In the past, carbohydrate restriction was indicated as a treatment for people with type 1 diabetes when exogenous insulin was not available. Now it is mainly used as an added treatment for people with type 1 diabetes on top of standard insulin administration and glucose monitoring. Despite previous studies, the impact of carbohydrate restriction on glycemic control and quality of life is still not clear. Furthermore, few studies exist on carbohydrate restriction in children with type 1 diabetes and combined with the use of hybrid closed-loop insulin delivery. Therefore this study will determine the impact on glycemic control and the feasability of a moderate carbohydrate diet compared to a traditional diet in children (7-17 years) with type 1 diabetes on top of using a hybrid closed-loop system. In this randomized, crossover study, 28 children will follow a moderate carbohydrate diet (four weeks) and a traditional diet (four weeks) in randomized order. With a run-in period (two weeks) prior to the first diet and a wash-out period (six weeks) between the two diets, the children will participate in the study for a total of 16 weeks. The primary endpoint is the difference of time spent in target range (defined as a sensor glucose value between 70 and 180 mg/dL) between the four-week moderate carbohydrate diet and the four-week traditional diet.