A nutrition expert says the government needs to to restrict advertising for unhealthy food, particularly messages aimed at children.
Jim Mann, a professor of human medicine and human nutrition at Otago University and an adviser to the World Health Organisation, is speaking about the confusion of conflicting messages surrounding food at a nutrition symposium in Wellington today.
He told Morning Report that conflicting diet advice, especially on social media, makes it hard for people to know what they should be eating.
Professor Mann said there should be a severe restriction on advertising to children.
"Advertising is grossly misleading and even some foods are sold as healthy foods when they're not so. But governments have been very reticent about any kind of restrictions on advertising unfortunately."
He said we should be looking to teach children about the foods that are suitable for good health.
"We've got to create an environment, and the government has a critical role to play here, we've got to create an environment where healthy eating is easy eating, and right now it isn't."
Some of the messaging about food was wrong 20 or 30 years ago and it led to a reduction in fat and an introduction of the wrong kind of carbohydrates which has caused a lot of confusion for consumers.
"So really what the messaging is is eat the right kind of fats, in moderation, eat the right kind of carbohydrates and don't go in for any extreme form of diets that you read about on social media or anywhere else because they're probably not going to be good for you."
The emphasis on diets such as keto, which involves eating a lot of proteins and vegetables, promotes rapid weight loss but there was no evidence that it was good for long-term weight loss or that it was safe in the long-term and many of those promoting it are sponsored by organisations that benefit from it.
He said a review of the overall body of evidence shows a wide range of food intakes is acceptable, and it doesn't matter whether a person follows a low fat or high carbohydrate diet. "What is important is the type of fat and the type of carbohydrate, and the sort of foods you eat.
"So for example a range of carbohydrate intake is fine, you can have a relatively low or relatively high carbohydrate diet but you've got to have the right kind of carbohydrates."
He said people do not realise that a lot of carbohydrate is very rapidly eaten and absorbed so it's not much better than sugar or glucose. Instead, people should eat the slower absorbed carbohydrates such as wholegrains and those in fruits and vegetables.