1. Hormonal Flux and Metabolic Response

When men fast, they often see measurable improvements in insulin sensitivity, growth hormone release, and testosterone levels. These help with fat metabolism and muscle maintenance. But for women, it’s complex. The female body is biologically programmed for reproductive protection and metabolic flexibility, so extended fasting or severe calorie restriction can disturb menstrual cycles, affect fertility, or elevate cortisol levels.

A 2016 study published in Frontiers in Psychology explored how an 18-hour fast influenced mood and behaviour in 52 healthy women. The researchers found that short-term fasting led to increased irritability, yet also heightened feelings of achievement, pride, reward, and self-control. This dual response is negative mood alongside a boost in perceived control, suggesting that fasting can be psychologically reinforcing for women, helping explain why some find it motivating despite transient discomfort.

2. Body Composition and Fat-Loss Patterns Differ

While both men and women can shed fat and improve their body composition through intermittent fasting, the process of losing it differs. According to a 2024 study published in the Journal of Health Sciences, men generally show a faster drop in abdominal and visceral fat, the type associated with heart disease and metabolic risk. Women, on the other hand, tend to lose subcutaneous fat (hips, thighs) more gradually and may retain lean muscle mass differently.

This happens because sex hormones shape fat storage and mobilisation differently. Oestrogen promotes lower-body fat storage and protects against central obesity, whereas testosterone helps preserve muscle and enhance fat oxidation. Consequently, men’s fat-loss results appear quicker and more visible, while women’s progress may unfold more slowly. But it can’t be denied that for long-term metabolic health, it’s ideal.

Related Story: The Best Weight Loss Strategy (as per Research): Calorie Counting or Intermittent Fasting

3. Energy, Mood, and Adaptation Vary

Fasting can sharpen focus and energy in men, but for women, it’s often a mixed experience. Many report fatigue, irritability, sleep issues, or mood swings, especially when fasting coincides with intense workouts or calorie restriction. A 2024 study published in the Journal of Health Sciences found that men adapt more readily to reduced meal frequency, whereas women’s energy, mood, and hunger fluctuate depending on their menstrual phase, hormone levels, and stress response.

Evolution has made it so that women’s bodies biologically tend to protect organs related to fertility. This is also why women are more sensitive to energy deficits. When fasting, cortisol and ghrelin (the hunger hormone) can rise faster in women, triggering fatigue, cravings, or anxiety. That’s why shorter fasting windows and cycle-based flexibility work better for most women rather than rigid, prolonged fasts.

Related Story: An Ob-Gyn’s Guide To 5 Female Hormones and Their Impact On Your Health

4. Differences in Insulin and Glucose Handling

Men may experience quicker improvements in glucose regulation and insulin sensitivity through fasting. A 2015 study published in Frontiers in Endocrinology found that during prolonged fasting, women had lower plasma glucose levels and higher levels of free fatty acids (FFA) compared to men, suggesting that women relied more on lipid oxidation.

This matters because female hormones, especially oestrogen and progesterone, modulate insulin differently throughout the month. When fasting coincides with the luteal phase (after ovulation), women might notice lower blood sugar tolerance or heightened cravings, a sign that their body needs extra nourishment rather than prolonged restriction.

5. Reproductive and Bone Health Considerations

Extended fasting or aggressive calorie restriction can sometimes disrupt menstrual cycles, lower oestrogen levels, and affect bone density in women. This link is less evident in men, whose reproductive systems are less sensitive to energy availability.

Oestrogen is vital for both fertility and bone strength. When energy intake drops too low, the body prioritises survival over reproduction, which may manifest as missed periods, hormonal imbalance, or long-term bone health risks.

6. Circadian and Feeding-Window Differences

A landmark 2018 study published in Cell Metabolism found that following an early 6-hour eating window for five weeks significantly improved insulin sensitivity, β-cell responsiveness, and blood pressure in men with prediabetes, even without weight loss. This shows that aligning food intake with daylight hours can rapidly enhance glucose control and metabolic health in men.

However, women’s metabolism tends to respond differently. Their glucose and cortisol rhythms are more sensitive to fasting duration and timing, and overly restrictive eating windows can disrupt circadian balance and hormonal stability. For many women, a gentler TRE pattern better supports steady energy levels, mood regulation, and menstrual-cycle health, while still promoting fat utilisation and metabolic balance.

Related Story: 6 Reasons To Try Circadian Rhythm Fasting

Fasting can be a powerful tool, but its effects differ sharply between men and women. If you’re a woman exploring intermittent fasting, start slow, observe how your body responds, and prioritise hormonal balance over rigid discipline.

Everybody is different. Your fasting approach should be guided by your unique biology, goals, and lifestyle. Get a personalised nutrition consultation with experienced nutritionists to craft a plan that supports your hormones, boosts energy, and helps you make smarter food choices every day.