The Gut-Fitness Connection: All You Need to Know

Written By


Expert Reviewed By

Dr. Lauryn Lax, OTD, MS

Dr. Lauryn, OTD, MS is a doctor of occupational therapy, clinical nutritionists and functional medicine expert with 25 years of clinical and personal experience in healing from complex chronic health issues and helping others do the same.

Gut-Fitness Connection Young Man Working-Out

The healthier your gut, the fitter, leaner and better athlete you can become. Unfortunately, mainstream diet and fitness advice hasn’t caught up to speed. There is such thing called “gut-fitness connection”.

“Move more, eat less” has long been touted as the mainstream advice  for improving body composition—from FitBit calorie trackers to Orange Theory treadmill workouts.

Gut-Fitness Connection Young Woman Working-Out

The Gut-Fitness Connection

As for enhancing performance, if there’s one thing no fitness expert can agree upon it is the best diet, supplement and training strategies for becoming superhuman. From intermittent fasting to carb cycling, protein shake slugging, hot-cold therapy, eating 6 small meals per day and everything in between, the debates are endless.

While different strategies certainly do work well for some people, research overwhelmingly shows that the number one factor that matters most for improving both body composition and fitness performance is not calories, meal timing, or drinking a protein shake. It is a varied, diverse biome.  

Research shows that the richer your bacterial diversity, the more athletic you can become—especially when extra stressors, like overtraining, chronic dieting, or even long term low carb diets, are not at play. A richer gut has better capacity to repair tissue and build strength, reduce inflammation, uptake oxygen, modulate the HPA Axis (stress response) and metabolize calories and macronutrients from the diet.

Have you ever wondered why eating more calories can yield a leaner physique and improved performance in some individuals, or why athletes seemingly can eat “whatever they want”, like swimmer Michael Phelp’s 10,000 calories per day routine? Is this related to the gut-fitness connection? Studies show when you eat more quality calories, particularly fiber, and maintain an active lifestyle, your gut bacteria adapt to metabolize, digest and utilize the energy by up to 150 to 200 calories.

A healthy, diverse gut is accomplished through many of the methods we’ve already discussed—properly managed stress, clean water hydration, digestive mechanics that work—stomach acid, enzymes and gallbladder function, probiotics and short chain fatty acids, a varied whole foods diet rich in different plant fibers, daily elimination, adequate rest and movement itself. Not too much. Not too little.

Dynamic fitness in particular (ie, HIIT, sprinting, strength training or CrossFit ) combined with low intensity daily movement like hiking and walking, yield positive profiles of gut bacteria balance (ie. not chronic cardio). For example, the anti-inflammatory bacteria Akkermansia  muciniphilia (A. muciniphilia) is more present in athletes than non-athletes, associated with a faster metabolism and leaner body composition. Another study comparing the microbiomes of runners before and after running a half marathon, found an anti-inflammatory shift takes place in gut bacteria directly following a fitness event.

Gut-Fitness Connection - Young Lady Getting Very Tired After Exercise

However, in those who run marathons or too much of a good thing is not a good thing. Overtraining kills gut bacteria in what researchers call a “wash out” of bacteria and promotes intestinal inflammation, resulting in dehydration, abdominal cramps, loose stools and leaky gut. If you train regularly and eat “clean” but still experience “gut problems”, look at your training intensity or frequency may be warranted. Think of the gut-fitness connection.

With these facts in mind, unique key gut-targeted strategies to improve your fitness and body composition include: Opting for dynamic exercise over chronic cardio; Eating enough nutrients—not less—particularly real foods and plenty of fiber; Probiotic and short chain fatty acid supplementation to diversify your bacterial profile; and avoiding overtraining at all costs—including plenty of sleep and active rest days.

Healthy Gut | The Gut-Fitness Connection: All You Need To Know

Source Mohr, A. E., Jäger, R., Carpenter, K. C., Kerksick, C. M., Purpura, M., Townsend, J. R., West, N. P., Black, K., Gleeson, M., Pyne, D. B., Wells, S. D., Arent, S. M., Kreider, R. B., Campbell, B. I., Bannock, L., Scheiman, J., Wissent, C. J., Pane, M., Kalman, D. S., & Pugh, J. N. (2020). The athletic gut microbiota. Journal of the International Society of Sports Nutrition, 17(1), 1–33.

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