Is Cortisol the Reason You Can’t Lose Fat While Training in Perimenopause?
If you are anything like me and have felt completely helpless around shifting your body weight as you hit midlife and still training, then you will enjoy this read, it wont make the stubborn fat disappear overnight but it might give you some food for thought!
For decades, the fitness industry has handed active women the same basic script: if you want to change your body, you need to eat less and move more. But as we enter midlife, this reliable formula often stops working. Active women frequently find themselves training harder than ever, cutting calories, and yet watching the scale creep up or their body composition shift in ways that feel entirely out of their control.
If this sounds familiar, you aren’t failing even though I know from experience that its exactly how it feels. Your physiology is navigating a profound hormonal shift. If you have read any of my other blogs you will have read those words before but truly, some days the ‘hormonal shift’ is the biggest understatement of them all. Recent longitudinal research reveals that the culprit behind this stubborn midlife plateau isn't a lack of willpower or meticulous tracking of macro’s, it is a complex intersection of estrogen withdrawal, elevated cortisol, and a physiological state known as Low Energy Availability (LEA) (Espinar et al., 2026; Liu et al., 2026). During midlife, erratic spikes and eventual drops in 17-beta-estradiol completely rewrite how your body handles fuel, stress, and recovery (Greendale et al., 2019; Liu et al., 2026).
Why Harder Workouts Stop Working in Midlife and can backfire
I really wish this wasn’t the case and that we could somehow magically train away all the issues that arise during midlife but I have come to learn and also slowly accept that this is in fact, not the truth. During the menopause transition, women undergo rapid and adverse changes in body composition that occur independently of chronological aging (Greendale et al., 2019). Data from the landmark Study of Women’s Health Across the Nation (SWAN), which tracked body composition in relation to the final menstrual period (FMP), revealed a stark reality: at the onset of the menopause transition, the rate of fat gain doubles (rising to an average increase of 1.7% per year), while lean muscle mass simultaneously begins to decline (Greendale et al., 2019). Yes, doubles….you are not imagining that.
This creates a massively frustrating physiological veil: because muscle loss and fat gain happen at the same time, a woman's overall body weight trajectory can appear as if it’s linear and steady (Greendale et al., 2019). However, under the hood so to speak, her metabolic engine is losing its most active tissue, muscle, all while rapidly accumulating fat (Greendale et al., 2019). I personally noticed this shift and often wondered where my waist had gone! It also felt like it happened overnight and felt impossible to stop or control.
When faced with this shift, the default response for most active women is to double down: they increase their training volume, add high-intensity workouts, and restrict their food intake. But this doing more strategy almost always backfires. Traditional calorie trackers and generic fitness advice were not built to handle a perimenopausal body (M Deats Wellness, 2026). Instead of burning fat, pushing your body harder while under-fueling signals extreme physiological danger, triggering chronic adaptations that shut down fat loss and accelerate muscle wasting (Espinar et al., 2026; Mountjoy et al., 2023).
Estrogen Withdrawal, HPA-Axis Reactivity, and the "Cortisol Trap"
To understand why hard training can stall fat loss in midlife, we have to look at the endocrine cascade of perimenopause. This transition is characterized by fluctuating and progressively declining levels of circulating estradiol (Liu et al., 2026). I liken it to a pinball machine. Beyond its role in reproduction, estradiol is a powerful regulator of metabolic homeostasis, brain health, mood and tolerance and inflammation (Liu et al., 2026). It literally controls or has a receptor on every cell in your entire body, which is why the changes are so cataclysmic.
Specifically, estradiol acts as a potent anti-inflammatory agent, actively inhibiting the transcription of proinflammatory cytokines like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) (Liu et al., 2026). As estradiol levels plunge, declining by an average of 34% over a 12-month period in perimenopausal women—systemic inflammation rises sharply (Liu et al., 2026). This decline in estrogen removes the body's natural buffer against physiological stress (Liu et al., 2026).
Without the protective shield of estradiol, the hypothalamic-pituitary-adrenal (HPA) axis—the command center for your body's stress response—becomes highly reactive (Liu et al., 2026; Mountjoy et al., 2023). When you overlay the physical stress of intense, uncompensated training onto this inflammatory environment, the HPA axis goes into overdrive. This creates the Cortisol Trap.
Persistently elevated cortisol is highly catabolic (meaning it breaks down muscle) (Espinar et al., 2026). It actively suppresses muscle protein synthesis , blocks tissue repair, and downregulates anabolic signaling or building muscle (Espinar et al., 2026). Instead of building a lean, metabolically active body, high cortisol levels tell your system to break down precious muscle tissue for fuel while fiercely holding onto visceral fat as a survival mechanism (Espinar et al., 2026; Mountjoy et al., 2023). And it clings on for dear life. This was a huge problem for me for a long time and truthfully speaking, how I was training for a large majority of my late 30’s leading up to the onset of perimenopause.
It’s Not the Exercise. It’s Low Energy Availability (LEA)
For years, sports scientists debated whether the hormonal disruptions seen in active women were caused by the physical stress of exercise itself. Clinical research has since solved this puzzle: it is not the exercise stress that disrupts your hormones; it is an energetic imbalance known as Low Energy Availability (LEA) (Espinar et al., 2026; Mountjoy et al., 2023).
Energy Availability (EA) is the amount of dietary energy left over for your body’s vital biological functions after subtracting the energy expended during exercise (Espinar et al., 2026). When your dietary intake is too low to cover both your workouts and basic metabolic needs (typically falling below a threshold of 30 kcal/kg of fat-free mass/day), your body enters LEA (Espinar et al., 2026; Mountjoy et al., 2023).
Energy Availability = (Energy Intake [kcal] - Exercise Energy Expenditure [kcal]) / Fat-Free Mass [kg]
Under LEA, your brain recognizes that energy is scarce. To ensure immediate survival, it downregulates non-essential biological systems, triggering a cascade of metabolic adaptations (Espinar et al., 2026; Mountjoy et al., 2023):
The thyroid axis is suppressed, significantly lowering circulating active triiodothyronine (T3) to slow down resting metabolic rate (Espinar et al., 2026; Mountjoy et al., 2023).
Leptin (the satiety and energy-sensing hormone) and insulin plunge, shifting your body away from building tissue and toward severe energy conservation (Espinar et al., 2026; Mountjoy et al., 2023).
Most importantly, moderate weight loss and caloric restriction in active women are associated with a significant increase in 24-hour cortisol levels, even when there is zero change in self-reported psychological stress (Ruffing et al., 2022, cited in Mountjoy et al., 2023).
In other words, you might feel perfectly relaxed, but if you are under-fueling your workouts, your body is experiencing severe internal stress, driving cortisol up and stalling your fat-loss goals.
4 Signs Your Training Is Triggering a Cortisol Spike
When your HPA axis is chronically stimulated by the combination of perimenopause and under-fueled training, your body will send clear distress signals (Espinar et al., 2026; Mountjoy et al., 2023). Recognizing these signs early is vital to avoiding long-term metabolic and performance decline:
You Are Losing Muscle and Strength Despite Lifting Weights Because elevated cortisol and low estrogen block muscle protein synthesis, your body struggles to repair fibers after a workout (Espinar et al., 2026). You may notice a loss of muscle definition, reduced neuromuscular power, and a lack of progress in the weight room (Espinar et al., 2026).
Your Sleep is Disrupted and You Feel "Wired but Tired" Chronic HPA-axis activation disrupts your natural diurnal cortisol rhythm. Elevated late-night cortisol makes it difficult to fall or stay asleep, leading to poor sleep quality and compounding daytime fatigue, mood changes, and irritability (Mountjoy et al., 2023).
Your Menstrual Cycle is Highly Irregular or Missing LEA directly suppresses reproductive hormones, leading to suppressed luteinizing hormone (LH) pulsatility and progesterone (Espinar et al., 2026; Mountjoy et al., 2023). This manifests as shortened cycles, luteal phase defects, or functional hypothalamic amenorrhea (FHA) (Espinar et al., 2026; Mountjoy et al., 2023). This started to happen to me when I started training more heavily.
Your Body Temperature and Metabolic Rate Have Slowed Down Sustained stress downregulates active thyroid hormones (T3), causing a drop in your resting metabolic rate (RMR ratio < 0.90) (Espinar et al., 2026; Mountjoy et al., 2023). If you constantly feel cold or have sluggish digestion, your metabolic engine has likely slowed down to conserve energy (Mountjoy et al., 2023).
How to Fuel, Recover, and Retain Lean Muscle in Perimenopause
Navigating perimenopause successfully requires shifting your mindset from restriction to restoration and eating enough, think abundance not famine. To retain your metabolic engine, your lean muscle mass, and lower cortisol, you must adjust your fueling and recovery strategy:
Prioritize Energy Availability: You must eat enough to match your physical demands (Espinar et al., 2026; Mountjoy et al., 2023). Reversing chronic deficits is the primary non-pharmacological way to lower cortisol, restore thyroid function, and allow your body to safely let go of stored fat (Espinar et al., 2026; Mountjoy et al., 2023). I have another blog on this here.
Never Restrict Carbohydrates While Training Hard: Carbohydrate availability plays an energy-independent role in endocrine health. Low carbohydrate availability (LCA) significantly magnifies the stress of training, doubling bone resorption markers and spiking inflammatory cytokines like IL-6 immediately after a workout, even in isocaloric conditions (Mountjoy et al., 2023). Eating high-quality carbohydrates around your training window keeps cortisol in check.
Match Target Variability: Your body is in a state of flux (change). Your energy needs during the estrogen-dominant follicular phase are vastly different from the progesterone-led luteal phase (M Deats Wellness, 2026). Rather than chasing static daily calorie targets, your fueling must adapt dynamically to match your cycle's changing physiological demands (M Deats Wellness, 2026).
Take the Guesswork Out of Your Fueling with Sérénité
If you are tired of fighting your own body, it’s time to track your nutrition through a lens built specifically for female biology. Traditional tracking apps assume your metabolism is static, often pushing you into chronic, stress-inducing deficits that drive cortisol up and metabolic rate down (M Deats Wellness, 2026).
Sérénité Active is a revolutionary, cycle-aware nutritional platform designed by me, a professionally qualified nutritional scientist to bridge the gap between your cycle and your plate (M Deats Wellness, 2026).
Adaptive Macro Targeting: Built on peer-reviewed female clinical research, Sérénité Active calculates your daily targets based on your true physiology, dynamically adjusting them within a safe, research-backed range of -150 to +250 calories as your body provides feedback (M Deats Wellness, 2026).
Metabolic & Cycle-Synced Coaching: Recalibrate targets as your metabolic rate shifts and receive tailored training and recovery guidance synchronized with your current cycle phase (M Deats Wellness, 2026).
Built-in Safety Guardrails: Advanced fiber and energy-availability guardrails quietly protect you from accidental under-fueling, ensuring your cortisol remains low and your lean muscle is preserved (M Deats Wellness, 2026).
Complete Transparency & Privacy: There are no "black boxes" here. Every formula used is transparently explained in plain language and cited to published clinical research (M Deats Wellness, 2026). Better yet, your intimate data is protected with a zero-ad policy, is never sold to third parties, and is entirely yours to delete at any time (M Deats Wellness, 2026).
You do not have to stop doing what you love but you do need to fuel yourself well in order to support your body, mood, hormones and body composition. It isn’t easy and believe me, as a women who has learned, repeatedly learned this the hard way, eating enough is the only way to protect your health and your body and sanity. I have recently had to really scale back my own training to a pace that feels worse than walking but the reality is that it is going to give me the ability to go further and stay healthy.
To learn more about the app click here .
References
Espinar, S., Sánchez-Fernández, M.A., Martin-Olmedo, J.J., Rueda-Córdoba, M. and Jurado-Fasoli, L. (2026). Rethinking Energy Availability from Conceptual Models to Applied Practice: A Narrative Review. Nutrients, 18(2), p.379. doi:10.3390/nu18020379.
Greendale, G.A., Sternfeld, B., Huang, M., Han, W., Karvonen-Gutierrez, C., Ruppert, K., Cauley, J.A., Finkelstein, J.S., Jiang, S.F. and Karlamangla, A.S. (2019). Changes in body composition and weight during the menopause transition. JCI Insight, 4(5), p.e124865. doi:10.1172/jci.insight.124865.
Liu, S., Huang, Z. and Zeng, Y. (2026). Estradiol reduction during perimenopause is associated with lower BDNF, elevated inflammation, hippocampal loss, and cognitive decline. Experimental Gerontology, 222, p.113219. doi:10.1016/j.exger.2026.113219.
M Deats Wellness (2026).Sérénité Active (Serenity Active) — Cycle-Aware Nutrition for Perimenopause. Available at: https://serenite.mdeatswellness.com/ (Accessed: 4 September 2026).
Mountjoy, M., Ackerman, K.E., Bailey, D.M., Burke, L.M., Constantini, N., Hackney, A.C., Heikura, I.A., Melin, A., Pensgaard, A.M., Stellingwerff, T., Sundgot-Borgen, J.K., Torstveit, M.K., Jacobsen, A.U., Verhagen, E., Budgett, R., Engebretsen, L. and Erdener, U. (2023). 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 57(17), pp.1073–1097. doi:10.1136/bjsports-2023-106994.
Ruffing, K.M., Koltun, K.M., De Souza, M.J., et al. (2022). Moderate weight loss is associated with reductions in LH pulse frequency and increases in 24-hour Cortisol with no change in perceived stress in young Ovulatory women. Physiology & Behavior, 254, p.113885. doi:10.1016/j.physbeh.2022.113885.
About the Author: Combining professional expertise with personal insight, I am a nutritional scientist dedicated to changing the conversation around women's hormonal health. Having navigated the hidden complexities of HRT over-treatment myself, I bridge the gap between clinical research and real-world experience to ensure women have the tools they need to advocate for their health. If you're a woman in perimenopause struggling with metabolic health despite doing "all the right things," the missing piece might be understanding your unique internal landscape.
