Bloating and gas after eating more fiber

Why it happens, what helps, and why it usually settles within a few weeks.

• Last checked: Oct 2026

More beans, lentils, whole grains and vegetables means a lot more fiber than most people are used to. Gas and bloating in the first weeks are normal — and for most people they settle.

Why it happens

Your stomach can’t digest some kinds of fiber, so they travel on to your large intestine. There, the bacteria living in your gut feed on them, and gas is what that fermentation produces. Beans also contain a sugar called raffinose that the same bacteria ferment.

Eating a lot more fiber all at once is what causes trouble: gas, bloating and cramps.

It usually settles

Your gut adapts. In one study, people who started eating beans had more gas at first, but within three to four weeks it was back to their normal level.

What helps

• Go gradually. Add fiber over a few weeks instead of all at once.
• Drink plenty of water. Fiber needs fluid to move comfortably through your gut.
• Soak dry beans for at least 12 hours before cooking; there is some evidence it reduces the raffinose that causes gas.
• Eat smaller meals more often instead of a few large ones.
• Eat slowly, with your mouth closed, so you swallow less air, and go easy on fizzy drinks.
• Move. Regular exercise helps.

When to see a doctor

See a doctor if bloating doesn’t go away even after changing what you eat, or if it comes with losing weight without trying or blood in your poo. Get help urgently if bloating comes with severe stomach pain, vomiting or a high temperature.

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