Clinical FeaturesEndocrine/MetabolicGastroenterology

Obesity Therapy in Patients with Inflammatory Bowel Disease


A person with a body mass index (BMI) over 30 is classified as having obesity, which can be defined as abnormal or excessive fat accumulation presenting a risk to health. With increasing research in this field, we are aware more than ever that obesity is a complex multifactorial disease with genetic, behavioural, socioeconomic, and environmental origins. According to the World Obesity Federation 2023 the prevalence of obesity is anticipated to rise from 14% to 24% of the population affecting nearly 2 billion adults, children and adolescents by 2035. The rising prevalence of obesity is expected to be steepest among children and adolescents, rising from 10% to 20% of the world’s boys during the period 2020 to 2035, and rising from 8% to 18% of the world’s girls demonstrating a need to provide greater preventative measures.


Inflammatory bowel disease (IBD) is a lifelong condition that can cause inflammation and ulcers in the gut. The two most common types of IBD are Crohns disease (CD) and Ulcerative Colitis (UC). People with the disease can go through periods of time where the disease is active or in remission.

The rate of IBD in Ireland is among the highest in the world. According to data from the Irish Society for Colitis and Crohn’s Disease (ISCC), it is estimated that around 40,000 people in Ireland have IBD, with approximately 1 in every 160 individuals affected. UC usually affects the rectum but it can extend into the sigmoid and beyond including the entire colon. CD can affect any part of the gastrointestinal tract but most often affecting the ileum and colon. Both the diseases are classified by location and extent; mild, moderate or severe.

IBD and Obesity

The incidence of IBD appears to be on the rise, particularly in developing nations where it was previously uncommon. The major common trend which can be noted among these areas is a rise in westernised diets. Modern westernised diets can be characterised by increased consumption of simple sugars and carbohydrates, higher quantities of animal sources compared with plant based sources, heavier reliance on processed foods and overall increase in caloric consumption.

In the ESPEN guideline on Clinical Nutrition in inflammatory bowel disease, they acknowledged that in the past obesity has not been associated with the disease, however they note that obesity does not stop in the IBD population and in fact obesity may worsen outcomes. Furthermore, it is increasingly recognised that obesity itself represents a low-grade inflammatory state and has been implicated as a risk factor for adverse outcomes in a number of other chronic inflammatory conditions, including psoriasis and rheumatoid arthritis, however, limited studies have been conducted to look at the relationship between IBD and obesity.

It is important to note that a significant percentage of the IBD population develop loss of lean body mass. With the increased risk of obesity this brings about a new concern over sarcopenic obesity which may occur due to chronically poor nutritional quality, increased rates of protein turnover and gut losses during phases of active flare.

It is important to note that a significant percentage of the IBD population develop loss of lean body mass. With the increased risk of obesity this brings about a new concern over sarcopenic obesity which may occur due to chronically poor nutritional quality, increased rates of protein turnover and gut losses during phases of active flare.

What is obesity therapy?

Obesity therapy is a way in which we can support weight loss in individuals living with obesity to improve health. There are multiple types of obesity therapy which are often offered in a step approach.

1. Diet and lifestyle

In Ireland, several services have been established to offer support to individuals through dietary and lifestyle modifications. These services are often provided as part of a multidisciplinary team, comprising professionals such as medical experts, dietitians, psychologists, and exercise specialists. Their aim is to assist individuals dealing with obesity by imparting knowledge on sustainable changes to enhance diet quality, decrease energy intake, boost physical activity, and cultivate new cognitive patterns conducive to altering eating habits.

2. Pharmacotherapy

Developments in pharmacotherapy over the past few years means there are more options available to support individuals living with obesity. Orlistat, a fat binding medication that when taken with food partially inhibits hydrolysis of triglycerides, thus reducing the subsequent absorption, was the only available option for many years. However, Liraglutide and Semaglutide have recently been approved by NICE for managing obesity and can be seen to support weight loss by reduced appetite and hunger with increased fullness and satiety. These medications are encouraged in addition to dietary, lifestyle and behavioural changes.

3. Bariatric surgery

Bariatric surgery is a surgical procedure used in the management of obesity offering interventions to achieve substantial and sustained weight loss. The two most commonly used surgical procedures are the Roux-en-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy (SG).

RYGB involves creating a small stomach pouch, restricting food intake. The small intestine is then rerouted to this pouch, bypassing a portion of the stomach and upper small intestine. The restrictive and malabsorptive components of RYGB contribute to weight loss. The reduced stomach size limits food intake, while bypassing part of the small intestine alters nutrient absorption. RYGB is associated with significant weight loss. Beyond weight reduction, it often leads to improvements in obesity-related comorbidities such as type 2 diabetes.

SG involves removing ~70% of the stomach, leaving a narrow tube or “sleeve.” This results in reduced stomach capacity and reduced production of hunger hormones. The procedure primarily relies on restrictive mechanisms, limiting the amount of food the stomach can hold. Additionally, hormonal changes contribute to appetite reduction and weight loss. SG is often chosen for its relative simplicity and lower risk of complications, with positive impacts on obesityrelated conditions.

Can weight loss improve IBD outcomes?

Patients within this population are at a high prevalence of sarcopenia and micronutrient deficiencies indicating that on a restrictive diet they may be at risk of further deficiencies and muscle mass loss, especially in catabolic states such as those associated with IBD flares. With limited studies into this field, more research is still required to understand this better.

Whilst one study looking at the association of obesity in UC found that as BMI increased by 1 kg/m2, the risk of hospitalisation and surgery rose by 3.4% and 5%, respectively1, another study concluded that patients with obesity had a lower risk of complications.2

Data is similarly limited in CD, with some suggesting that obesity may actually have a protective effect3, a more recent publication found that obesity is associated with decreased rates of disease remission and increased risk of complicated disease course in CD over a six-year follow-up period.4

The impact of obesity therapy on IBD outcomes?

Diet and lifestyle interventions as previously discussed, are known as the first line approach for weight loss and should also be considered in the IBD population. It would be advised that specialist dietetic input is provided to ensure the specific needs of this population are being met, depending on type and severity of disease burden as it may not be possible for patients to tolerate the level of ‘healthy’ foods such as fruits and vegetables often encouraged.

In addition to diet led interventions, increasing exercise may be linked to reduced risk of active disease state in UC and CD and has been shown to increase psychological impact in this patient group, as well as weight.5

Pharmacological approaches, such as GLP-1 therapies listed above offer a promising avenue for promoting weight loss. However, use in IBD patients remains limited. One study does report reduced risk of adverse clinical events in individuals with IBD which includes the need for oral corticosteroids, TNF alpha inhibitors, hospitalisation and IBD related surgeries, suggesting these medications may have a positive effect on disease activity.6 However more research is still needed, including looking at CD and UC as distinct entities. Bariatric surgery has been demonstrated as a safe and effective weight loss therapy for those with pre-existing IBD7, however it is important to note that the type of surgery may be an important consideration. This is supported by research that shows that in patients with CD, RYGB is associated with increased IBD medication, whereas SG may result in less weight loss but has a lower rate of severe complications.8 No controlled intervention study has addressed the treatment of obesity in patients with IBD, therefore current ESPEN guidelines recommend against low-calorie diets in patients with active disease and instead recommends endurance training as the first step in any effort to lose weight.


Understanding the relationship between obesity and IBD is crucial, given their substantial health impacts. The projected global prevalence of obesity, affecting nearly 2 billion by 2035, demonstrated urgent preventive measures. Simultaneously, the rising incidence of IBD across the world, which includes CD and UC, aligns with an increased shift towards modern Western diets.

Although past perceptions did not link obesity to IBD, emerging research does demonstrate potential exacerbations of outcomes in the IBD population. Obesity, recognised as a lowgrade inflammatory state, raises concerns of sarcopenic obesity in IBD patients.

Obesity therapy adopts a multicentered approach, including diet and lifestyle modifications, pharmacotherapy, and bariatric surgery.

While studies explore the impact on IBD outcomes, limited evidence suggests varied outcomes. Exercise and pharmacological interventions show promise, yet comprehensive research, especially distinguishing between CD and UC, remains imperative. Bariatric surgery remains as an additional option, but considerations regarding surgery type, potential complications, and the absence of controlled intervention studies in IBD emphasise the need for cautious implementation.

Addressing the complexities of obesity and IBD requires more evidence-based strategies, with ongoing research to support increasing numbers of individuals navigating this complex area.

References available on request

Written by Kate Parry 1,2 and Werd Al-Najim 1,3,4

1 BeyondBMI, Ireland, 2 Kings College Hospital, London, United Kingdom, 3 Conway Institute, University College Dublin, Ireland, 4 ProHealth36, 5 Physiotherapy & Nutrition, Ireland

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