Most research related to sports performance and nutrition is studied from the perspective of (male) athletes who have gotten sick or injured and want to know:
Why did I get a stress fracture?
Why do I take longer than others to recover from hard workouts?
Why was I the only one on the team who got sick?
The Wu Tsai Human Performance Alliance is looking at what makes us healthy, including studies with female athletes.
This summary highlights some Wu Tsai research presented at the first Wu Tsai Female Athlete Research Meeting (Stamford Univ., Nov. ’25). Exercise and nutrition scientists shared recent studies as well as educational efforts to improve our often-unhealthy sports culture. (Example: You might proudly talk about how hard you train—but do you ever brag about how much you rest? Well-rested athletes, after all, are better able to win at season’s end… )
The Healthy Runner Project
Between the years of 2010 to 2013, 38% of Stanford University’s female athletes suffered bone stress injuries. Could nutrition interventions prevent stress fractures and bone injuries? The Stanford healthcare team designed a study to figure out if the injuries were due to poor nutrition, over-training, impact forces and/or other factors. Given weight-conscious runners commonly undereat, the likelihood of insufficient food being at the core of the problem and hurting bone health seemed plausible
In the Healthy Runner Project study, each athlete filled out extensive questionnaires, had bone density measured, and met with a registered dietitian (RD) for a nutrition assessment. Each season, the RD talked with the running team plus met with each individual, encouraging her to make just one or two small dietary changes. Examples of a small change included choosing more carbohydrate-rich foods, refueling sooner after workouts, or adding a snack to boost daily energy intake. During the 7 years of the study, many of the females reported resumption of regular menstrual periods, which contributed to improved bone density. Bone stress injuries dropped in half—from 63 to 27 injuries per person-year. In comparison, UCLA runners (with no nutrition goals), reported no change in bone injury rate.
This successful project had strong support from coaches, athletes, and administrators alike. They were able to change the food culture so that runners felt comfortable eating larger portions and enjoying food as one of life’s pleasures. They stopped fearing food as the fattening enemy. The Juniors and Seniors on the teams became role models for effective fueling; they positively influenced the newcomers. The athletes learned to embrace the importance of eating well for the whole season, their future career, and their long-term health.
If you stop eating at meals because you think you should or the food is gone (and not because you feel content), I suggest you think again, talk with a sports RD, and invest in your health.
Eating Times, Circadian Rhythms & Performance
Daytime is best for fueling and performing. Darkness is best for rest, recovery, and fasting. To determine if eating within a certain time-window (time-restricted eating, TRE) impacts performance, the researchers first studied mice. Mice ate either ad lib (whenever they wanted) or within a 9-hour interval. They ate standard mice chow or high protein or high fat chow. With TRE, within one week on the high fat diet, the female mice ran longer and even outran the male mice. Unlike the males, they didn’t gain weight with the high fat diet and were more sensitive to meal timing.
Does this mouse research translate to humans? Obviously, many differences exist between humans and mice. Humans are more genetically diverse and harder to monitor in terms of food intake. (What people say they are eating can be very different from what they actually eat!)
TRE can be difficult for (student) athletes to follow due to a tight daily training and work/class schedule. For health benefits, the speaker encouraged everyone (not just athletes), to enjoy meals at similar times each day and try to refrain from eating about 12 consecutive hours a day, let’s say from 7:00 p.m. to 7:00 a.m.
Fiber, fermented food, the microbiome & inflammation
Athletes (and all humans) are a walking ecosystem with trillions of bacteria (microbes) living in our guts. Lots of cross-talk happens between the microbes and your body. A diverse population of microbes contributes to a healthy microbiome and has a positive influence on your metabolism. For example, a healthy microbiome can influence how many calories your body stores or burns, as well as your ability to fight off infection. Your microbiome also influences your moods and behaviors via connections between your gut and your brain.
Compared to genetics (that we can’t easily change), the microbiome is highly malleable. Hence, we need more research to better understand what defines a healthy microbiome and how microbes make us healthy. What foods should we be eating to enhance microbe diversity?
Historically, our food has come from hunting and gathering. The food system then evolved to farming, and now to commercial farms and ultra-processed foods. These changes have altered today’s microbiome. Our ancestors used to have about 700 species of microbes in the gut. With industrialized (ultra-processed, packaged) food, the number of species has dropped to about 200.
Our depleted Western microbiome has come with a shift towards chronic inflammation, which we know is bad for our health. (Diseases of inflammation include heart disease, diabetes, Alzeihmer’s.) Higher diversity is linked with better health. Shifting to a diet high in fermented foods (yogurt, kefir) and fiber (whole grains, fruit, veggies) can make a powerful health difference. By enjoying fermented and fiber-rich foods daily, you can increase the diversity in your gut and improve markers of inflammation. Until we can better track food intake accurately, researchers won’t precisely know how changes in diet impact gut microbiomes, so stay tuned for more great research from the Wu Tsai Human Performance Alliance to answer our remaining questions.
Nancy Clark MS RD CSSD counsels both fitness exercisers and competitive athletes in the Boston-area (617-962-4382). Her best-selling Sports Nutrition Guidebook is a popular resource. Visit nancyclarkrd.com for more information.