Constipation can happen during weight loss, even if you are trying to eat more healthily. It may happen because you are eating less food overall, drinking fewer fluids, eating less fibre, moving less, or changing your usual routine.
Some people notice constipation when they start a new diet. Others experience it when they reduce portion sizes, cut carbohydrates, skip meals, or begin weight management treatment. Constipation can feel uncomfortable and frustrating. It may also make the scale look stuck because stool and fluid can affect body weight for a short time.
The NHS explains that common causes of constipation include not eating enough fibre, not drinking enough fluids, not moving enough, changes in diet or routine, medicines, and stress. You can read more in the NHS guide to constipation causes and treatment. The NHS Eatwell Guide also gives a useful framework for balanced eating.
Constipation is common, but it should not be ignored if it is severe, persistent, painful, or linked with symptoms such as blood in your stool, unexplained weight loss, vomiting, severe abdominal pain, or a major change in bowel habit. NICE guidance on constipation in adults highlights the importance of identifying red flag symptoms that may need further medical assessment.
If you are using treatment and want more specific guidance, NewGen Pharmacy’s article on constipation during weight loss treatment may help.
Why Constipation Can Happen During Weight Loss
Constipation can happen when bowel movements become less frequent, harder to pass, or more uncomfortable. During weight loss, several changes can contribute.
Eating less food means there may be less bulk moving through the bowel. If fibre intake drops at the same time, stools can become harder. Low fluid intake can make this worse because the bowel may absorb more water from the stool.
Some people also reduce carbohydrates when trying to lose weight. This can accidentally reduce fibre if they stop eating oats, wholegrain bread, potatoes with skin, beans, lentils, fruit, or wholegrain cereals.
Activity levels can also matter. Movement helps support bowel function. If your diet changes but your movement drops, constipation may become more likely.
Stress, disrupted sleep, travel, new routines and some medicines can also affect bowel habits.
Weight Loss Can Reduce Food Volume
A smaller food intake can reduce bowel movement frequency. This is not always a problem, but it can become uncomfortable if stools become hard or difficult to pass.
Some people eat much less during weight loss and may not replace the missing food volume with fibre-rich options. For example, they may skip breakfast, eat a small salad for lunch, and have a low-fibre dinner. This can leave the bowel with less bulk.
Balanced weight loss should not mean eating as little as possible. Your body still needs nutrients, fluids and enough food structure to support digestion.
If your appetite is reduced, smaller meals can still include useful nutrition. Soup with lentils, yoghurt with oats and berries, eggs on wholegrain toast, beans with vegetables, or chicken with potatoes and salad can support both fullness and digestion.
NewGen Pharmacy’s article on eating less without missing key nutrients explains why reduced intake still needs careful food choices.
Fibre Matters for Bowel Health
Fibre helps add bulk to stool and supports bowel regularity. It also helps meals feel more filling, which can support weight management.
Fibre-rich foods include vegetables, fruit, oats, wholegrain bread, brown rice, wholewheat pasta, beans, lentils, chickpeas, peas, seeds, nuts, and potatoes with the skin on.
The British Dietetic Association explains that fibre intake should be adapted to medical history and tolerance, especially for people with conditions such as IBS. You can read more in the BDA guide to fibre and digestive health.
It is usually better to increase fibre gradually. Adding too much fibre too quickly can cause bloating, wind or discomfort.
A simple starting point may be adding one extra portion of vegetables daily, choosing oats at breakfast, adding beans or lentils to soups, or switching from white bread to wholegrain bread.
Hydration Is Just as Important as Fibre
Fibre works best when you drink enough fluids. If you increase fibre but drink very little, bloating or constipation may worsen.
During weight loss, some people drink less without realising. This may happen if they are eating smaller meals, feeling nauseous, skipping breakfast, or replacing meals with snacks.
Low fluid intake can contribute to hard stools, headaches, tiredness and dizziness.
Water is usually the best option. Tea, coffee, sugar-free drinks and other low-sugar fluids can also contribute for many people. If you feel nauseous, small regular sips may be easier than large drinks.
NewGen Pharmacy’s guide to protein, fibre and hydration explains how these basics work together during weight management.
Protein Is Helpful, but Balance Matters
Protein can support fullness and muscle maintenance during weight loss. Many people increase protein when trying to lose weight, which can be helpful.
However, constipation may become more likely if protein increases while fibre and fluids decrease. For example, a plan based mainly on meat, eggs, cheese, protein bars or shakes may not provide enough fibre unless it also includes vegetables, fruit, wholegrains or pulses.
Good protein options include eggs, fish, chicken, turkey, Greek yoghurt, cottage cheese, tofu, beans, lentils and chickpeas.
Beans, lentils and chickpeas can be especially useful because they provide both protein and fibre. They can be added to soups, curries, stews, salads and wraps.
The aim is not to reduce protein. The aim is to balance protein with fibre-rich foods and fluids.
Common Diet Changes That Can Trigger Constipation
Some weight loss plans make constipation more likely without meaning to. This can happen when people cut out too many high-fibre foods.
Common triggers include:
- Skipping breakfast
- Eating very small meals
- Reducing fruit and vegetables
- Cutting out oats, potatoes, beans or wholegrains
- Drinking less water
- Using many protein shakes or bars
- Eating fewer meals overall
- Reducing activity
- Ignoring the urge to go to the toilet
Very low-calorie or highly restrictive diets can also affect bowel habits. They may reduce food volume and make stools less frequent.
A safer approach usually includes balanced meals, protein, fibre, fluids and movement.
Constipation During Weight Loss Treatment
Some people experience constipation during weight loss treatment. This may happen because appetite changes, portions become smaller, food volume drops, fluid intake reduces, or digestion changes.
Treatment should support health and wellbeing. If constipation becomes uncomfortable, persistent or severe, seek advice rather than simply pushing through.
Helpful steps may include increasing fluids, adding fibre gradually, keeping meals regular, moving more if possible, and discussing pharmacy options where suitable.
NewGen Pharmacy’s guide to what to eat while using weight loss treatment gives practical meal ideas that may help patients stay nourished while managing appetite changes.
Do not change treatment doses, stop medicines, restart treatment, or combine products without professional advice.
How Constipation Can Affect the Scale
Constipation can make weight loss progress look slower than it really is. Stool, fluid retention and bloating can all affect scale weight.
This can feel discouraging. You may think your plan has stopped working when the issue is partly bowel-related.
Try not to react to one weigh-in. Look at trends over several weeks. Also consider other progress markers such as waist measurement, clothing fit, appetite, energy and activity.
If constipation improves, the scale may change again. However, the main goal should be comfort, bowel health and safe weight management, not just a lower number.
Foods That May Help Constipation
Food choices can help support bowel regularity.
Useful options may include oats, wholegrain bread, bran cereals, vegetables, fruit, beans, lentils, chickpeas, peas, brown rice, potatoes with skin, nuts and seeds.
Some people find prunes, kiwi fruit, pears, berries, soups, stews and warm drinks helpful.
Increase fibre gradually and drink fluids alongside it. This can reduce the chance of bloating or discomfort.
Simple meal ideas include:
- Porridge with berries and seeds
- Lentil soup with wholegrain bread
- Jacket potato with beans and salad
- Chicken wrap with vegetables
- Greek yoghurt with fruit and oats
- Chickpea curry with brown rice
- Vegetable omelette with wholegrain toast
Choose foods that fit your culture, budget, preferences and medical needs.
Foods and Habits That May Make Constipation Worse
Some habits may worsen constipation during weight loss.
Eating very little can reduce bowel movement frequency. Low-fibre diets can make stools harder. Low fluid intake can make the bowel absorb more water from stool.
Large amounts of cheese, low-fibre snacks, processed foods, and low-carbohydrate diets may make constipation worse for some people.
Some people also ignore the urge to go because they are busy, uncomfortable using public toilets, or trying to rush through the day. Ignoring the urge can make stools harder to pass later.
Stress and anxiety may also affect bowel patterns.
A simple routine can help. Try to eat regular meals, drink fluids, move daily and allow time to use the toilet without rushing.
Movement Can Support Bowel Function
Movement can support bowel activity. You do not need intense exercise.
Walking, stretching, cycling, swimming, gardening, gentle strength exercises or simply standing more often can help some people.
If you sit for long periods, try short movement breaks. Even a five- or ten-minute walk after a meal may support digestion and routine.
People with pain, mobility issues or long-term conditions should choose activity that feels safe. A healthcare professional can advise if you are unsure.
Movement also supports mood, sleep, energy and long-term weight management.
Pharmacy Support for Constipation
Pharmacists can help with constipation advice. They can ask about symptoms, medicines, diet, fluids, bowel pattern and red flags.
A pharmacist may suggest lifestyle changes first. They may also recommend a suitable laxative if appropriate.
Different laxatives work in different ways. Some add bulk to stool, some draw water into the bowel, and others stimulate bowel movement. The right option depends on symptoms, medical history, medicines and how long constipation has been present.
NHS Inform explains that if diet and lifestyle changes are not enough, a pharmacist may recommend an oral laxative to help empty the bowels. You can read more in the NHS Inform guide to constipation treatment and pharmacy support.
If you need advice, you can contact NewGen Pharmacy for pharmacy support.
Medicines Can Contribute to Constipation
Some medicines can make constipation more likely. These may include some pain medicines, iron tablets, antacids containing aluminium or calcium, some antidepressants, some antihistamines, some blood pressure medicines, and some medicines used for bladder symptoms or nausea.
Do not stop prescribed medicines without advice. Instead, speak to a pharmacist, GP or prescriber.
A medicines review may help identify whether a medicine could be contributing and whether changes are possible.
If constipation started after a new medicine or dose change, mention this when seeking advice.
When Constipation Needs Medical Advice
Most mild constipation improves with food, fluids, movement and pharmacy advice. However, some symptoms need medical review.
Seek advice urgently if you have severe abdominal pain, vomiting, swollen abdomen, blood in your stool, black stools, unexplained weight loss, fever, or you cannot pass wind or stool.
You should also seek medical advice if constipation is new and persistent, if bowel habits change without an obvious reason, if symptoms keep returning, or if you have a family history of bowel cancer.
Pregnancy, older age, severe pain, neurological symptoms, or significant long-term conditions may also need more careful assessment.
Do not rely on online advice if symptoms are severe or unusual for you.
Practical Constipation Checklist During Weight Loss
A simple checklist can help you review common causes.
Ask yourself:
- Am I eating enough food volume?
- Am I getting fibre daily?
- Have I reduced oats, wholegrains, fruit or vegetables?
- Am I drinking enough fluids?
- Has my activity reduced?
- Am I ignoring the urge to go?
- Did constipation start after a new medicine?
- Am I using many protein shakes or bars?
- Do I have pain, bleeding or other warning symptoms?
This checklist can help you decide whether simple changes may help or whether pharmacy or GP advice is needed.
How NewGen Pharmacy Can Help
NewGen Pharmacy can support patients with constipation advice, weight management guidance and safe signposting where needed.
Our pharmacy team can help patients understand how reduced food intake, low fibre, low fluids, medicines, activity and treatment changes may affect bowel habits.
Where appropriate, our pharmacists and clinicians can advise on lifestyle steps, discuss suitable pharmacy options, explain when symptoms need GP or urgent review, and support patients using weight management treatment.
You can contact NewGen Pharmacy for pharmacy support if constipation is affecting your comfort, routine or weight management plan.
You can also learn more about online consultations or read about NewGen Pharmacy’s weight management support if you are considering a wider review.
Frequently Asked Questions
Can weight loss cause constipation?
Weight loss itself does not always cause constipation, but changes linked with weight loss can. Eating less, reducing fibre, drinking fewer fluids, moving less, and changing routine can all contribute.
Why am I constipated after starting a diet?
Your new diet may contain less food volume, less fibre or fewer fluids than before. Some people also reduce wholegrains, fruit, beans or potatoes, which can affect bowel regularity.
Does fibre help constipation during weight loss?
Yes, fibre can help many people by adding bulk to stool and supporting bowel regularity. Increase fibre gradually and drink enough fluids.
What foods help with constipation?
Helpful foods may include oats, vegetables, fruit, wholegrain bread, brown rice, beans, lentils, chickpeas, potatoes with skin, prunes, kiwi fruit, nuts and seeds.
Can drinking more water help constipation?
Fluids can help, especially when fibre intake increases. Low fluid intake can make stools harder and more difficult to pass.
Can protein diets cause constipation?
High-protein diets may contribute if they replace fibre-rich foods or reduce fluid intake. Balance protein with vegetables, fruit, wholegrains or pulses.
Is constipation during weight loss treatment common?
Some people experience constipation during weight loss treatment because appetite, food volume, fluids or digestion may change. NewGen Pharmacy’s article on constipation during weight loss treatment may help.
Should I take a laxative?
A pharmacist can advise whether a laxative may be suitable. The right option depends on symptoms, medical history, medicines and red flags.
When should I seek urgent help?
Seek urgent advice for severe abdominal pain, vomiting, swollen abdomen, blood in stool, black stools, unexplained weight loss, fever, or inability to pass wind or stool.
Can constipation affect my weight on the scale?
Yes. Stool, fluid and bloating can affect scale weight temporarily. Look at longer trends rather than reacting to one reading.
Final Thoughts
Constipation can happen during weight loss because of lower food volume, reduced fibre, low fluid intake, less movement, medicine effects or changes in routine.
A healthier approach should support digestion as well as weight loss. Fibre, fluids, regular meals and movement can all help.
Pharmacy support may be useful if constipation continues or if you are unsure which treatment is suitable. Medical advice is important if symptoms are severe, persistent, unusual or linked with red flags.
NewGen Pharmacy can help patients review constipation during weight loss and understand safe next steps through confidential pharmacy-led support.
Compliance note: This article provides general information only. It does not replace personalised medical advice, diagnosis or treatment. Patients with severe pain, blood in stool, black stools, vomiting, unexplained weight loss, fever, swollen abdomen, sudden bowel habit changes, pregnancy, or symptoms that feel unusual should seek GP, NHS 111 or urgent care support as appropriate. Prescription treatment can only be discussed privately after an appropriate consultation and where safe, lawful and clinically suitable.
Author & Content Writer: Dr Naeem Aslam
