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Is fasting a safe way to diet? Why is fasting for women different than men? How can mistimed fasting affect a woman’s hormones?

In Fast Like a Girl, Mindy Pelz says that fasting won’t work for women if they don’t cater their diets to their hormonal cycles. The solution is to align fasting schedules and hormonal cycles.

Read below for an overview of Fast Like a Girl.

Fast Like a Girl by Mindy Pelz

Fasting has gained popularity for offering a myriad of health benefits: It can improve your immune system, help you lose or maintain a healthy weight, and enhance your mental clarity.

In Fast Like a Girl, Mindy Pelz suggests that many women fail to benefit from fasting because they don’t understand how hormonal cycles impact their bodies. This lack of understanding often leads them to mistime fasts, resulting in hormonal imbalances and uncomfortable symptoms. Pelz argues that aligning fasting schedules with hormonal cycles can help women overcome these challenges and maximize the benefits of fasting.

Mindy Pelz is a chiropractor, speaker, and fasting expert. She is also the author of The Menopause Reset, The Reset Factor, and The Reset Factor Kitchen. Her influence extends widely, reaching over 60 million people through her YouTube channel and over 50,000 active participants on her members-only Facebook group. Her podcast, The Resetter Podcast, has claimed a spot among Apple’s top 40 U.S. science podcasts and has featured a variety of guests, including Dave Asprey (author of Super Human and Fast This Way) and Rhonda Byrne (author of The Secret). She leads a private coaching group for women that includes high-profile clients such as LeAnn Rimes and former race car driver Danica Patrick.

Part 1: Why Fasting Is Good for Your Health

In this first part of the guide, we’ll cover Pelz’s insights on the health benefits of fasting—which involves consuming only water or zero-calorie drinks such as black tea or coffee for at least eight continuous hours. We’ll explain how your body processes energy from the food you consume, why typical diets deplete your health, and how regularly fasting from food restores your health.

How Your Body Processes Energy

Pelz explains that your body converts what you eat into energy in two ways: It either burns sugar in your bloodstream to produce glucose or it burns your fat stores to produce glucose for energy plus ketones as a byproduct. Ketones can serve as an alternative energy source when glucose levels are low.

When you consume food, your blood sugar level increases and your body converts this sugar into glucose for energy. To keep your blood sugar level stable, your body releases insulin, a hormone that exports glucose to your cells and stores the rest in your muscles and liver as an energy reserve. If your body doesn’t use this energy reserve, the insulin converts any excess glucose into fat and stores it away.

After you stop consuming food, your blood sugar level gradually decreases and your body relies on the excess glucose stored in your muscles and liver for energy. Once this excess glucose runs out, you enter a fasted state, during which time your body converts your fat stores into ketones for energy.

Typical Diets Deplete Your Health

Typical diets tend to restrict food intake, either by limiting the types of food you eat or the amount of food you consume. However, they often don’t restrict when you consume that food. This lack of restriction results in a tendency to eat continuously.

When you eat without long breaks and prevent your body from entering a fasted state, your body relies solely on glucose for energy. According to Pelz, continuous reliance on glucose can lead to chronically high insulin levels, contributing to insulin resistance

Insulin resistance is a condition where cells become less responsive to the effects of insulin and can’t efficiently use glucose for energy. This condition diminishes the effectiveness of insulin in regulating blood sugar levels, creates an excess of glucose that your body stores as fat, and disrupts hormonal balance. Pelz argues that these effects lie at the root of numerous health issues, such as obesity, chronic fatigue, high blood pressure, and diabetes.

Fasting Restores Your Health

Pelz suggests that regular fasting restores and optimizes your overall health by improving your immune system, aiding in healthy weight maintenance, and enhancing mental health and cognitive functioning. Let’s explore how fasting contributes to these three effects.

1) Fasting Improves the Immune System

As your body’s primary defense against illnesses, your immune system plays a crucial role in maintaining your overall health. Pelz says that fasting strengthens your immune system by:

Triggering autophagy: Lowering glucose levels forces your body to turn to cellular debris as an alternative energy source. This process, known as autophagy, strengthens cellular health by detoxifying, repairing, and removing damaged components and harmful pathogens. It makes cells more resilient against age-related decline and inhibits viral replication, counteracting degeneration and inflammation that can lead to various health challenges.

Improving gut health: Fasting, by allowing the digestive system to rest, reduces gut inflammation, fostering the ideal environment for beneficial bacteria to thrive and spread. This rest phase also stimulates the growth of gut-healing stem cells. According to Pelz, these processes promote a microbial balance that supports your immune system in multiple ways, including enhancing cellular health and glucose regulation.

2) Fasting Aids in Weight Maintenance

According to Pelz, fasting helps you lose weight or maintain a healthy weight by:

Balancing insulin levels: When you fast, you prompt your body to metabolize its stores of glucose and fat for energy. This stabilizes your blood sugar levels, lowers your insulin production, and helps regulate your weight by preventing excessive fat storage.

Suppressing appetite: Pelz suggests that each time you fast, ketones (chemical byproducts of fat metabolism) inhibit your hunger hormones, making you less inclined to overeat.

Metabolizing stubborn fats: Pelz says that fasting promotes the conversion of stubborn subcutaneous fats into metabolically active fats, which are easier for your body to burn for energy. \

Stimulating growth hormone production: Pelz explains that, by decreasing blood sugar levels, fasting triggers a significant increase in hormones that facilitate fat-burning, muscle growth, and a healthy body composition.

3) Fasting Enhances Mental Health and Cognitive Functioning

Pelz argues that fasting improves both your mood and your mental acuity by:

Repairing neurons: Elevated ketone levels during fasting support the regeneration of damaged neurons, enhancing memory, focus, and mental clarity.

Providing consistent energy: Pelz explains that, unlike glucose, ketones offer a stable energy source, preventing fatigue and supporting overall cognitive function.

Resetting dopamine pathways: Continuous eating elevates your dopamine (a pleasure-related neurochemical) baseline. Over time, this leads to an increased need for food to achieve the same level of pleasure. Pelz suggests that fasting diminishes this dependency and enhances the sensitivity of dopamine receptors, reducing your reliance on food for a sense of well-being.

Calming anxiety: According to Pelz, increased ketone levels trigger the release of GABA, a calming neurotransmitter that promotes relaxation and emotional stability.

Part 2: How to Maximize Fasting Benefits

We’ve just discussed how fasting enhances overall health. While fasting doesn’t seem complicated—it’s just a matter of not eating for a certain amount of time—Pelz offers a couple of tips for maximizing the benefits of fasting: Incorporate different-length fasts into your routine and pay attention to the foods you eat when you’re not fasting. Let’s explore these two tips in detail.

Tip #1: Incorporate Different-Length Fasts Into Your Routine

According to Pelz, incorporating different-length fasts into your routine prevents your body from adapting to the fasting state, ensuring continued long-term benefits. To clarify how this works, we’ll explore how your cells respond to both glucose and ketones, then explain how strategically switching between these two fuel sources (by varying fasting lengths) guarantees ongoing benefits.

Up until now, we’ve touched on the downsides of relying solely on glucose as an energy source. However, this doesn’t mean you should always prevent your body from burning glucose. Both fuel sources are essential for your body to function optimally.

  • When your body burns glucose, it activates mTOR signaling, a process that builds new cellular structures and contributes to hormone production, muscle building, and cell regeneration. 
  • When your body burns ketones, it activates autophagy, the cellular detox process we discussed above that breaks down and removes damaged components.

Pelz explains that switching between these two states (by eating and fasting) creates hormetic stress, a beneficial form of stress that encourages cellular adaptation and resilience—like the way new exercises challenge muscles. However, sticking to the same fasting routine every day reduces this stress, causing you to miss out on the beneficial effects of switching between fuel sources. This is because your body gets too comfortable with routine—just as doing the same exercises every day stops having an effect. Therefore, Pelz argues that incorporating different-length fasts prevents your body from adapting to a specific fasting pattern, ensuring it benefits from fasting over the long term.

Tip #2: Pay Attention to What You Eat

While fasting alone offers benefits, paying close attention to your post-fast meals can elevate those gains. Pelz explains that being mindful about what you eat can prolong and enhance the positive effects of fasting. She suggests two key pieces of advice:

1) Prioritize healthy, organic foods over processed, chemical-laden ones, such as those containing hydrogenated oils, preservatives, or artificial dyes and flavors. Consuming nutrients in their natural form enables efficient absorption without the burden of processing harmful additives, thereby minimizing the cleanup workload for your body.

2) Maintain stable blood sugar levels by balancing your intake of complex carbohydrates (including fiber), grass-fed proteins, and “good” fats (such as olive oil, nut butter or oil, or grass-fed butter). According to Pelz, this supports a smooth transition from the fasting state and prevents energy crashes by slowing the absorption of glucose into your bloodstream.

Part 3: What Women Can Do to Maximize Fasting Benefits

We’ve just covered how to practice and benefit from fasting. Now, let’s narrow our focus to how women can further enhance their fasting experience. Why focus on women specifically? Pelz says that, unlike men, women experience monthly and menopausal hormonal cycles that significantly impact how fasting affects them.

In this final part of the guide, we’ll first explain why women need to pay more attention to their fasting and eating habits. Then, we’ll explore Pelz’s advice for tailoring a fasting schedule that aligns with your hormonal cycle.

Mistimed Fasting Creates Hormonal Imbalance

Pelz explains that a woman’s hormonal cycle spans the time from the onset of menstruation (the first day of bleeding) to the beginning of the next period. On average, this takes 28 days, but it’s normal for cycles to be a bit longer or shorter. 

Throughout each cycle, the levels of three key hormones—estrogen, progesterone, and testosterone—rise and fall. Pelz emphasizes that each of these hormones thrives on specific blood sugar and insulin levels. When you provide the necessary environment for each hormone, you enhance your overall health. However, mistiming your fasting or consuming the wrong foods can deprive these hormones of the nourishment they require to keep your body in balance, leading to a spectrum of unpleasant symptoms.

Align Your Fasting Schedule With Your Hormonal Cycle

Pelz suggests that you can establish and maintain hormonal balance by following her fasting schedule. If you have a regular cycle, start the schedule on your first day of bleeding and follow it until your next period. If your cycle is irregular or nonexistent due to factors like birth control, stress, or menopause, start when you want and follow a 30-day continuous schedule.

Fast Like a Girl by Mindy Pelz: Book Overview & Takeaways

Katie Doll

Somehow, Katie was able to pull off her childhood dream of creating a career around books after graduating with a degree in English and a concentration in Creative Writing. Her preferred genre of books has changed drastically over the years, from fantasy/dystopian young-adult to moving novels and non-fiction books on the human experience. Katie especially enjoys reading and writing about all things television, good and bad.

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