I recently completed the ProLon Five Day Fasting Mimicking Diet and tracked the results using Oura Ring and Garmin Index S2 data. While this is a sample size of one, the results were significant across nearly every recovery, sleep, and body composition metric I monitor.

The program provided all meals and snacks for each day, eliminating the need to plan, prepare, or calculate food intake. This simplicity made it easier to focus on completing the program successfully.

Oura Results

Recovery Metrics (Weekly Average)

Sleep Metrics

Both deep sleep and REM sleep increased substantially during the fasting period.

Stress and Recovery

These changes suggest a significant improvement in recovery and overall physiological resilience during the five-day period.

Additional Observation

I achieved five consecutive days of Oura’s highest daily readiness indicators, earning three crowns each day.

For Oura users: IYKYK.

Garmin Index S2 Results

One of the more interesting outcomes was the increase in body water percentage despite losing eight pounds. While bioimpedance scales have limitations, the increase in body water suggests the weight loss was not simply the result of dehydration.

Personal Experience

The most challenging aspect of the program was not the reduced calorie intake itself, but breaking established eating habits and routines. Hunger was manageable, but the psychological habit of wanting to eat more frequently was noticeable.

Other than increased hunger and adjusting to a different eating pattern, I experienced no negative side effects.

Recommendation

Based on my experience, I would recommend the ProLon program.

It is certainly possible to recreate a fasting mimicking diet independently, but doing so requires significant planning, meal preparation, and discipline. Because the fasting component is already challenging, there is value in having a structured program that removes decision-making and provides everything needed each day.

The most important question now is how many of these improvements persist after returning to normal eating and exercise habits. Regardless, the short-term results demonstrated meaningful improvements in sleep quality, recovery, stress management, cardiovascular metrics, and body composition over a five-day period.

Summary

Over five days, I observed:

• 8 pounds of weight loss
• 2.8% reduction in body fat percentage
• 1.2% increase in body water percentage
• 4 bpm reduction in resting heart rate
• 32% increase in HRV
• Significant increases in REM and deep sleep
• Dramatic reduction in daytime stress
• More than doubling of restorative time
• Improved cardiovascular age and respiratory rate

For a five-day intervention, the results exceeded my expectations and provided a strong foundation for continued focus on recovery, nutrition, fitness, and long-term health.

If you’re interested in doing the fast, use this link for 20% off, valid through June 8th. https://prolonlife.refr.cc/prolonlife/u/thomascanavan?s=sp&t=cp