Are processed foods making us obese?

There’s been much talk in the media lately about processed foods and the perils of eating too much sugar, with some suggesting this is the cause of the current obesity crisis. The desire to identify the cause of weight gain is not a new one – in the 80s it was dietary fat that got all the blame. But in reality, the causes of weight gain are many and complex.

Obesity rates have risen sharply in recent decades, for which many blame the ‘obesogenic’ environment we live in. Processed foods – high in calories which tend to come mostly from sugar – are cheap and widely available, and there’s less need to be physically active, due to the automation of many jobs and the rise of screen-based entertainment. However, if that were the case, wouldn’t we all be overweight?

What’s actually happened, though, is that the distribution of body weight has shifted. People have become heavier overall, but the change is greatest at the upper end: a much larger proportion of people now have ‘morbid’ obesity – a very high body mass index (BMI) that comes with a host of associated health problems.This suggests that if an obesogenic environment does exist, its main effect is to make people who were already predisposed to obesity become disproportionately heavier.

In 2007, the late Prof Jane Wardle proposed a behavioural susceptibility theory of obesity to explain how genetic and environmental factors interact and cause people to gain weight. She believed that genetically predetermined differences in appetite could play a key role in determining who gains weight. Individuals whose genes make them highly responsive to food cues are more likely to overeat when palatable food is readily available, andso will tend to eat more often. Those whose genesmake them less responsive to feelings of ‘satiety’ or fullness are more likely to overeat in response tolarger portion sizes, and so will tend to eat largermeals. These differences begin to have an effect onweight very earlyin life.

The differences inaverage food intakebetween people whoare overweight andthose who aren’t arequite small (lessthan 70 calories aday, according tosome studies – aboutthe same as adigestive biscuit), butjust a small numberof extracalorieseach dayadds up over monthsand years. So ratherthan trying topinpoint a single cause of obesity oridentify a quick fix such as cutting outsugar, people may find it more useful tothink more broadly about how theyrespond to food, and identify strategiesto help take control of their eating.

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