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Constipation Advice for Weight Loss

Date: April 2022

Review Date: April 2024

Ref: C-490 

PDF:  Constipation Advice for weight loss final April 2022.pdf [pdf] 320KB  

What is constipation?

Constipation is a common condition that can affect people of all ages. It means that you are not emptying your bowels of poo (medically known as stools) regularly or not at all. Regularity means anything from three times a day to three times a week. Think about what is normal for you prior to having surgery. Constipation causes your stools to become hard and lumpy and can be large or small. It is most common around the time of your surgery due to following the liver reduction diet and in the early days post-surgery. Regularity of emptying your bowels will also likely to be different. 

What does constipation feel like?

You may have a feeling of straining, feeling blocked up or that you can’t empty your bowel completely. If you are constipated, you may get one or more of the following:

• Cramping

• Bloating

• Nausea

• Pain in your rectum from straining.

What causes constipation?

Common causes include:

• Not having enough fibre

• Not drinking enough fluid

• Being less active or not exercising

• Changing your diet or routine • Side effects of medication

• Stress, anxiety, or depression

• Frequently ignoring the urge to go to the toilet

How can I reduce my risk of getting constipated before my operation?

Whilst you are on your Liver Reducing Diet (LRD), you may experience symptoms of constipation, and this is due to having less fibre in your diet. It is important that you drink at least 2 litres of water a day. If you experience constipation whilst on the LRD then we recommend that you purchase some gentle laxatives. These are widely available in chemists and supermarkets.

Please see our recommendations below: 

What are laxatives and how do they help with constipation?

Laxatives are a type of medication that can treat constipation. There are 4 main types of laxatives.

Bulk-forming laxatives

Bulk-forming laxatives work by increasing the "bulk" or weight of your stools, which in turn stimulates your bowel.

• They take 2 or 3 days to work.

• Bulk-forming laxatives include: Fybogel

Osmotic laxatives

Osmotic laxatives draw water from the rest of the body into your bowel to soften your stools and make it easier to pass.

• They take 2 or 3 days to work.

• They include Lactulose or Macrogol (also called by brand names, Movicol or Laxido)

Stimulant laxatives

These stimulate the muscles that line your gut, helping them to move stools along to your back passage.

• They take 6 to 12 hours to work

• They include: Bisacodyl (Dulcolax) and Senna (Senokot)

We do not advise to use Senna as it is a lot harsher on the gut than Bisacodyl. 

Softener Laxatives

This type of laxative works by letting water into the stool to soften it and make it easier to pass

• They take 1-2 days to work

• They include Docusate Sodium (Brand name DulcoEase)

What we recommend whilst on the LRD.

If you experience constipation early into the LRD then we recommend use either:

• Docusate Sodium: starting with 1 tablet twice a day. If this does not help we may advise you to increase your dose up to a maximum of 5 a day.

• Macrogol: starting with 1 sachet twice a day, this can be increased with specialist advice from the team.

If you have not had a bowel movement 2-3 days before surgery, we would recommend that you take the Bisacodyl: 1-2 tablets at night before you go to sleep.

How can I reduce my risk of constipation following surgery?

Your bowel habit is likely to change after surgery. This is due to the limited fluid intake and the reduction in fibrous foods or medication changes. To try and prevent or reduce constipation it is important to: Drink at least 2 litres of fluid per day

• Include fibre in your diet.

• Establish a regular eating pattern 

How does Fibre help with constipation?

Fibre is a type of carbohydrate that your body cannot easily digest. It passes through the gastrointestinal tract into the colon (large bowel) and forms the bulk of the stool. Foods that contain fibre are vital for the health of the colon. The presence of faeces in the colon will stimulate the peristalsis (wave like movements) required to move it through to the rectum. There are two types of fibre that can affect the bowels. They are called soluble and insoluble fibre and both have health benefits.

Soluble fibre: Dissolves in water within your bowel. It forms a soft gel- like substance. The natural bacteria in your gut breaks the gel down, producing gases. The soluble fibre acts a probiotic helping to promote the growth of ‘good’ bacteria in your bowel. This helps your bowel stay healthy and make the passage of stools easier.

Foods that contain high amounts of soluble fibre include:

• Oats (example porridge)

• Fruits with skins or seeds, dried fruit (prunes and apricots)

• Vegetables that have skins or seeds

• Beans (baked beans, kidney beans, butter beans)

• Peas

• Lentils. 

Insoluble fibre: This type of fibre absorbs the water from the bowel but does not dissolve. The bacteria in your gut find it harder to break it down. The advantage of this type of fibre is it adds bulk to your stool making it larger. Then with the peristalsis movements of your bowel, your stool will be softer and easier to pass easily and regularly.

Foods that contain Insoluble fibre include:

• Wholemeal bread

• High fibre breakfast cereals (examples: Weetabix®, Shreddies®, Bran flakes)

• Rye bread

• Wholemeal pasta

• Potatoes cooked in their skins.

• Wholemeal pitta bread.

What fibrous food can I eat during the 4 stages of diet progression?

Stage 1: Day of surgery, end of week 2: Liquids: ensuring there are no lumps and not too thick.

• Fruit or vegetable milk-based smoothies

• Smooth thin soups containing vegetables, beans, peas and lentils

• Meal replacement drinks such a Slimfast® or Tesco Slim®

• Prune or apricot juice mixed with water (ensure you sip this slowly to reduce the risk of dumping)

• Keep portions small, approximately 100-150 mls 

Stage 2: Weeks 2-4: Puree foods

• Puree fruit and vegetables

• Breakfast cereals such as Weetabix® or Ready Brek®

• Meals containing pureed peas, beans, or lentils such as stews or casseroles

Stage 3: Weeks 4-6: Soft foods

• Whole-wheat and wholegrain breakfast cereals such as Shreddies®, Bran flakes, Weetabix®, Porridge or Shredded wheat®

• Whole-wheat or wholegrain crackers and oatcakes (avoiding seeded crackers)

• Wholemeal toast (avoid seeded)

• Soft fruits such as melon, mango, kiwi, strawberries, grapes, bananas and blueberries • Tinned fruits in natural juice such as apricots, prunes, peaches and pears

• Soft cooked vegetables such as cauliflower, broccoli, swede, sweet potato and butternut squash

• Add peas, beans and lentils to soups and stews

Stage 4: Week 6 onwards: Normal Textured Diet

When you have reached this stage, most fibrous foods can be introduced. Please make sure you are well established on Stage 4 before you introduce the following foods with caution:

• Rice

• Pasta

• Bread

• Stringy Vegetables

• Sweetcorn

• Whole mushrooms

• Pips

• Seeds 

If you can tolerate rice or pasta, choose wholegrain or whole-wheat versions as they are higher in fibre. If you are tolerating Stage 4, try adding milled linseeds to smoothies, soups, yoghurts, stews, sauces, salads and breakfast cereal. Aiming to introduce two table spoons full a day.

Gradually increase the amount and ensure you increase your fluid intake. This will help prevent too much gas and bloating. We recommend starting with 1 tablespoon a day and having an additional 150 mls of fluid per tablespoon of linseeds taken.

Fibre Supplements: If there is little improvement with your bowel habit after increasing the fluid and fibre into your diet, you may wish to try a fibre supplement. There are a number of natural fibre supplements that you are able to buy from health food shops and online.

These fibre supplements can be added to your food or fluid. They do not thicken the fluid and they are tasteless. You need to gradually increase to about 3g a day. They include:

• Wheat Dextrin (Benefiber)

• Nestle Optifibre 

Remember if you do increase your fibre intake using these supplements.

• Do it gradually to avoid gas and bloating, allowing your gut to adjust to the higher intake of fibre.

• Drink plenty of fluid. Fibre draws water into the bowel. You may become dehydrated if you do not drink enough.

What else can you do to help with constipation?

Sitting correctly on the toilet and exercise will both help with maintaining regular bowel movement and preventing constipation.

How should you sit on the toilet?

Sitting on the toilet incorrectly prevents you from emptying your bowel completely and can lead to straining  

Correct position for sitting on the toilet:

Correct position: Relaxes and straightens the rectum 

• Put your feet on a small step or box

• Knees higher than your hips

• Lean forward • Put your elbows on your knees

• Bulge out your abdomen

• Straighten your spine

Incorrect position: Bowel is pinched and blocked

Exercise: Exercise such as walking, climbing the stairs, swimming and yoga can help move your bowels.

After surgery you must build up your exercise gradually. Too much too soon can lead to complications such as hernias. Start of gradually with short walks and climbing your stairs at home.  

Food Diary

You may find it helpful to keep a food diary to record what you eat and drink. You can then look at the fibre content of your food to make sure you are getting enough and also drinking plenty.

It is recommended by that adults should have least 30g of fibre a day. Following surgery, this may be difficult to achieve, but where possible choose high fibre foods to help increase the amount of fibre you eat.

Reading Labels: When reading the food labels for fibre content, consider foods that have the following amounts:

High Fibre 6g per 100g

Medium Fibre 3g per 100g 

Some of the best fibre rich foods are, including the amount of fibre per 100g.

Shredded whole wheat or bran cereals 13-24.5g

Wholemeal bread (1 slice) 3.5g

Wholemeal spaghetti (boiled) 4.2g

Strawberries 3.8g

Parsnips (boiled) 4.7g

Broccoli (boiled) 2.8g

Almonds 7.4g

Peanuts 7.6g

Sesame Seeds 7.9g

Sunflower seeds 6.0g

Peas (boiled) 5.6g

Baked beans (in tomato sauce) 4.9g

Green beans (boiled) 4.1g


If you take medication that can cause constipation, following your surgery your health conditions may improve and you may not need as much or none at all. Ask your GP to review your medication.

Common drugs that can cause constipation:

• Opioids: Morphine, Tramadol, Codeine

• Antihypertensive: Blood pressure lowering medication, Commonly Calcium Channel blockers (Amlodipine, Felodipine, Nifedipine and Diltiazem) or Beta Blockers (Atenolol and Propranolol).

• Antacids: Omeprazole, Lansoprazole.

• NSAIDS (Non-Steroidal Medication): Ibuprofen, Naproxen • Antidepressants

Contact Details

If you want to discuss your constipation with the team our contact details are below: 

Generic e-mail: plh-tr.DerrifordBariatrics@nhs.net

Specialist Nurse: Monday – Friday: 01752 431725

Specialist Dietitian: Monday, Tuesday, Thursday: 01752 437279

Specialist Dietitian: Wednesday-Friday: 01752 431509 



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