An Australian Institute of Health and Wellbeing report on Australians' health in 2012 found that obesity rates are increasing, with six in 10 adults overweight or obese and one in four children having unhealthy body weights.

Diet or meal replacement shakes have been touted as a solution to lose weight.

But how effective are these diet shakes when it comes to weight loss?

Dietitian and exercise physiologist from Fairy Meadow's Altitude Health and Fitness, Kate Battocchio, warns such meal replacement shakes are only a temporary fix.

"Instead of proper food for lunch, the idea of meal replacement programs are that you just make a shake or a soup from a packet," she says.

Ms Battocchio says that depending on the program, sometimes meal replacements are all that is consumed, while others are eaten along with low starch vegetables and/or salads.

"Healthy carbohydrate foods such as bread, cereal, rice, pasta, noodles, fruit, milk and yoghurt are usually forbidden or allowed in minimal amounts," she says.

"The theory is these shakes work by restricting kilojoule intake to roughly three to four thousand kilojoules per day, so if you stick to the program, you will lose some weight because the average person requires approximately eight thousand kilojoules per day.

"This deficit in energy can result in a loss of glycogen, water, and fat from storage sites within the body."

But dietitians and nutritionists remain sceptical about their benefits.

"Meal replacements may help as a quick fix, but they don't address the real problem, which is changing your eating habits and lifestyle," Battocchio says.

"As soon as you stop taking them, you revert back to your old eating patterns and the weight creeps back on. Initial rapid weight loss usually has little effect on body fat either.

"It is the weight of glycogen and water lost when you stop eating carbohydrates."

Ms Battocchio does note, however, that meal replacement program Optifast has become an exception to this advice.

"When taken as part of a particular program that's supported by health professionals including the Accredited Practising Dietitians, Optifast is a shake program that is supported to work for weight loss. This is only available for people with a BMI over 30 or over 27 and at least one risk factor for disease though," she says.

The Dietitians Association of Australia has identified that 95 per cent of all dieters will regain their lost weight in one to five years.

Ms Battocchio says learning healthy eating habits and making ongoing changes for a life of healthy food and exercise is far more effective in losing weight and keeping it off.