Fasted Zone 2 Morning Run: 45-Minute Fat Adaptation Session

Session Overview

A 45-minute fasted Zone 2 run performed before breakfast to encourage fat as the primary fuel source. Including one or two fasted aerobic sessions per week builds metabolic efficiency — one of the most valuable long-course triathlon adaptations you can develop during the race season.

What You’ll Need

• Running shoes
• GPS watch with heart rate monitor
• Water or electrolyte drink — sip if needed, no carbohydrates
• Chest HR strap (optional but recommended for accurate Zone 2 monitoring)

Warm-Up (5 minutes)

Walk briskly for 2 minutes, then begin running at a very easy pace for 3 minutes. In a fasted state your body may feel sluggish early — resist the urge to push harder. Allow the first 5–8 minutes to serve as your genuine warm-up rather than a separate warm-up block.

Main Set

Run 35–40 minutes at true Zone 2 heart rate. Use the conversational pace test if you do not have zones set — you should be able to speak in full sentences throughout. Any harder and you have drifted into Zone 3.

• Heart rate target: 60–70% of maximum HR (Zone 2). For a 45-year-old with max HR 175, this is 105–122 bpm.
• Pace: Expect this to be significantly slower than your normal easy runs in a fed state — that is expected and correct.
• Terrain: Flat is ideal. Hills spike HR into Zone 3 and shift the metabolic stimulus.
• Duration: 35 minutes is the minimum for meaningful fat oxidation stimulus. Extend to 60+ minutes once adapted over several weeks.

Cool-Down (5 minutes)

Walk for 3–5 minutes post-run, then eat a protein-rich breakfast within 30 minutes to support muscle recovery. The fast ends when the run finishes — do not delay eating.

Coaching Notes

• Only do this session when you are well-rested — do not run fasted after a hard previous day.
• Limit to 1–2 fasted sessions per week; quality training still requires adequate fuelling across most sessions.
• If you feel lightheaded or significantly impaired, stop and consume carbohydrate immediately.
• Beginner modification: start with a 20-minute fasted walk-run before building to 45 minutes continuous.
• This session suits base-building phases best — not race week or high-intensity training blocks.