Is alternate-day fasting a safe alternative to dieting?

Fasting diets are not new, but alternate-day fasting is a particular interval eating plan gaining praise for a range of health benefits.

Alternate day fasting prescribes eating typically one day and skipping meals the next – creating a cycle of around 36 hours without food.

What are the health benefits of alternate day fasting?

Alternate day fasting has been credited as an effective eating plan to assist people to lose weight.

Research by Austria’s University of Graz looked at the effects of having no food for 36 hours, followed by 12 hours of regular eating.

The study found that, over four weeks, alternate-day fasting helped people eat about 35 per cent fewer calories and lose an average 3.5 kg.

And there are other health benefits, too.

The Austrian found the levels of ketones – formed when we burn fat – were raised even on non-fasting days.

Markers in the body linked to age-related disease and inflammation improved, and alternate-day fasting also lowered cholesterol and belly fat.

Such findings were supported in a meta-analysis that concluded alternate day fasting also produced substantial improvement in risk indicators for diseases in obese or normal people.

Why alternate day fasting works

If weight loss is your goal, alternate-day fasting will get you the most bang for your buck, according to leader of the obesity and metabolism group at the University of Adelaide, associate professor Leonie Heilbronn.

“You have three-and-a-half days a week when you are fasting, which is quite a big restriction on energy,” assoc prof Heilbronn says.

Kate Gudorf, of the Dietitians Association of Australia, says fasting triggers a cascade of responses in the body that ultimately lead to hunger signals and hunger hormones being released.

After this, our body then breaks down glycogen stored in muscles and the liver and then breaks down and uses up fat stores – particularly around our middle.

“For generally healthy people without any medical conditions, fasting works,” Kate says.

“It helps them improve cardiovascular risk factors and helps them lose weight.”

How to make alternate day fasting work

“Fasting also depends on what your diet looks like on the days you are eating,” Kate says.

“You may reduce your calorie intake – but are you just eating cakes on the days you can eat?

“Overall diet quality is important for your risk factor for developing chronic disease.

“For example, fruit and vegetables are important for decreasing the risk of certain cancers like bowel cancer.

“What fats you eat are also important in determining your risk of cardiovascular disease and your choice of carbohydrate foods is important for your risk of developing diabetes.

“We can’t just look at calorie intake and exclude diet.”

Is alternate day fasting safe?

While according to the Austrian study, alternate day fasting is a safe method of caloric control, however fasting isn’t recommended for everyone.

Women who are pregnant or breastfeeding, people who are elderly and those with certain medical conditions should talk to their doctor before commencing any fasting diet.

Written by Sarah Marinos.

Updated March 2022.