Certain smells can help you lose weight, according to an international expert visiting Sydney this week.

Research by Chicago-based neurologist and psychiatrist Dr Alan Hirsch has found a link between scent and the amount we eat. He discovered that the more we smell food the less of it we want to put in our mouths.

Ninety percent of what we call taste is really smell, so when you talk about craving a food like chocolate, you’re actually craving the smell of it, said Hirsch.

Hirsch first made the link between scent and hunger when working with people who had lost their sense of smell following head trauma. Most patients gained between four and nine kilos.

So we thought that maybe if we gave people extra smell they would lose weight, he said.

Hirsch led a study of 3,193 overweight people who were given different odours to smell over six months.

The scents were banana, green apple and peppermint -“ which were the smells people responded best to. And it’s the smells people like the most that are most effective, Hirsch said.

Over the six months Hirsch found an average weight loss of 2.1 percent of body mass per month, or approx 14kg over the entire period.

Using Hirsch’s findings a new weight-loss product, SLIMist, has been created and is now available in Australia.

It combines a series of scented inhalers (banana, green apple and peppermint) and an oral spray.

Some practical things you can do at home to lose weight, Hirsch said, is to sniff your food before eating it and chew it a lot to release the smell.

However, the best way to lose weight, he believes, is exercise.

The Smell and Taste Institute and Research Foundation in Chicago, where Hirsch works, currently has around 85 active studies looking into how odour can affect things like strength, migraine headaches, personality, claustrophobia and learning ability.

They’re also looking into the link between smell and sexual arousal (while working with the head trauma patients Hirsch found 25 percent of them developed sexual dysfunction).

Using a device to measure the amount of blood flow to erectile tissue in the penis, it was found the odour that turned men on the most was a combination of lavender and pumpkin pie.

The odour with the second greatest effect was a combination of donuts and liquorice.

Hirsch said he was unable to speak about advice he gave to Pope John Paul II or comment on his involvement in the Clinton-Lewinsky investigation in Washington.

However, it is known Hirsch’s expertise was sought by White House investigators on the way people touch their nose when they lie, commonly known as the Pinocchio Effect.

When you feel guilty there’s a nervous system discharge and rise in blood pressure to the erectile tissue in the nose, which causes the nose to internally engorge which causes histamine to be released, which makes the nose itch, Hirsch explained.

Which is why you scratch your nose when you lie.

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