By Jennifer Whitmire, MS, MEd, MH, CHES, NEP

What happens when I clean up my diet, remove all of the obvious problem foods, and still feel like something is wrong?

I also never know how I’m going to feel in the morning. Sometimes my energy is up and sometimes I just don’t want to move. My digestion isn’t even an afterthought on some days, and some days, I’m bloated and gassy and afraid to go anywhere. 

I can go hours after breakfast without ever feeling hungry, but 2 hours after lunch, I’m eating everything in sight. I’m trying to do the right things, but my body is not responding the way I think it should.

This is how I felt when I first started on this journey, and it’s what I hear day in and day out with my clients. 

I have found that fiber is usually the issue!  I (and they) went from a very low fiber diet to a very high fiber diet, or they think they’re eating fiber when they aren’t.  My diet used to be PB toast with banana for breakfast, Lean Cuisine with an apple or orange for lunch, and spaghetti with green beans or a taco salad for dinner. I was rarely meeting my fiber needs.

Fiber Is Not a Detail

Fiber tends to be treated like something to “increase” or “be mindful of,” but if we’ve been ignoring fiber, our body (actually our microbiome) isn’t getting what it needs to create what our body needs to function optimally.

Back in the 90s, I was taught in grad school that fiber help bulk the stool. It is basically to help people poop.  If they are constipated, maybe they had too much fiber and need more water.

Fiber is not an add-on to an otherwise complete diet. You can’t just take a fiber pill and say you’re getting your fiber.  It is part of the structure that allows the body to regulate itself. Fiber actually has several roles in the body.

When it is missing or consistently low, the body compensates enough that things feel slightly harder than they should.

Fiber is needed in the colon to:

• maintain steady energy. 
• feel full without overeating. 
• keep digestion predictable.
• produce vitamins like vitamin K and most B vitamins
• produce short chain fatty acids needed to protect the gut lining
• produce neurotransmitters
• produce many amino acids

None of those show up as a clear deficiency, but they show up as patterns when we look at labs and stool tests of those with chronic illnesses like autoimmune, heart, and brain disorders.

What Is Actually Happening

Fiber moves through the digestive system differently than other macronutrients, and that difference is what makes it so influential.

It is not broken down in the stomach and small intestines and absorbed early in digestion. It travels into the large intestine, where it feeds the gut microbiome. That interaction shapes how nutrients are processed and absorbed and how signals are sent throughout the body.

Some fibers slow digestion. That helps with blood sugar balancing by changing how quickly glucose enters the bloodstream and how the body responds to it.

Some fibers add bulk and support movement through the digestive tract.

Other fibers are fermented by gut bacteria, producing compounds that influence inflammation, metabolic function, and even how the gut lining maintains its integrity to prevent and/or repair leaky gut.

This is a series of processes that overlap.

The Part That Gets Missed

Most people are not eating in a way that allows fiber to do what it is designed to do. They may be eating foods that are considered healthy, but the overall daily pattern is still low in fiber.

•  Animal foods do not contain fiber.
• Processed foods often have it removed.
• Even “better” choices don’t always contain plant foods.

The body is trying to regulate blood sugar, digestion, and inflammation without one of the primary tools it uses to do that, and that is where the disconnect starts.

Why Energy Feels Unpredictable

When fiber is low, digestion tends to move quickly. Glucose enters the bloodstream faster, insulin goes up in response, and energy rises and falls inconsistently.

Over time, this becomes normal. People get used to needing something mid-morning. That 10am banana. They expect an afternoon drop and reach for that “treat and tea or coffee.” They assume that feeling slightly off is just part of getting older.

When fiber increases, that pattern changes. Absorption slows down the process. Energy becomes more stable throughout the day. Hunger signals start to align more closely with what the body actually needs. (Now, we still have to break that mid-morning and mid-afternoon habit, but….)

Slowly increasing fiber can make a difference.

Digestion Is Usually the First Signal

Most people notice changes in digestion before anything else which makes sense. I remember when we first went to 100% WFPB. I never knew that things could move through so easily and on schedule, just like when my kids were toddlers learning how to potty train.

Fiber is directly involved in movement through the digestive tract and in feeding the bacteria that live there. When fiber intake is low, those systems become less efficient. We lose motility in the intestines and the little contractions and movements slow down and become insensitive.

When fiber intake increases, especially through a variety of plant foods, the environment changes, and regularity improves. Most people notice bloating decreases once the body adapts. 

I say once the body adapts, because if you go from 10 grams of fiber a day to 75 grams of fiber, your body isn’t prepared for that kind of jump. Someone on 10 grams of fiber has the microbes to feed on 10 grams. GIve them 75 grams, and of course you’re bloated! That’s a huge jump.

This Is Where It Shows Up in Real Life

This is one of the first things that becomes obvious when I am working with someone in a kitchen.

We don’t do anything extreme. We are not creating complicated meals.

We are creating meals differently and are slowly introducing:

• More beans. 
• More vegetables.
• More variety.
• More consistency.

Within a short period of time, the feedback changes.

People notice that they are not thinking about food the same way. They are not wishing for more energy. They are not trying to correct how they feel halfway through the day with a snack.

That shift does not come from one ingredient but from the structure of the meal.

Fiber and the Gut Microbiome

This is where the conversation usually becomes more technical, but it is worth understanding at a basic level.

As I mentioned above, the gut microbiome relies on fiber as a primary fuel source. When fiber intake is low, beneficial bacteria do not thrive in the same way. When fiber intake increases, those bacteria produce short-chain fatty acids, which influence inflammation, immune function, and the health of the gut lining. 

You may have heard of butyrate, acetate, and propionate. These affect more than digestion. These act as signalling molecules and directly influence our immune function, brain health, as well as, our gut health.

Why This Does Not Get Emphasized

Fiber does not get the attention like other parts of nutrition. Protein?!

It is not marketed in the same way. It is not tied to a single food or food trend. It requires a pattern of meal consistency and there are no shortcuts.

It gets reduced to a number. “Adults need Twenty-five to thirty eight grams of fiber daily.” It’s just something else to track. To me, 25-38 grams is the minimum amount needed for optimal health. Unfortunately, most Americans only get 15 grams a day with only 5-7% meeting this minimum. No wonder there’s a chronic disease epidemic!

Tracking fiber does not reflect how fiber actually works in the body. The body does not respond to a number but to what is consistently present in each meal.

What Changes When the Pattern Changes

When meals are created around whole plant foods, fiber intake increases without needing to calculate it.

Beans, lentils, vegetables, fruits, nuts, and seeds all contain fiber and contribute in different ways. They provide different types of fiber that support different functions.

This is why variety is so important.

Over time, the body begins to regulate more efficiently. Energy becomes steadier as meals become more consistent. Digestion becomes more predictable, and hunger becomes easier to interpret (Am I really hungry?  Or am I just bored? Or is my “treat” just a habit I need to break?

Stability is what most people actually need! In their diet, their sleep, their meal timing, their exercise, their hydration, ….

A More Useful Way to Approach This

Instead of trying to add fiber to what you are already doing, it is more effective to look at how meals are created.

If fiber is not part of the foundation of the meal, it will always feel like something you are trying to add on.

If it is part of the structure, it takes care of itself.

This was one of the hardest things for me to do when we went WFPB, because I had no idea what a meal even looked like without meat. Meatloaf with mashed potatoes becomes mashed potatoes and green beans – this is not a filling and complete meal. Steak with baked potato or sweet potato and a side salad ends up just potato and small salad – where’s the rest of it?

We have to create something new, get creative, and come up with ideas where a plant food becomes the main.

Bringing It Back

Fiber is not a trend, and it is not a small tweak here and there. It is part of how the body regulates energy, digestion, immune function, brain and heart function, etc.

When it is consistently present throughout the day, things tend to feel more stable. It’s not immediate but more predictable.

For most people, that is the difference between constantly managing how they feel to finally having a pattern and routine that supports them.