If you want to know whether the low FODMAP diet help you lose weight I’m going to jump straight in and say the low FODMAP diet is not considered a weight loss diet. 

The purpose of cutting out all those foods is not to reduce your energy intake, it’s to remove fermentable starches to give your digestion a break. You can read more about the low FODMAP diet and what it involves. 

Hi I’m Anna Mapson, a registered Nutritional Therapist working with people who have IBS and SIBO to improve gut health and reduce painful and unpredictable digestive issues. 

A case study

One of my previous clients felt they should have been losing weight, because they only ever experienced this level of restriction when they were on a weight loss diet. 

For this person, being on a ‘diet’ of any kind brought back feelings of deprivation, having to really think about food all the time. These associations reminded her of calorie controlled diets, and brought back bad memories. 

This client felt very cheated when after all this work they didn’t actually lose any weight.

Dark grey background showing foods spread out including carrots, chicken, prawns, peppers. Words Low FODMAP and Weight Loss against a yellow banner across the photo

Why weight loss is not recommended on the low FODMAP diet

From working with hundreds of clients my recommendation is to first address your digestive issues and then focus on your weight. Reasons not to do both at the same time include:

  • It’s too complicated – Following the low FODMAP diet is difficult, I’m not going to lie! It requires a lot of thought at first to check you’re not inadvertently eating higher FODMAP foods, and it’s not a very intuitive diet. Adding on further controls in terms of energy intake will be adding to your workload and could see you giving up! 
  • You need to keep up your energy levels – If you drop your calorie intake and this leaves you lacking in energy, or affecting your sleep then this could mess up your FODMAP challenges. 

Reasons you might lose weight on the low FODMAP diet

So, will the low FODMAP diet help me lose weight? Well, yes, some people find they do lose weight when on the low FODMAP diet. This could be down to factors such as:

  • As part of controlling the portions of high FODMAP foods many of my clients find they reduce their overall portions of carbohydrates (e.g. pasta and bread) and eat more protein. 
  • You develop a better understanding of portion sizing. Once you start checking the recommended serving sizes of some foods you might realise you were eating more than the recommended portion sizes for certain foods. 
  • Avoiding unintentional snacking – when the office biscuits come out and you turn them down, you might find you reduce your energy intake. If you feel like you’re missing out on too many social occasions bring some food with you so you can at least eat something with the others. 

But if you want to lose weight you might find some of these changes to your normal way of eating beneficial. But what about if you don’t want to get any smaller?

An assortment of meat and low FODMAP veg against a marble grey work top, and the words Low FODMAP and Weight Loss against a yellow banner

How to avoid weight loss on the low FODMAP diet

Some of my clients are already in a smaller body than they want to be. This could be down to over restriction, fear of foods setting off symptoms, or not eating enough food. Here are some tips on avoiding weight loss during the low FODMAP restriction and challenge phase. 

  • Increase the size of your protein portions at every meal. Animal sources of protein contain no FODMAPs so you can freely eat eggs, meat, fish and seafood. Vegetarians can include tofu, nuts, and low lactose dairy.
  • Try eating 4-5 smaller meals instead of 3 large meals. Make the additional meals a proper meal, not just biscuits, crisps, but actually adding protein and healthy fats. This allows you to space out the FODMAP rich food, but increase your calories throughout the day. 
  • Concentrate on low FODMAP wholegrains such as rice, quinoa, oats and potatoes. 
  • Go easy on the fats as high fat intake can trigger symptoms for some people with IBS, but ensure there is a small amount of fat at every meal. This could include butter, nut butters, oily fish, and small portions of nuts.

I’ve written a longer blog post about how to gain weight with IBS

It’s tricky to change your diet if you have IBS, so please don’t go it alone. If you want to help just ask to arrange a discovery call, and we can talk about working together in the 3 month Gut Reset.

Hi I'm Anna Mapson, registered Nutritional Therapist.

I help people with IBS and SIBO get control of unpredictable gut symptoms to find long term relief from painful and embarrassing IBS without restrictive dieting.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • develop better digestion and more energy

Find more about my 3 month 1:1 Gut Reset programme

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