Does Intermittent Fasting Help Women Lose Weight? The Truth Will Surprise You

Jenna Johnston on October 6, 2025

In recent years, intermittent fasting has gained significant attention, but its effectiveness has been a subject of debate. Although some research has shown it can help with weight loss and lower the risk of chronic conditions like diabetes and heart disease- other evidence suggests that it may not be as beneficial for women as it is for men. And because of this, women may need to follow a modified approach to fasting based on their current health status and personal health goals.

What is intermittent fasting? 

Intermittent fasting is a dietary pattern- not a diet plan. What this means is that it does not involve eating or avoiding specific foods, or tracking calories. Rather, it focuses on when to eat by incorporating regular short-term fasts on a daily or weekly basis. 

Essentially, intermittent fasting is more of a lifestyle than a diet. 

Many people use intermittent fasting to help them lose weight because it offers a simple way to reduce overall caloric intake without the need to count calories (which can be tedious!). This can make it easier for some to stick with it for long periods. 

The most common types of intermittent fasting include:

  • Alternate-day fasting: Fast every other day and only consume a very small amount of calories on fasting days
  • Time Restricted Eating (TRE) 16:8 method: Fast for 16 hours and eat within an 8-hour window each day
  • 5:2 method: Eat normally for 5 days a week and restrict calories to 500-600 on two non-consecutive days
  • Eat-stop-eat: Fasting for 24 hours, once or twice a week

What the Research Shows

Research on intermittent fasting has shown promising benefits, including:

  • Weight loss and fat reduction (including abdominal fat)
  • Improved insulin sensitivity
  • Lowered cardiovascular risk factors
  • Preservation of muscle mass compared to traditional calorie restriction
  • Reduced inflammation, which is often linked to chronic diseases (1)

Intermittent fasting also promotes metabolic flexibility and improves the body’s ability to burn fat and use it as fuel. Moreover, during fasting, the body can focus on rejuvenation and repair, which helps promote healthy aging and healing any damage done by chronic diseases or even cancers.(1) 

The Problem: A Lack of Research on Women

Although these benefits are all amazing- there is one issue: most research is on men.

Most existing research on intermittent fasting has focused on men and there is limited data for the benefits it has for women, which creates a gap in understanding how suitable it is for women.(2)

One study that included both non-obese men and non-obese women found that blood sugar control actually worsened in women after 22 days of alternate-day fasting (36 hour fasts), but this did not happen in the men.(3)

Beyond clinical studies, anecdotal evidence from women who have tried intermittent fasting includes:

  • Changes to their menstrual cycle, such as irregular bleeding or loss of menstruation.
  • Negative effects on mood and energy levels.

These negative health shifts may occur because female bodies are very sensitive to calorie restriction.The body can perceive a significant drop in calories as a state of starvation, which affects the hormonal communication between the brain, ovaries, adrenals, and thyroid. This can lead to changes in menstrual cycles and other health issues related to sex and stress hormones.  

Benefits for women and a modified approach

Fortunately, women can still benefit from intermittent fasting- including women who are overweight/obese and want to reduce body fat (especially abdominal fat) , improve insulin sensitivity (including those with PCOS), lower blood pressure, reduce inflammation, and improve cellular health.(2)(4) 

However, it’s important that they “tread lightly” and take a modified approach. 

Based on current research, women should stick with Time-Restricted Eating (TRE) protocols and avoid prolonged fasting periods like alternate-day fasting, which are more likely to cause hormonal disruption.

Key Components of a Woman-Friendly Fasting Plan

  1. Modified TRE: Start with a 12:12 eating/fasting cycle and cautiously progress to a 14:10 or 16:8 cycle if your body responds well.
  2. Circadian Rhythm Syncing: Research shows that TRE should align with our natural circadian rhythms and we should eat during the day and fast at night. This is because our bodies are better at processing food during the day when we are exposed to light and are active. This promotes better digestion, metabolic activity, and blood sugar control.

    Studies suggest that eating an early dinner, practicing overnight fasting(12-16 hours), and eating breakfast within 90 minutes of waking up is the most effective approach for women .(5)(6)    
     
  3. Cycle Syncing (for menstruating women): Adjust your fasting schedule based on your menstrual cycle to support hormonal balance.
  • Follicular Phase (Days 1-14): Estrogen levels are rising, and your body can more easily burn fat. Longer fasting periods (14:10 to 16:8) may be tolerated well.
  • Luteal Phase (Days 15-21): Progesterone rises, and your body shifts towards using and storing more energy. A 12:12 to 14:10 cycle is more appropriate.
  • Late Luteal Phase (Days 22-28): High progesterone and low estrogen increase the body’s sensitivity to cortisol. To avoid a stress response, keep fasting to a minimum of 12 or 13 hours (overnight) (7).

If women take a modified approach with intermittent fasting, they can improve metabolic health and see benefits like weight loss (including abdominal fat loss), blood sugar control, and reduced inflammation.(7) 

Who Should Avoid Intermittent Fasting? 

Some women should avoid intermittent fasting protocols, including those with:

  • Unstable blood sugar conditions (e.g., Type 1 diabetes or hypoglycemia).
  • Suspected or confirmed thyroid conditions (e.g., hypothyroidism).
  • Pregnancy or breastfeeding.

Additionally, it’s vital to ensure you are consuming a nutrient dense diet while integrating intermittent fasting into your routine. Your body needs an abundance of micronutrients and phytonutrients to support overall health and without getting enough of the right nutrients, you risk developing health issues like bone loss, a weakened immune system, hormonal imbalances, etc. 

Conclusion 

While intermittent fasting offers numerous health benefits, women must approach it with caution due to their unique hormonal makeup. Unlike men, women may experience negative side effects from prolonged fasting periods. By adopting a modified approach- focusing on time-restricted eating and syncing their fasts with their natural circadian rhythms and menstrual cycles- women can safely harness the benefits of intermittent fasting for weight loss, improved metabolic health, and overall well-being.

REFERENCES
  1. Song DK, Kim YW. Beneficial effects of intermittent fasting: a narrative review. J Yeungnam Med Sci. 2023;40(1):4-11. doi:10.12701/jyms.2022.00010
  2. Healthline. Intermittent fasting for women: a beginner’s guide. Healthline website. https://www.healthline.com/nutrition/intermittent-fasting-for-women. Published July 22, 2018. Updated May 3, 2024. Accessed September 24, 2025.
  3. Heilbronn LK, Civitarese AE, Bogacka I, Smith SR, Hulver M, Ravussin E. Glucose tolerance and skeletal muscle gene expression in response to alternate day fasting. Obes Res. 2005;13(3):574-581. doi:10.1038/oby.2005.61
  4. Velissariou M, Athanasiadou CR, Diamanti A, Lykeridou A, Sarantaki A. The impact of intermittent fasting on fertility: A focus on polycystic ovary syndrome and reproductive outcomes in Women-A systematic review. Metabol Open. 2025;25:100341. Published 2025 Jan 6. doi:10.1016/j.metop.2024.100341
  5. Chawla S, Beretoulis S, Deere A, Radenkovic D. The Window Matters: A Systematic Review of Time Restricted Eating Strategies in Relation to Cortisol and Melatonin Secretion. Nutrients. 2021;13(8):2525. Published 2021 Jul 23. doi:10.3390/nu13082525
  6. Barcelona Institute for Global Health (ISGlobal). Overnight fast and early breakfast. ISGlobal website. https://www.isglobal.org/en/-/overnight-fast-and-early-breakfast. Published September 30, 2024. Accessed September 24, 2025.
  7. Kalam F, Akasheh RT, Cienfuegos S, et al. Effect of time-restricted eating on sex hormone levels in premenopausal and postmenopausal females. Obesity (Silver Spring). 2023;31 Suppl 1(Suppl 1):57-62. doi:10.1002/oby.23562