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Are Women Fueling The Wrong Way?

In 1980, women made up only 11 percent of the running population. Today, they make up almost half the running population. Women outnumber men in half marathons and are taking to triathlon in growing numbers. Female-centric races such as the Women’s Running Series and Espirit de She have sprung up all over the country, and clothing manufacturers have finally (finally!) figured out how to craft training gear for women that goes beyond “shrink it and pink it.”
One thing that hasn’t changed much, however, is the set of fueling guidelines for active women, which are the same as men’s.
Historically, sports nutrition research has been done on male subjects, as women have been deemed “too difficult to study” due to the complexity of the menstrual cycle. The results have been generalized to women, with an overall acceptance of “well, it’s good enough.”
But Stacy Sims, PhD, refused to accept that logic. As a female athlete, she wanted to know how to maximize her own performance. To do that, she knew she’d have to answer the questions about women researchers found “too difficult to study.”
I recently had the chance to chat with Stacy about her discoveries — what women need for sports nutrition, how hormones affect a woman’s training, and the hydration and recovery products that go beyond “shrink it and pink it” to help women perform their best.

Interview With Stacy Sims About Women’s Sports Nutrition

I have to start with the obvious: Why is there a belief in sports nutrition research that women are so hard to study? Women’s hormones are constantly in flux due to the complexity of the menstrual cycle. Designing studies around the two phases (follicular, or low-hormone phase, and luteal, high-hormone phase) can be time-consuming and complicated.
But what does that have to do with what we eat and drink while training or racing? The fluctuations of estrogen and progesterone affect much more than the reproductive system!
Progesterone competes with aldosterone, a hormone that is key for sodium balance, and arginine vasopressin, a hormone necessary for  water and thirst.

There are also significant changes in a woman’s physiology during a woman’s cycle, especially in the two weeks preceding the start of her period. There is a drop in plasma volume — the watery part of blood — of approximately 8 percent. That means there is less total blood for circulation and thermoregulation.
During the cycle, there’s an increase in core temperature by .5 degrees celsius, which shortens an athlete’s time to fatigue as well as decreases heat tolerance.
The body sees a change in metabolism to spare glycogen and increase reliance on fatty acids, reducing a woman’s ability to hit intensities.
Progesterone causes an increase in muscle catabolism — in other words, the body can’t recover from a workout as well. There is a higher amount of sodium lost, and plasma osmolality is lower, predisposing women to hyponatremia.
Wow! So when I’m feeling sluggish while training, there might be more going on than “just a bad day,” huh? Yes! Estrogen and progesterone also affect central nervous system fatigue. Most women feel this as a lack of “mojo”— in other words, they can’t push through a hill or sprint that normally would be just fine. Most are thinking they are having a few shitty days on the bike, but it’s physiology, not fitness!

Wait, so if it’s a hormonal thing, would taking birth control pills help or hurt a woman’s training? What about menopause — how do those hormone changes affect athletic performance? With birth control pills, the circulating amount of estrogen and progesterone is six to eight times as high, and the “low-hormone/placebo week” is actually not low in hormones; estrogen rebounds, so you end up with a high circulating amount of estrogen. The IUD is a much better option because it is just localized doses of progesterone, which significantly reduces the amount of hormones circulating.
Peri- and post-menopausal women have an additional challenge: they have a predisposition to store abdominal fat due to leftover signals from estrogen. They also have a significantly more difficult time maintaining muscle integrity due to increased catabolic drive, which decreases muscle reparation and hypertrophy. This population of women has a difficult time gaining and maintaining lean mass and the neuromuscular drive to produce power.
You took all of this research and created Osmo for Women — sports nutrition products for hydration and recovery. How is Osmo for Women different from other sport drinks or fueling options that market to women? I developed the formulas based on true sex differences and knowing how physiology changes. This isn’t a “shrink and pink” or a marketing play to attract women, this is based on real science to help female athletes take away that 2 to 5 percent increase in stress to give them better training, better adaptations, better racing and better recovery. I’m about science and education, only putting things out there that have a strong science backing. I’m not marketing or “shrink and pink.”

Mango Osmo

Osmo Hydration for Women in mango flavor.

So what’s so special about the formulas themselves? How are they different from traditional sports drinks (or even the original Osmo Nutrition formula) — special ingredients, different ratios, what? In the Women’s PreLoad Hydration, I added branched chain amino acids (BCAAs) to work with sodium. This expands total body water to increase the amount of amino acids circulating and dampen the breakdown effects of progesterone post exercise. The BCAAs also cross the blood-brain barrier to support the central nervous system to reduce CNS fatigue.
Women’s Active Hydration has a different ratio of glucose to sucrose to facilitate a bit more glucose circulating- this helps pull more fluid in at the level of the intestines as well as increase blood glucose availability to access glycogen to hit intensities. There is a greater sodium level per serving to offset the reduced plasma volume and the greater sodium losses coupled with a bit more potassium (women need more potassium esp with fluid balance).
Women’s Acute Recovery gives a big hit of protein, in both slow and fast release forms, to really shut down the breakdown effects progesterone has on exercise. This also increases the amount of circulating amino acids to promote muscle synthesis. Finally, I added a bit more glucose to facilitate glycogen recovery; a woman’s window of recovery is short: 90 minutes, as opposed to men’s three to six hours.
Osmo Recovery for Women

Osmo Acute Recovery for Women in Honey Spice flavor.

If these are created to combat the changes in hormones during the menstrual cycle, should women only be drinking these products during a specific high-hormone phases during the cycle? Because women aren’t textbook, we can’t say exactly when a specific woman’s hormones go up. We know when they come down, because that starts bleeding (menstruation), but not when they go up. We also don’t know for sure how long a woman’s high hormone phase is — some are short, some are long — or what her specific ratios of estrogen to progesterone are. It is complicated! To mitigate all of theses types of issues, I suggest using a women’s specific product across the board to support an active body.
Thanks, Stacy, for answering our questions! For more information on the science behind Osmo for Women (including links to the full studies), visit the Science Archives of Osmo Nutrition.
FBG Readers: Have you tried a female-specific formula for nutrition? Did you notice a difference in your performance? I’m interested in hearing about your experiences! —Susan

FTC disclosure: We often receive products from companies to review. All thoughts and opinions are always entirely our own. Unless otherwise stated, we have received no compensation for our review and the content is purely editorial. Affiliate links may be included. If you purchase something through one of those links we may receive a small commission. Thanks for your support!