Gorge one day, fast the next?

The new diet causing a stir in the States

Eat everything I want, lose weight and live longer? Yes, please!

Fad diets are known for their ridiculous names, their ridiculous restrictions and their propensity to fail miserably. There's the Breatharian diet (based on the belief that humans need neither food nor water — only air — to survive), the age-old grapefruit diet (which, you guessed it, involves eating only grapefruit) and the Shangri-la diet (which promotes appetite suppression by eating only bland foods).

So when I heard about the UpDayDownDay Diet, also known as the alternate-day diet, I figured I'd stumbled on yet another diet with a silly name, unreasonable restrictions and dire health consequences.

The diet, created by New Orleans plastic surgeon James B Johnson, works exactly the way it sounds. That is, one day you eat whatever you want (the 'up' day) and the next, you suppress your kilojoule intake to 20 percent of what it normally is (the 'Down' day).¬

Sounds fairly radical, but according to scientists at the University of Washington, adults who have followed a similar diet for six years have not only lost weight (and kept it off) but also have better elasticity in their hearts. Other US researchers have found that intermittent fasting can slow the brain's ageing process and reduce the risk of Alzheimer's and Parkinson's diseases.

Dr Johnson, who lost 15 kilograms on the diet, created the plan after learning that, on average, animals live 40 percent longer if they're fed 30 to 40 percent less kilojoules. Johnson believed that permanently restricting kilojoules by this amount would be too prohibitive for dieters to stick to regularly. Instead, by only cutting down half the time, Johnson feels that dieters can sustain the plan for longer.

So how does it work? Basically, by restricting kilojoule intake, the body undergoes a mild form of stress. This causes the body to turn on a gene called SIRT1, also known as "the skinny gene". This helps the body shed fat by releasing fat from the cells around our organs.

Sydney dietician Susie Burrell is wary of the UpDayDownDay Diet, saying that it "sounds too good to be true", adding that there is no scientific evidence to confirm that the plan works.

We decided to speak to the man himself, Dr Johnson, to get the skinny on this rather bizarre eating plan.

Do you follow the diet yourself?
I attempt to reduce my intake by 50 percent every other day. I find it difficult to do 20 percent, and the 50 percent level helps me to not gain weight. Ninety percent of us have to be concerned about excess weight and some have to be more vigilant than others. The alternate day diet makes it possible to control your weight without feeling deprived.

This is a fairly radical diet — you must have your fair share of critics. What do you say to them?
Scientists have reacted positively. People who choose to ignore the underlying science and react to the simplified description of the diet with their own prejudice find it strange, especially since they have heard all their lives that one should eat three solid meals a day.

Some people have construed our advice to eat whatever they want to eat as permission to gorge or binge on 'up' days. This is just plain silly. Common sense dictates that overall calorie intake and expenditure determines body weight. Our point is that it is the number of calories consumed rather than the type of food that is important because the low energy intake on the 'down' day turns on the caloric restriction mechanism regardless of the type of calories.

The number of calories on the 'down' day depends on whether you are trying to lose weight (20 percent) or maintain your weight (50 percent) and get health benefits.

How does the diet protect against disease?
It has long been known that reducing calories prolongs lifespan and prevents disease. It has usually been assumed that to get these benefits extreme thinness is required. It is now known that reducing calories for 36 hours, as in the [alternate-day diet], turns on the same genes and we create a shield to protect our cells from damage due to free radicals, a main cause of aging and disease. This occurs by way of activation of a gene called SIRT1 which, in turn, sets in motion other genes which help to prevent unnecessary cell death, repair damage to DNA, reduce inflammation and body fat, and improve brain function all of which promote health.

Is the diet sustainable?
Yes, the whole point of this approach is that from a behavioural standpoint it is much easier to restrict your intake half the time than it is to do all the time, and you can experience dramatic health benefits. There are people, including myself, who have followed it for five years.

Do you find the people are compelled to eat more than normal on 'up' days because they deprive themselves the day before?
In our diet asthma study, hunger was no greater on 'up' days than the base line level before the study started. In fact, virtually everyone reports that they are amazed to find that they are not hungry the day after a 'down' day. However, people do experience hunger on the 'down' day itself.

Are there health risks associated with the diet?
On the contrary, health improves very rapidly on the diet by numerous measures, as we showed in our asthma-diet study. There is every reason to expect it will work in many different disease states.

Plus: Cosmo investigates why we're obsessed with celebrity diets and the celebs who love junk food.