An international warning against low-carb high-fat fad diets from a group of Otago nutrition experts.

They've published a commentary about the dangers of saturated fats for medical journal The Lancet.

Professor Jim Mann from Otago University says saturated fats increase blood cholesterol.

He admits some saturated fats are better than others.

But he says claims that we can have as much saturated fat as we like are simply wrong in scientific terms.

Jim Mann says intake of saturated fats, sugar and sodium should be restricted.