University of Graz-led Study Showcases Potential Benefits of Alternate Day Fasting (ADF) in Healthy Individuals

Aug 28, 2019 | Alternate Day Fasting, Calorie Intake, Obesity

University of Graz-led Study Showcases Potential Benefits of Alternate Day Fasting (ADF) in Healthy Individuals

A study led by the University of Graz, Austria, shows that alternate day fasting (ADF) is a simple alternative to calorie restriction and triggers similar improvements on cardiovascular parameters and body composition. In this Austrian-led research, ADF was evidenced to be safe and beneficial in healthy, non-obese participants—not impairing immune function or bone health. 


The results of this study, published in Cell Metabolism, involved contributors from Europe, North America, and Asia but was led by University of Graz, Austria.

With the growth in obesity worldwide, there has been a surge in studies assessing the biologic impacts of different kinds of fasting diets in both animal and human models. The authors purport that this specific study was the largest of its kind to investigate the effects of strict ADF in healthy individualsit turns up some interesting and promising findings.

The Study

The participants alternated 36 hours of zero-calorie intake with 12 hours of unlimited eating. The findings were published in the journal Cell Metabolism.

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. In both groups, the participants were of average weight and healthy. The participants in the ADF group underwent active continuous glucose monitoring to ensure they didn’t eat.  Participants also filled in diaries to document the fasting days.

Also included in this study was a group of 30 people who had already practiced more than six months of strict ADF previous to the study enrollment. The research team 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.


The investigators found that the ADF group would eat more on the days they could eat—but not that much more. Overall, for the ADF participants, a mean calorie restriction of about 35% was achieved at an average weight loss of 7.7lb in just four weeks.

The investigators found several biological effects in the ADF group:

  • The participants had fluctuating downregulation of amino acids, in particular the amino acid methionine. Amino acid restriction has been shown to cause lifespan extension in rodents.
  • They had continuous upregulation of ketone bodies, even on nonfasting days. This has been shown to promote health in various contexts.
  • They had reduced levels of sICAM-1, a marker linked to age-associated disease and inflammation.
  • They had lowered levels of triiodothyronine without impaired thyroid gland function. Previously, lowered levels of this hormone have been linked to longevity in humans.
  • They had lowered levels of cholesterol.
  • They had a reduction of lipotoxic android trunk fat mass—commonly known as belly fat.


The investigators post that, despite the benefits, they do not recommend ADF as a general nutrition scheme for everybody.  They are leaning toward the notion that it may be good for certain obese individuals or as a clinical intervention in inflammation-based diseases. But they are certain further research is required prior to application in daily practice. And there are many issues associated with fasting. For example, if an individual has a viral infection fasting may not be advisable as the immune system requires, more than likely, immediate energy to fight viruses. A doctor must be consulted for any fast.

The researchers will further study the effects of strict ADF in varying groups of people including those with obesity and diabetes. They will also conduct comparative analysis—ADF to other dietary interventions to further explore the molecular mechanisms in animal models.

Lead Research/Investigator

Frank Madeo, professor of the Institute of Molecular Biosciences at Karl-Franzens University of Graz

Call to Action: As obesity conditions rapidly expand worldwide, we face an unprecedented health crisis in the developed world as well as the undeveloping world. Hence why this research was included in TrialSite News aggregation and curation service. The study’s lead was Frank Madeo who works out of the Institute of Molecular Biosciences, University of Graz, Austria, email For those interested in learning more about AF and this study, he represents a great point of contact.  Feel free to tap into the TrialSite Network for the matching service as well.


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