In 2008, the messages being given out in local primary schools about food became very black and white. Jamie’s School Dinners campaign had started in 2005 and gathered steam and the Children’s Food Trust had been established. These, and other broad messages about food and diet, had filtered down into schools in a very rigid way. Foods were suddenly either good or bad. For example, crisps were banned at my son’s after-school football club and rice cakes were encouraged instead.

Regular government initiatives have since built upon this. They have encouraged “healthy schools status” with a whole-school food approach to children’s diet, including new standards for school lunches and how children should be taught about “healthy eating”. Teaching about “healthy eating” was presumed to help children make informed decisions in their food choices. There have also been numerous iterations of guidance about how much exercise children should be doing.

This approach to diet and health, which schools bought into and which has been repeatedly re-enforced and built upon, has serious flaws. And all of those working in education need to recognise them.

In the first couple of years of the healthy eating strategy, the eating disorders clinic in London in which I work saw an increase in the number of pre-pubertal children presenting with anorexia. A sub-group of hard-working, obedient children, mainly girls, took the messages they were getting at school as gospel: they stopped eating all sugar, jumped on a trampoline for an hour every evening (the government recommended 60 minutes of exercise per day after school), and started to lose weight. One of the side-effects of weight loss is an increase in obsessive thinking about food, and we saw these children become more and more pre-occupied with healthy eating and quickly trapped in an anorexic catch-22. The increase in affected children seen by our service was reflected across the country.

Trying to avoid anything leads to the ‘what the heck’ effect

There is no direct evidence that the healthy schools teaching was causal in this increase: it may have been a coincidence. Anecdotally, however, at the start of therapy, I nearly always ask my patients, “How did this all start?”

For the older girls, the answer is generally along the lines of “someone said I was fat” or “I was going on holiday and had to be in a bikini” - answers tend to be appearance-orientated.

For the younger patients - the primary school girls and boys - the answer is frequently “we were studying healthy eating in school”.

Perhaps the increase in pre-pubertal anorexia is an unfortunate but necessary side-effect of reducing the obesity epidemic? This would be undesirable, but childhood anorexia is still relatively rare compared with childhood obesity. However, is there any evidence that this change in school dinners and teaching has had a positive impact on obesity levels?

Ten years on in this diet crusade, the evidence is not overwhelming. Indeed, the National Child Measurement Programme has shown an increase in the number of obese and overweight Year 6 children from 2006 to 2015. Our local figures show that 1 in 3 children in Camden are obese by Year 6. Why should this be?

The psychological evidence suggests that messages about avoiding or banning certain types of food is completely counterproductive.

Psychologically, there is nothing more likely to make most children want something, than to tell them they can’t or shouldn’t have it. From research into dieting, we know that trying to avoid anything completely leads to the “what the heck” effect: if you don’t meet the standard of no biscuits, you may as well eat all the biscuits. Restriction inevitably leads to bingeing, which is why 80 per cent of diets fail within a two-year time frame.

So is it possible that the black-and-white messages about healthy and unhealthy foods in schools are contributing towards this dichotomous increase in anorexia and obesity? Trying to teach total avoidance or abstinence from sweets, burgers, chips and cakes is impossible for most and unrealistic in a consumer society where these products are marketed everywhere.

Cognitive dissonance

Psychologically, it is well established that it is difficult for us to hold two contradictory messages in our head - a concept called “cognitive dissonance”. We try to reduce this dissonance between contradictory thoughts by discounting one of the messages.

Are we placing our children in a state of cognitive dissonance with respect to food? If children are put in the position where they get the message from their school that “sweets are bad and should only be an occasional treat” and yet also know “all my friends go and buy sweets every day and they are fine”, they will try and lessen the psychological dissonance by rejecting one of the messages. In a small group of perfectionist girls and, occasionally, boys, it is the latter information that gets ignored (ie, most people eat sweets); in the majority, it is the message given by their teacher (that sweets should be an occasional treat).

So, in my opinion, the messages about food through education and health have been too militant and extreme. The School Food Plan in 2013 seems completely pie in the sky: no salted nuts or seeds, no crisps, nothing with chocolate on it - not even breadsticks allowed as a snack. Similarly, the Eatwell food group “plate” promoted by the NHS, as well as education, doesn’t place crisps and chocolate on the plate at all.

These standards seem well beyond most people’s reach, when we consider that McDonalds serves 3.5 million customers each day in the UK. In contrast, only a very few people seem to be using the NHS Change4Life webpage, where they promote healthy recipes for children and families: at the time of writing, just 245 people have signed up to say they have made the “carrot and courgette muffins” and only 40 people for the “crunchy salad pittas”.

Education could be leading the way in society by attempting to teach a less simplistic and more realistic message about healthy, balanced eating. There should be no good or bad foods; no banned foods; no healthy and unhealthy foods. Many slim and healthy people eat chocolate, sweets, crisps or fried food every day, and this is OK, as long as portion sizes are reasonable, they stop when they are full, and that their intake is balanced with vegetables, complex carbohydrates and protein.

Children should be tempted into school dinners through tasty foods that they want to eat, such as pizza, pasta, chips, meatballs, curry and frozen yoghurt - but made with natural ingredients, reduced fat, sugar, preservatives and colourings, in sensible portion sizes and accompanied with vegetables. The “healthy” dinners should not be so healthy that no one wants to eat them - be honest, does anyone really fancy a courgette muffin?

But more than this, years of talking with patients about food and eating has taught me that the what, why, where and how much of what we eat is far more complex than knowledge about nutritional content. The concept of “informed choice” has contributed towards the obesity epidemic: we can’t expect children to resist foods high in fat and sugar, which our bodies are designed to crave and store, through education alone. Time has shown us that this is an unrealistic aim for most adults, let alone children.

Eating for any individual occurs in their social, emotional, cultural, and financial context. Any meal or snack, at any time, can be influenced by that person’s mood, upbringing, tiredness, values, willpower, motivation, ability for delayed gratification, as well as who they are with.

Nuanced discussion

Schools could be influential in society by starting a more nuanced discussion about food and helping children develop a more complete understanding of their own eating. As with other curriculum areas (sex, drugs, religion), food and weight require understanding the multiple factors that impact on human behaviour, not just being told what to do.

Thus, healthy eating should be taught through understanding the motivations and drives that lead us to make food choices, as well as the impact of those choices on weight and health. Children should be taught about the impact of their intuition on eating, the multitude of factors that impact on intuition, and then how to find a balance between their intuition and their nutritional needs.

Similarly they should be warned against starting a repetitive diet/gain weight cycle, which is likely to lead to a lifetime of yo-yo weight loss and gain. Instead, children should be taught how powerful physiological and emotional drives can lead to eating too much, understand how to name and tame these drives, and how to stop eating when they are full but still want more.

With every magazine and newspaper schizophrenically full of very thin models, cream laden recipes, diets and critiques of celebrities weight and shape, children need to be educated, too, on the powerful and manipulative effect that traditional and social media can have on their eating.

Finally, it’s a shame that in its recently published Childhood Obesity Plan, the government has watered down the Health Select Committee recommendations for tackling obesity. It has rejected regulation on the reduction of sugar in drinks and food in place of a voluntary code. It has not tackled other issues recommended, such as addressing price promotions on sugary food (buy-one-get-one-free) or curbed the advertising powers in food promotion.

Successive governments have repeatedly used legislation to encourage us in a variety of behaviours, such as saving for a pension or giving up smoking, and yet they shy away from giving us similar financial or logistical nudges towards eating in more balanced way. It is seen as a “nanny state” to do so, and “informed choice” based on nutritional education is the policy.

The message needs be more complex than this. In this political context, teachers can be at the forefront of educating and communicating these complicated ideas.

Dr Tara Porter is a highly specialist clinical psychologist at the Royal Free London NHS Foundation Trust Child and Adolescent Mental Health Services, and in private practice