The fundamental messages about diet continue to be consistent.
Although the details are fine-tuned and even on occasions changed, the essence of moderation, balance, variety and quality food have been consistent underlying themes for decades.
As the science of human nutrition continues to develop, an open and inquiring attitude is to be encouraged.
But so too should a critical scepticism of the latest fads and caution about extreme views.
A current popular evil is sugar, viewed in some quarters as a poison.
That is going too far.
Rather, free sugar is basically just empty calories, a source of energy without the added benefits of vitamins and minerals.
It makes dietary sense to cut down on sugar, just as it does for saturated fats.
But a zealot’s approach is unnecessary for most. It goes against the sensible and practical principles of moderation and promotes what can be an unhealthy food obsession.
Prof Jim Mann, from the University of Otago, a respected international figure, has recently spoken out about criticism of official dietary guidelines.
A trend has been to pit carbohydrates against fats, to claim carbohydrates — and not just free sugar — should be restricted.
Prof Mann and other New Zealand-based researchers, say in a commentary published in the British medical journal The Lancet that diet guidelines around the world consistently advise the quality of fats and carbohydrates eaten is more important than the proportion of fat versus carbohydrate.
"Pitting one nutrient against another — such as fat versus carbs — risks confusing the public, health professionals and policy-makers, and undermines confidence in evidence-based nutrition advice," Prof Mann says.
Through the decades he has seen all sort of diets in vogue — from paleo to the pineapple to the high-carb.
Many have not been properly researched and might cause long-term harm.
In contrast, the guidelines are based on many studies of many different kinds across the world.
Most look at evidence and evaluate results on health outcomes rather than being theoretical and based on the latest hypothesis.
As was also said, there is no "magic" answer to diets.
Otago nutrition department research fellow Lisa Te Morenga said it was all about "promoting healthy eating rather than pushing diets" and about the food environment.
After all, the psychology and physiology of restrictive diets means their long-term success rates are virtually nil.
Because vitamins, minerals, trace elements and everything to do with the way food interacts with the human body can be incredibly complicated (much is yet to be understood), it makes sense to promote a variety of foods and food types.
This, fad diets usually fail to do.
The other message being promulgated is about the quality of food.
Consistently, fibre-rich fruit and vegetables, legumes, pulses, nuts, wholegrains, and plant oils are supported.
Food is closely linked to culture and tradition, and the point is made about the benefits from the traditional high-carbohydrate and low-fat diet from Japan as well as from the relatively high-fat and high-carb Mediterranean fare.
There is, indeed, a wide range of healthy carbohydrates and fats.
It is unfortunate in New Zealand so many of the cheap, instant and popular foods are packed with sugar, saturated fats or salt; the high-profile carbonated drinks, the takeaways and the two-minute noodles.
It is discouraging that fruit and vegetables are often expensive.
Although the obesity epidemic in New Zealand is alarming and has serious health implications, it is also helpful to recognise people come in different shapes and sizes.
It is far better just to eat a variety of mostly healthy food and not stress about treats, about "good" food and "bad" food or a light consumption of sugar and saturated fat.
