"The only reason that we are overweight now is because we are consuming a substance which interferes with our control system - and that's sugar."
So, the best way to maintain a healthy weight is to eliminate all sugar from your diet, he says. Gillespie managed to shed 40kgs with this tactic. This means cutting out all processed foods, some which have surprisingly huge amount of the stuff in them - tomato sauce is at least a quarter sugar, barbecue sauce is up to 60 per cent and sweet chili sauce is packed with a whopping 80 per cent.
"If I asked you to go to the supermarket and make me a list of every food that did not have sugar in it you would need a postage stamp to write that on, and you'd probably still have room for the Lord's Prayer.
"Sugar is white gold to food manufacturers. Because it's addictive, food manufacturers know that their products sell better with sugar than without.
"Exercising will power to control weight is about as effective as exercising willpower to control height. You can really manage it for about six months, absolute maximum.
"The research consistently shows that the best indicator that you will be overweight in two years time is being on a diet now."
He says people consume, on average, over 30kg of sugar each year.
2. You will lose weight if you exercise:
"There's lots of good reasons to do exercise, it's just that weight loss isn't one of them," Gillespie says.
Studies show people who do an hour of exercise every day for 18 months with a personal trainer don't have a very different outcome to those who are told just to "do your best".
"Exercise alone as a weight loss tool is a complete waste of time, yet that's the primary reason most people do it," he said.
"You will lose more weight laying in bed than getting up and going for a run."
This is because if your diet is still stuffed with sugar you are going to struggle to shift the extra weight, he says.
3. Fat makes you fat
Back in the 1950s nutritionists did some sums and concluded that food packed with fat was making people, well, fat. But the problem with this, Gillespie says, is that our bodies don't work this simply.
"Our bodies calculate how many calories we're consuming and adjust our needs accordingly," he says.
He says studies prove that hormones and our appetite control totally defeats this notion and low fat and no fat branding is "pointless rubbish" and should raise alarm bells that it's high in sugar.
4. Vitamin tablets are good for you:
"We get all the vitamins we need from our food, in fact we probably get quite a bit more than we need, but our bodies are extremely efficient at picking up the stuff that it needs and chucking the rest," Gillespie says.
"If you supplement it with expensive vitamins all you're really doing is producing expensive urine."
He says the only exception to this is if you've been prescribed as vitamin deficient by a doctor, but this is rare. The reason supermarket shelves are packed with rows of vitamin tablets is because people believe that if they top up their intake, they'll feel better. But Gillespie says the reason they're feeling sick - and chronic disease is on the up - is because of sugar-laden diets.
"The vitamin industry is quite happy to tell us they have the answers so we self medicate ... with vitamins."
So what should we do?
* Eliminate sugar from your diet. Gillespie lost 40kgs doing that and has managed to keep it off for eight years. He says he eats whatever he wants, whenever he's hungry. But he never eats anything containing sugar. "My appetite control has reset and works as designed."
* The best way to beat all the processed, sugary goods in the supermarket is to shop around the edge, he says. That's where the fruit and vegies are, the dairy, the meat, the bread - "all the stuff you really need." If you do duck through the middle aisles, avoid putting anything in the trolley with more than 3g of sugar per 100g, he says.
* When you first quit sugar you'll feel withdrawals for anything from two weeks up to six months, depending on how addicted you were. But usually after about a month the cravings will start to ease and you'll "wake up one morning and you go I'm not attracted to sugar any more than I'm attracted to broccoli." Food will taste better and flavours will be more intense.
Big Fat Lies, by David Gillespie is available now, published by Penguin. RRP $37
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