Fast versus slow weight loss: which is better?
That's the question Australian researchers hope to answer when they place 100 obese women on low-calorie diets to test how their body responds.
The study will focus on the `famine reaction' - when the body responds to dieting by increasing appetite and reducing metabolic rate - which is why most diets ultimately fail.
Associate Professor Amanda Salis from the University of Sydney hopes to turn off this reaction through rapid weight loss.
While health professionals have long recommended slow and steady weight loss, these programs do not stop people from feeling hungry, she said.
But rapid weight loss, she says, reduces people's hunger.
"There's this liberation from hunger, and I think that's something that needs further investigation," Ms Salis told AAP on Wednesday.
She said research at the university's Boden Institute of Obesity, Nutrition and Eating Disorders had shown people on low-calorie diets using meal replacement formulas did not feel starved.
"It's a severe calorie restriction... but paradoxically, there's no increase in hunger."
The study is seeking 100 women aged 45 to 65 years with a body mass index of between 30 and 40.
With the help of nutritionists, their daily calorie intake will be reduced to around 800 calories for four to five months.
This will involve replacing food with nutritionally balanced meal replacement formulas in the form of thickshakes.
Two cups of non-starchy vegetables, a teaspoon of fat and two litres of water are also permitted each day.
Professor Salis, who has lost 28 kilograms and kept it off for 15 years, admits the intake looks "frighteningly small" but says it works.
"After a couple of days, the hunger disappeared," she said.
"After consuming one of these formulas, I felt like I'd just eaten a two-course meal. It was phenomenal."
Anyone interested in the Tempo Trial should contact the University of Sydney.
