Alternate-day fasting a safe option to cut calories: Study

Researchers have found that alternate-day fasting (ADF) can be a safe option for calorie restriction.

The study published in the journal Cell Metabolism looked at the effects of strict alternate-day fasting on healthy people and found several health benefits.

"In this study, we aimed to explore a broad range of parameters, from physiological to molecular measures. If ADF and other dietary interventions differ in their physiological and molecular effects, complex studies are needed in humans that compare different diets," said Frank Madeo, Professor at the University of Graz in Austria.

In a randomized controlled trial, 60 participants were enrolled for four weeks and randomized to either an ADF or an ad libitum control group, the latter of which could eat as much as they wanted.

Additionally, the researchers studied a group of 30 people who had already practised more than six months of strict ADF previous to the study enrolment.

They compared them to normal, healthy controls who had no fasting experience. For this ADF cohort, the main focus was to examine the long-term safety of the intervention.

"We found that on average, during the 12 hours when they could eat normally, the participants in the ADF group compensated for some of the calories lost from the fasting, but not all.

"Overall, they reached a mean calorie restriction of about 35 per cent and lost an average of 3.5 kg [7.7 lb] during four weeks of ADF," said study researcher Harald Sourij.

The researchers found several biological effects in the ADF group: the participants had continuous upregulation of ketone bodies, even on non-fasting days. This has been shown to promote health in various contexts.

The participants had lowered levels of cholesterol. They had a reduction of lipotoxic android trunk fat mass, commonly known as belly fat.

"The elegant thing about strict ADF is that it doesn't require participants to count their meals and calories: they just don't eat anything for one day," said Thomas Pieber from the University of Graz.