Abstract
Background: People with inflammatory bowel disease (IBD) often modify their diet and physical activity to manage symptoms. While potentially helpful short-term, these changes may negatively affect long-term health. Emerging evidence indicates that individuals with IBD are at increased risk of cardiovascular disease (CVD), not only due to chronic systemic inflammation but also because of common modifiable CVD risk factors. However, data specific to the New Zealand population are limited. This thesis aimed to: (1) examine lifestyle habits and CVD risk factors in adults with IBD and (2) assess the impact of a personalised diet and physical activity intervention in modified CVD risk factors among those with inactive IBD.
Methods: The IBDeat study was a cross-sectional survey and clinical assessment. A nationwide online questionnaire collected data on demographics, IBD-related measures, quality of life, physical activity, and dietary intake. Clinical assessments included anthropometrics, blood pressure, body composition (bioimpedance analysis), and biological markers (lipid profile, C-reactive protein, and faecal calprotectin). The IBDLiFE study was a randomised controlled trial comparing dietitian delivered personalised versus generic dietary and physical activity advice over six months. The primary outcome was change in body fat percentage (dual-energy X-ray absorptiometry); secondary outcomes included changes in other body composition parameters, biomarkers, blood pressure, quality of life, food-related quality of life, dietary intake, and physical activity.
Results: A total of 213 participants completed at least one questionnaire in the IBDeat study (53% Crohn's disease, 70% female, median age: 37 years [IQR: 26–50]). Food avoidances (69%) and barriers to physical activity (63%) were common and associated with lower quality of life. Many had inadequate nutrient intakes, particularly calcium (67%). In a subset of 102 from Dunedin, modifiable CVD risk factors were prevalent, including central adiposity (64%) and high body fat (42%). In the IBDLiFE trial, 61 participants were randomised and 52 completed the study (61% Crohn's disease, 59% female, 85% in biological remission). No between-group differences in fat mass were observed, but the personalised group showed significant dietary improvements: increased fruit (0.5 serves/day; 95% CI: 0.1, 1.0) and fibre intake (3.1 g/1000 kcal/day; 95% CI: 1.1, 5.1), and reduced discretionary food (-1.7 serves/day; 95% CI: -3.0, -0.3) and sodium intake (-911 mg/day; 95% CI: -1783, -40).
Conclusions: Adults with IBD in New Zealand face dietary and physical activity challenges and reduced quality of life. They also present modifiable CVD risk factors. Personalised dietitian-delivered diet and physical activity intervention can improve dietary habits without worsening disease activity and should be integrated into routine IBD care.