Obesity is back on the news agenda. The coronavirus pandemic has shone the spotlight firmly on our health and diet. While this is good news, we are deluding ourselves if we believe Boris Johnson’s plan to ban buy-one-get-one-free deals and junk food adverts before the watershed, and to legislate for calorie counts in restaurants, is going to work better than a sticking plaster on a severed limb.

We are already the fattest nation in western Europe. Using data from the 4 million users of the Covid Symptom Study app, which I helped set up, UK citizens on average put on almost another kilo in the three months after lockdown started in March. We also have the worst diets, eat proportionally the most ultra-processed food and snack more than any other European nation.

Junk food is bad for us – especially when labelled misleadingly as “low fat, low carb, low sugar”. Diets containing high levels of ultra-processed foods have now been shown in clinical trials to increase hunger and the amount people eat. They also lead to a lack of diversity of gut microbes and poor gut health, which causes yet more metabolic problems.

Johnson’s reluctance to do the obvious and extend the successful sugar tax to other sweet products and ultra-processed foods is likely due to the lobbying of the rich and powerful food and drink companies, which aren’t going to disappear any time soon. Without government action, the disparity between junk and real food pricing will continue to grow. The Henry Dimbleby national food strategy report has proposed extending free school meals, which will help the most deprived, but more is needed and education is the key.

Doctors like me learned virtually nothing about nutrition at medical school, and the same is sadly true today. With the UK lacking a traditional food culture, most of us are very ignorant. Food education should be a compulsory subject, from nursery school to university, like maths and English.

Parents should be encouraged to introduce a much wider range of healthy foods to their infants and toddlers. Primary school kids should start learning about plants and how to grow and cook them, and these lessons should increase in secondary school so they learn more about agriculture, food production and the relationship between our environment, nutrition and health. Before leaving school, everyone should be able to prepare a healthy meal from scratch with a few simple ingredients, just as we learn our multiplication tables or how to write a letter.

All health professionals should undergo more rigorous training in nutrition as a core subject, and receive annual updates once qualified, so that they can spread the word based on knowledge not bluff. We need a huge dose of education, education, education to reverse years of brainwashing by big food.

Tim Spector is professor of genetic epidemiology at King’s College London, lead researcher of the Covid Symptom Study app and author of Spoon-Fed: Why Almost Everything We’ve Been Told About Food Is Wrong (Jonathan Cape)