This clamour of conflicting messages includes advice from celebrities that –as we now know from concerns about the baby formula recipe in a book co-written by chef Pete Evans – isn't always credible. While Evans deserves a big tick for putting more vegetables on the plate, his advice on how we should eat fruit is curious. "Enjoy fruit in small amounts," he writes in his paleo cookbook Family Food. "Occasionally eating a small amount of seasonal fruit is optional (but not necessary) while following the paleo way."

It's true we don't need lots of fruit, but what's wrong with the two pieces a day the Australian Dietary Guidelines want us to eat – a target that only about 50 per cent of us actually meet? Fresh fruit is, after all, a handy package of fibre and nutrients that's easy to eat on the run, drop in a school lunch box or fill the gap between meals – and isn't wrapped in plastic. Wipe that off the menu of fast healthy snack foods and there's not much left.               

 "Nutrition wisdom from celebrities isn't a bad thing if it gets us eating more vegetables and less added sugar," says Rebecca Reynolds who lectures in nutrition at the University of NSW. "Where it's not helpful is when people with no formal training in nutrition science tell us to avoid grains, legumes and dairy and, in the case of the I Quit Sugar 8 Week Program, to avoid fruit for the first six weeks because it 'allows you to break your sugar addiction'."   

 There might be evidence that foods such as pizza, chips, chocolate and sweet, fatty refined carbohydrate foods may have addictive qualities, but where's the research nailing apples and pears as addictive? 

So why do we listen to health advice from people who are expert in areas such as cooking or acting but not nutrition science? 

It's partly because dietary advice and nutrition science have focused too much on single nutrients rather than patterns of eating, says Dr Gyorgy Scrinis, lecturer in food and nutrition politics and policy at the University of Melbourne.

This "nutritionism", as it's become known, has made it easier to vilify or celebrate single food components such as sugar or omega-3 fats, rather than considering the overall quality of the foods they're part of, he points out. 

"Promoting the idea that we should think about foods in terms of their nutrients and that we should construct a nutritionally precise diet to suit our particular health needs has contributed to anxieties about nutrition - and made us more susceptible to the marketing of unconventional diets or dietary advice, and to the marketing of nutritionally enhanced foods," says Scrinis, author ofNutritionism. The Science and Politics of Dietary Advice.

"The popularity of these unconventional diets and self-proclaimed nutrition experts suggests that many people consider mainstream dietary advice to be unreliable or that it's not meeting their own precise dietary requirements."

"We're also looking for quick fixes," Reynolds adds. "We're sold a lifestyle and the idea that food can be a magical elixir that can cure everything, and we're drawn in by fancy blogs, colourful cook books and Instagram feeds of stylised food photography shoots. It's easy to see why this is more appealing than listening to government guidelines. "

Perhaps, she muses,  we could  take a leaf from the celebrity book and repackage nutrition advice so that it has more appeal – and like the "experts" who blame single issues such as sugar or gluten for our health problems, we could start with just one thing: vegetables.

"There's more to healthy eating than vegetables, but Rome wasn't built in a day and it might make sense to start small and take one nutrition issue at a time and work on that," Reynolds says. "Only around 7 per cent of us eat the recommended five or six serves of vegetables daily but, if 100 per cent of the population ate that amount, it would make a big difference to the nation's health – there'd be less room for junk and it would have a significant effect not just on weight but on our risk of chronic disease."