Is exercise safe during fasting periods?

Published: October 26, 2025
Updated: October 26, 2025

Exercising while fasting requires careful planning of intensity levels and timing. Low and moderate-intensity activities (like walking or yoga) remain generally safe while fasting. Higher intensity workouts require strategic scheduling around meal times to fuel performance and recovery.

Fasted training improves fat oxidation generally because muscle glycogen is lower overnight. Exercising in the morning in a fasted state can elicit a 20% increase in fat oxidation compared to strength training in a fed state. This is a metabolic advantage gained from training in a fasted state due to the decreased glycogen levels, thus low-moderate intensity cardio type work is optimal during fasting and strength training should occur during refuelling times.

Low Intensity

  • Examples: Walking yoga tai chi
  • Fasting timing: Any period
  • Benefits: Enhances fat burning without fatigue
  • Duration: 30-60 minutes maximum

Moderate Intensity

  • Examples: Cycling jogging swimming
  • Fasting timing: Early in fasting window
  • Benefits: Maintains endurance capacity
  • Duration: 45 minutes maximum

High Intensity

  • Examples: Weightlifting HIIT sprints
  • Fasting timing: Last 1-2 hours before eating
  • Benefits: Maximizes performance results
  • Duration: 30 minutes maximum
Exercise Timing Recommendations
Fasting PhaseFirst 4 hoursBest Exercise TypeYoga/stretchingElectrolyte Needs
Low: Water only
Fasting PhaseHours 5-12Best Exercise TypeWalking/cyclingElectrolyte Needs
Moderate: Salt water
Fasting PhaseHours 13-16+Best Exercise TypeLight resistanceElectrolyte Needs
High: Electrolyte mix
Adjust based on individual energy levels

Electrolyte balance should be the main focus when fasting and exercising. To prevent cramping, dizziness, and various other symptoms, sodium, magnesium, and potassium are needed. Drink mineral water, or add a pinch of sea salt to your drinks when fasting for extended periods. One tends to become dehydrated when engaged in exercise, thus it would be wise to check the color of the urine frequently.

Individuals in special populations require tailored strategies. People with diabetes must check their blood sugar levels before engaging in any exercise. If fasting is new, try periods of 10 minutes in duration before attempting longer periods. If dizziness or nausea occurs, stop immediately. The body sends you signals that give better limits than do any rules.

Read the full article: 8 Most Effective Fasting Methods Explained

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