Protein has been getting a lot of attention lately, and for good reasons. It protects muscle, keeps you full, and supports healthy weight loss. But there's another nutrient doing equally important work, and most of us aren't getting nearly enough of it.
That nutrient is fiber. Most adults eat about half the fiber they need, and that gap affects far more than digestion. Fiber affects your blood sugar, your appetite, your gut health, and even how your body makes its own fullness hormones.
Whether you're taking a GLP-1 medication or not, here's why fiber deserves a place at every meal.
What Fiber Is (and Why You Want Both Kinds)
Fiber is the part of plant foods your body can't digest. Because you can't break it down, it travels all the way to your large intestine, where it does its most important work. There are two main types of fiber (and you want both).
• Soluble fiber dissolves in water and forms a gel. It slows digestion, helps steady blood sugar, softens stool, and is the main food for your gut bacteria. You'll find it in oats, beans, lentils, chia and flax seeds, apples, oranges, and carrots.
• Insoluble fiber adds bulk and helps keep things moving. You'll find it in whole grains, vegetable skins, nuts, seeds, and leafy greens.
A good daily goal for most adults is about 25 to 30 grams of fiber from food. If you're well below that now, build up gradually over a couple of weeks and drink more water as you go. Fiber needs water to do its job, and adding a lot at once can leave you bloated and uncomfortable.
Fiber Feeds the Gut That Takes Care of You
Your large intestine is home to trillions of helpful bacteria, and fiber is their food. When these bacteria ferment fiber, they produce small compounds that have a big job:
• They fuel and protect the cells lining your gut.
• They strengthen the gut barrier.
• They help calm inflammation.
• They signal your gut to release your body's own GLP-1 (more on that below).
A diet low in fiber and high in refined, processed foods does the opposite. It starves helpful bacteria, weakens the gut lining, and increases inflammation, a pattern linked with obesity and type 2 diabetes. The encouraging news is that your gut responds quickly. In one well-known study, the gut bacteria of people who changed their diet began shifting within just a few days.
Variety matters too. Each type of plant feeds a different family of bacteria, which is why many gut researchers encourage eating a wide range of plants across the week, with some suggesting a goal of 30 different plant foods. That number sounds like a lot until you realize how much counts: vegetables, fruits, beans, whole grains, nuts, seeds, and even herbs and spices.
Fiber and Your Body's Own GLP-1
This is one of my favorite things to explain to clients, because it connects everyday food to the science behind today's most talked-about medications.
Your gut wall contains special cells, called L-cells, that release your body's own GLP-1, the same hormone family that GLP-1 medications are based on. When your gut bacteria ferment fiber into short-chain fatty acids, those compounds signal the L-cells to release GLP-1. That natural GLP-1 helps you feel full and helps steady blood sugar after meals.
Your natural GLP-1 is short-lived and much gentler than a medication, so fiber isn't a substitute for treatment. But it works through the same fullness pathway, which makes it a natural teammate.
Calming Inflammation
Inflammation is a low, silent, body-wide irritation that, over years, raises the risk of diabetes, heart disease, and other chronic conditions. Higher fiber intake is consistently linked with lower levels of inflammation markers in the blood, and calming inflammation appears to be one of the main ways fiber protects metabolic health.
A Mediterranean-style way of eating, built on vegetables, fruits, whole grains, beans, nuts, olive oil, and fish, is the best-studied eating pattern example that does this well. It's also naturally high in fiber.
On a GLP-1? It's About More Than Protein
If you're taking a GLP-1 medication, you've likely heard a lot about protein, and it is important for protecting muscle and hair. But fiber does several jobs that protein can't, and it often gets overlooked when appetite is small.
• It helps with the most common GI side effects. Constipation is one of the most frequent complaints on GLP-1 medications. Insoluble fiber adds bulk and keeps things moving, while soluble fiber can help firm up loose stools.
• It helps you feel satisfied on smaller portions. Fiber adds volume and slows digestion, supporting the fullness your medication already creates.
• It supports steadier blood sugar. Soluble fiber slows how quickly sugar enters your bloodstream, which means fewer spikes and crashes.
• It may help you keep your results. Experts see fiber and GLP-1 medications as complementary. Fiber supports your body's own GLP-1 and a healthier gut, so building a fiber habit now may help protect your progress if you reduce or stop your medication later.
A gentle caution: because these medications slow digestion, adding a lot of fiber at once can increase bloating or fullness. Go slowly, spread fiber across the day, and keep your fluids up.
Easy Ways to Add Fiber Throughout Your Day
Adding fiber doesn't require a complete diet overhaul. A few small, steady changes at each meal add up quickly.
I've put together a free Fiber Cheat Sheet with simple, practical ways to add fiber at every meal, from breakfast to snacks to dinner. Click here to download your free Fiber Cheat Sheet.
if you'd like a plan built around your body, your goals, and any medications you take, I'd love to help. Book a call with me and we'll find the right fit for you.
Cristen Benz, MS, RDN is a registered dietitian in private practice at Benz Wellness in Fort Collins, Colorado. She specializes in GLP-1 success, weight loss, women’s health, gut health, and autoimmune conditions. She works individually with clients to build practical, customized ways of eating that fit real life. She also works with organizations to provide resources and guidance so employees are more productive, focused, and feeling healthy. Learn more at benzwellness.com.
References:
1. Dietary Fiber and Glucagon-Like Peptide-1 Receptor Agonists in Obesity Management: Converging Mechanisms, Interactions, and Strategies for Durable Weight Control. Advances in Nutrition. 2026. Wang Y, et al. Review
2. Nutritional Priorities to Support GLP-1 Therapy for Obesity: A Joint Advisory From the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and the Obesity Society. The American Journal of Clinical Nutrition. 2025. Mozaffarian D, Agarwal M, Aggarwal M, et al. Guideline
3. Nutritional Modulation of Endogenous Glucagon-Like Peptide-1 Secretion: A Review. Nutrition & Metabolism. 2016. Bodnaruc AM, Prud'homme D, Blanchet R, Giroux I. Review
4. Diet Rapidly and Reproducibly Alters the Human Gut Microbiome. Nature. 2014. David LA, Maurice CF, Carmody RN, et al.
5. American Gut: An Open Platform for Citizen Science Microbiome Research. mSystems. 2018. McDonald D, Hyde E, Debelius JW, et al.
6. Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels. Diabetes Care. 2015. Shukla AP, Iliescu RG, Thomas CE, Aronne LJ.
7. I Am Taking a GLP-1 Weight-Loss Medication—What Should I Know? JAMA Internal Medicine. 2025. Mehrtash F, Dushay J, Manson JE. Clinical Reference
