Chronic fatigue is highly prevalent in patients with conditions characterized by chronic inflammation of the gastrointestinal tract, also known as Inflammatory Bowel Disease (IBD). Chronic fatigue has multiple causes, including alterations in immune system or gut microbiota, psychological factors, and sleeping problems. Unsurprisingly, fatigue has been associated with decreased quality of life, general well-being, and work productivity. Very few patients experience resolution in fatigue, emphasizing the need for new therapies. It has been shown that lifestyle interventions can improve most of fatigue-driving factors. Hence, the investigators hypothesize that a multimodal lifestyle intervention focusing on nutrition, sleep, stress, and exercise will improve chronic fatigue in patients with IBD. During this multicenter, controlled trial, the investigators will compare a multimodal lifestyle intervention to a standard therapy (i.e., an informational brochure on how to cope with chronic fatigue).

Inclusion Criteria:

• Adults (≥18 years old)
• Established IBD diagnosis (Crohn's disease, Ulcerative colitis, or IBD-unclassified)
• Biochemical remission (fecal calprotectin ≤150 mcg/g)
• Clinically significant fatigue (visual analog score 4-8 out of 10)
• Willing and able to attend digital group sessions as a part of the intervention

Exclusion Criteria:

• Documented comorbidities such as severe cardiac failure (classified as NYHA 3-4), chronic kidney disease, myelodysplastic syndrome, Chronic Obstructive Pulmonary Disease (COPD), inherited metabolic diseases (e.g., phenylketonuria, mitochondrial or uric acid cycle pathologies), diabetes type 1
• Documented history of malignancy within the last three years before inclusion except for dermatological cancers such as basal cell carcinoma or squamous cell carcinoma
• Documented history of psychiatric diseases, eating disorders, or addiction. Exception: patients with a history of depression and/or under treatment with antidepressants; however, at inclusion the patients must have a Hospital Anxiety Depression Scale (HADS) score <11 for the depression subscale
• Documented familial hypercholesterolemia
• Diabetes type 2 treated with insulin or other medications such as sulfonylureas, glinides, alpha-glucosidase inhibitors, etc. The only exception is biguanides-metformin
• BMI <18.5 or >35 kg/m2
• Clinically significant anemia (Hb <7.0 mmol/l in females, Hb <8.0 mmol/l in males) with the exception of marginal normocytic or macrocytic anemia (MCV >100 fL and Hb >7.0 mmol/L for females and Hb >8.0 mmol/L for males) as a result of IBD-therapy related myelosuppression
• Vitamin B12 or folic acid deficiency
• Iron deficiency (defined as ferritin <30 μg/l)
• Vitamin D deficiency (<30 nmol/l)
• History of prior bariatric surgery or upper gastrointestinal surgery such as Roux-Y reconstruction or (partial) gastrectomy due to benign or malignant pathologies
• Pregnancy or active breastfeeding
• Unwillingness to follow the lifestyle program, i.e. people that do not want to eat fish, vegans
• Any change in IBD-related systemic medication within the last three months of intervention. Changes in medication dose are allowed up to 1 month before the start of the intervention. Exception: changing the route of administration (e.g., switching from intravenous infliximab to subcutaneous infliximab) or change in therapy due to side effects such as an allergic reaction or cutaneous conditions.
• Recent major surgery, e.g. laparotomy in the last four weeks
• Extended hospitalization (a >2-week admission) within four weeks before inclusion
• Unable to speak and understand Dutch language
• Participation in another study with lifestyle intervention or active consultation with a lifestyle coach on patient's initiative
• Previous participation in the IBD-tailored program by Voeding Leeft