Fast Like a Girl

dr mindy pelz, fast like a girl, a woman's guide to using the healing power of fasting to burn fat, boost energy and balance hormones.

what's the first thing that pops into your mind when you hear the word fasting?

is it an ascetic monk giving up all but the barest sustenance?

is it going without food for days on end?

is it starving yourself?

the truth isn't quite so dramatic.

sure, you'll find descriptions of fasts that last up to or even beyond 72 hours in this chapter to dr mindy pelz's fast like a girl.

but for the most part, intermittent fasting, which means fasting 13 to 15 hours a day, is the backbone of the fasting lifestyle.

not so intimidating, right?

if it still sounds hard, don't worry, this chapter will walk you through the science behind fasting, a key concept called metabolic switching, and how fasting can work within the cycle of a woman's hormones.

we'll finish with a 30-day reset designed to help you begin fasting and provide a few tips and tricks for breaking a fast in a way that supports your goals.

we won't be able to cover all the specific foods that can best support a healthy and fasting lifestyle, but by the end, you'll have the basic information needed to begin fasting safely, and a great springboard for how to craft a fasting lifestyle that fits your unique body.

just a quick note before we get started.

for the sake of this chapter, the term woman refers to anyone whose body goes through a hormone cycle involving estrogen, testosterone and progesterone.

this includes people who have gone through menopause or those who might not get their period due to stress or birth control.

let's dive in!

the science calories in must be less than calories out.

how many times have you heard about or tried a diet that focuses on this idea?

it's been a popular mantra for years.

if we eat fewer calories than we burn working out, we'll lose weight and be healthier.

however, studies have recently shown it's less about how much you eat and more about when you eat.

a 2018 study in the journal of nutrition, health and ageing found obese individuals experienced metabolic improvements just by reducing the window in which they ate every day.

participants ate whatever they wanted, but only during an 8-hour period, and saw dramatic results.

another study published in 2020 in cell metabolism found that people who ate during a 10-hour period experienced greater metabolic effects than when the exact same things were eaten during a 14-hour period.

so with just 4 extra hours of fasting and no change to their diet, people saw significant metabolic results.

how is this possible?

well, let's look at the science behind fasting.

our ancestors evolved to have energy even after fasting.

they ate during the day and then their bodies entered a fasting state overnight.

when they woke up, they needed enough energy to get more food.

they got that energy from ketones their body produced while in a fasted state.

this shift from using glucose as a source of energy to ketones is known as metabolic switching.

metabolic switching is essentially the transition from a sugar-burning mode to a fat-burning mode.

when our bodies aren't in a fasted state, we're in sugar-burning mode.

our bodies burn the glucose we eat to energise us.

when the body's in a fasted state for long enough, it uses the fat-burning system to make energy.

sugar is stored in the body in the form of glycogen, which is deposited in the muscles, liver and fat.

exercising burns glycogen in muscles.

through fasting, we can also start burning glycogen stores in the liver and fat tissues.

and that's not all our body does in a fasted state.

it regenerates neurons damaged by exposure to toxins and too much sugar, helps heal our mitochondria, reduces the chance of developing cancer and balances our gut.

pretty important stuff!

metabolic switching worked perfectly with our ancestors' habits.

today, we often don't fully reach a fasted state because we have access to food 24-7.

the benefits of fasting vary with the length of the fast and we'll cover different fasting windows and their uses later in the chapter.

but first, let's look at another important component that impacts the science of fasting.

a woman's cycle.

hormone cycles and fasting.

let's review the biology of a woman's hormonal cycle before jumping into how it interacts with fasting.

a cycle is measured between menstrual periods.

it starts on day one of bleeding and ends when the next period begins.

on average, this takes 28 days, but it's normal for a cycle to be a bit longer or shorter.

estrogen, testosterone and progesterone are low on day one of the cycle, when bleeding begins.

as the uterus sheds its lining, the body slowly builds up its estrogen stores to prepare for a new round of ovulation.

this causes the uterine lining to grow and thicken.

ovulation occurs between days 11 to 15.

estrogen levels peak near day 13 in the middle of ovulation.

higher estrogen levels often leave women feeling more optimistic because estrogen is a precursor to neurotransmitters like dopamine and serotonin.

along with elevated testosterone, this is generally when a woman feels her happiest and most powerful.

over the next three days, days 16 to 18 of the cycle, hormone levels dip as the body gears up to make progesterone.

energy levels often fall during this time too.

around day 19, the body starts creating progesterone.

this hormone prepares the uterus to receive a fertilised egg.

if no fertilised egg appears, the body stops making progesterone.

as both progesterone and estrogen levels decrease, the uterus gets ready to shed its lining.

the start of menstrual bleeding signals the beginning of the next cycle.

now let's tie the cycle into fasting.

according to dr mindy peltz, there are three types of phases within a cycle.

power, manifestation and nurture.

they're based on which hormones are influential in each phase.

days 1 to 10 are the first power phase, days 11 to 15 are manifestation, days 16 to 19 are the second power phase and day 20 until bleeding begins again is the nurture phase.

a perfect time to fast is when your body is making estrogen.

during the power phases, fasting decreases insulin levels, which estrogen loves.

fasts of any length during these phases are helpful.

peltz recommends experimenting with intermittent fasting all the way up to 72-hour fasts during power phases.

of course, for longer fasts, think 24 hours and above, give your body plenty of time to replenish before doing another fast of that length.

don't try to cram more than one 72-hour fast into your cycle.

while estrogen loves fasting, progesterone can suffer when you fast because it decreases when cortisol increases.

if you're stressed during the days in your cycle when your body is trying to make progesterone, your nurture phase, your body won't be able to function as it should.

also, progesterone thrives with higher glucose levels.

fasting decreases those levels, which hinders progesterone production.

so you'll want to avoid fasting when your body's trying to make progesterone.

the final phase, which comes second chronologically during your cycle, is the manifestation phase, when the body ramps up testosterone production.

there isn't any research on female testosterone levels and fasting, so peltz used studies of men and her own clinical experience to determine how to fast during this phase.

she recommends fasting no longer than 15 hours a day during the ovulation window.

phew, that was a lot of information.

let's recap.

days 1-10 of your cycle are a power phase, where you can fast between 13 and 72 hours.

days 11-15 are the manifestation phase.

keep fasts between 13 and 15 hours a day.

days 16-19 are another power phase, and fasts of any length are great.

finally, from the 19th day of your cycle until you start bleeding again, is the nurture phase.

avoid fasting during this stretch.

types of fasting and the 30-day reset.

a fast is a fast is a fast, right?

well, not quite.

in fact, peltz covers six different lengths of fasting.

intermittent fasting refers to fasts that last from 12 to 16 hours a day.

autophagy fasting, when your cells start healing themselves, begins once you hit 17 hours of fasting.

a gut reset is a 24-hour fast, a fat burner fast is 36 hours, and a dopamine reset fast lasts 48 hours.

and finally, a fast that's 72 hours or longer resets your immune system.

that's right, 72 hours, three straight days of fasting.

if it seems impossible, that's okay.

it's highly inadvisable to jump right into such an intense fast without any preparation or practice.

if you wanted to start running, you wouldn't immediately do a marathon, would you?

of course not.

it's the same for fasting.

you should begin slowly and build strength and ability over time.

to start, peltz recommends a 30-day reset to ease your body into accessing a fasted state.

like the fasting cycle you learned about in the last section, the reset uses fasts of different lengths to best support your body as your hormones cycle.

if you've never fasted before, you should do a two-week pre-reset before the 30-day reset.

during this time, avoid hydrogenated oils, synthetic ingredients, and any foods that are high in sugars or refined flours.

instead, add more good fats and healthy proteins.

we'll get into specifics in the next section.

also, begin compressing your eating window.

start by pushing your breakfast back an hour or moving your dinner up an hour.

day by day, reduce your eating window by one more hour until you're fasting for 13 hours each day.

for the full 30-day reset, continue to avoid bad oils, synthetic and chemical ingredients, refined sugars and flours, and alcohol.

begin on the first day of your period.

fast for 13 hours on days 1 to 4, 15 hours on day 5, and 17 hours on days 6 to 10.

for days 11 to 15, fast 13 hours each day.

during days 16 to 19, fast 15 hours each day.

to finish the reset, don't fast on days 20 to 30.

once your period starts again, or your 30 days are up, you're ready to experiment with longer fasts and tailor a fasting lifestyle that works best for your body.

types of eating and breaking a fast.

so far in this chapter, we've explored why and how fasting can help you unlock your body's natural power.

we've outlined a general fasting schedule according to your cycle, and we've summarised the 30-day reset.

now let's take a closer look at an important detail of fasting – the food you pair it with.

there are two different ways of eating while you fast – a ketobiotic diet and hormone feasting.

the concept of ketobiotic foods is based on the popular ketogenic diet.

peltz adapted the style of eating to better interact with both a woman's cycle and a fasting lifestyle.

she recommends a general split each day of 75g of clean protein and max 50g of carbohydrates.

over 60% of your food should be made up of good fats.

this split is meant to keep glucose low, which helps during the power phases of your cycle.

hormone feasting, on the other hand, is largely meant to support progesterone production.

this helps when your hormone levels are higher during the manifestation and nurture phases.

the split for this style of eating is no more than 150g of carbs, no more than 50g of protein and whatever healthy fats you desire.

now let's talk about an often overlooked aspect of fasting – breaking the fast.

it doesn't seem complicated at first.

it's just a matter of not eating and then eating again, right?

well, not quite.

if you want to continue and support the good work your body has done while in a fasted state, it's important to choose your next meal carefully.

your goals for fasting directly influence this choice.

if you'd like to work on your gut microbiome, choose foods that are some combination of probiotic-rich, prebiotic or polyphenol.

probiotic-rich foods add bacteria – the good kind – to your gut.

prebiotic foods feed those bacteria.

and polyphenol foods help prepare your gut's mucosal lining, which is key to eliminating leaky gut symptoms.

these are foods like fermented yogurt – non-dairy versions like coconut yogurt work too – kombucha and all sorts of seeds and seed oils.

if your goal is to build muscle, break your fast with protein-rich foods.

great choices are eggs, sausage, beef jerky and chicken for meat eaters, or broccoli, mushrooms, chickpeas, avocado and plant-based protein shakes for vegans.

when you're fasting to try and burn fat, the best food to break your fast with is – perhaps counter-intuitively – some type of fat.

why?

good fat actually helps stabilise blood sugar and usually doesn't pull people out of the fasted state, so the body continues to burn body fat.

technically, eating fat after fasting doesn't break your fast – it helps you fast a little longer.

good fat sources include avocados, bone broth, any type of nut or nut butter, and olives.

we've just finished our chapter to fast like a girl by dr mindy peltz.

here's the key takeaway.

fasting isn't a one-size-fits-all plan, but it can fit any lifestyle.

ultimately, understanding how fasting affects your body and interacts with your hormone levels gives you a springboard for tailoring a schedule and food plan that works for you.

as you begin fasting, remember to talk with your primary physician and listen to your body.

everyone is unique, so something that works for your best friend might not work for you.

that's totally okay.

be open to experimenting and be gentle with yourself.

if you've got a big vacation planned, maybe don't start your 30-day reset that month.

or if you enjoy a wonderful holiday meal with your family, don't beat yourself up.

just get back into your fasting lifestyle the next day.

remember it might take some time, but you will see results.

after all, our bodies are built for this.

thanks so much for listening.

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see you in the next chapter.