Book Review: “ROAR: How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body For Life” by Stacy Sims, Ph.D

Rachel PerkinsJanuary 30, 2020
“ROAR: How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body For Life” by Stacy Sims, Ph.D is an excellent resource for female athletes, parents, and coaches. (Photo: Screenshot

This book is for female athletes ages 12 to 92. Or for parents of female athletes. Or coaches of female athletes. Or anyone who wishes to otherwise support female athletes. 

In 2016, Stacy Sims, Ph.D sparked a shift in training philosophy with her simple message to female athletes: “You are not a small man. Stop eating and training like one.” 

Although the fact that there are physiological differences between men and women are abundantly clear, the implications in the realm of athletic performance do not date back to proto-humans.

In her book, “ROAR: How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body For Life”, Sims explains that for generations, research in exercise physiology excluded women because the varying hormone levels depending on age and phase within the menstrual cycle created anomalies in data. It was assumed — perhaps naively by male scientists — that women followed the trends seen in studies performed on males. 

Sims experienced this phenomenon first-hand during her own career as an elite triathlete; she competed in the Ironman World Championships in Kona, HI and the XTerra Worlds in Maui. She recognized that the training plan her male peers followed did not work as well for her, and that she and her female teammates recognized their fueling and hydration needs and performance were impacted by their menstrual cycles. So she set out as a scientist to better understand female-specific physiology. 

Stacy Sims, Ph.D, is an exercise physiologist and nutrition scientist who specializes in female performance. (Photo: Screenshot

From 2007 – 2012, Sims studied “sex differences of environmental and nutritional considerations for recovery and performance” at Stanford University. Basing “ROAR” on the outcomes, Sims offers women research-based methods to align their training, fueling, and hydration with their female physiology to improve performance. 

“Sex differences extend far beyond ponytails and sports bras,” she writes in the introduction.

Some of the topics in the book include aligning training and performance schedules with phases of the menstrual cycle, understanding how female hormones affect nutrition and hydration needs, the impacts of hormonal birth control, and the effects of aging and menopause on physiology and performance. While the supporting science is included, it is well explained and can be easily understood without a degree in exercise physiology, endocrinology, or nutrition.

Though I have been training, competing, and menstruating for more than half my life, I found “ROAR” to be eye-opening and an invaluable tool to identify opportunities to improve my own training and nutrition as I prepare for the American Birkie. I highly recommend it as a resource for female athletes of all levels and for anyone who works with female athletes. 

Here are some of my biggest takeaways. 

“Chapter 1: Demystifying and Mastering Your Menstrual Cycle.” 

Right off the bat, Sims states that periods should not be avoided, and the absence of menstruation is a major red flag indicating that the athlete is not properly fueling their body, resulting in RED-S. She emphasizes that an under-fueled athlete cannot achieve peak performances and is impairing their overall health. Sims advocates for an “all in” approach to naturally restoring the body’s hormone balance by decreasing training intensity and volume (athletes can shift focus to technique here), and increasing caloric intake.

Dr. Stacy Sims, author of “ROAR: How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body For Life”, sends a clear message to female athletes experiencing menstrual disfunction. (Photo: Instagram @drstacysims)

In this chapter, Sims also unravels the phases of the menstrual cycle, providing information on the physiological effects of hormonal fluctuation.

One of the biggest surprises she shares is that competing during your period actually aids performance, because that is the phase of the cycle when estrogen and progesterone are at their lowest. In the hormonal sense, this is when women and men are most alike. 

“Once you’re in the clear of the possibility of pregnancy, the body goes into a more relaxed mode and all those energy systems used in the high-hormone phase are at your disposal for exertion,” Sims writes. 

She explains that this optimal window extends through the low-hormone follicular phase in the week following menstruation. This window is also when women are at their strongest and can experience increased pain tolerance and decreased recovery time. This is the best window for an intense training block or a peak race, though the latter is not always in our control.

Anecdotally, my summer goal race, the Lead King Loop 25k trail run, fell during my period. While I was expecting the worst (since I had not yet read the book), I ended up crushing my time goal, finishing third for women, and feeling the strongest I had in years. 

Conversely, during the luteal phase of the cycle when estrogen and progesterone are at their highest. Though performance metrics like VO2 Max and lactate threshold remain constant, it is harder for women to build and repair muscle. Carbohydrate demands are higher during this phase, which affects fueling needs during exercise and may explain why many women experience cravings during the week before their period. Blood volume is also impacted, which can make it harder to control body temperature — not the easiest time to race in the heat!

There are also the lovely symptoms of PMS which include cramping, headaches, GI issues, bloating, and mood swings. Sims explains why each of these symptoms occurs and offers suggestions for mitigation.

Her overarching message is not to dwell on manipulating the cycle to align the low-hormone phase with peak performance, and especially not to fear the menstrual cycle as an athlete. Rather, by understanding the female physiology throughout the cycle, athletes can feel empowered to adjust their nutrition and hydration accordingly to optimize training and performance at any phase of the cycle.

One addendum: the impacts of high levels of estrogen and progesterone also explain the negative performance impact many women experience from hormonal contraceptives. This method of birth control uses artificial forms of these hormones throughout the cycle to manipulate the lining of the uterus and prevent ovulation, essentially prolonging the high-hormone phase. 

“Chapter 10: Daily Fueling”

I found this takeaway less revolutionary, but so important to repeat. Sims advises women to eschew diet culture, in particular the low-carb high-fat trends, like the Ketogenic diet. She explains that while some males respond well to this type of fueling, women experience elevated levels of the stress hormone cortisol, which increases muscle breakdown and impairs the body’s ability to repair. A double whammy. 

“In the end, a low-carb diet compromises your ability to maintain high-intensity or prolonged periods of exercise and puts your body under exorbitant stress.”

Sims recommends a well rounded diet that includes roughly 30% of calories coming from protein, 30% fat, 40% carbohydrate. 

No surprise — the longer and harder you train, the more carbohydrates your body needs. The same goes for protein. She offers a formula to calculate individual need for these macronutrients based on the current demands of your training program.

From her guidance, I recognized that I need to include a bit more protein before and after my workouts (Sims recommends 10-15 grams before, 25-30 grams after hard exercise). I have also begun including a bit more protein in my bedtime snack, which typically looks like some Greek yogurt and a piece of whole grain toast with peanut butter. 

Alayna Sonnesyn (SMST2) captions this shot of cooking with Jessie Diggins, “Gotta fuel hard to train hard!”. (Photo: Instagram @asonnesyn)

Sims also recommends front-loading calories, in particular carbohydrates, during the morning when the body’s natural hormone stasis makes it “primed for carbohydrates”, whereas it can rely more on fats and protein later in the day. This helps keep blood sugar levels balanced, preventing spikes and crashes in energy throughout training and life. 

Are you, like me, a 5 AM alarm clock athlete? Just give me some coffee (life-blood) so I can properly tie my shoes and get out the door! It turns out, training first thing in the morning with an empty stomach is a recipe to put your body in an over-stressed state. 

“[Fasted training] is particularly bad in the morning because your cortisol (a stress hormone) levels are already elevated. If you go out and exercise first thing, your body wants to pump out more cortisol, but needs the right ingredients to manufacture it, which are your sex hormones – testosterone, estrogen, and progesterone.”

High levels of cortisol stimulate fat storage and impair muscle repair and growth — not what you were hoping to get out of that gym session! You’re also digging yourself into a calorie depleted hole… 

To counter these effects, Sims recommends consuming some protein and carbohydrates before the session, which boosts blood sugar and drops cortisol levels. In an Outside Magazine piece, Sims shares that one of her go-to’s is oats soaked overnight in almond milk and topped with greek yogurt and a little maple syrup. Yes — you might need to give yourself a little extra time to digest before getting after it, but that gives you time to do that foam rolling or activation drills you’ve been neglecting, or to mindlessly scroll Instagram. Just me?

“Chapter 11: Sport Specific Fueling”

This is where Sims dives into the nitty gritty. Her advice for pre, during, and post-workout fueling include explanations of how various carbohydrates are broken down in the gut and suggestions to troubleshoot GI issues like cramping, bloating, and sloshing. And though her book is based on female physiology, this section is beneficial to those with Y-chromosomes as well. 

One of the most revealing messages regarded the breakdown of sports gels in the stomach. I have never had much luck with gels during races or training — I inevitably end up with a bloated crampy belly and sticky residue in my mouth, on my hands, and wherever I stash the wrapper. Perhaps I was just looking for Sims to confirm this bias, but her explanation of the digestive process sealed the deal that candy and real food alternatives will continue to be my fuel of choice. 

“The trouble with gels”, as Sims puts it, comes down to two factors: osmolality and the mix of sugars contained in the gel. Osmolality is “the concentration of dissolved particles such as electrolytes in your blood plasma. The higher the carb concentration, the higher the osmolality, and the slower it leaves your stomach and your intestines.” 

Essentially, the viscous sugary gel is too thick to be absorbed readily during exercise when your body is diverting blood flow into your working muscles and away from your stomach. Even washing it down with water, as is recommended, does not transform the gel into an optimal form. 

Dr. Stacy Sims, author of “ROAR: How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body For Life”, provides revolutionary information on performance hydration and nutrition. (Photo: Instagram @drstacysims)

This concept is explored further in the subsequent chapter, “Hydration is Power”, which transformed my understanding of hydration. Sims explains that many electrolyte drink solutions aim to be a source of fuel and fluids, but this doesn’t jive with the body’s digestive processes either. Sims recommends the approach of “hydration in your bottle, fuel in your pocket”, meaning separating the two for better overall fueling. The chapter is so rife with information that summarizing it here does not do it justice — go read the book!

Back to gels. The second factor of the problem is that most gels contain a blend of three sugars: glucose, fructose, and maltodextrin. The first is good, the second two are difficult for the body to digest, requiring water to be drawn from the bloodstream into the gut during digestion, which leads to the suboptimal sloshy gut feeling. No bueno.

That said, Sims acknowledges that gels do work well for some athletes. If this is the case for you, there is no need to fix what isn’t broken.

What should you use if you need an alternative? Sims recommends using 100-200 food calories per hour containing primarily carbohydrates, though some protein and fats are okay. For the above reason, she recommends avoiding fructose — which is found in fruits — and sticking to low-fiber foods that contain glucose and dextrose, which can be found in bread, and sucrose, which is table sugar. In essence, nibbling on a PBJ might keep your stomach happier and your body better fueled during a training session than sucking down a couple of GUs. 

She also speculates that many people place too much emphasis on fueling during races, but it is not a “more is better” scenario.

“Contrary to what you may have heard, when in doubt, err toward the lesser amount [of food]. It is very common for athletes to overeat during training and racing with the thought that they are supplying their muscles with needed carbohydrate. But in reality, you’re consuming more than your gut can absorb, so the excess just remains in the stomach or intestinal tract too long, causing nausea, pain, and discomfort (which, of course, impairs performance).”

Sims also emphasizes that when it comes to performance in long events, like the Birkie, hydration is king. Your over-distance training session bonk might actually be a result of dehydration, not of under-fueling. 

“I’m going to drill the point home here. The solution to staying strong and delaying fatigue is taking care of hydration first and foremost — reducing your loss of blood volume — and topping off your stores with small amounts of carbohydrates from real food when possible, not the kind you drink or slurp.”

The Consensus

These points hardly scratch the surface of what “ROAR” has to offer. It is a worthwhile read for any female athlete, regardless of age or performance level, and can certainly be a valuable tool for a coach looking to direct developing female athletes to sound nutritional guidance to help build a healthy body that also performs its best. Having a period is a good thing. Fueling the body is essential. “Women are not small men.”



Rachel Perkins

Rachel is an endurance sport enthusiast based in the Roaring Fork Valley of Colorado. You can find her cruising around on skinny skis, running in the mountains with her pup, or chasing her toddler (born Oct. 2018). Instagram: @bachrunner4646

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