We've been told for years that high-fat diets are bad. Then came the Atkins diet which said the opposite.
There's new advice confirming we should be eating more fat, and that it will help us lose weight.
A new report from two UK health charities says the current dietary advice of a low fat, high carbohydrate diet is having "disastrous health consequences.
The report, titled Eat Fat, Cut The Carbs and Avoid Snacking To Reverse Obesity and Type 2 Diabetes, was published by the Public Health Collaboration and the National Obesity Foundation, two UK-based charities.
But experts in New Zealand and in the UK say it’s not that simple.
Otago University Nutrition Professor Jim Mann of talks to Jesse Mulligan.
Read an edited snapshot of their conversation
Who are the Public Health Collaboration and the National Obesity Foundation? What do you know about them?
Jim Mann: Actually the short answer is not a lot. But not only do I know no a lot but nobody knows about them because they’re actually a self-selected group of people, most of whom have never researched in this area, but who believe in high-fat diets for whatever reason. And I think it’s important to realise their report has not been peer-reviewed, it has not been published in any scientific journal and this group don’t actually represent any professional organisation or group of individuals other than themselves.
Why is there so much conflicting information around what should be a straight forward topic?
This is a brilliant question. I wish I knew the answer in full. But at least in part, number one, there is a vested interest. There is no question a vested interest underlies a lot of this controversy. Secondly, I think people have always thought themselves as experts in nutrition. I mean everyone’s an expert in nutrition because everybody eats. And people acquire views that may be right, and they may be wrong, and they may also acquire views based on short-term observations and I think this is where this high-fat thing has started. There’s no doubt that high-fat diets help people to lose weight in the short term. Some of the weight they lose is water. Some of the weight they lose is actually because when you cut out fat you tend to cut out sugar as well, because a lot of fat and sugar tends to go together. It is also quite a novel diet compared with some of the other diets around….
But if you look at the long-term studies, which are ignored in this so-called report, [they] actually show that whether people lose weight in the long term is whether they follow the diet that they’re trying to follow, whether that’s high in fat, or carbohydrates, or whatever. You lose weight when you reduce calories to a lower level than is compatible with your level of physical activity.
So there is actually nothing in it in the long term as far as weight is concerned.
Sugar is a big enemy at the moment, has your thinking around sugar changed over the course of your career?
Jesse, I did my PHD in sugar in the mid-1970s and we actually said the exact thing in the mid-1970s that we’re saying now – sugar should be as low as you can possibly keep it. The World Health Organisation has just issued guidelines which really clarify that if you don’t want to be overweight and you don’t want rotten teeth and you don’t want all the consequences of being overweight you really need to keep sugar to definitely below 10 percent of your calories and ideally below five percent.