Here's another one.

Excluding waste and sweating, it's true that the calories we take in have to be turned into either energy or weight. So it ought to be true that taking in less will cut weight. But what usually happens first is that we get hungry (and add back the calories, leaving our weight unchanged) or lethargic (expending less energy so that more of what we take in is directed to maintaining our weight).

It's almost as if our weight wants to be maintained; as if it has a will of its own and manipulates the rest of us to get what it wants.

Which is probably what happens.

Tumours act as if they have minds of their own. They press-gang whatever they can find into making themselves grow. Children do it. During growth spurts their growth hormones direct whatever's coming in to building bones and muscles, leaving the rest of the body bereft or hungry.

Only in a trivial sense is it true to say that children grow because they eat more. They eat more because they are growing. And that growth is regulated by hormones.

In 1977 Rosalyn Yalow won the Nobel Prize for tracking the hormone insulin. When it's released, fat cells start packing in fatty acids. And they also close the exits so the fatty acids can't escape while the insulin is there. It's why, oddly, we often feel weak or hungry after having sugar. The energy we thought we'd get isn't accessible. So we want to eat more, which also gets tucked into fat cells if there's insulin around; which there will be if what we've eaten is rich in sugar or other carbohydrates.

Veteran science journalist Gary Taubes has just set out his findings in a book entitled The Case Against Sugar, which follows Why We Get Fat, and Good Calories, Bad Calories. He is more of a forensic examiner of evidence than he is a purveyor of diets, and his main finding is that much of the evidence has been buried.

He says in the 1960s it was fairly widely accepted that carbohydrates (especially sugar) boosted the production of fat and increased appetites. It's one of the reasons we use bread as a starter at meals; it prepares us to eat.

Fat, by contrast, doesn't bring on the production of insulin at all. It may eventually be stored in fat cells, but it doesn't make those cells pack fat in and prevent them letting fat out. It's one of the reasons it rarely makes us hungry. Try eating half a slab of butter and see whether it boosts your appetite.

But in the 1970s, in the United States and in Australia, where our dietary guidelines follow the US, a new more plausible theory took hold. It was that fat causes fat. Nutritionist Ancel Keys laid it out in the massive Seven Countries Study which compared nations including the US, Finland and Japan and concluded that the nations that ate the most fat suffered the most heart disease.

Later research concluded that the results derived were particular to the seven countries chosen. Had Keys chosen other countries, such as France and Switzerland with high rates of fat consumption and low rates of heart disease, the correlation would have disappeared. But by then an abhorrence of fat had been written into the guidelines.

Consuming less fat meant consuming more carbohydrates, especially sugar which improves the taste of low-fat foods. So obesity climbed. The University of Sydney's Charles Perkins Centre is one of the few that disputes the connection. It produced a paper defending sugar that later had to be corrected after economist Rory Robertson ripped into it for misuse of statistics. Columnist Peter Fitzsimons details links between sugar and those dietitians promoting sugar in his book The Great Aussie Bloke Slimdown.

Just last month an industry-funded paper purporting to defend sugar fell apart when one of the funders, Mars Inc, disassociated itself saying it made all industry-funded research look bad.

Naturally, I am unable to guarantee that giving up sugar will make you lose weight. But I can guarantee that if you are anything like me it'll make you less hungry. I ditched sugar several new year's days ago, lost weight, and never got it back.

Peter Martin is economics editor of The Age. This story was first published on The Age.