Should Women Intermit Fast? A No-BS Guide Based on Science and Hormones

Many women can do a 16-hour fast safely at any point in their cycle, but the effects (and ease of it) can vary across the different phases due to shifts in hormones, energy demands, insulin sensitivity, and mood.

It’s best to fast during the Follicular phase, especially for beginners.

Follicular Phase (Day 3–14)

Best time to fast!

Pros

• Body is more insulin sensitive → better fat utilisation and stable energy

• Rising estrogen supports focus and metabolic flexibility

• Fasting feels easier, physically and mentally

• Less cravings, more control over appetite

Cons

• If you’re under-eating or overtraining, this is where nutrient depletion can begin

• First couple of days of your period: rest is more important than fasting for some women.

  
  

Why not in the luteal phase? (Day 14–28)

Progesterone starts to increase

Pros:

• Helps with bloating and cravings if done gently

• Experienced women may be okay for shorter fasts (14–16 hrs max)

Cons:

• Cravings go up

• Blood sugar less stable, leading to carb cravings

• Body less effective at producing energy

• Fasting can increase cortisol and worsen PMS symptoms (mood swings, anxiety, sleep issues)