A single-center observational study to investigate the effects of combined lifestyle intervention (CLI, in Dutch: gecombineerde leefstijlinterventie, GLI) in patients with Inflammatory Bowel Disease.

This is an exploratory observational study of IBD patients ≥ 18 years old with a BMI ≥ 30 mg/kg2 or a BMI between 25 and 30 and an increased risk of diabetes or cardiovascular disease, who are or have been referred to the CLI.

During the 2-year CLI program, fitness measurements take place according to CLI protocol and by the CLI provider: bodyweight, BMI, waist circumference, fat percentage and the EQ-5D-5L are recorded at baseline and 1-year and 2-year timepoints. Whilst patients are offered a CLI referral, willingness to partake will be recorded.

Inclusion Criteria:

• Age ≥ 18 years old;
• Diagnosis of IBD (Ulcerative Colitis, Crohn's Disease or IBD-Unclassified) confirmed by clinical, endoscopic, and histological evidence prior to screening as per standard criteria;
• BMI ≥ 30 mg/kg2 or a BMI between 25 and 30 mg/kg2 and an increased risk of diabetes or cardiovascular disease;
• Patients that are or have been referred to the CLI;
• Oral informed consent must be obtained and documented in EPIC.

Exclusion Criteria:

• Serious underlying disease other than IBD that in the opinion of the investigator may interfere with the subject's ability to participate fully in the study or would compromise subject safety (such as major neurological disorders, certain orthopedic impairments or any unstable, uncontrolled or severe systemic medical disorder);
• If female, the subject is pregnant or lactating;
• Illiteracy (disability to read and understand Dutch).

Patients ≥ 18 years old with a BMI ≥ 30 mg/kg2 or a BMI between 25 and 30 mg/kg2 and an increased risk of diabetes or cardiovascular disease, who are eligible to be referred to the CLI or have already been referred to the CLI.