Intensive Dietary and Activity Counselling (IDAC)

The aim of this intervention study is to investigate if a intensive dietary and physical activity counselling during the first two years of life in children with increased (genetically) risk for Type 1 Diabetes (T1D) can promote a healthy beta-cell environment, in order to reduce increased weight gain and development of islet autoimmunity (beta-cell autoantibodies). The main hypotheses are: * Early lifestyle influences the susceptibility to islet autoimmunity (IA) by increasing beta-cell vulnerability. Introducing a "healthy beta-cell lifestyle" from infancy will reduce beta-cell vulnerability and the likelihood of IA. * Will promotion of a healthy beta-cell environment during early childhood in children with increased genetic risk of T1D reduce beta-cell stress, increased weight gain and development of islet autoantibodies? The primary objective is to determine whether an Intensive Diet and Activity Counseling (IDAC) from age 3 months to age 2 years improves beta-cell health in children with increased risk for islet autoimmunity. Secondary objectives are to determine whether IDAC is associated with infant and early childhood growth and body composition and to determine whether IDAC reduces the cumulative incidence of islet autoantibodies or type 1 diabetes in childhood. Participants will be randomized (ratio 1:1) to control group and intervention group. Breastfeeding status at time of randomization will be taken into account. Participants will be enrolled by the age of four months and visit the research clinic ever third months up until the age of 24 months, and then yearly up until the age of 6 years. * Anthropometric measurements and blood draw will be taken at each visit. * Questionnaires focusing on breastfeeding and early infant feeding habits will be used at each visit. * 24hrs recalls will be done at the age of 6, 9, 12, 18 and 24 months of age. * Physical activity will be estimated using questionnaires (3, 6, 9 months) and accelerometer data (12, 18 and 24 months). * Stool samples will be collected at 6, 12 and 18 months of age