weight loss.

Their calculations reflect the fact that one person may lose weight faster or slower than another, even when they eat the same diet and do the same exercise...

...This means that all diets with similarly reduced energy content will have the same effect in the short term, whether the food cut out is fat or sugary carbohydrates...

But why has the old system, with its flaws, had such a stranglehold on how we diet?

...Helen Bond, from the British Dietetic Association, admitted: "We all recommend it - it's what we are taught. But I don't know what the scientific evidence for it is...”

That was a Brass Eye moment. Sadly, the researchers themselves have a few absurdities they haven't got rid of:

...However, Dr Hall says the computer model also shows how people can achieve more rapid weight loss if that is what they desire...

...At the end of the day, it still boils down to willpower. There is no quick fix to dieting and if you want it to work you need to stick at it, says Dr Hall...

And so we come full circle. If you're fat, it's through a personal defect. It's not because of major lifestyle changes in the last 50 years, greater reliance on processed foods, genetics (behold the many young men in most cities who live off chicken and chips bathed in lard but never get fat), the variable moods of the body or the intimate link between physiology and psychology. No, despite his research pointing to the fact that diets only work under specific circumstances, even Dr. Hall thinks that we'd all be a bit thinner if we just tried harder, dammit.

The faint moral smugness and finger-pointing aside, a geneticist or a sociologist would get to the matter much sooner. Are both or at least one of your parents overweight? There are good odds you will be too.

Meanwhile, tonight lots of overweight, obese or even average women will troop dutifully to their local church halls, perch on the scales and obsess about not losing a pound this week. It's all their fault, you see. Not enough willpower...


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Alexander Hay

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