Calorie count does a fat lot of good, scientists say

New research puts paid to the weight loss mantra: 'fewer calories in, more calories out'.

The overweight are told to simply eat less and move more, but new research suggests empty calories may be sabotaging the best-intentioned efforts. istock photo

Of its many sources of energy, there's one the UAE would cheerfully say goodbye to: the excess weight carried by so many people living here.

Around a third of the adult population is clinically obese, meaning each is carrying well over 10 kilograms of excess fat. That's also a staggering amount of surplus stored energy - roughly equivalent to a day's output from a nuclear power station.

Put like that, the size of the region's obesity epidemic seems truly staggering. But it also seems faintly ludicrous. Can our collective weight problem really be expressed in such crude engineering terms?

That's certainly the view of most nutritionists, who for more than a century have claimed to understand weight gain in terms of one of the most basic laws of engineering, and indeed physics: the law of conservation of energy.

According to this, energy cannot be made or destroyed, but merely converted from one form into another.

In the case of food, the energy is in the form of the chemical bonds within it, and digestion is the process of getting at this energy, and either using it immediately or storing it for later use.

Seen in those terms, the whole problem of obesity is simple. As the World Health Organisation puts it: "The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended."

So people who get fat have only themselves to blame. Put bluntly, they're stuffing more calories into their faces than they're using up. And if they just cut back on the calories, took more exercise, or preferably both, they'd be just fine.

As for what calories to cut back on, nutritionists are keen to nudge us towards a "healthier" diet, while stressing that ultimately we've just got to eat less stuff, because - as the saying goes - "a calorie is a calorie".

Yet growing numbers of researchers in human nutrition now have grave doubts about these mantras. They believe the attempts to characterise the causes of obesity as some kind of school physics problem is hopelessly simplistic. And frankly, the wonder is that it has taken so long, given the dismal failure of attempts to combat the global obesity epidemic.

Efforts to apply the laws of physics to human nutrition in terms of energy conservation go back well over a century, to a time when these laws were being recognised as the key to every natural phenomena.

Scientists measured the energy content of different types of food, producing the calorie (or, more recently, kilojoule) data read so avidly by dieters.

Their aim was to demonstrate that the laws of physics apply just as much to humans as they did to steam engines or the whole universe. The energy in food was just another form of chemical energy, whose precise form was wholly immaterial.

Yet even at the time, there were suspicions that the processes of life were somewhat more complex than those propelling steam trains.

As long ago as 1902, the pioneering German physiologist Max Rubner expressed concern that the type of food was highly significant, because of the resulting hormonal response, and thus the way our bodies deal with the calorie content. The laws of physics do apply, but at a molecular level of relatively little relevance to weight gain.

Nutritionists tried to find rules of thumb taking this into account, but these could barely cope with simple foods, let alone entire meals. And they never came close to threatening the core belief that "a calorie is a calorie". That is now changing, with new research confirming Rubner's century-old concern about the link between food types, hormones and calories - and thus obesity.

It's now well-established that some foods, like beans and green leaf vegetables, contain insoluble fibre which passes pretty much straight through us - along with much of the calorie content.

In contrast, highly-refined carbohydrates are rapidly digested, and trigger a massive release of insulin, the hormone implicated in both obesity and diabetes.

So the increasing acceptance that a calorie is not just a calorie brings good news: we can all take a big step towards avoiding obesity by avoiding refined carbs, especially sugar. The bad news is that the multinational food industry is seemingly determined to keep us hooked on the stuff.

Researchers at the University of North Carolina recently published a study of over 85,000 food lines sold in US supermarkets, and found that almost 80 per cent contained added sugar.

Worse still, food manufacturers were found to use over 50 different terms for it, from "fruit juice concentrate" to "high-fructose corn syrup". The names may differ but they all have an impact on hormone levels and thus weight-gain - with fructose being especially potent.

Food scientists says that sugar is added to boost shelf-life and "palatability", but there is mounting evidence they also trigger an addictive response that few can resist. That may be good for the industry's bottom line - but it is disastrous for consumers' waistlines.

That, in turn, is prompting calls for a radical overhaul of anti-obesity campaigns. In the current issue of the European Journal of Clinical Nutrition, Prof Jonathan Wells of University College, London, argues that governments should stop trying to lay the blame at the "greed" and "idleness" of their population. Instead, they should be pressurising the food industry to act more responsibly.

The problem, he says, is that governments want to have their cake and eat it. "They desire minimal prevalence of obesity in order to cut health costs, but maximal retail sales to increase revenue".

According to Prof Wells, the latest research shows that while we can all do something to control our weight, we can do less than we think. We need help - and quickly. He says: "Rather than populations failing to heed governments' public health advice, governments are currently failing the public."

Some will see this as a call for the "nanny state" to rescue those with no willpower - and perhaps it is. But with rates of obesity and diabetes soaring, it's clear that health ministers must do more than trot out dodgy science and wag their fingers.

Robert Matthews is visiting reader in science at Aston University, Birmingham, England