The study is a randomised, placebo-controlled, double-blind, parallel study in obese children. A total of 75 obese children in the age 5 to 10 years, enrolled in a childhood obesity treatment program, will be included. The participating children will be randomised into one of three groups consuming either HMO (two groups) or placebo (one group).

The primary objective of the study is to establish the effects of HMOs on the faecal microbiota in children. Secondary objectives are to evaluate safety of HMO supplementation in children and the effect on gastrointestinal symptoms (tolerance), bowel habits, metabolic profile and body composition in obese children.

Inclusion Criteria:

1. Informed, written consent by the child's representative(s) and informed verbal assent by the child
2. Age ≥5 and <11 years at visit 0
3. BMI SDS of ≥ 2.3
4. Enrolment in the childhood obesity treatment program at the Children's Obesity Clinic
5. Ability and willingness to understand and comply with the study procedures
6. The child's representative(s) need(s) to read, speak and understand Danish

Exclusion Criteria:

1. Participation in another clinical intervention study one month prior to the screening visit and throughout the study.
2. Any gastrointestinal disease(s) that may cause symptoms or may interfere with the trial outcome, as judged by the investigator.
3. Other severe disease(s) such as malignancy, kidney disease or neurological disease, as judged by the investigator.
4. Psychiatric disease, as judged by the investigator.
5. Use of probiotic supplements (yoghurt allowed) 3 months prior to screening and throughout the study.
6. Consumption of antibiotic drugs 3 months prior to screening and throughout the study.
7. Consumption on a regular basis of medication that might interfere with symptom evaluation (as judged by the investigator) 2 weeks prior to screening and throughout the study.
8. Lack of suitability for participation in the study for any reason as judged by the investigator.