The purpose of this study was to determine if intermittent fasting increases or decreases physical performance measures in healthy male exercisers during a 4-week intervention. Six males between the ages of 21--27 years fasted for 16 hours each day for a total of 4-weeks. During this time, physical performance measures were tested at baseline, 2-weeks of intermittent fasting, and 4-weeks of intermittent fasting. The physical performance tests ran included a Wingate test for anaerobic peak power and total anaerobic capacity, a VO2max test for aerobic capacity where RER was also monitored for substrate utilization, and hand grip strength tests. Finally, energy intake was recorded using the MyFitnessPal app to compare to energy recommendations from the Harris Benedict and Mifflin St-Jeor equations.

An evaluation of results using non parametric statistics Freidman Test and Wilcoxon Signed Rank Test using SPSS software concluded that participants did not meet their energy recommendations during the intermittent fasting intervention, when comparing both the mean Harris Benedict energy recommendation (3111 kcals/day) to the mean reported intake of participants (2064 kcal/day) and the mean Mifflin St-Jeor energy recommendation (2916 kcal/day) to the mean reported intake of participants (2064 kcal/day), with both significant values, Z = --2.02, p = .043. VO2max was statistically significant when the means were compared from baseline (60.50 ml/kg/m) to final measures (45.37 ml/kg/m), Z = --2.20, p = .028. Anaerobic capacity, anaerobic peak power output, crossover point of substrate utilization, and handgrip strength, did not meet statistical significance over the 4-week intervention using a Friedman statistical test. The findings suggest that a decrease in energy intake during a 16 hour fast per day may decrease exercise attempts and consistency. Since exercise training directly affects VO2max, the decreased energy intake may correlate to the significant decrease in VO 2max values over time.