The intermittent fast diet for adolescents with obesity: a pilot study

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This study will examine the effect of a 12 week eating plan, an intermittent modified fast diet, that involves 3 days each week of a Very Low Energy Diet (VLED, consuming a very limited amount of food) and a healthy diet on the other 4 days, in adolescents with obesity. We think this diet will be more acceptable and therefore more likely to be adhered to by adolescents than a diet requiring them to limit their food every day. We speculate that this will result in body weight and body fat loss, and a reduction in cardiometabolic risk factors. Adolescents with obesity will be invited to participate in the study by their clinician when attending Endocrinology, Dietetics or Weight Management services at The Children’s Hospital at Westmead. The details of the study will be explained to them and they will be given written information. If they agree to be in the study and their parent/carer also gives consent, a 3 hour appointment will be made for them to see the study dietitian, who will explain the diet and will measure their height, weight, waist circumference, blood pressure and percentage body fat. At baseline questionnaires on demographic, medical and family history will be completed by the parent/carer, and adolescents will complete questionnaires on their quality of life and eating behaviours. Adolescents will have vascular structure and function tests and have a fasting blood test to measure their blood sugar, insulin, blood fats and liver function at The Children’s Hospital at Westmead. All of these measurements, tests and questionnaires will be repeated at week 12 and at the final visit during week 26 of the study. Participants will return to the hospital for appointments with the study dietitian at 2, 4, 8 and 12 weeks for their diet to be reviewed. The 12 week appointment will be for 3 hours during which they will have an interview with the study dietitian to determine how acceptable the diet was for them, as well as complete the measurements, tests and questionnaires as at the start of the study. During weeks 1, 3, 6, 9 and 11 of the study, adolescents will receive support from a dietitian via their choice of email, Short Messaging Service (SMS) or telephone call. At the 12 week visit, adolescents will choose one of four diets to follow for weeks 13 to 26: (1) Three VLED days per week plus 4 days of a healthy diet or (2) Two VLED days per week plus 5 days of a healthy diet or (3) One VLED day per week plus 6 days of a healthy diet or (4) Seven days per week of a healthy diet Participants will meet with the study dietitian at 16 and 20 weeks, and receive regular support up to the final visit. At 26 weeks from the start of the study, participants will return to the hospital for a final 3 hour visit during which they will have final measurements, testing and questionnaires completed, as well as an interview with the study dietitian about the acceptability of the diet chosen for the final 14 weeks of the study.