15: Fasting in Perimenopause: When to Try It (And When to Skip It)

Introduction

You’ve heard about intermittent fasting. Maybe you’ve tried it. Maybe your friend swears by it. Maybe you’re wondering if skipping breakfast will finally shift those stubborn pounds or give you the energy boost that everyone is talking about. Today, I’m going to help you figure out if fasting belongs to your perimenopause toolkit and what to do if it doesn’t.

Quick note before we dive in: if you have a history of disordered eating, this episode may not be for you.

The Perimenopause Matrix Framework

Let’s talk about fasting through the lens of my Perimenopause Matrix framework. For those new here, the Matrix has six pillars: Fuel, Move, Recharge, Regulate, Connect, and Clean. Today we’re focusing on where fasting fits—or doesn’t fit—in your FUEL strategy and how it impacts your REGULATE and RECHARGE pillars. Because here’s the thing: in perimenopause, nothing happens in isolation.

My Fasting Journey: Lessons in Stress Cups & Timing

Let me start with my own journey because it taught me everything about the stress cup and timing.

Before entering grad school, fasting was all the rage. So obviously I played around with it. My first bout was intermittent fasting—I ate between 11 a.m. and 6 p.m. I felt absolutely amazing for a while and then crashed hard. I didn’t do any testing at the time, but knowing my body and how I felt, I think I really, really messed up my hormones.

Here’s what I didn’t understand then that I understand now: I was working out six days a week—HIIT training, power yoga, group classes. I was going through a challenging time in my marriage. I had just started grad school. I was an insomniac. My stress cup was overflowing. And I added fasting on top of all of that.

Looking back through my Perimenopause Matrix framework, I was ignoring my REGULATE pillar completely. My body interpreted fasting as one more emergency, not as a helpful tool.

My second bout of fasting was a water fast and I ended it with a sausage. Terrible idea. And my GI tract was not happy about that—fatty solid food after 24 hours of nothing.

Today I generally eat from around 7:30 in the morning until about 6 p.m. at night. This works for me and my body and feels good. Why? Because my FUEL strategy now prioritizes my RECHARGE pillar. I eat to support my circadian rhythm and sleep, which matters more to me right now than the potential benefit of a restricted eating window. That’s a choice that I’ve made based on where I am in my life and what my body is telling me.

What Is Fasting?

So what actually is fasting? There’s no standard definition, but generally it describes restricting food in some way.

The most common type that you’ll hear about is intermittent fasting—a time-restricted eating window like 10 a.m. to 5 p.m. Many religions use intermittent fasting as part of their yearly rituals. There are also extended water fasts lasting one to several days and fasting-mimicking diets developed by Valter Longo that involve very low caloric intake over several days.

But here’s what matters: Why are you interested in fasting? Let’s figure that out.

Why Do People Fast? The Weight Loss Question

Most people come to fasting for weight loss, but here’s what matters more in perimenopause: Are you losing fat or muscle?

Weight loss is the first thing that comes to mind—this is where we need to get specific. When someone says “weight loss,” what they actually mean or should mean is fat loss. You do NOT, especially in perimenopause, want to be losing muscle. Your muscle is your metabolic engine. It’s your glucose management pro. It is your longevity bestie. In my Perimenopause Matrix, muscle preservation is critical to both your MOVE and FUEL pillars.

It takes months to put on a pound of muscle. Trust me, I have tracked, I have tried, it is work. It is not worth the trade-off to lose it.

The Muscle Loss Problem

Here’s the reality: Extended fasting leads to half to two-thirds of weight loss being lean mass. That’s much, much higher than caloric restriction through GLP-1 usage or bariatric surgery, which causes about a third of the weight loss to be lean mass.

Why does this matter? Because those interventions aren’t magic. The main mechanism is forced caloric restriction, but extended fasting creates even more muscle loss than those approaches. So if you’re fasting for weight loss, keeping your protein steady is really important. And doing this with a resistance training routine is essential to maintaining muscle mass.

The problem with fasting for weight loss? Most people regain the weight after they resume their old dietary pattern.

Fasting for Weight Maintenance

Now some people use fasting differently—as a way to maintain weight, not lose it. It’s easier for many people to stick to an eating window rather than counting calories. This can be a great long-term tool, but it’s a lifestyle change. So slow and steady here, my friends.

You can start by walking your eating window back by 30 minutes and seeing how that feels. You don’t want to go from a 16-hour eating window to an 8-hour eating window overnight.

The Circadian Rhythm Connection

Here’s something important: A 10 to 12-hour overnight fast tends to be optimal for overall health. Think of this less as a fasting tool and more as a circadian rhythm tool. As in, your organs need time to do their business. If you’re always eating, they don’t get a break. Sleep plus a few hours gives them time to clean house.

Dr. Satchin Panda’s research shows that adhering to a 10-hour eating window can improve sleep, promote weight loss, and decrease BMI as well as abdominal fat in people with metabolic syndrome. His myCircadianClock app research has also shown improvements in insulin resistance. This is where your FUEL and RECHARGE pillars intersect beautifully.

Beyond Weight Loss: Other Fasting Benefits

Autophagy & Exercise

Some people are interested in fasting for autophagy—that cellular cleanup process where cells degrade and are recycled. Fasting does help create conditions for autophagy, which is important for reducing chronic disease and increasing lifespan.

But here’s what you need to know: You don’t need to fast to trigger autophagy. Exercise is a powerful autophagy trigger. And yes, exercise is a stressor on your body. But if you’re already working out, you’re already getting those benefits without adding fasting as a stressor on top.

If we have to pick one tool for longevity, exercise wins every single time. It’s the best longevity drug available, hands down. Much better bang for your buck than fasting. So before you add fasting, optimize your MOVE pillar first.

Inflammation, Ketosis & Long-Term Questions

Fasting can also help decrease inflammation and if long enough, put you in ketosis when your body starts using fat as its primary fuel source for the brain and the heart. Fasting also increases fat breakdown and metabolic changes that are supportive of longevity.

But—and this is important—right now we have a lot of research on short-term benefits of fasting but not long-term. Do the benefits remain after you start eating again? We don’t really know yet, especially for chronic disease prevention. Just a reminder: mice and humans are very different.

What I See in My Practice: The Stress Cup Reality

Okay, let me tell you what I see in my practice because this is where theory meets reality. I work with women using the Perimenopause Matrix and here’s where fasting usually shows up: in an already overflowing stress cup.

Fasting can be a really wonderful tool, but it is not for everyone. I don’t think it’s fair to make blanket statements because I’ve seen a range of reactions. There’s a lot of nuance here and it’s important to remember that YOU are the only expert in your body. No one else is.

A doctor, a trainer, a nutritionist can only provide data from trials and clinical experience. That’s not the same as YOUR experience in YOUR body.

My Self-Selected Bias

Here’s my self-selected bias: My clients aren’t coming to see me because they feel amazing. They’re coming because they don’t feel amazing and want help getting to the bottom of their symptoms. I have met plenty of women who love and thrive with fasting, but they’re typically not my clients.

Fasting as a Stressor

So with that in mind: Fasting is a stressor on the body, just like exercise. It can be a really, really good stressor, but depending on the person and how their body responds, it can also be a negative stressor.

Historically, no food means famine. Your body can interpret fasting as an emergency and not respond in the most positive way.

Assessing Your Stress Cup

Think about your stress cup. What is going in there?

• Is your job crazy stressful right now?
• Do you have littles at home?
• Are you caring for aging parents?
• Do you have strained family relationships?
• Are you managing a chronic condition?
• Do you have insomnia?
• Is your bandwidth limited?

These are all things that decrease the size of your stress cup, so it takes less for it to overflow. Fasting can be the thing that tips it over. This is your REGULATE pillar sending you a message.

The Perimenopause Factor

It’s also important to remember: When you’re in perimenopause, your hormones are fluctuating and not just what you think of as reproductive hormones. Your insulin and melatonin are also affected. Your body is not removing fat at the same rate as it did before your hormones started stepping down. There are changes in your response to metabolic signals. Your mitochondria—those little energy factories in the cells—don’t regenerate as well, and your insulin signaling is impaired.

All of that to say: There is a lot going on physiologically. And your body may not love adding fasting stress to the mix.

If the stress cup concept is clicking for you, it’s probably clicking for a friend too. Please take 10 seconds right now and text this episode to someone who’s also navigating this wild perimenopause ride. She’ll thank you, I promise.

Why Most Fasting Research Doesn’t Apply to You

Here’s why most fasting research doesn’t apply to you: It’s done on men or in mixed groups that don’t separate women-specific data or in post-menopausal women. Your cycling hormones change everything.

One of the things that makes research on fasting and perimenopausal women scarce is our hormonal cycle. It requires more effort to work with a hormonal cycle. And women on birth control don’t respond the same way as women who are not on birth control. Dr. Sarah Hill calls this out in her book This is Your Brain on Birth Control.

So remember: You are not a small man. Thank you, Stacy Sims, for that reminder.

The Monthly Energy Shift

Here’s what matters: Women create a brand new endometrium every single month to line the uterus. It’s labor and resource intensive. Men create sperm continuously, but they don’t have a process to generate and shed tissue every month.

During your luteal phase—when the endometrial lining is thickening—there’s between an 8 and 16% increase in your 24-hour energy expenditure. That is a pretty big difference when it comes to energy balance. This is why women need between 150 to 200 more calories during their luteal phase.

Hello cravings—your body is smart and knows what it needs.

Individual Variation

So why the physiology lesson? Because your body is not the same as a male body. Some women don’t experience much difference in their mood and energy during their cycle, but some women do. Some women have a significantly different experience during the second half of their cycle and require more food, sleep, and rest.

If you’re going to experiment with fasting, your follicular phase—roughly the first 14 days of your cycle—is when you’re more insulin sensitive and less likely to be affected by lower caloric intake.

The Decision Framework: Is Fasting Right for You?

Okay, so fasting—is it right for you? Let’s figure this out together.

Based on the data right now: There’s no proven long-term risk reduction for chronic disease from fasting. Fasting does not create more benefits than caloric restriction for fat loss and muscle preservation over the short term. So if you want to use fasting as a way to restrict calories, it can be a very useful tool, but it’s not magic.

Three Questions to Answer Honestly

Here’s how to know if fasting fits your perimenopause. I want you to answer these three questions honestly:

Question 1: How full is your stress cup right now?

Think about: demanding job, caregiving responsibilities, relationship strain, chronic health conditions, sleep issues, and limited bandwidth.

Question 2: Where are you in your body composition journey?

Do you have adequate muscle mass? Excess fat you want to address? Or are you already lean with minimal muscle to spare?

Question 3: What are you actually trying to achieve with fasting?

Be honest—is it weight loss, convenience, autophagy, because you’ve heard it’s good for you?

Your Decision Tree

Now here’s your decision tree:

IF your stress cup is overflowing: Fasting is not your tool right now. Focus on your REGULATE pillar first. Manage the stressors you can manage before adding another one.

IF you have minimal muscle mass: Don’t fast. Instead, focus on your FUEL pillar to increase protein intake and your MOVE pillar to build your metabolic engine through resistance training.

IF you want autophagy or anti-inflammatory benefits: Exercise first. Optimize your MOVE pillar. It’s a powerful trigger that doesn’t require caloric restriction.

IF you have solid muscle mass and you want to experiment: Try fasting in your follicular phase if you’re still cycling. Start by adjusting your eating window by 30-minute increments. Track your energy, your sleep, your mood in a journal so you actually know if you’re getting benefits. And please work with a practitioner who understands the Perimenopause Matrix and knows how to support fasting—not just your average online influencer.

IF you have a history of disordered eating: I strongly encourage you not to use fasting as a tool.

IF your goal is improved body composition—more muscle mass: Extended fasting is not the best route.

You’re the Boss of Your Body

At the end of the day, your body is your body and you are the boss. If you want to experiment with fasting, you should. Just pay attention to what your body is telling you.

Closing

Everything I talked about today—the stress cup, the six pillars, understanding why your body isn’t responding like it used to—this is all part of my Perimenopause Matrix framework. I created the Perimenopause Decoder specifically for busy perimenopausal women who want to understand what’s happening in their bodies without drowning in information.

Grab it in the show notes below.

Thanks for being here, my curious peri friend. I will see you next week.

Final Note

Can you do me a favor? If this was helpful, share it with one person who might need to hear it today. Our bodies didn’t come with a user manual and this perimenopause thing can feel confusing and lonely, but you’re not alone. You’re not crazy and you’re definitely not broken. And maybe someone in your life needs that reminder too. Let’s spread the word and be kind to each other and ourselves.

Now the legal bit: I’m a nutritionist, but I’m not your nutritionist. This podcast is for information and education only. No client relationship was formed. Always seek medical advice when necessary.

I’ll see you next Wednesday morning.