There was a time when the most confusing thing about fat in the diet was its vocabulary. But once we'd figured out the difference between saturated, polyunsaturated and mono-unsaturated fat, one thing seemed clear. Saturated fat was bad and polys and monos were good.

Now, there are conflicting views, including recent headlines suggesting polyunsaturated fat, recommended to prevent heart disease, could actually cause it.

There is also a new book by Australian lawyer David Gillespie claiming polyunsaturated vegetable oils make us so cancer-prone that ''every mouthful of vegetable oil you consume takes you one step closer to a deadly (and irreversible) outcome''.

In Toxic Oil (subtitled ''why vegetable oil will kill you and how to save yourself''), he takes a swipe at seed oils (canola, sunflower, rice bran, soybean, grape seed and sesame) with the same zeal his book Sweet Poison singled out sugar, especially fructose, as causing obesity. Seed oils, he says, contribute to vision loss from macular degeneration as well as heart disease and cancer.

Gillespie's solution? More saturated fat: ''Eat butter, drink full-fat milk, chomp through bacon and eggs for breakfast and enjoy a meat pie for lunch and the science says you will significantly increase your chances of living a long and hopefully happy life.''

This depends on whose science you'd rather believe. The World Cancer Research Fund has a different take on reducing cancer risk that includes ''limit intake of red meat and avoid processed meat, eat at least five serves of vegetables and fruit every day and eat relatively unprocessed grains and/or pulses with every meal''.

This advice isn't reflected in Gillespie's ''sample day in the life of someone living a seed-oil-free, sugar-free life'' which includes:

Breakfast - untrimmed bacon and egg; morning tea - Anzac biscuit made with dextrose (sugar without fructose); lunch - ham, cheese and lettuce sandwiches on sourdough with butter; afternoon tea - chocolate slice with dextrose; dinner - beef with potatoes, broccoli and carrot. That sounds light on veg to me, and what about the salt and preservatives in processed meat?

I agree with Gillespie that Western diets include too much sugar and processed food. I'm also no fan of margarine and seed-based cooking oil (give me avocado and olive oil). But it is simplistic to imply fixing chronic disease is just about cutting out sugar and seed oils and ignoring things like the need for more vegetables (and some fruit), more fibre and less sedentary living.

''There's no evidence that polyunsaturated fats cause cardiovascular disease or cancer,'' says nutritionist Rosemary Stanton, a member of the National Health and Research Council's working committee on the latest dietary guidelines. ''Although there was evidence that very high levels of polyunsaturated fats caused heart disease in a study published recently in the British Medical Journal, it's important to realise that the research was based on data from the '60s and '70s when the polyunsaturated margarines used still contained trans fats.''

Stanton and others agree diets high in polyunsaturated omega-6 fats from sources such as cooking oil, margarine and many processed foods can upset our balance of dietary fat. We need a healthy balance of both omega-6 and omega-3 fats (from fish and nuts, for example) and when it's disrupted the result is low-level inflammation that's linked to chronic illness, including heart disease and some cancers. This may explain why some research has linked diets high in polyunsaturated omega-6 fats to an increased risk of macular degeneration, Stanton says, although the jury's still out.

So where should we get our fat? Gillespie says eat more animal versions, including lard and dripping. Stanton's preference is for nuts, seeds, avocado, fish, olive oil and oats. Me? I'm inclined to take dietary advice from respected nutritionists, rather than lawyers.

Paula Goodyer blogs at