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Updated: Apr 13, 2026

Assessment of the Metabolic Effects of Isocaloric 2:1 Intermittent Fasting in Mice
Published on: November 27, 2019
Safety of alternate day fasting and effect on disordered eating behaviors
Kristin K Hoddy1, Cynthia M Kroeger2, John F Trepanowski3
1Department of Kinesiology and Nutrition, University of Illinois at Chicago, 1919 West Taylor Street, Room 506 F, Chicago, IL, 60612, USA. khoddy2@uic.edu.
Background:
Alternate day fasting (ADF; ad libitum intake "feed day" alternated with 75% restriction "fast day"), is effective for weight loss, but the safety of the diet has been questioned. Accordingly, this study examined occurrences of adverse events and eating disorder symptoms during ADF.
Findings:
Obese subjects (n = 59) participated in an 8-week ADF protocol where food was provided on the fast day. Body weight decreased (P < 0.0001) by 4.2 ± 0.3%. Some subjects reported constipation (17%), water retention (2%), dizziness (<20%), and general weakness (<15%). Bad breath doubled from baseline (14%) to post-treatment (29%), though not significantly. Depression and binge eating decreased (P < 0.01) with ADF. Purgative behavior and fear of fatness remained unchanged. ADF helped subjects increase (P < 0.01) restrictive eating and improve (P < 0.01) body image perception.
Conclusions:
Therefore, ADF produces minimal adverse outcomes, and has either benign or beneficial effects on eating disorder symptoms.
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