IBS: Why Eating Enough Matters for Gut Health
When people think about managing IBS, the focus is often on what foods to avoid: FODMAPs, gluten, dairy, sugar, or “trigger foods.” What’s talked about far less is how much you’re eating.
As a dietitian, one of the most common patterns I see in clients with IBS is chronic under-eating, whether intentional or unintentional. And here’s the important part: not eating enough can directly disrupt GI function and worsen IBS symptoms, even when food choices are “perfect.”
The Gut Needs Fuel to Function
Your digestive system is incredibly energy-dependent. Adequate intake supports:
Gastric acid production
Digestive enzyme secretion
Bile flow
Intestinal motility
Integrity of the gut lining
When energy intake is too low, the body shifts into conservation mode. Digestion becomes a non-essential function, which can lead to:
Slowed motility leading to possible constipation or bloating
Delayed gastric emptying leading to possible intense fullness or nausea
Increased visceral sensitivity leading to possibly more pain with normal digestion
IBS symptoms don’t always mean something is “wrong” with the food, it may mean the gut doesn’t have enough energy to do its job.
Under-Eating Can Worsen IBS Symptoms
IBS is a disorder of gut–brain interaction. Consistent nourishment helps regulate that connection.
When intake is inadequate, we often see:
Increased gut sensitivity and pain perception
Irregular bowel patterns (both constipation and diarrhea)
Heightened stress response in the GI tract
Poor tolerance of foods that were previously well-tolerated
This is why someone may feel like their IBS is “getting worse” even while eating more restrictively.
Restriction Does Not Lead to Symptom Control
Many people with IBS unintentionally fall into a cycle:
Symptoms → restrict food → temporary relief → worsened tolerance → more restriction
Over time, this can:
Reduce dietary variety
Increase fear around eating
Lower overall intake
Worsen gut sensitivity
This doesn’t mean elimination diets are never appropriate, but they must be paired with adequate total intake and a plan for liberalization.
Adequate Eating Supports the Gut–Brain Axis
Eating regularly and sufficiently helps:
Stabilize blood sugar
Reduce cortisol and stress hormones
Improve vagal tone (parasympathetic activity)
Decrease GI reactivity
For IBS, this is as important as fiber type or FODMAP content.
What “eating adequately” looks like will differ from person to person, especially for those with IBS.
Adequate intake is not a one-size-fits-all meal plan or a specific calorie target. Intake is individualized based on symptoms, energy needs, medical history, lifestyle, and current relationship with food. A dietitian trained in GI nutrition can help determine whether under-eating is contributing to symptoms, support gradual increases in intake, and tailor food choices to prioritize both digestive comfort and nutritional adequacy. Rather than focusing solely on avoidance, this approach helps build a more resilient, well-nourished gut over time.
IBS management involves creating internal environment where digestion can actually work, not just identifying “trigger foods.”
Eating enough is not a “nice extra.” It’s a foundational part of GI function. When the gut is adequately fueled, it’s often more resilient, more predictable, and more tolerant than we expect.
Written by Kaitlyn Schlangen, MS, RD
Kaitlyn specializes in: Eating disorders, disordered eating patterns, gastrointestinal (GI) disorders and diseases. She is dedicated to supporting individuals across all spectrums of these challenges.