If you work with athletes, it’s rare for them to come to you saying, “I think I have low energy availability.” Usually, they come in with a host of symptoms, like they’re always bloated, can’t use the bathroom regularly, always feel full, or can’t tolerate food during training. Too often, providers are chasing the symptom, recommending restrictive diets like cutting out dairy, gluten, fiber, or going low FODMAP. But here’s the problem with that… when you chase symptoms without understanding the system, you often make things worse. Instead of looking for a single “problem food,” we need a framework that connects fueling, stress physiology, gut motility, absorption, and eating patterns. That’s where the Five Factors of Fueling comes in. Read on to learn more about this REDs-informed framework for assessing athlete gut symptoms, without restriction or bandaging symptoms.
Why Symptom-Chasing Fails (and Drives Restriction)
Here’s the thing about gut symptoms… they’re complex. They can have multiple root causes and be triggered by different things in different people.
Bloating could be:
- Slow motility
- Poor absorption
- Underfueling
- High fiber intake
- Stress
- Eating patterns
Constipation could be:
- Low intake
- Dehydration
- Disrupted routine
- Nervous system dysregulation
Reflux could be:
- Timing
- Stress
- Volume
- Food composition
When we assume one symptom = one cause, we default to restriction to try to solve it.
Cut out dairy. Try gluten-free. Lower your fiber.
For athletes, this type of restriction often leads to:
- Lower energy availability
- Worsening GI symptoms
- Reduced tolerance
- A deeper REDs cycle
We need a systems-based approach to addressing athlete gut symptoms, not a food-elimination approach.
The Five Factors of Fueling
The Five Factors of Fueling is a REDs-informed framework for approaching gut symptoms in athletes. It helps you assess the gut through five interconnected lenses:
- Factory Belt (motility)
- Flow (absorption)
- Feeling (gut-brain axis)
- Fiber (composition + fullness)
- Feeding (timing patterns)
Let’s break each one down.
Factor 1: Factory Belt (Motility)
Think of digestion like a conveyor belt.
Food moves from mouth → stomach → small intestine → colon in a coordinated sequence.
This is GI motility.
Why it matters:
- If motility is too slow, it leads to constipation and bloating
- If it’s too fast, urgency and poor absorption occur
- Symptoms may reflect meals from days ago, not the last thing eaten
Common athlete disruptors:
- Irregular meal timing
- Underfueling
- Dehydration
- High training stress
- Ignoring bowel cues
What to assess:
- Bowel movement frequency and consistency
- Timing patterns (same time daily or not?)
- Hydration habits
- Meal regularity
If an athlete is experiencing digestive issues, it’s not always what they ate, it’s how their “factory belt” is moving. If it’s moving slow (or at a stand-still), that’s where issues pop up.
Factor 2: Flow (Absorption + Intestinal Integrity)
Once food is digested, it needs to be absorbed. That’s how we actually take advantage of the nutrients in the food and get fuel.
This happens in the small intestine via structures called villi—tiny finger-like projections that increase surface area.
Why this matters:
When the body is under stress (training, underfueling, lack of sleep), these villi can become:
- Blunted
- Less effective
- Slower to absorb nutrients
This can lead to:
- Bloating
- Gas
- Food “intolerances”
- IBS-like symptoms
It’s important to remember, tolerance is not fixed.
I often hear athletes say, “I suddenly can’t tolerate foods I used to eat.”
But this doesn’t always mean it’s a permanent intolerance.
It may reflect:
- Reduced gut integrity
- Reduced enzyme activity
- Temporary stress on the system
The goal isn’t lifelong elimination. It’s restoring function so tolerance can return.
Factor 3: Feeling (Gut-Brain Axis + Interoception)
The gut is often called the “second brain” for a reason.
The gut-brain axis, primarily via the vagus nerve, controls:
- Hunger signals
- Fullness signals
- Motility
- Digestive readiness
Oftentimes, what happens in athletes is that stress overrides hunger.
This can look like:
- No appetite before training or competition
- Forgetting to eat during busy days
- Feeling “not hungry” despite high output
Over time, athletes lose interoceptive awareness:
- They can’t tell if they’re hungry, full, or bloated
- They confuse stress signals with fullness
A few ways athletes can support interoceptive awareness is implementing “rest and digest” practices, slowing down before meals, or doing simple “digestive warm-ups,” like breathing, movement, and pausing.
If the nervous system isn’t ready to digest, the gut won’t perform well.
Factor 4: Fiber (and Fluids/Protein as Fullness Drivers)
Factor #4 is where “fake fullness” comes in.
Fiber, fluids, and protein are all important, but highly satiating. The issue with this is, they can create early fullness without adequate energy intake. Loading up too much on these can make it difficult to consume enough other necessary nutrients, such as carbs, which are key for energy and performance.
This can look like:
- Very high fiber diets (often >50–80g/day)
- Large fluid intake with meals
- Protein-heavy eating patterns
- Low energy density meals
All potentially leading to:
- Early satiety
- Bloating
- Reduced caloric intake
- Energy deficiency
This is what I mean when I say, they take up space without paying rent.
Factor 5: Feeding (Timing Patterns + Grazing Paradox)
Many athletes eat frequently, but still underfuel.
How does this happen?
Because of grazing patterns… eating multiple small meals and snacks per day, but never enough to truly fuel them in one sitting.
This can lead to:
- Constant low-level fullness
- Disrupted hunger signals
- A gut that never gets a “rest phase”
This also brings up the issue of timing compression. Athletes who train early may rush breakfast. Midday training sessions may lead to an early lunch with too much time before dinner. Late dinners after a busy day of work and training can lead athletes to skipping dinner or eating less due to tiredness.
To help combat this, athletes can try:
- Anchoring meals to their circadian rhythm
- “Foundation fueling” (eating within an hour of waking)
- Using snacks to support, not replace, meals
We’ve been told that eating more frequently throughout the day is a good way to keep metabolism up and stay fueled, which can be true, if we’re eating enough of the right foods.
Putting It All Together: A Quick Clinician Checklist
When an athlete presents with GI symptoms, instead of asking, “What food is causing this?”, ask these questions based on the Five Factors of Fueling Framework;
Factory Belt (Motility)
- How often are you having bowel movements?
- Is there a consistent daily rhythm?
Flow (Absorption)
- Have your food tolerances changed recently?
- Do symptoms worsen during high training stress?
Feeling (Gut-Brain Axis)
- Do you feel hunger regularly?
- Do you eat before training even if you’re not hungry?
Fiber (Composition)
- What does a typical day of fiber intake look like?
- Are fluids or protein crowding out intake?
Feeding (Timing)
- Are you eating full meals or grazing?
- How long are gaps between meals?
When to Intervene vs Refer
Start with:
- Improving meal structure
- Supporting energy availability
- Adjusting fiber/fluid/protein balance
- Anchoring timing
Refer out when:
- Severe or persistent symptoms occur
- Blood in stool
- Unexplained weight loss
- Suspected GI disease (IBD, celiac, etc.)
Final Takeaway
Athlete gut symptoms are rarely about a single food. They’re about systems.
When you zoom out and assess:
- Motility
- Absorption
- Nervous system
- Food composition
- Eating patterns
You can move from symptom-chasing to root-cause resolution.
Want to Learn This Framework in Practice?
This framework is part of my REDs Informed Provider Certification Program® curriculum and something I am passionate about teaching my clinicians. We approach this topic in the program with case studies, assessment tools, and step-by-step implementation to help you fully understand and implement it with confidence.
Learn more inside the REDs Informed Provider Certification Program® and take the next step to becoming a certified REDs informed provider!
Already completed the program and want monthly case discussions, CEU trainings, and ongoing support? Join the REDs Performance Mastermind! This is where we take frameworks like this and apply them in real athlete cases every month.