MintflowNutrition

GLP-1 Fiber Calculator

Fiber keeps you regular, and constipation is one of the most common side effects of GLP-1 medications. Enter your age and sex for a daily target, split into a per-meal number, with advice on building up to it gently.

Sex
Meals you can realistically manage

Enter your age to see your daily fiber target.

Now fit it into your meals

Fiber works best alongside protein and plenty of fluid. Find meals that bring all three, and check how much you should be drinking.

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How the target is worked out

In the US, the National Academies set a daily fiber intake of 25 g for women and 38 g for men up to age 50, and 21 g and 30 g over 50, because people tend to eat less as they get older. In the UK, the advice is 30 g a day for every adult, while most adults eat about 20 g. The calculator shows the range between the two for your age and sex, then splits it across the meals you can manage.

Fiber on a GLP-1

  • Start gently. The 2025 joint advisory from four US obesity and nutrition societies suggests avoiding high-fiber foods in the first few days of treatment, when stomach side effects are most likely.
  • Then build up over a few weeks. Adding fiber gradually helps you avoid bloating and discomfort.
  • Drink more as you go. Water helps fiber pass through your gut, and an expert consensus on GLP-1 side effects recommends more water, fiber and movement for constipation. The water calculator gives you a daily number.
  • Ease off if it makes things worse. High-fiber foods slow the stomach further, and the advisory notes this can worsen constipation for some people, sometimes needing a temporary cut back. If constipation lasts, talk to your prescriber.

Fiber in common foods

Rough values per realistic serving, to help you build meals that reach your target.

FoodFiber
Lentils, cooked (100 g)8 g
Chickpeas, drained (100 g)8 g
Half an avocado (70 g)5 g
Chia seeds (1 tbsp, 12 g)4 g
Edamame, shelled (80 g)4 g
Apple, medium (180 g)4 g
Porridge oats (40 g, dry)4 g
Mixed berries (80 g)3 g
Almonds (25 g)3 g
Wholegrain bread (1 slice, 40 g)2 g
Broccoli (80 g)2 g

A worked example: porridge with chia and berries for breakfast (11 g), a soup with 100 g of lentils for lunch (8 g), and chicken with broccoli and half an avocado for dinner (7 g) comes to about 26 g. More in fiber on a GLP-1 and constipation on a GLP-1.

Frequently asked questions

How much fiber should I eat on Ozempic or Mounjaro?

The same as anyone else. In the US, the target is 25 g a day for women and 38 g for men up to age 50, and 21 g and 30 g over 50. In the UK, it's 30 g for all adults. On a GLP-1, build up to it gradually, and go easy on high-fiber foods in your first few days of treatment.

Can fiber help with GLP-1 constipation?

It can, together with enough fluid and moving more. Add fiber slowly and drink more as you do. For some people a lot of fiber makes constipation worse, because it slows the stomach further; if that happens, ease back and talk to your prescriber.

Why are the US and UK fiber targets different?

They come from different expert bodies. The US sets separate figures by sex and lowers them after 50, because people tend to eat less as they get older; the UK sets one figure of 30 g for every adult. Anywhere in the range the calculator shows is a sensible target.

Which foods are highest in fiber?

Beans, lentils and chickpeas (about 8 g per 100 g cooked), chia seeds (about 4 g per tablespoon), avocado, oats, berries, wholegrain bread and vegetables. Most people fall short, averaging about 20 g a day, so a few of these each day makes a real difference.

References

  1. Report offers new eating and physical activity targets to reduce chronic disease risk: dietary reference intakes for fiber (National Academies, 2002)
  2. How to get more fibre into your diet (NHS)
  3. Fiber (MedlinePlus, US National Library of Medicine)
  4. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory (American Journal of Clinical Nutrition, 2025)
  5. Clinical recommendations to manage gastrointestinal adverse events in patients treated with GLP-1 receptor agonists: a multidisciplinary expert consensus (Journal of Clinical Medicine, 2022)