The Last Restart

Episode 7: What the heck perimenopause

EPISODE SUMMARY If you have ever left a doctor's appointment feeling dismissed, dramatic, or like you were told to just push through it — this episode is for you. Perimenopause is one of the most misunderstood and most under-supported transitions in a woman's life. In this episode we break down what is actually happening in your body, why so many women are not getting the care they need, what the research actually says about hormone therapy, and what you deserve to have access to. This is not about fear. It is about information, language, and empowerment. LISTEN IF... You have been told your labs are normal but you know something is off You are experiencing sleep disruption, mood changes, brain fog, joint pain, or unexplained weight gain You have never had a real conversation with a provider about perimenopause You want language and tools to advocate for yourself in a medical setting You are in your late 30s or 40s and want to get ahead of this transition BEFORE YOU LISTEN This episode is part of a connected arc. For the fullest picture, go back and listen to: Episode 5 — Hormones: estrogen, progesterone, cortisol, and insulin and how they govern your health after 35 Episode 6 — Metabolism: metabolic myths and how to fuel your body to support your hormones WHAT WE COVER What Perimenopause Actually Is Perimenopause is not a moment — it is a transition that can last anywhere from two to ten years. It begins as early as the mid-30s and is characterized by erratic, fluctuating hormones rather than a simple linear decline. Understanding this distinction changes how you experience and interpret your symptoms. The Hormonal Mechanics Progesterone tends to decline first — this is why wired-but-tired, anxious, and sleepless can show up before your cycle is even irregular Estrogen fluctuates — it spikes and crashes unpredictably, which is what drives the chaotic, erratic symptom experience many women describe Because estrogen influences the brain, bones, cardiovascular system, sleep, mood, metabolism, gut, and skin — you feel the fluctuation everywhere Why FSH Is Not the Gold Standard FSH (follicle stimulating hormone) is the most commonly used diagnostic marker for perimenopause — but it fluctuates just like everything else You can have a normal FSH and be fully in perimenopause. You can have an elevated FSH one month and a normal one the next The North American Menopause Society is clear: perimenopause is primarily a clinical diagnosis based on symptoms, history, and cycle changes — not a single lab value If you were told you're fine because your FSH was normal, that may be an incomplete picture The Stages of Perimenopause (STRAW) Early perimenopause: cycle length changes by 7 or more days Late perimenopause: cycles of 60 days or more Menopause: 12 consecutive months without a period Postmenopause: everything after Note: women on hormonal birth control may have difficulty staging perimenopause, as it can mask cycle irregularity. This is not a reason to stop birth control — it is just a variable worth knowing about. The Symptoms That Get Dismissed — and What They Actually Mean Sleep disruption: declining progesterone reduces GABA activity, changing sleep architecture. Waking between 2–4am is common. Night sweats compound this. This is hormones, not just stress or aging. Mood changes and anxiety: estrogen directly influences serotonin, dopamine, and GABA. Erratic estrogen = erratic mood regulation. The perimenopausal window is a documented period of heightened depression risk. Being prescribed an antidepressant without a hormonal conversation may be an incomplete treatment plan. Brain fog: estrogen has neuroprotective properties and supports the prefrontal cortex — working memory and decision-making. Cognitive changes during perimenopause are real, measurable, and largely temporary. Women with ADHD may also notice their symptoms intensify during this time. Abdominal weight gain: estrogen shifts fat distribution centrally. Combined with elevated cortisol and declining muscle mass, this is endocrinology — not willpower or discipline. Joint pain and stiffness: estrogen has anti-inflammatory properties and supports synovial fluid (joint lubrication). When it drops or fluctuates, joint pain in the hands, knees, and hips is common. This is almost never connected to hormones in a standard doctor's visit. The cascade: poor sleep elevates cortisol → cortisol disrupts insulin → insulin affects energy and metabolism → poor energy affects mood → mood affects motivation → motivation affects movement → movement affects everything. This is the perimenopausal cascade, and it is why early, proper support matters. HRT and Bioidentical Hormones Hormone replacement therapy can be life-changing for some women — and the decision is nuanced and personal. A few things worth knowing: There are real risks and real benefits to HRT. Understanding your individual risk-benefit profile requires a thorough conversation with a provider who is willing to have it. Not all hormone therapy is the same. Bioidentical hormones (chemically identical to what your body produces), synthetic progestins, oral versus transdermal delivery, and compounded versus FDA-approved formulations all carry different profiles. The conversation to ask for: "I am experiencing symptoms consistent with perimenopause. I'd like to discuss whether hormone therapy is appropriate for me, what formulations you'd recommend, and what the risk-benefit picture looks like given my health history." Be cautious of peptides and protocols promoted by social media influencers without clinical oversight. Medical Gaslighting — Why It Happens and What It Costs Being told to "just deal with it" when describing real physiological symptoms is gaslighting. It happens for a few interconnected reasons: Historical: women's health research was conducted primarily on male subjects for decades. Many providers lack a confident, current framework for perimenopause. Systemic: a 15–20 minute primary care visit cannot do justice to a complex hormonal history. Cultural: women in midlife are still taught — explicitly and implicitly — that their symptoms are less credible, that they might be emotional or dramatic. This is gender bias embedded in medicine. The cost of undertreated perimenopause is not just discomfort. Chronic sleep deprivation increases cardiovascular risk. Bone density loss compounds into osteoporosis. Mood dysregulation affects relationships, careers, and quality of life. This is what the cascade looks like over years. What You Actually Need Not minimization. Not catastrophizing. Support. Specifically: Real, current, science-based information — not dismissal, not an antidepressant as a first resort, not "just toughen up" A provider who sees you as a whole person. You are allowed to find someone new. You are allowed to bring questions. You are allowed to say you are not done talking. Lifestyle fundamentals that support your hormones: strength training, protein, nervous system regulation, sleep. These are not a replacement for medical support when medical support is warranted — they work alongside it. Community. Women who are in this with you. The isolation of feeling like something is wrong with you — when something is just shifting — is one of the heaviest parts of this transition. Permission to take care of yourself now. Not after you feel rested. Not after the fog lifts. Now.

Episode 5: Your hormones don't need perfection

Episode Overview If you've ever been told your hormones are 'out of whack' — or spent serious money chasing a fix that left you more depleted than before — this episode is your reality check. Natalie cuts through the noise, the grift, and the pseudoscience to deliver the honest conversation about hormonal health that most of the wellness industry doesn't want you to have. The truth? Your hormones aren't broken. They're feedback. And once you understand what they're actually responding to, everything changes. In this episode, Natalie breaks down the four key hormones every woman over 35 needs to understand — estrogen, progesterone, cortisol, and insulin — and makes the case that hormonal balance isn't about a perfect morning routine or a $90 supplement stack. It's about consistency, recovery, and the three free things your body is asking for most. What You'll Learn in This Episode Why 'hormonal imbalance' is a description, not a diagnosis — and what it actually means How estrogen, progesterone, cortisol, and insulin are being impacted by your daily inputs Why perimenopause feels so chaotic (and why it's not your fault) The real reason the 'eat less, move more' approach backfires for chronically stressed women What 'hormonal balance' actually looks like in a real woman's real life The Holy Trinity for hormonal health: sleep, stress, and muscle mass Six small, sustainable shifts that move the needle — starting today A tiered action plan so you know exactly where to begin Key Takeaways Hormones Are Communicators, Not Malfunctions Hormones don't break. They respond. To your sleep, your stress load, your nutrition, your movement, your inflammation, and your history of dieting. When something feels off hormonally, the right question isn't 'how do I fix this?' It's 'what is my body responding to?' That single reframe shifts you from chasing a product to actually working with your body. The Perimenopause Window Is Real — And Underserved Perimenopause is not just a trend and it's not all in your head. Estrogen doesn't decline steadily — it fluctuates wildly, which is why it can feel like a hormonal rollercoaster with no warning. Add to that declining progesterone, rising cortisol sensitivity, and shifting insulin response, and you have a perfect storm that too many practitioners dismiss and too many grifters exploit. The Four Hormones That Matter Most Estrogen: A full-body hormone — not just reproductive. Supports bone density, cardiovascular health, mood, sleep, metabolism, and insulin sensitivity. Wants consistency in sleep, nutrition, and strength training. Progesterone: Your calming, sleep-supporting, anti-anxiety hormone. Often the first to drop in perimenopause. Highly sensitive to chronic stress — when cortisol is constantly elevated, progesterone takes a hit. Cortisol: Not the villain. In short bursts, it's essential. The problem is chronic elevation with no genuine recovery. Adds fat storage (especially midsection), suppresses progesterone, disrupts sleep, and breaks down muscle. Exercise alone won't fix it — you can't bully your physiology. Insulin: Your blood sugar management hormone. Disrupted by poor sleep, chronic stress, sedentary behavior, and low muscle mass. The fix isn't keto — it's muscle, quality sleep, balanced meals, and movement that isn't only chronic cardio. The 'Wellness Industry' Version of Balance Is a Full-Time Job 5 a.m. wake-ups, lemon water rituals, adaptogens, green smoothies, fasted workouts, in bed by 9 p.m. — that's not balance. That's a privilege available to almost no one. Real hormonal balance is your body's ability to regulate and recover — to handle stress without being destroyed by it, to eat well most of the time without obsessing, and to move between activation and rest. You don't need perfect. You need consistent. Chronic Inconsistency Is Harder on Your Hormones Than Occasional Imperfection Your body thrives on regular, predictable inputs — even imperfect ones. Two solid weeks of a perfect protocol followed by a complete crash is harder on your hormonal system than consistently showing up imperfectly. Stop optimizing for perfection. Start optimizing for sustainability. The Holy Trinity: Sleep, Stress, Muscle Mass Sleep is the single most powerful free hormonal intervention available to you. Growth hormone peaks, cortisol drops, insulin sensitivity resets, and progesterone and leptin do their jobs. One poor night disrupts everything. Chronic poor sleep creates a hormonal cascade that no supplement can compensate for. Stress regulation is not about eliminating stress — it's about building your nervous system's capacity to activate and then genuinely recover. Not doom-scroll recovery. Actual physiological down regulation: slow exhale breathing, hobbies without guilt, nature, physical touch, light movement, doing less. Muscle mass is the most underrated hormonal asset you have. It improves insulin sensitivity, supports estrogen metabolism, boosts growth hormone, reduces inflammation, protects bone density, and improves cortisol clearance. You will not bulk up by accident. Women over 35 — and into their 40s, 50s, 60s, and beyond — can absolutely build meaningful muscle with the right stimulus and adequate protein. Your Homework: Pick Your Tier and Start There Tier 1 — Start Here For five days this week, wake up within the same 30-minute window. That's it. No dietary changes, no new workouts. Just anchor your wake time and notice what happens to your energy and mood by the end of the week. Tier 2 — Build On It Add protein to your first meal (aim for 20–30 grams) and take a 10-minute walk after eating. Do this for five days and check in with your energy, hunger, and mood — not the scale. Tier 3 — Full Integration Add a consistent wind-down routine starting at least 30 minutes before sleep — no screens, something quiet, paired with your wake time anchor, protein at breakfast, and post-meal walks. If you're not already doing it, add one structured strength training session per week and build from there. Give it four weeks before adding more. The Six Sustainable Shifts Anchor your wake time (within 30 minutes, yes, even weekends) — it stabilizes your cortisol morning peak and sets your hormonal rhythm for the day. Lead with protein at your first meal — 20–30 grams blunts the blood sugar spike from a carb-forward breakfast and regulates hunger and cravings all day. Walk after meals — 5 to 15 minutes within 30–60 minutes of eating uses muscle contractions to clear blood glucose without additional insulin. Free, well-researched, highly effective. Train for strength 2–3x per week — not cardio, not HIIT. Progressive resistance training with enough load to challenge your muscles. Start with one day if you're at zero. Create a hard stop in your evening — pick a time and let that signal to your nervous system that threats are done. Screens off, work closed. Consistency matters more than the ritual. Stop treating rest as a reward — schedule rest the same way you schedule workouts and appointments. A chronically under-recovered body is a hormonally dysregulated body. Referenced Episodes Episode 4 — Lift Heavy Sh*t: Why strength training and muscle mass are non-negotiables for women over 35 Episode 3 — Nutrition and metabolic adaptation (protein, carbohydrates, and fueling for your body's needs) Previous episodes — Nervous system regulation as the foundation for everything

Episode 4: Lift Heavy Sh*t: The nervous system approach to strength training for women over 35

Episode Overview You've heard it. Lift heavy. Lift heavy. Lift heavy. But nobody's telling you what that actually means for your body, your nervous system, and your real life. In this episode, Natalie Guevara breaks down why strength training is non-negotiable for women over 35 — and why the way most women have been told to train is either leaving them stuck, injured, or burned out. This isn't a lecture about getting to the gym. It's a complete reframe of what intelligent, sustainable, results-driven training actually looks like when your nervous system is part of the equation. Expect science, expect nuance, expect Natalie to call out the fitness industry's most profitable lies. What You'll Learn in This Episode Why cardio alone will never get you the results you're chasing — and what actually will The truth about the word "toned" and why it's keeping women weak and underfueled What "lifting heavy" actually means (hint: it's relative, and it doesn't mean a barbell) How chronic cardio spikes cortisol and tanks your hormones, metabolism, and sleep The LIT Method's four-day wave: a nervous system-led approach to progressive overload Why muscle loss starts in your 30s and how to fight back before perimenopause accelerates it What EPOC is and why strength training burns fat long after your workout ends How lifting protects your bones, reduces chronic pain, and builds real-life capability The difference between challenging your body and destroying it — and how to find that line What to look for in a strength training program and why personalization beats perfection Key Takeaways The Case for Muscle Starting in your 30s, you lose 3–8% of your muscle mass per decade. Muscle is metabolically active tissue — it burns calories at rest, supports joint health, regulates blood sugar, and is your best defense against osteoporosis and falls as you age. It is not optional. It is the foundation. Cardio Isn't the Enemy — It's Just Not the Answer Cardio is essential for cardiovascular health, and most women aren't doing enough of it. The problem is too much chronic or high-intensity cardio spikes cortisol, disrupts hormones, doesn't build muscle, and doesn't protect bone density. The goal isn't to cut cardio — it's to stop treating it like the primary driver of fat loss and body composition change. That's strength training's job. "Toned" Is Just Muscle With Low Enough Body Fat to See It You cannot tone a muscle. You either build it or you don't. Those light weights and 20-rep sets aren't toning anything — they're frying your nervous system and creating injury risk without building the tissue you actually want. To look lean and defined, you have to build muscle. And to build muscle, you have to eat enough to support it. Heavy Is Relative "Lift heavy" doesn't mean sling a barbell. It means lift relative to your capacity with progressive overload over time. Natalie was humbled by a 5-pound steel mace after years of lifting 25–35 pound dumbbells. Heavy means challenging enough that reps 8–9 feel hard. It means your form stays intact but you couldn't go all day. It means you feel the work — not wrecked by it. The LIT Method Four-Day Wave Natalie's nervous system-led training approach uses a four-day intensity wave: Day 1: No to low intensity — stability, mobility, breath pacing, core reeducation Day 2: Low to moderate intensity — loading the body while maintaining breath pace Day 3: Moderate to high intensity — increasing challenge and load progressively Day 4: High intensity immediately followed by intentional downregulation This structure allows you to meet your body where it is, warm the nervous system appropriately, and push hard without burning out. It also builds the nervous system's capacity for stress regulation — which carries directly into daily life. What Strength Training Actually Does for You Builds muscle, raises metabolism, improves body composition Increases insulin sensitivity and regulates blood sugar — a major driver of hormonal chaos after 35 Supports healthy testosterone levels: critical for energy, libido, mood, and heart health Creates EPOC (excess post-exercise oxygen consumption) — elevated calorie burn for up to 48 hours post-workout Protects and builds bone density — your best defense against osteoporosis Reduces chronic pain by building stability and strengthening connective tissue around joints Improves mental health, confidence, and body image in ways cardio simply cannot replicate Progressive Overload: The Non-Negotiable If your body isn't being progressively challenged, it has no reason to change. That doesn't mean adding weight every week — it means intentional, incremental progression through weight, reps, sets, form, or exercise variation over time. If you've used the same 10-pound dumbbells for six months and it still feels easy, something needs to change. Recovery Is Where You Actually Build You don't build muscle during your workout. You build it during recovery. That means eating enough — especially protein. Sleeping enough. Taking rest days. Managing stress. If you're already depleted and you're pushing hard without recovering, you're not building anything. You're just breaking yourself down. Your Homework This Episode Start moving — and match your movement to your breath. If you have resistance to training or strength work feels like a distant concept right now, start with what Natalie calls movement snacks: small, intentional moments of movement throughout your day paired with conscious breath. Squat to sit down at your desk — inhale on the way down, exhale on the way up. Pay attention to how your body moves through space. From there: If you're brand new or returning after a break: start with bodyweight, breath, and core two days a week. Consistency over intensity. If you've been training but spinning your wheels: look honestly at your programming. Are you progressively overloading? Are you recovering? Are you actually eating enough to build? If you've been avoiding the gym out of fear or intimidation: you don't need it. A yoga mat, a couple of dumbbells, and your living room is enough to start. Pick a solid program from someone you trust and stick with it long enough to see results. Stop program hopping. The magic is in the consistency. About The Last Restart The Last Restart with Natalie Guevara is the podcast for women over 35 who are done with the cycle of starting over. Every episode delivers no-nonsense, evidence-based guidance across four pillars: nervous system regulation, your relationship with food, body image, and strength training. Because feeling lean, strong, hormonally balanced, and pain-free isn't about doing more — it's about doing it smarter. New episodes drop weekly. Subscribe, share, and leave a review if this one landed. Find Natalie on Instagram: @NatalieBrookeGuevara

Episode 1: Why You Keep Starting Over

If you’ve ever felt stuck in the cycle of starting a new meal plan, pushing hard for a few weeks… then quitting when life gets overwhelming — this episode is for you. In this foundational episode, Natalie introduces the core philosophy behind her LIT Method™ (Lean. Intentional. Thriving.) and explains why nervous system regulation — not more discipline — is the missing piece in midlife fat loss and sustainable health. If you’re tired of restarting every Monday, every January, or every time summer approaches… keep listening. In This Episode, You’ll Learn: Why willpower and discipline aren’t the real problem What nervous system regulation actually means (and what it doesn’t) The difference between fight-or-flight and rest-and-digest Why chronic stress makes fat loss harder after 35 How survival mode sabotages your nutrition, workouts, sleep, and consistency Why restrictive meal plans feel like “another bear” to your brain How resilience is built (and why it matters for hormone health) The 4 pillars Natalie uses inside her LIT Method™: Nervous System First Food Strength Hormones The LIT Loop: Locate → Integrate → Transform Why Midlife Fat Loss Feels So Hard If you’re over 35 and wondering why: The same diet that worked in your 20s doesn’t work anymore You lose 5 pounds… then plateau Your sleep is worse Your anxiety is higher Your bloating won’t go away You keep quitting programs that “should” work It’s not because your metabolism is broken. It’s because your nervous system is running the show. When you’re living in chronic fight-or-flight mode — from work stress, parenting, overstimulation, social media, expectations, and hormones — your brain prioritizes survival over fat loss. And when your body doesn’t feel safe? It holds on. What Nervous System Regulation Really Means Regulation isn’t about being calm all the time. It’s the ability to move from: Fight or flight (sympathetic nervous system) into Rest and digest (parasympathetic nervous system) It’s about building the capacity to recover from stress — faster. Without this skill: Meal plans feel overwhelming Workouts feel like punishment Meditation apps collect dust You spiral at 3am You restart over and over again With regulation: You build resilience You increase emotional capacity You create safety in your body You can finally follow through consistently Who This Podcast Is For This show is for: High-achieving midlife women Moms juggling career and family Women navigating perimenopause Women with autoimmune conditions like Hashimoto’s or PCOS Women who are exhausted from dieting Women who want to lose fat but refuse to wreck their nervous system doing it If you want to feel strong, lean, intentional, and thriving — without living in survival mode — you’re in the right place. About Natalie Guevara Natalie Guevara has been in the health and wellness industry since 2009. She is a functional nutritionist, strength coach, yoga teacher, and behavior change specialist. She has worked in: Weight loss clinics University fitness programs Personal training gyms Yoga teacher trainings Trauma-informed somatic movement spaces She specializes in nervous-system-led fat loss, hormone health, and sustainable strength training for midlife women. Natalie is also a mother of four, including toddlers and teens, and brings both lived experience and evidence-based coaching into every conversation. What’s Coming Next In Episode 2, Natalie continues the conversation by breaking down: How your nervous system is running the show in ways you don’t even realize — and how to start locating the patterns that keep you stuck. Because awareness is the first step toward transformation. Keywords & Topics Covered Nervous system regulation for women Midlife fat loss Perimenopause weight gain Stress and weight loss Hormone balance for women over 35 Behavior change psychology Sustainable health habits Autoimmune and metabolism PCOS and weight loss Resilience and trauma-informed fitness Why diets don’t work long term If this episode resonated with you, be sure to subscribe, leave a review, and share it with a friend who’s tired of starting over.

Episode 2: Your Nervous System Is Running the Show (And You Didn’t Know It)

Welcome back to The Last Restart, the podcast for women over 35 who are done with the diet cycle, hormone chaos, and feeling disconnected from their bodies. In Episode 2, Natalie Guevara gets “nerdy” (in the fun way) and breaks down how your nervous system acts like the motherboard of your body—quietly influencing your cravings, stress eating, sleep, digestion, hormones, and even why fat loss feels impossible no matter how “good” you’re being. If you’ve tried meal prepping, lifting, supplements, tracking, and “being disciplined”… and it still doesn’t stick, this episode will feel like someone finally turned the lights on. In This Episode, You’ll Learn Why you can’t out-diet, out-exercise, or out-supplement a dysregulated nervous system How your nervous system confuses “real danger” with modern stress (emails, traffic, Instagram, tantrums) The difference between fight-or-flight (sympathetic) and rest-and-digest (parasympathetic) What chronic stress does to your body: cortisol, blood sugar, digestion, sleep, hormones, and belly fat storage The real-life signs of nervous system dysregulation (physical, emotional, behavioral) Why dieting + over-exercising can make cortisol and stress responses worse A simple, realistic nervous system tool you can use anywhere: box breathing How to start building awareness using Natalie’s LIT framework: Locate → Integrate → Transform The Big Idea: Your Nervous System Is the Foundation Natalie makes it plain: Your workouts, meal plan, supplements, and motivation are not the “base layer.” Your nervous system is. When your body is stuck in fight-or-flight, it’s not prioritizing: fat loss digestion hormone balance recovery sleep calm decision-making It’s prioritizing survival. And that’s why you can be doing “all the right things” and still feel like: your energy is unpredictable your cravings are intense your sleep is trash your belly won’t budge your digestion is a mess you’re snapping at everyone you love That’s not laziness. That’s biology. What Chronic Dysregulation Looks Like (Do You Relate?) Natalie paints a painfully accurate picture of modern fight-or-flight: Waking up exhausted even after 7–8 hours Needing coffee immediately to feel human Afternoon crashes + intense sugar/carby cravings Feeling wired at night but dragging all day Bloating, constipation, IBS-like symptoms Irritability, overwhelm, and “small things” feeling huge Holding weight around your midsection despite “being good” Period changes that make you wonder if it’s perimenopause (or something else) If you’re nodding along, you’re not broken. Your nervous system is doing what it was designed to do—protect you—it just doesn’t know that your stressors aren’t life-threatening. Cortisol Isn’t the Villain (But Chronic Stress Is) This episode also clears up one of the biggest Instagram myths: “cortisol is the problem.” Natalie explains: Cortisol is essential (it wakes you up, regulates inflammation, helps you respond to stress) The issue is cortisol being elevated all the time Chronic cortisol can contribute to: belly fat storage disrupted sleep worsened digestion cravings for quick energy (sugar) hormone disruption (thyroid, estrogen/progesterone, testosterone) And here’s the kicker: Dieting and overtraining can increase stress signals too. So the harder you push, the more your body braces. No wonder you feel like you’re losing your mind. Simple Practice: Box Breathing for Nervous System Regulation Natalie gives you a practical tool you can use in real life (without adding another “perfect routine” to your day): Box Breathing (2–3 minutes): Inhale 4 counts Hold 4 counts Exhale 4 counts Hold 4 counts Use it: right when you wake up before meals after school drop-off after traffic before bed in the shower whenever you feel activated Because intentional breathing tells your body: “I’m safe.” And safety is where digestion, sleep, and consistency live. What’s Coming Next In Episode 3, Natalie shifts into food and tackles a big one: Why eating less after 35 is some of the worst advice you’ve ever been given. (And what to do instead.) Connect with Natalie Instagram: @NatalieBrookeGuevara If this episode hit home, share it to your stories and tag Natalie—she wants to know what’s resonating. Keywords & Topics Covered nervous system regulation for women over 35 chronic stress and weight loss cortisol and belly fat fight or flight vs rest and digest perimenopause symptoms vs nervous system dysregulation stress eating and cravings hormone balance and nervous system digestion and anxiety box breathing technique sustainable fat loss after 35 behavior change and nervous system