Bloating: Why Your Belly Swells, and How to Find the Cause

'I'm bloated by the end of every day, no matter what I eat.'

A flat stomach in the morning, and looking 6 months pregnant by evening. Gas, pressure, and waistbands that dig in by 3 PM. Constipation, loose stools, or both in turn.

For decades, many Women never had to think about digestion, and then, somewhere in their 40's, the bloating arrived and stayed.

Before I knew I had SIBO, healthy food made me miserable. Within 10 minutes of eating garlic, onions, celery, mushrooms, or certain fruits, I was so bloated, and it would not go down.

Because eating made me so uncomfortable, I began to eat less, and that calorie restriction deepened the nutrient deficiencies I already had. My breath test later showed extreme methane.

Bloating usually has a findable cause. Rule out the serious causes first, and then do the root-cause work with a clear mind.

When Bloating Needs a Doctor Promptly

New bloating that persists, nearly every day, needs a prompt doctor's visit, especially with pelvic or belly pain, feeling full quickly, trouble eating, or needing to urinate urgently or often, because these can be early signs of ovarian cancer. The American Cancer Society advises seeing your doctor if you have these symptoms more than 12 times a month.

Call your doctor promptly, before any protocol, supplement, or elimination diet, if you also notice:

• Blood in your stool, or black, tarry stools
• Weight loss you did not try for
• Diarrhea or belly pain that wakes you at night
• Iron deficiency or anemia with no clear cause
• A lasting change in your bowel habits, especially after 45
• Fever with belly pain, vomiting that keeps coming back, or trouble swallowing
• A family history of colon cancer or IBD alongside new symptoms

Colon cancer screening now begins at 45 for adults at average risk. I avoided my own colonoscopy because I was scared, and when I finally did it, it came back perfectly clean. The peace of mind it gave me was enormous. 'The Gut, In Depth' and 'The Mimics' go deeper into these red flags.

For your routine colon screening, and the stool and blood test options if a colonoscopy feels too hard right now, see 'Your Midlife Screening Calendar: The Tests That Protect You, and Your Options'.

What Can Be Behind It

Digestion runs from the top down. Stomach acid breaks protein apart, enzymes and bile finish the job in your small intestine, and a steady wave of muscle contractions sweeps the leftovers along. When any step comes up short, partly digested food lingers where bacteria can ferment it, and fermentation makes gas.

Low stomach acid. Food that sits like a stone, early fullness, burping, and reflux point toward your stomach. Autoimmune gastritis, H. pylori, long-term acid-blocking medication, and meals eaten in fight or flight can all lower stomach acid, and about 40 percent of people with Autoimmune gastritis also have Hashimoto's.

You cannot tell too much acid from too little by how the burn feels. 'Your Stomach: Low Stomach Acid, Heartburn, and Why You May Not Be Absorbing Your Nutrients' goes deeper.

Enzymes and bile. Bloating after starchy meals, with food that passes undigested, can point toward pancreatic enzymes. Bloating or nausea after fatty meals, with pale or floating stools, points toward bile. 'Digestive Supports, and How to Know Which You Need' in 'Your Stomach' goes deeper.

Read this chart as text

Concept diagram titled 'Your symptoms as clues: which digestive step needs support'. A drawing of the liver, stomach, gallbladder, pancreas, and small intestine, with a note that food travels top to bottom. Step 1, Stomach acid: heavy after protein; early fullness, burping; low iron or B12. Stomach lining, marked with a warning sign: burning, gnawing pain; pain that wakes you. The label reads 'See a doctor first'. Step 2, Pancreatic enzymes: bloating after starch; undigested food. Step 3, Bile: pale, greasy, or floating stools; nausea after fat. Footer note: 'Shows the idea, not measured data. Symptoms are clues, and testing gives answers. A good response to enzymes does not diagnose a pancreas problem.'

SIBO. In small intestinal bacterial overgrowth, bacteria that belong in your large intestine settle in your small intestine and ferment your meal early, making hydrogen, methane, or hydrogen sulfide gas. A flat belly in the morning that swells through the day, starting within an hour or 2 of meals, points here. Methane slows the gut, which is why methane-type overgrowth so often brings constipation. 'SIBO: The 3 Kinds, How to Test for Them, and How Each Is Treated' goes deeper.

IBS. Irritable bowel syndrome is a disorder of gut-brain interaction, and the pain, bloating, and urgency are fully real. Through a Functional Medicine lens, IBS often has findable drivers underneath it: SIBO, food reactions, low stomach acid, a slow thyroid, and a Nervous System stuck in alarm.

An IBS label is a starting point for better questions. 'Leaky Gut, IBS, IBD, and SIBO' in 'The Gut, In Depth' goes deeper.

Food sensitivities and celiac disease. Bloating after specific foods points toward a food sensitivity, and gluten, dairy, and soy are common ones. Celiac disease travels with Hashimoto's and can be called IBS for years. High-FODMAP foods such as garlic, onions, mushrooms, celery, apples, and pears can bloat a sensitive gut, which is exactly what happened to me. 'The Autoimmune Protocol' is built to reveal your own reactions.

Motility and your thyroid. Between meals, a cleansing wave called the Migrating Motor Complex sweeps your small intestine clean, and grazing all day never lets that cycle finish a single pass. A slow thyroid slows that wave and the whole digestive tract. In a 2007 study of people with hypothyroidism, about half had SIBO, compared with about 5 percent of healthy controls.

'Give Your Gut Time to Rest Between Meals' in 'The Gut, In Depth' and 'Your Thyroid, In Depth' go deeper.

Read this chart as text

Concept diagram titled 'Give your gut time to rest'. Spaced meals: a meal, then 4 to 5 hours during which the Migrating Motor Complex sweeps through, then the next meal. Grazing all day: a row of 8 small dots for eating at short intervals, with the note 'the cleansing cycle never finishes a single pass'. Footer note: 'Shows the idea, not measured data.'

Progesterone and your cycle. Progesterone relaxes the smooth muscle of your intestines, which is part of why bloating and constipation build before your period. In Perimenopause, when progesterone lurches and drops, bowel patterns can swing from sluggish to loose without warning. 'How It All Connects' goes deeper.

Estrogen and fluid. Progesterone gently counters aldosterone, the hormone that holds on to salt and water. When progesterone falls and estrogen runs high relative to it, bloating and water retention can build in the week or 2 before your period and ease once it arrives.

Mild fluid retention is also a common early effect of starting hormone therapy, and it usually settles. 'What Is Actually Happening in Your Midlife Body' and 'Hormone Therapy 101' go deeper.

Estrogen and your microbiome. Estrogen helps keep your gut lining sealed and supports a diverse microbiome, and after Menopause many Women's gut bacteria become less diverse. A gut that handled wine, bread, and late dinners at 30 may protest at 48. 'The Gut, In Depth' goes deeper.

Stress. About a third of the acid released with a meal is triggered by your brain through the vagus nerve, and that signal works best in rest-and-digest. A meal eaten in fight or flight starts with less of that first wave, and stress hormones also open the gut. 'Stress: The Load Women Stop Noticing' goes deeper.

Constipation. Low thyroid, low magnesium, and too little water, fiber, or movement all slow your bowels, and a backed-up colon bloats. 'Your Liver, Your Kidneys, and Your Gut' goes deeper.

Medications, antibiotics, sugar, and alcohol. Long-term PPI use has been linked to about twice the odds of SIBO. Every course of antibiotics touches your microbiome, and sugar and alcohol loosen the gut barrier. 'Why the Gut Gets Harder in Midlife' in 'The Gut, In Depth' goes deeper, and any change to a prescribed medication stays with your prescriber.

Overgrowth and parasites. Candida and other overgrowth, and for some Women parasites, add to the gas. 'Root Causes: Parasites, Heavy Metals, Mold, and Environmental Toxins' goes deeper.

What Helps

Your stool test and your breath test decide the plan. Treat the order as carefully as the tools: thyroid first, then SIBO, a lesson my own body keeps teaching me.

• Eat in rest-and-digest. Sit down, take 1 breath first, inhale deep, exhale long, and chew until the texture is gone. 'How You Eat Is Part of How You Digest' in 'Your Stomach' goes deeper.
• Leave 4 to 5 hours between meals if you can, so the Migrating Motor Complex can sweep your small intestine. Water between meals is fine, and any food resets the wave. Let your body and your prescriber outrank this rhythm when needed.
• Choose cooked vegetables while you heal. Aim for 6 to 15 different kinds of vegetables a day, more vegetables than fruit. Cooked vegetables are gentler on the gut during gut healing, and raw can bloat some Women.
• Calm the gut for 90 days. The Autoimmune Protocol removes the common reactors and shows you your own. 'The Autoimmune Protocol' shows you how.
• Treat SIBO with a knowledgeable practitioner. Prescription or herbal antimicrobials, sometimes a low-FODMAP stretch, and for some Women the elemental diet. 'SIBO' tells my own protocol step by step.
• Keep it from coming back. Support your stomach acid, your motility, and your thyroid, and ask about a prokinetic after treatment. 'Why SIBO Comes Back' in 'SIBO' goes deeper.
• Match digestive support to the step that falls short, after testing: betaine HCl with pepsin for a stomach that makes too little acid, never with a PPI, an ulcer, gastritis, NSAIDs, or steroids, and enzymes for the pancreas step. 'Your Stomach' gives the cautions.
• Ask your prescriber whether your PPI is still needed, and never stop it suddenly, since rebound acid is common.
• Walk after meals, and keep your bowels moving, with water, fiber from vegetables, and magnesium after testing.
• Supplements, after testing. Enteric-coated peppermint oil has trial evidence for IBS symptoms and can worsen heartburn, and ginger can help your stomach empty. 'The Mimics' and 'Supplements: Test, Don't Guess' give the evidence and the cautions.
• Track it. For 2 weeks, log what you ate, when the bloating began, your cycle day, and your stool type on the Bristol stool chart.

When Constipation Is Part of the Picture

A backed-up colon is 1 of the most common reasons a belly swells, and it deserves its own plan. The Hashimoto 411 educators sort their approach into daily habits, short-term helps, and a few things to use with care, and I teach it the same way.

Constipation that is new, comes with blood, weight loss, or pain, or will not respond to these steps is a reason to see your doctor promptly.

Daily habits:

• A footstool under your feet, knees above hips. 'Your Bowels and a Footstool', in the Pelvic Floor chapter, has the research.
• A walk every day, and after meals when you can.
• Plenty of fluids through the day.
• Probiotics, and fermented vegetables such as sauerkraut, if you tolerate them.
• Digestive enzymes, betaine HCl with pepsin for protein meals, and ox bile for fatty meals, after testing, with the cautions in 'Your Stomach'.
• 6 to 15 different kinds of vegetables a day, including greens such as kale and collards, and beets. Fiber gives stool its bulk and feeds the bacteria that keep it moving.
• A large green smoothie built from AIP-friendly vegetables and greens, a daily habit many of the educators keep.
• Coconut oil, which some Women find helpful, a traditional remedy with little research behind it.
• Grain-free eating, as the Autoimmune Protocol teaches.
• Warm baths with Epsom salt or magnesium chloride, as Nervous System care.

Looking upstream:

• Your thyroid. Enough T3 sets the pace of your gut, as 'Why a Slow Thyroid Shows Up in Your Hair and Your Gut', in 'Your Thyroid, In Depth', explains.
• Your adrenals. A body held in fight or flight slows digestion.
• Your vagus nerve. Singing, humming, and hard gargling exercise the nerve that tells your gut to move, as 'More Ways to Tone the Vagus Nerve', in the Stress chapter, describes.
• SIBO and candida. Methane-type SIBO in particular slows the gut, and 'SIBO' shows how to test.
• Your iron supplement. Harsh iron salts such as ferrous sulfate commonly constipate. Iron from food, liver capsules, or a gentle capsule such as the Iron Repair I take, described in 'When You Do Need Iron', is often easier on the gut.

Short-term helps:

• Magnesium citrate, taken to bowel tolerance, which is how I use it.
• Milk of magnesia, plain, without added flavors or colors, for occasional use.
• Prunes. In a 2011 trial, prunes increased bowel movements and softened stool more than psyllium did.
• Castor oil packs, on your belly for constipation, or over your liver, on the right side just under your ribs, to support its clearing work. I use them on my liver and my breasts. The research on them is still thin.
• Haritaki, 1 of the 3 fruits in triphala, a traditional Ayurvedic support with limited clinical research. Banyan Botanicals sells it as a powder.
• A low-FODMAP version of AIP, for a short stretch, if gas and bloating travel with the constipation. 'SIBO' explains how.
• A saline enema, for occasional relief.
• Colon hydrotherapy, which some Women use. 'Colon Hydrotherapy: My Experience, and the Evidence', in the Liver chapter, gives my experience, the evidence, and the risks.
• Pelvic floor physical therapy and biofeedback. When the pelvic muscles tighten instead of relaxing during a bowel movement, called dyssynergic defecation, biofeedback retrains them, and it has the strongest evidence of any treatment for that pattern. Some programs pair biofeedback with gentle electrical stimulation of the pelvic floor, which has smaller studies behind it, so ask your pelvic floor therapist which approach fits you.

Use with care:

• Polyethylene glycol laxatives, PEG, such as MiraLAX. Some of the educators prefer to avoid them. The American Gastroenterological Association and the American College of Gastroenterology give PEG a strong recommendation for chronic constipation, based on moderate evidence, so bring your own question about it to your practitioner.
• Laxatives mixed into large volumes of sports drinks. This mix is used as a colonoscopy prep, and cases of dangerously low sodium have been reported, so use it only as your doctor directs.
• Stimulant laxatives, such as senna and cascara sagrada, including the senna in many detox and 'dieter's' teas. The 2023 guideline supports stimulants for short-term or rescue use and gives senna a conditional recommendation, and the educators caution against leaning on them for months. The FDA removed cascara sagrada and aloe from over-the-counter laxatives in 2002, because manufacturers had not supplied the safety data it asked for.
• Aloe. The educators add a caution from a practitioner model of immune balance: aloe may stimulate the TH1 side of the immune system, so they avoid it unless you know you are not TH1 dominant. That model is a practitioner framework, and TH1 and TH2 testing is not standard.

The gentlest fix is the 1 that answers your own root cause. 'Your Pelvic Floor and Bladder' shows how straining affects your pelvic floor, and 'How It All Connects' shows how daily bowel movements help you clear estrogen.