If you can bare it, Layne Norton did a video on his channel on this study. Credit to him, he tried to present it in a balanced way but he was clearly trying to contain his glee and an urge to stick up two fingers to Jason Fung.
I was not surprised by the findings as it chimes with another study done years before:
Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism; [Leonie K Heilbronn et al]
The American Journal of Clinical Nutrition , Volume 81, Issue 1, January 2005
Subjects here again lost both FM and FFM. Fat oxidation went up and glucose oxidation went down. And there was only a small drop in resting energy expenditure after 22 days.
In another metanalysis paper looking at ADF in non-lean subjects, the results were different:
Effect of alternate-day fasting on obesity and cardiometabolic risk: A systematic review and meta-analysis
August 07, 2020 DOI
The authors here stated: ‘Subgroup analyses indicated that significant intervention effects were observed for BMI, BW, FM, and total cholesterol when compared to the control, the participants were overweight, and the study duration was <6 months. ADF is effective in reducing waist circumference in adults aged ≥40 years with obesity. However, there was no difference between ADF and continuous energy restriction, time-restricted feeding, or control with regard to lean body mass.’
Based on these combined findings, you may argue that ADF is not an optimal strategy for preserving LM if you are already lean but more efficacious if you are overweight. Of course, adding resistance training and/or undertaking ADF when fat-adapted may skew these findings yet again.