Sample Size Matters When Drawing Conclusions on Alternate-Day Fasting Diet

To the Editor We read with interest the Original Investigation by Trepanowski et al¹ published in a recent issue of JAMA Internal Medicine; to the authors’ knowledge, it was the longest and largest randomized trial evaluating alternate-day fasting diet against calorie restriction diet and placebo. Trepanowski et al¹ concluded the investigational intervention’s lack of superiority in terms of weight loss or metabolic outcomes against the comparators. We found this publication provocative and interesting; however, we want to highlight some design characteristics that may have impacted the trial outcomes and, thus, limited the power and external validity of the results.