For most of the past century, exercise physiology was built on data collected almost entirely from men. Training protocols, nutrition guidelines, recovery prescriptions — the foundational research was done overwhelmingly on male subjects, and the findings were generalised to women on the assumption that female physiology was just a smaller, lighter version of male physiology. Dr Stacy Sims, the New Zealand-based exercise physiologist and nutrition scientist, has spent two decades dismantling that assumption.
Her message is simple enough to fit on a t-shirt: women are not small men. The implications run deeper than the slogan suggests. Women metabolise carbohydrates differently across their menstrual cycle. They respond differently to fasted training, to cold water immersion, to high-intensity work. The threshold at which low calorie intake starts disrupting the endocrine system sits more than twice as high in women as in men. The recovery cadence that works for a male athlete will, in many cases, blunt adaptation in a female one.
Sims has published more than 70 peer-reviewed papers, written two books —Roar and Next Level — and consulted for elite teams including USA Cycling and the USOC. Her work sits at the intersection of academic rigour and applied performance, which is rare in a field where the loudest voices on women’s training tend to be either underqualified influencers or researchers with no practical coaching experience.
In an extended interview with Unfiltered Editor-in-Chief Joe Warner, Sims set out the science underpinning her core argument and translated it into specific, practical guidance. She explained why women shouldn’t exercise on an empty stomach, why the same ice bath that helps a female athlete recover can dampen adaptation in a male one, why tracking the menstrual cycle is the single most useful thing most active women can do, and why the medical establishment’s handling of perimenopause remains, in her words, “not the right answer.”
The full interview is presented here in three video chapters, with deeper written features linked under each.
Chapter 1: Optimal female recovery strategies
Sims’s research on recovery overturns one of the most commercially successful trends in modern fitness: cold water immersion. The protocol that has been sold as a universal recovery hack turns out to be deeply gendered in its effects. Men’s blood pools centrally after exercise; cold exposure adds cooled blood to that central pool and dampens the very adaptation signal training is meant to produce. Women’s blood vasodilates to the periphery; cold exposure helps shuttle it back centrally and accelerates flushing of metabolic waste from the muscles. Same protocol, opposite effect.
The recovery cadence picture is similarly different. Sims explains that women can typically sustain two to three really intense days before needing one or two days of genuine recovery — a rhythm at odds with the seven-days-on, one-day-off pattern that works for many male athletes. Get the cadence wrong and the training stops working.
Read: Should women do ice baths after exercise? →
Chapter 2: Common female training myths debunked
The fear that lifting weights will make women bulky has, by Sims’s account, cost a generation of women the most powerful tool they have for protecting their long-term health. The biology she describes is unforgiving: bone density, neuromuscular function, falls risk and frailty in later life are all materially shaped by whether a woman lifts heavy in her thirties, forties and fifties.
Sims walks through why women in particular benefit from power-based training, why the muscle-bulk fear is a misreading of what resistance training actually does, and why the demographic most likely to dismiss strength training — women in their late thirties and older — is the demographic that will benefit from it most. The discussion extends into plyometrics, perimenopause-specific training adaptations, and why a 35-minute session of compound lifts plus sprint intervals can outperform an hour of steady-state cardio for women approaching the menopause.
Read: Will lifting weights make women bulky? →
Chapter 3: The best sports nutrition supplements for women
Sims’s supplement hierarchy is short and contrarian. Creatine sits at the top — a supplement long associated with male strength athletes, but one she argues every woman should take, particularly through perimenopause and beyond. Iron comes next, but not as a daily blanket dose; she recommends cycling iron intake to align with the hormonal phases of the menstrual cycle, taking advantage of the windows when the body is best able to absorb it.
Adaptogens — rhodiola for premenopausal women, ashwagandha for those approaching or past menopause — round out the protocol, with DIM added for women dealing with the migraines, bloating and mood symptoms that come with disrupted estrogen metabolism.
The interview also covered material that sits outside these three video chapters: the kisspeptin neuron system that sets women’s calorie thresholds at more than twice male levels, the pharmacological scale of the oral contraceptive pill (its hormones exert up to 500 times the cellular effect of endogenous ones), the differential presentation of relative energy deficiency in male and female athletes, and the cultural and clinical reasons that perimenopause continues to be misdiagnosed by GPs. We’re publishing those pieces in the coming weeks.
What unifies the body of work is the same insight Sims has been making for two decades: applying male data to female bodies produces protocols that, in the best case, leave performance on the table — and in the worst case, actively undermine the health they’re meant to protect. The fix isn’t more science, although more science would help. The fix is using the science we already have, and noticing when it doesn’t transfer.
Roar: How to Match Your Food and Fitness to Your Unique Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life and Next Level: Your Guide to Kicking Ass, Feeling Great, and Crushing Goals Through Menopause and Beyond by Dr Stacy Sims (Rodale) are out now. Visit drstacysims.com.
