Inclusion and exclusion criteria

Male and female patients aged 18 years or older, referred to the bariatric service for assessment of severe obesity were eligible for inclusion. Our clinical practice is to define severe obesity as a body mass index (BMI) ≥ 40 kg m⁻² (or ≥ 35 kg m⁻² with co-morbidities such as type 2 diabetes or obstructive sleep apnea syndrome). Patients must have been willing to attend all the 14 scheduled intervention visits. Females of childbearing potential who were pregnant, breast-feeding or intended to become pregnant or were not using adequate contraceptive methods were not considered eligible for the programme. Those with a recent myocardial infarction (within 6 months), untreated arrhythmia, untreated left ventricular failure, recent cholelithiasis (within the past year), hepatic or renal dysfunction, type 1 diabetes, untreated major psychiatric disorders, eating disorders, cancer, previous bariatric surgery, a BMI < 35 kg m⁻² or those deemed unlikely to attend for the full programme (e.g. frequent clinic non-attendance) were excluded from the programme. Excess alcohol consumption, defined as more than 21 units per week for men and more than 14 units per week for women, was also an exclusion criterion. Moreover, patients were requested to avoid any alcohol whatsoever during the 6-month intervention. Patients with a history of lactose intolerance or allergy to milk or other dairy products were excluded from participation in the milk diet.