Why diet fads will not stop obesity epidemic

Opinion: While previously fat was demonised, today passionate arguments advocating restriction of carbohydrates are frequently aired

The scale of our worldwide obesity problem is difficult to overstate – The World Health Organisation (WHO)estimates that it has doubled since 1980. By 2008, 1.4 billion adults 20 and older, worldwide were overweight, and of these about were 500 million obese. It is not just adults who are affected, with more than 40 million children in 2012 were struggling with weight issues, accoding to the WHO.

The health burden of this is enormous, and sufferers have a hugely elevated risk of heart problems, strokes, diabetes and early death.

The financial impact is also severe, as obesity-related problems financially strain healthcare systems. But why has our collective weight increased so dramatically, and what can be done?

On a superficial level, the cause of obesity is obvious – it is the net result of consuming more calories than one burns. This aspect is not particularly surprising – humans, like everything else in the universe, are bound by the laws of physics and the first law of thermodynamics states mass and energy cannot simply be conjured from the void. A more pertinent question is why this energy imbalance is increasingly common.


There are several contributory reasons – some rare genetic conditions can contribute to weight gain and there are indications that some overeating may be indicative of psychological eating disorders. Yet while these factors shouldn’t be overlooked, their contribution to the current epidemic is minor. In a 2001 review, Prof John Wilding concluded it is “more plausible that the increasing weight of most populations is an appropriate biological response to an abnormal environment, characterised by easy availability of cheap, energy- dense food, coupled with a massive decline in physical activity levels in the population”.

High-calorie food

This is the crux of the issue – easy access to high-calorie food and an increasingly sedentary lifestyle are the true culprits for our globally expanding waists. While this is undoubtedly true, certain foods may exacerbate this problem – while previously fat was demonised as the agent of obesity, today passionate arguments advocating restriction of carbohydrates are frequently aired.

There is good evidence that high-protein/low-carbohydrate diets aid in weight loss, but equally there exists similarly strong data which suggest such a diet long-term increases incidence of cardiovascular disease and ultimately mortality. Sugar has also come under renewed scrutiny. Prof Robert Lustig posits that sugars, in particular high-fructose corn syrup (HFCS), may not trigger the appropriate chemical signals for the sensation of satiety, prompting overindulgence.

Soft drinks

As the levels of HFCS added to soft drinks and foodstuffs over the last few decades have massively increased, this idea is certainly worthy of investigation. Yet, as with anything in science, a hypothesis must be rigorously tested before we can claim causality, and there is conflicting clinical evidence for this conjecture.

Despite the constant stream of fads and celebrity pronouncements, diets are a spectacularly ineffective way of managing weight. A 2007 meta-analysis by UCLA found that while dieters initially lose weight, most relapse and gain more than they lost, due largely to the unsustainability of such restrictions long-term.

Similarly, diet products are unlikely to make much of a positive difference. In Europe and America, the typically unregulated diet-pills sector is a multibillion euro industry, but a shamelessly disingenuous one. A 2010 German study found no discernible difference between diet pills and placebo drugs. More worryingly, a 2012 Oregon university study found that not only were the bulk of products ineffective, many had potentially dangerous side-effects. This might foster the impression that sustaining a healthy weight is impossible, but this is not the case. While dieting fads are unlikely to work and may even be detrimental, losing weight and keeping it off is entirely possible; a 2011 University of Pennsylvania study found that with appropriate lifestyle changes, a majority of people lost significant weight and kept it off when measured four years later.

While easy diet fads and quick-fix promises are frequently marketed as panaceas, we would do well to remember Wilde’s quip on the truth being “rarely pure and never simple”. Dietary science is complex, and despite the perpetual barrage of self-serving nonsense from the diet industry, best evidence indicates the only reliable way to control one’s weight is through sustainable long-term lifestyle changes, increased exercise and a balanced diet.

It is in our hands to prevent obesity and our quality of life is dependent on us realising this. Dr David Robert Grimes is a science writer and physicist at Oxford University. He blogs at davidrobertgrimes.com