Radical ideas: Diets make you fat

As someone who writes about food and health, I’m sometimes asked what the modern equivalent of the health crisis caused by smoking will be. What are we doing now that we will look back on in horror, and ask ourselves ‘how did we not see the harm’?

My answer is dieting. I believe that in 50 years’ time, our grandchildren will ask us why we thought that short-term starvation was an effective way to permanently alter our weight. And they might also ask us how we became so obsessed with making the wonderfully diverse set of human bodies exactly the same shape and size.

In the UK, almost half of us will have attempted a weight loss diet over the past year. Studies suggest that almost all dieters will eventually regain any lost kilos, with most ending up heavier than before. Long term behavioural studies have shown dieting to be one of the strongest predictors of future weight gain. Work on twins indicates that this effect might be causal; our obsession with reducing fat is ironically causing us to become larger.

Although the media would have us believe in the infinite malleability of the human form, body fatness is rarely within our control. Our genes have repeatedly been shown to be one of the most powerful predictors of how much we weigh, and when food is freely available, weight is one of the most heritable characteristics ever studied, in much the same ballpark as height. There are many physiological systems that contribute to this. For instance, leptin is a substance produced by our fat tissue, and as we lose weight the level of this powerful hormone starts to fall. This signals to primitive parts of our brain, powerfully driving us to eat more. Although longer timescales give us an illusion of control, this urge to eat is much like our need to breathe. We can exert control over it for days, weeks, or perhaps even months. But eventually, hunger will win.

To make things worse, hormones can drop our metabolic rate in response to a lack of food, shutting down non-essential functions to save calories. These systems evolved long before celebrity diet gurus, and can’t tell the difference between the latest diet and life-threatening famine. It’s not much fun: this calorie conservation is likely to cause lethargy, mood disorders, low immune function and a reduced sex drive.

These rounds of failure can also cause psychological harm, with unsuccessful dieters cast as failures in a world that places thinness and physical conformity as the ultimate goal. Instead of treading a well-worn path to failure, we might be better off thinking about what, other than weight loss, might improve our health. Exercising, eating higher quality food, stopping smoking, improving sleep and reducing stress all have the potential to make us happier and healthier. But in a society obsessed with fat, such things are often cast aside as trivialities if they do not cause weight to be shed.

Fat is seen as the only problem, and countless chancers line up to sell us their wares. All diet gurus claim they have the one true solution, and promise to finally fix our errant bodies. But perhaps the real problem is not that we are yet to find the correct diet. Maybe it is simply our refusal to accept that temporary starvation is just not an effective way to improve our health.

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