An Intermittent Fasting Guide for Men & Women


Lately, I’ve talked quite a bit about intermittent fasting. However, there’s an important distinction to make before you jump in and extend your evening fast or introduce daily fasts. You certainly want to be aware of your body chemistry and in tune with what your body needs, but if you are a woman you may not notice some of the changes that a fast instigates.

Due to the nutritional load that hormonal shifts require, women often need more regular meals than men do, and the benefits that we cite for intermittent fasting are likely more prominent in men than in women. Should you avoid intermittent fasting altogether if you are a woman? Let’s walk through the actions and implications to see how fasting affects men and women differently.

The Concept of Intermittent Fasting

Nutritionists and wellness advocates are hearkening back to our ancestral roots more and more, tapping into the original intent for our complex design after centuries of lifestyle changes that have moved us further and further away from nature. Intermittent fasting has its roots in this concept, building on the idea that moving back toward natural wellness includes patterns of eating as much as what we eat.

Looking beyond people, intermittent fasting is frequently reflected in nature, as carnivorous mammals often hunt and consume a large amount of food at once to sustain them for a while, compared with foragers who snack constantly. Much debate has centered around the hunter vs. gatherer ideal, but the point remains that there is strong natural precedent for spaced meals.

Within the human body itself, there are metabolic indications that intermittent fasting is beneficial even now, when “hunting” is little more than being patient in the grocery store or trekking through the farmer’s market.

Ketosis is one notable factor that many rely heavily on when intentionally fasting. When the body believes food sources are scarce, it turns to stores of fat for its energy rather than muscle and circulating carbohydrates. When the fat begins to release and burn, a process called ketogenesis, the chemical byproducts called ketones are released into the urine.

For those pursuing intermittent fasting for specific health goals, weight loss in particular, ketogenesis is often a goal. Some go as far as measuring the ketones in their urine daily, with an at-home test strip. It should be noted that ketogenesis is not always considered a positive effect. For diabetics, for example, a state of ketosis is a dire one, and medical help should be accessed immediately.

Inflammation may be decreased in a fasting state, as well, as researchers found when studying a group of people observing a month long religious fast. During Ramadan, meals are only consumed after sunset. The participants were compared with people who were eating normally, and those fasting saw decreases in inflammation markers during that month, while the others did not. (1)

Intermittent fasting takes these concepts and potential benefits and builds them into everyday life. Some push the morning meal out to noon, while others wait until late afternoon or evening to eat at all. Other forms of intermittent fasting include entire days where no food is consumed.

On paper and as a concept, intermittent fasting seems to make sense. But whenever we are looking for the evidence of benefit for a certain action or protocol, we have to take the demographic into consideration, as well. And for intermittent fasting, gender seems to play a significant role.

Ancestral Gender Differences

If ancestry is our inspiration for intermittent fasting, we have to consider the ancestral roles each gender played. Some factors clue us in to ways we can apply centuries old lifestyle patterns to today’s society.

Childbearing is a wonderful and amazing blessing today, but in previous eras it was vital. Birthing and raising children allowed the family to continue on, adding extra hands to make lighter work and ensuring the continuation of lineage.

By virtue of childbearing alone, women were highly likely to stay in the camp, village, or community while the men were out hunting. Yes, the “big meal” was still the party catch and yes, there were still gaps between game – but what were they doing during the hunt? Certainly not expending great amounts of cardio energy chasing after prey.

More likely, they were tending children, crops, and cooking. From early ancestors as late as pioneers and farmers, keeping the home or homestead required strength and constant effort, day in and day out, on top of the physical rigors of childbearing, breastfeeding, and hormonal fluctuation to facilitate it all.

Not only did ancestral women need to build and sustain muscle, but they also needed some element of fat storage in order to support biological functions. We have known for decades that body composition is related to menstrual onset, and that malnourishment can affect luteinizing hormones and the menstrual cycle. This was explored in studies in the 1970s, analyzing the way the hypothalamus reacts to a woman not eating. (2)

Conclusions vary as to how hormones are impacted by fasting and why, but experience tells us that there is almost undoubtedly a connection – and it makes sense historically. Energy derived from muscles stores would have been efficient for the female body, with muscles rebuilt regularly through constant work, while intentionally depleting literal life-giving fat stores would be biologically counterproductive and potentially dangerous.

Not every woman stayed home from the hunt and not every man chased prey, of course. And while not every woman, ancestral or modern, will have children, the biological processes remain the same. In a generalized look at ancestral eating, the glaring difference in gender roles brings light to biological differences that may affect intermittent fasting in modern times.

Hormonal Shifts for Women vs. Men

The way that the endocrine system communicates with the body, distributing cellular directives and managing vital functions and responses, has been and will likely always be under heavy research by scientists of nearly every field. Hormones are intricate and incredible.

Between the genders, hormones have varying responsibilities though the hormones themselves are shared – e.g., luteinizing hormone affects the egg and menstrual cycle in women, while it triggers testosterone production in men.

As such, we know that each person’s body chemistry is unique, but we also know that men and women will generally be affected differently when hormones are altered. And hormones are definitely altered by diet.

The impact of fat stores and body composition on the menstrual cycle and fertility hormones has been observed for ages. Malnutrition and underweight has long been associated with infertility, no doubt contributing to the artistic attraction to larger women for centuries in contrast with today’s thinner models.

This connection between nutrition and fertility is the subject of much research and has been referred to as nutritional infertility. The link is hypothesized to be a complicated hormonal response to nutritional input. In 2013, study findings were published that researched this concern specifically related to intermittent fasting. The results appear to confirm that intermittent fasting can alter the hypothalamus to the point of nutritional infertility. (3)

Interestingly, the neuropeptide kisspeptin was named as a potential contributor to nutritional infertility. Kisspeptin, in a study published just a year later, has also been linked to obesity and metabolic disorders. When its signals are altered, metabolic processes seem to slow and malfunction. (4) Could intermittent fasting alter these signals in women – affecting both fertility and working against a healthy metabolism?

Even when a woman isn’t looking to conceive, hormonal imbalance stretches beyond childbearing and into everyday life and overall health. Aside from metabolic concerns, the stress of intermittent fasting could impact a woman’s adrenal stress disproportionately to what men deal with. This was demonstrated in 2007, when researchers found that female mice on significant calorie restriction reacted quite poorly

“…females became emaciated, ceased cycling, underwent endocrine masculinization, exhibited a heightened stress response, increased their spontaneous activity, improved their learning and memory, and maintained elevated levels of circulating brain-derived neurotrophic factor.” (5)

Males do not seem to exhibit these strong, negative effects. The researchers in that study noted that the females increased their daytime activity by four fold while the males did not. Since mice are nocturnal, this was certainly not a benefit for the females.

Warning Signs and When to Take Heed

It should be acknowledged that the majority of our detailed studies on the endocrine response are carried out on animals rather than humans, and while we have much to learn from these studies, they may not translate directly to human interpretation.

The way mice can be studied, particularly because of their short lifespan, is vastly different from the way humans can be studied. As such, it’s unsurprising to see studies that seem to indicate intermittent fasting is safe – or, at the very least, benign – for human women. In 2012, for example, a study was published indicating intermittent fasting could be beneficial for obese women, and that it “improved coronary heart disease risks. (6)

You know your own body better than anyone, and women are out there who are proponents of intermittent fasting. However, before you jump right in to extended fasts, take note that human studies are often short term – observing Ramadan, for example, for a month – while mice studies span their entire lifetime. Weeks for a mouse is like years for a human. What are these studies telling us about long term risks to women?

If you experience any warning signs of hormonal imbalance after practicing intermittent fasting, it’s prudent to stop and either modify your approach or work with a healthcare professional who can help. Some potential signs that intermittent fasting is a problem for you might include:

  • Trouble sleeping
  • Hair loss
  • Low daytime energy
  • Menstrual irregularity
  • Irritability
  • Extreme weight loss
  • Unexplained weight gain
  • Light headedness/dizziness

Remember that our commitment is to long-term health – not to a diet or trend, no matter how popular it may seem to be. Something that works on paper is not the same as something that can play out successfully in your life.

Intermittent Fasting Modified

If you’d still like to pursue the benefits of intermittent fasting as a woman, it’s wise to make some alterations to the plan compared with a strict program or what might work for a man. Pay attention to hunger cues, and don’t be afraid to heed them when you are sure it’s more than boredom or habitual eating. If your body seems to need food, we have a good body of evidence that tells us it knows what it’s talking about!

Include healthy fats.

Fat is not a dirty word – essential fatty acids must be consumed in the diet regularly to fight inflammation and improve brain function, among other things. Incidentally, the brain houses endocrine control centers. Choose healthy fats like coconut oil and grassfed butters. Not only will significant internal work be underway, but you’ll feel more satiated and receive adequate calories even in the shortened eating time. You can even consume high amounts of good fats — with nothing else — during your fasting periods, and you won’t interrupt your body’s state of ketosis.

Choose low-impact foods.

Intermittent fasting gives the digestive tract the opportunity to rest and rebuild, which can be facilitated nearly as well if low-impact foods are chosen in place of complete fasting. Low glycemic index fruits, steamed vegetables, and nutritionally-rich “green powder” drinks are excellent options.

Shorten the fast.

The nightly fast during sleep can simply be extended a few hours – perhaps until noon – rather than far into the day. You’ll still be allowing your body to ease into the day, but you won’t be extending that effort and subsequent stress.

Pay attention to your body’s cues if you attempt intermittent fasting. You could be one of the women it works for, or you may need to alter your habits significantly to apply the principles in another way. Being aware of the potential risks ensures that you approach intermittent fasting and similar diet plans with your eyes wide open, seeking only the best for your body and life.


Dr. B.J. Hardick

About Dr. B.J. Hardick

Dr. B.J. Hardick is a Doctor of Chiropractic and internationally-recognized natural health author and speaker. His health journey began as a child — alternative medicine is the only medicine he has ever known. In 2009, he authored his first book, Maximized Living Nutrition Plans. In 2018, he authored his second book, Align Your Health. An energizing and passionate speaker, Dr. Hardick shares his lifestyle methods to numerous professional and public audiences every year in the United States and Canada. His teachings encompass the principles of ancestral nutrition, detoxification, functional fitness, mindfulness, and green living. Learn More