On average, a person will try five diets in a year to lose weight – only to succumb to old routines and end up right back where they started.

These constant setbacks are frustrating and exhausting, leaving many yo-yo dieters scratching their heads as to where they went wrong.

Some people will blame lack of willpower, but this accounts for only 5 per cent of the problem, said Dr Nick Fuller, an obesity researcher from the University of Sydney.

Dr Nick Fuller. Photo: Ogilvy Health & Dan Gosse Images

The other 95 per cent is down to other factors, including underlying biological “protections”.

“Everyone can lose weight, but then after three to six months, a weight-loss plateau sets in as the body is working differently and has put all protections in place to prevent further weight loss,” he said. 

According to Dr Fuller, who created the interval weight-loss plan, a “month-on, month-off” approach to dieting could make all the difference to reaching your goals.

What is interval weight loss?

The basic premise of the interval weight-loss plan is that a person is required to lose a small amount of weight, for example two kilograms, over a month, and maintain that weight for another month.

This step is repeated over and over until your target weight is reached.

It’s a marathon, not sprint, approach to weight loss that requires making small, easy changes in one month and then keeping up those healthy habits for the following 30 days.

Dr Fuller said there was no need to ban any major food groups. However, as with any healthy eating plan, you need to curb salty or sugary snacks.

“There are some foods that need to be kept in the ‘treat’ or occasional category,” he said.

“Importantly, the plan teaches a person how to wean off their addiction to processed foods (those foods high in fat and sugar), which now make up 70 per cent of a person’s diet.”

There’s always a catch … sugary foods should still remain only a treat. Photo: Getty

Weight loss and the protective response

As you lose weight, the body becomes stressed and this triggers our natural protective response, Dr Fuller says.

“Biological protections are cleverly regulated systems in our body that work to regulate our body weight,” he said.

“These biological protections start to work differently when a stress is imposed on the body. And one such stress is weight loss.”

Part of this system’s job is to receive signals from different parts of the body, such as the gut, to produce appetite hormones and peptides. These signals can tell our brain to either eat less or more.

“The body is very smart and cleverly wired to help remove this stress by changing its functioning and ensuring things go back to how they were, for example weight regain back to one’s starting point.”

Getting past the ‘set point’

The key to maintaining weight loss is getting past the starting point, or “set point” as Dr Fuller calls it.

“Even in the instance where people are taking on healthy, balanced weight-loss approaches, they will fail because of the body working to protect itself and defend its ‘set point’ or level of fatness,” he said.

Imposing “diet breaks” – specifically every second month – allows your body to rest and adjust to its new lowered set point.

“These periods of rest from weight loss ensure the body doesn’t defend the weight loss – it doesn’t start to work differently and the biological protections fail to be activated.”

Interval weight loss for life, by Dr Nick Fuller, is published by Penguin Life. RRP $32.99.