BORIS Johnson clearly hasn’t been in control of his weight for years. It took coronavirus to make him realise that those extra stones he’s been carrying are a marker for poor metabolic health, which predisposes you to all sorts of disease: heart, cancer, stroke, Type 2 diabetes, the list goes on. So he’s waging a war on fat, quoting his government’s so-called nutrition experts: count calories, up your physical fitness, and avoid foods that are high in fat, sugar, and salt. This advice is worse than useless. It got us into our current mess.

If I can summon up a scrap of compassion for Johnson, it’s this. Public health advice in this country has been so misguided for so long, it’s quite hard to take in just how counterproductive it is. In the Anglophone world, from Auckland and Austin to Aberfeldy, nutritional guidelines been wrong since the 1970s, and have barely changed in the five decades since, despite the fact they demonstrably don’t work. They were concocted by committees of apparently august scientific experts, who either represented vested interests in the food industry, or who went along like sheep with this bankrupt advice. Now it’s just too embarrassing for them to admit that this hokum has actively contributed to the public’s ever-expanding waistline and ill-health.

Fortunately, an alternative nutrition establishment has emerged. It deals not in fuzzy epidemiological associations of the “a rasher of bacon makes you 50% more likely to die of cancer” sort, but in rigorous, randomised, controlled trials and intervention studies. Doctors Zoe Harcombe, Aseem Malhotra, and Malcolm Kendrick in the UK, Dr Garry Fettke and Belinda Fettke in Australia, Dr Tim Noakes in South Africa, Nina Teicholz in the US. Their work is freely available online and well worth perusing, but here’s my executive summary.

Over 50% of the food we now consume in the UK is ultra-processed, that is, so transformed from its natural form that even the bulk ingredients are no longer recognisable, let alone the synthetic chemical additions: flavourings, colourings, stabilisers, emulsifiers, and more. My book, Swallow This, investigated these food-like constructions and explains why they are the main driver of obesity globally. Government diet advice should be unflinching here. You want to stay slim and fit? Then avoid ultra-processed food.

If you just eat real food in natural forms – it’s quite hard to overeat. Very few of us could eat more than one apple at a go, but many could gulp down a large glass of apple juice, which is effectively sugar with all the fibre removed, in a flash. Real food sates your appetite. Ultra-processed has dissatisfaction built in; it leaves you craving more.

Calorie counting is a distraction. What matters is the nutritional quality of those calories. Puffed rice crackers, for instance, are low calorie, eggs are much higher, but in terms of nutrient density and satiety, no prizes for guessing which is the more health-promoting food.

The high fat, sugar, salt obsession presents multiple fatal errors. On fat, it fails because it cleaves to the outdated belief that saturated fat is a killer. Systematic reviews and meta-analyses of randomised controlled trials put a lie to this. But the industrial, ultra-processed, polyunsaturated fats – ‘vegetable oil’, spreads, et al – the type we’ve been been told are better for us, are doing us harm. There’s no argument about sugar. The less we have, the better. But diet guidelines tell us to base our meals on starchy foods, which raise our blood sugar levels just as surely as straight sugar. Salt is demonised because it can raise blood pressure, yet there’s no sound science to show that normal seasoning with salt in home cooking is anything other than tasty. On the other hand, there is abundant research to show that you can’t exercise off a bad diet. Being fit and active has many wellbeing and health benefits, but weight loss isn’t one of them.

Brazil, a country that grapples with a massive obesity problem, changed its diet guidelines in 2014. “Always prefer natural or minimally processed foods and freshly made dishes to ultra-processed products” is the nub of them. I wish the UK would do the same. It’s the only bit of diet advice we really need to know.

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