Can constipation cause weight gain?

Yes - constipation can cause weight gain! We frequently see this in our clinic, and when we resolve constipation, people often find that they revert to a weight prior to the commencement of their gut or health issues, without any drastic diet changes. This is really quite remarkable. 


How does this work?

There is so much we don't yet know about the gut microbiome, and despite the aid of microbiome testing, and the usual tools available for a nutritional therapist, I'm still in awe over how much we don't yet know, which has become clear by the results produced by some nutritional interventions.

Some bacteria have been associated with alterations in metabolism - that we know - but my feeling is that there's more to it than that.

Three potential causes of weight gain in constipation 

1. Water retention

Many of my clients complain of water retention when they're particularly constipated, which eases when constipation lessons. Perhaps this is the body's way of trying to hold on to water to ease constipation - or it could be related to gut bacteria, we just don't know. Either way, it can create rapid and uncomfortable weight gain. 

2. The thyroid and constipation

In some cases of persistent constipation, an underachieve thyroid gland may be involved, which could promote weight gain.

Chronic constipation alters the microbiome, which can become unbalanced and unfavourable. 

If the thyroid function is found to be a little low, we want to think about specific nutrients the thyroid needs to function well. Sufficient protein and iron are the two main nutrients I would assess, followed by iodine and selenium. Many vegetarians think they consume enough protein, but I'd recommend you use software to calculate this for a couple of weeks to assess if your thyroid is struggling. If you have gut problems, you may struggle a little bit to absorb plant sources of protein.

3. Small intestine bacterial overgrowth (SIBO)

Persistent constipation will almost always cause SIBO to some level, and SIBO often tends to be associated with weight gain, likely due to the bacterial action in the small intestine directly.

It also tends to be associated with food intolerances or worsening of symptoms with certain foods (but you may be struggling to identify which exactly). SIBO is also associated with inflammation. This can manifest as skin eruptions, rashes and joint pain to mention some.  

Gut molecules - serotonin and short-chain fatty acids (SCFA)

Our gut bacteria are responsible for producing a number of molecules that are responsible for gut motility (movement), namely SCFAs and serotonin. It's quite common to discover that people have very low, or even undetected levels of particular bacteria responsible for producing some very beneficial SCFAs, which can stem from not eating enough fibre, or possibly past antibiotic courses (interestingly, serotonin is involved in appetite regulation, and SCFAs are key players in our metabolism and how we use our stored energy!)

These bacteria are restored, however, by using probiotics and fibre, however, if you have SIBO, be careful with what you introduce as you may not tolerate these well. 

Establishing whether you have troublesome gut bacteria is the first thing to do. Simply guessing will lead you around the houses and lead to a loss of valuable time and life quality. 

To find out if gut bacteria is causing your weight gain, fill in this two-minute form for your free health review.

Nutritionist Resource is not responsible for the articles published by members. The views expressed are those of the member who wrote the article.

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London, W1B 1PF
Written by Linda Albinsson, Advanced Gut Health Nutrition Clinic
London, W1B 1PF

Linda Albinsson is a highly experienced and qualified nutritionist specialising in areas of the microbiome, gut health, inflammatory conditions (skin, cardiovascular, pain and joint) and others

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