Famine cheating diets put to the test
Australian researchers are looking to recruit 100 women to take part in a three-year study aimed at comparing the effects of fast versus slow weight loss on the ‘famine reaction’ – a biological response to dieting that is thought to be the reason why most diets fail.
Half of the women will be placed on a low calorie ‘starvation diet’ followed by a period of weight maintenance over a 12 month period, while the other half will be on a more moderately restricted diet over 12 months.
The study is being led by Associate Professor Amanda Salis of Sydney University’s Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders.
“We’re looking for 100 post-menopausal women who are willing to work with us for three years,” she said.
“And what we’re going to be asking these women to do is to find out and compare the effects of fast versus slow weight loss on the famine reaction.”
Associate Professor Salis told the recent Sydney University 21st Century Medicine Lecture Series that the famine reaction has been identified as the number one physical reason why most diets fail.
“Our bodies are not designed to cope with changes. And what happens when you start to lose weight is that your body sets off a physical reaction that I call a famine reaction, and this is what makes your life miserable when you’re on a diet,” she said.
The famine reaction is controlled by a part of the brain called the hypothalamus. One of the functions of the hypothalamus is to keep the level of body fat at a constant and optimum level.
Associate Professor Salis said that, in mice, it has been observed that when the animal is not getting enough to eat, there is an increase in the amount of the chemical neuropeptide Y in the brain.
She said her doctoral research showed that neuropeptide Y is one of the main ringleaders in instigating the famine reaction that makes every dieter’s life a challenge.
“When you first start a diet, losing weight is easy,” she said. “But after you’ve lost a certain amount of weight, your hypothalamus says ‘I don’t like this’, and that’s when it brings on these chemical changes that induce the famine reaction.”
Associate Professor Salis said the famine reaction does three main things: it makes you feel hungry for substantial, fattening food that will stop you from losing more fat, and preferably gain it back; it makes you feel lethargic, which is another mechanism the body uses to protect you from wasting away; and it drops the metabolic rate, causing your weight loss to plateau.
To investigate this, Associate Professor Salis, who said she had been overweight as a young adult, embarked on a conventional diet of eating less and moving more.
“But when I felt the famine reaction kick in, instead of trying to fight back, like all the diets tell you to do, I just went with the flow and said ‘why don’t I eat and deactivate that famine reaction?’”
“After a while of eating to satisfy that famine reaction, I no longer felt hungry and I could start dieting again and lose a bit more weight.”
All up, she lost 28 kg.
In the upcoming study, Associate Professor Salis will be looking at the role of ketones, which are produced naturally by the body when it is not getting enough carbohydrate to fuel the brain. Ketones are produced in higher quantities during very rapid weight loss.
She said studies have shown that people on very low calorie, or ‘starvation’ diets, don’t feel hunger, and it is thought that the elevated level of ketones that occurs when people are on a very fast weight loss diet may suppress appetite.
“During the trial, what we want to do is to compare head to head, for the first time, the famine reaction and the strength of the famine reaction during weight loss that’s achieved with a faster diet or a slower diet,” she said.