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Two-thirds of the UK population are either overweight or obese – a crisis that billions each year in and lost productivity. Yet, in a of nearly 700 obesity-related policies in England, researchers at the University of Cambridge found no evidence they had successfully reduced obesity. A House of Lords committee last month there had been an “utter failure to tackle this crisis”. It suggested an ambitious strategy to “fix our broken food system”.

The Lords committee wants the UK government to adopt a series of recommendations, including requiring businesses to report the percentage of healthy foods they offer, imposing taxes on salt and sugar, banning the advertising of unhealthy foods, and improving maternal and infant nutrition.

But suggests that, despite its ambition, the committee’s plan underestimates the complexity of the problem.

An example of this inherent complexity is the recommendation to expand sugar taxation beyond drinks to other food items. The , introduced in the UK in 2018, prompted manufacturers to reduce sugar content. A introduction, the sugar from soft drinks were 3g a day less in children and 5g in adults (12 and 20 calories).

To a small extent, sugar taxation has reduced the incidence of obesity in , but more in areas of deprivation. Taxing sugary drinks had no effect in younger girls, or boys of any age. This research concluded that “additional strategies in addition to sugar sweetened beverage taxation will be needed to reduce obesity”.

In some countries, sugar reduction has coincided with increased obesity. For example, in 2000, Norwegians 43kg of sugar a year, but by 2018 only 24kg. But obesity in women from 10% to 25%, and in men from 17% to 27%.

In the US, the purchase of sugar by 37g a day between 2002 and 2020, while from 30.5% to 41.9%.

These examples show how obesity reflects the entire diet and lifestyle. High levels of sugar go with an overall poor diet, long screen times, less sleep and minimal exercise. All these factors contribute to weight gain but are not influenced by just removing sugar.

In fact, obesity is influenced by more than a including psychological, social and biological variables. They also differ from person to person.

Another Lords committee recommendation is banning the advertising of less healthy food on TV and in paid-for online slots. shows that influences eating behaviour, but it doesn’t follow that a ban will necessarily influence obesity.

TV and paid-for online advertising are merely two influences among many. Advertising now reaches beyond traditional channels, with food promotions woven into and amplified by individual influencers – a landscape far harder to regulate. This complicates any attempt to restrict exposure to unhealthy food advertising, particularly for young people who spend more time online than watching television.

Excess calories

A crucial factor overlooked by the committee is the number of calories a person eats. Food diaries – often used to track eating habits – caloric intake. A more accurate method of working out caloric intake is the gold-standard , which is a method of measuring energy expenditure based on the estimation of the rate of carbon dioxide elimination from the body.

using this method found that UK men consumed around 3,119 calories a day, though food diaries suggested just 2,100. That’s an excess of around 4,300 calories each week, when compared with the recommended daily intake of 2500 calories, and amounts to the equivalent of 15 cheeseburgers.

For women, the actual daily intake was around 2,393 calories, compared to the 1,600 calories recorded in diaries. Compared to the recommended 2,000 calories per day, this adds up to about 2,750 extra calories each week.

The way forward

The House of Lords committee has produced a list of recommendation, with the expectation that a series of minor changes would add up, although this is the human body works.

Obesity results from a , that reflects a multitude of factors, interacting in unpredictable ways. The examples of taxing sugar and banning advertising illustrate those unpredictable consequences, which differ depending on education, deprivation and finance. Any chance to remove calories should be taken, of course, but so much more is required.

With complex systems you hope to find “leverage points”, where one change influences the entire system. The modern diet is viewed as driving the obesity epidemic, so is changing the diet the only way forward? Is the taxing of unhealthy ingredients enough?

An alternative explored in my is a traffic-light label system on food packaging. A “red” label, for example, would indicate a high-calorie product, and could push manufacturers to create lower-calorie options. This kind of labelling could both empower consumers and encourage reform in the food industry.

My research also explores whether obesity is now so ingrained in our collective psychology, culture and food environment, that change is out of reach. It may be time to accept the world as it is, and instead teach people how to adapt.

Policy either offers advice or a healthy choice but is only effective if people engage. Without commitment, policy fails. There is a role for education, monitoring of progress, providing feedback and support. But the food system will only be by novel policy, without which, future generations are condemned to poor health and shortened lives.