Intermittent fasting is a feeding method whereby food is restricted. In time-restricted feeding (TRF) the fast can last for hours to days with a typical fast to feed ration of 18:6, where one fasts for 18 hr and the feeds within the 6 hr window. Studies show that alternate-day fasts and whole-day fasts are effective at weight reduction, body fat reduction and cholesterol. Studies investigating the relationship between alternate- and whole- day fasts and athletic performance show that power is reduced. Fewer studies have investigated the relationship between TRF, body composition and athletic performance. Here I subject myself to a TRF protocol and monitor both body composition and athletic performance.

The TRF Protocol


I subjected myself to a 18:6 fasting/feeding regime, where I fed from 2PM to 8PM seven days per week. The trial lasted for 9 weeks, Mar 7 through May 9. Feeding during the window was not restricted, i.e., I are at-will.

The Athletic Trials


Each week a 1-min cycling power test was performed on a Wattbike Pro. The power test was always preceded by a 15 min warm-up ar Zone 1, i.e. HR under 120. In addition a 10-min endurance cycling test was also performed each week, this test was also preceded by the same pre-workout regime. Over the course of the 9-wk study, exercise averaged 15-hr per week and was composed of cycling, weight-lifting and cross country skiing.

Body Composition


Body weight was measured each morning before consumption of any fluids. Body fat was calculated using the Navy protocol, method available here.

Sleep


Sleep was measured and recorded with the garmin fenix 5x.  The reported sleep values are weekly averages.

Results


Over the course of the 9-wk study, power, as measured by the 1-min test, was unchanged. The initial power in watts per kilogram was 6.7 W/kg on Mar 6 and after slight fluctuations was also 6.7 W/kg at the conclusion of the study (See FIgure 1 Panel A). The 10-min endurance results showed that endurance increased by 14.2% over the 9-wk study (See Figure 1 Panel B).

Body Composition


Both body weight and body fat declined over the study period. Body weight changed from 82.4 to 76.4 kg, a decline of 7.25 %. Similarly, body fat declined from 18 to 12%, a reduction of 33.3 %.

Effects on Sleep


Weight loss appears to negatively impact sleep. In this study a linear relationship was found between weight loss and sleep.

Conclusions


TRF appears to be a viable diet regime for increasing lean muscle mass with simultaneous athletic improvements. Although 1-min power remained unchanged, endurance increased significantly.