Fasting has been practiced for many reasons throughout history—religious beliefs, medical procedures, and, more recently, weight loss. For weight loss many people will try different types of fasts and the one that appears most popular is intermittent fasting (IF).
When you fast, your body goes through several metabolic stages. After several hours without food, it burns through its stored glucose (sugar). Once those stores become depleted, the body begins to rely more heavily on fat for fuel, a process known as ketosis – which is another diet all on its own that people use for the same reasons. Like many extreme diets Ketosis has its own challenges and precautions, which I have written on in the past. For this corner I want to focus on how intermittent fasting affects people and specifically women vs men.
While intermittent fasting can provide metabolic benefits for many men, women really have to pay attention to how long the fast is. Men can do more flexible fasts even longer ones and see improvements in insulin sensitivity, better blood sugar regulation, and greater metabolic flexibility.
For women, extended fasting can be interpreted by the body as a survival stressor. This may increase cortisol (the stress hormone), disrupt sleep, and lead to poorer blood sugar regulation. It can also interfere with the hormones that regulate hunger. Ghrelin, the hormone that signals hunger, and leptin, the hormone that signals fullness, can become disrupted. When this happens many women will experience intense evening hunger and cravings that can feel almost impossible to control. Unfortunately, this is the time of day when our bodies are naturally preparing for rest rather than needing a large influx of energy.
For premenopausal women, prolonged fasting may also suppress kisspeptin neurons, which play a key role in regulating reproductive hormones. This can disrupt menstrual cycles, ovulation, and fertility because the endocrine system depends on a consistent supply of energy. Even after menopause, women are often more sensitive to extended fasting than men and can still experience increased stress responses and metabolic changes.
So, what is the best approach?
For most women, it’s beneficial to:
- Avoid skipping breakfast.
- Eat the majority of your calories earlier in the day.
- Finish eating a few hours before bedtime to allow digestion before sleep.
This approach supports your body’s natural circadian rhythm rather than fighting against it.
Does that mean intermittent fasting is always bad for women? Not necessarily.
Many women can benefit from a 12- to 14-hour overnight fasting window, which naturally occurs between dinner and breakfast, otherwise known as time restricted eating pattern, rather than “fasting.” Some women may occasionally tolerate an actual 16-hour fast, but this should be used sparingly and only once per week max, if at all.
When fasting windows become too long or too frequent, the body begins to conserve energy. This can slow metabolism, making weight loss more difficult. It is important to note, even for men if fasting is for too long, lasting for weeks, metabolism will also stunt itself, so there should be breaks taken.
For women rather than following prolonged fasting protocols, a better strategy to see long-term results is to adopt the time-restricted eating, as referred to earlier. This aligns more with the body’s natural circadian rhythm by nourishing your body consistently during the day when energy is needed. Also emphasizing protein, fibre, and balanced meals, will help support hormone health, energy levels, and sustainable weight management far better than simply eating less for longer periods.
https://www.thewellnessway.com/fasting-vs-time-restricted-eating-why-women-shouldnt-fast-like-men/
Mikkie Nettles-Pollon, Certified Personal Trainer/Holistic & Sports Nutritionist
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