A REVIEW OF DIETARY FACTORS IN THE DEVELOPMENT OF INFLAMMATORY BOWEL DISEASE AND A STUDY OF A POTENTIAL ROLE FOR OBESITY AND THE RELATIONSHIP OF THE TIMING OF ITS MEASUREMENT TO THE ONSET OF DISEASE

Christine Chapman-kiddell (2011). A REVIEW OF DIETARY FACTORS IN THE DEVELOPMENT OF INFLAMMATORY BOWEL DISEASE AND A STUDY OF A POTENTIAL ROLE FOR OBESITY AND THE RELATIONSHIP OF THE TIMING OF ITS MEASUREMENT TO THE ONSET OF DISEASE MPhil Thesis, School of Medicine, The University of Queensland.

       
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Author Christine Chapman-kiddell
Thesis Title A REVIEW OF DIETARY FACTORS IN THE DEVELOPMENT OF INFLAMMATORY BOWEL DISEASE AND A STUDY OF A POTENTIAL ROLE FOR OBESITY AND THE RELATIONSHIP OF THE TIMING OF ITS MEASUREMENT TO THE ONSET OF DISEASE
School, Centre or Institute School of Medicine
Institution The University of Queensland
Publication date 2011-06
Thesis type MPhil Thesis
Supervisor Dr Graham Radford-Smith
Assoc Prof Peter Davies
Dr Lynda Gillen
Total pages 74
Language eng
Subjects 1111 Nutrition and Dietetics
110307 Gastroenterology and Hepatology
Abstract/Summary INTRODUCTION The inflammatory bowel diseases (IBDs), which include Crohn’s disease (CD) and Ulcerative Colitis (UC), are characterized by acute and chronic inflammatory changes in the small or large bowel, or in both. Increasing incidence and prevalence figures for IBD, both in the developed and developing world indicate that environmental factors are at least as significant in IBD as genetic susceptibility. Of these, diet and the host microbiota are likely to play important but as yet poorly defined roles. The major constituents of a standard ‘‘Western’’ diet may contribute to, or protect against, intestinal inflammation via several mechanisms. These include the effects of insulin resistance and short-chain fatty acids such as butyrate, modification of intestinal permeability, the anti-inflammatory role of polyunsaturated fatty acids, and the effect of sulfur compounds from protein on host microbiota. Recent evidence suggests an indirect role for diet via obesity which represents a low grade, chronic inflammatory state. This thesis critically assesses the evidence for the role of diet and in the development of IBD. 4 The incidence of CD appears to be increasing at a faster rate than UC which suggests environmental factors such as obesity may be playing an increasing role in the development of CD. No studies to date have investigated a direct role for obesity in the development of CD. However two studies have investigated the effect of increased BMI on disease distribution and severity of CD with obese CD patients being older at diagnosis and having an increased frequency of perianal complications. In both these studies weight was determined at time of diagnosis and during the course of the disease. This raises the possibility that weight loss prior to diagnosis may have resulted in misclassification of subjects previously obese as normal or underweight thereby biasing the results obtained. The aims of this research are to investigate this possibility by determining changes in body weight during the time between symptom onset and diagnosis and to assess differences in disease distribution, behaviour and severity between ‘overweight’ (BMI ≥ 25 kg/m2) and ‘normal weight’ (BMI < 25 kg/m2) CD patients at both time points. METHODS Patients with a diagnosis of CD were identified from the Brisbane Inflammatory Bowel Disease (IBD) database. Data regarding height and weight at onset of disease symptoms and at diagnosis were collected by patient postal questionnaire and chart audit. Outcomes included age at diagnosis, disease behaviour, disease distribution, bowel resections, immune-suppression, and family history. Incidence of overweight (BMI = 25 kg/m2) at onset of symptoms and at diagnosis was determined. Statistical analysis using chi-squared compared patients with BMI >25 against those with BMI ≤25. Information regarding length of time between onset of symptoms and diagnosis was obtained by chart audit. RESULTS A total of 341 subjects with CD who attended the RBWH between 1996 and 2006 were identified from the IBD database. Weight at onset of symptoms was determined for 163 (47.8%) and weight at diagnosis for 168 (49.3%) of the 341 CD patients identified from the IBD database. Data were available for 155 (45.5%) patients at both time points allowing calculation of weight change for this group. The majority lost weight (119 (76.8%)) with 59(38.10%) losing 10kg or more. Weight was stable in 30 (19.4%) subjects and 6 (4.1%) gained weight. Mean weight change was -8.6 ± 9.2 kg (range -46 to +7 kg). Compared to patients with a BMI < 25 kg/m2 patients with a BMI ≥ 25 kg/m2 were significantly older at onset of symptoms and at diagnosis (p=0.003 at onset of symptoms, p= 0.01 at diagnosis). Compared to patients with a BMI < 25 kg/m2 more patients with a BMI ≥ 25 kg/m2 had colonic disease at diagnosis (34.8% v 16.5% p = 0.08). There were no differences in gender, smoking 5 habits, Vienna classification, presence or absence of bowel resection, perianal disease, use of immunosuppressive drugs or family history between the BMI categories at either of onset of symptoms or diagnosis. Median length of time between symptom onset and diagnosis was 9 months (range 0-144 months) Mean length of time between symptom onset and diagnosis was 20.4 ± 23.4 months. CONCLUSIONS This study failed to reproduce the results of other studies but has shown that a considerable period of time may elapse between the onset of symptoms and diagnosis in adult patients with CD. During this time people may experience substantial weight loss resulting in misclassification of weight status. Therefore previous studies results, based on weight at diagnosis may be biased. When investigating associations between BMI and CD the BMI at disease symptom onset rather than diagnosis should be ascertained.
Keyword inflammatory bowel disease
Crohn’s disease
ulcerative colitis
dietary carbohydrate
dietary fibre
dietary fats
dietary proteins
obesity
Additional Notes Landscape 24,25,27,28,32,34,37,38,39,41

 
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