Should I train fasted?

Short answer: sometimes, and only with a plan. Fasted training means starting a session after an overnight fast or with low muscle glycogen. It can raise fat oxidation and metabolic signals, but it can also blunt high-intensity power and slow recovery if you overdo it. Use it as a tool, not a lifestyle.

What fasted training does (and doesn’t) do

Riding with low glycogen changes which fuels your body prefers and which cellular pathways switch on. That can be useful—within limits.

• What it can do: increase fat oxidation at a given pace, upregulate enzymes linked to endurance (AMPK, PGC‑1α), and improve metabolic flexibility for steady aerobic work.
• What it doesn’t do: it doesn’t magically raise FTP by itself, and it often reduces your ability to hit high watts in VO2 max, threshold, or sprint work.
• Trade-offs: higher perceived effort, elevated stress hormones, and potentially more immune and recovery cost when used too often.

Practical rule: fuel for the work required. Save “train low” for low-intensity rides. Fuel high for hard work.

Who should consider it—and who should skip it

Fasted or low-glycogen sessions can suit some riders and contexts.

Good candidates

• Experienced riders during base periods who want a metabolic nudge without chasing high watts.
• Time‑crunched athletes doing short, easy morning spins before breakfast.
• Ultra and long‑distance cyclists who need comfort riding steady on lower carb availability.

Be cautious or avoid

• Key training days: threshold, VO2 max, race simulations, or any session where you target specific watts or FTP gains.
• Riders with history or signs of low energy availability/RED‑S, frequent illness, poor sleep, or stalled progress.
• Adolescents, pregnant athletes, and anyone with menstrual irregularities.
• Type 1 diabetes or medical conditions requiring specific fueling—follow medical guidance.
• Masters athletes in heavy weeks—recovery cost can outweigh benefits.

How to use fasted rides safely

Set the right session

• Frequency: 1–2 times per week is plenty for most.
• Duration: 45–90 minutes for newer riders; up to 120–150 minutes for well‑trained athletes who tolerate it.
• Intensity: keep it easy—zone 1–2. Roughly 56–70% of FTP, or 65–75% of max heart rate. No sprints, no tempo blocks.

Before and during the ride

• Hydrate: water plus electrolytes. Black coffee is fine if you tolerate it.
• Warm up a bit longer. Power may feel suppressed early.
• Use “guardrails”: if RPE climbs, heart rate drifts unusually, or cadence drops to hold the same watts, take 20–40 g/h of carbs and finish the ride strong.
• Skip doubling up with heavy strength work while fasted.

After the ride: recovery matters

• Protein: 20–30 g high‑quality protein within 60 minutes.
• Carbohydrate: 1.0–1.2 g/kg in the first hour, then regular meals. Go to the higher end if you train again the same day.
• Fluids: replace 100–150% of body mass lost through sweat across the next few hours.

Advanced “sleep low” strategy (use sparingly)

This pairs an evening glycogen‑depleting workout (tempo/threshold with carbs) with a low‑carb dinner, then an easy fasted ride next morning. It amplifies the low‑glycogen signal but raises stress and can impair recovery. Limit to once every 1–2 weeks, avoid during build/race blocks, and monitor how you feel and perform.

Sample week using “fuel for the work required”

• Mon: rest or easy spin (fueled as desired)
• Tue: VO2 max intervals—fully fueled (60–90 g/h carbs)
• Wed: easy endurance 60–90 min—optional fasted
• Thu: threshold/tempo—fully fueled
• Fri: off or skills—light fueling
• Sat: long ride or group ride—fuel 60–90 g/h (up to 90–120 g/h if long/intense)
• Sun: recovery spin—optional fasted, then good brunch

How to know it’s working (and when to stop)

• Positive signs: lower HR at the same watts in zone 2, fewer carbs needed for steady endurance, stable mood and sleep, steady or rising FTP over weeks.
• Red flags: persistent fatigue, irritability, poor sleep, recurring illness, reduced power in intervals, menstrual changes, stalled or dropping watts. If these show up, reduce or remove fasted work and prioritize fueling and recovery.

Bottom line: fasted rides can be a useful, small dose stimulus for fat adaptation. They won’t replace high‑quality, fueled training for raising FTP and peak watts. Use them intentionally, recover well, and judge success by consistent performance—not by how few grams of carbohydrate you can ride on.