Personalized Nutrition and eHealth: Lifestyle Intervention (LION) Study for Weight Loss Maintenance

Step I - Screening and baseline phenotyping When a potential suitable participant is interested, a screening interview to check eligibility will take place by phone after oral agreement is given. The structured screening interview is carried out by means of a questionnaire in the format of a Case Report Form (CRF). Suitable persons are provided with participant´s information and data protection sheet and with the "declaration of consent". Sufficient time for consideration is given between the screening interview and visit 1A, where written consent is signed. After the telephone-based screening interview, eligible participants are required to provide written consent. Participants will undergo clinical examinations at two visits (V1A + V1B), serving primarily for phenotyping as well as for detection of potentially unknown exclusion criteria. The order of some measurements carried out during V1A and V1B as well as the type of lipid challenge is randomized. Data collection V1A: * Resting metabolic rate * Metabolic response to meal challenge * Anthropometry * Vital parameters * Blood parameters * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Sampling of blood samples for further research questions Data collection V1B: * Metabolic response to meal challenge * Vital parameters * Blood parameters * Urine parameters * Hand Strength Measurement * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Sampling of blood, urine and saliva * Optional: Adipose tissue distribution by MRI measurement; parameters for physical strength, motor function and body static condition; 24h urine collection; fecal samples Step II - Weight loss intervention Once participant is still deemed eligible after V1A and V1B, the formula-based low calorie diet (LCD) starts as weight loss intervention. Formula products will be provided once per week. An additional daily intake of 200 g raw or cooked non-starchy vegetables is allowed. Participants fulfill a food diary to record eaten products including drinks and vegetables and to record well-being or side effects. Furthermore, participants are phenotyped by a continuous glucose measurement during the first four weeks of intervention. Data collection V2: * Anthropometry * Vital parameters * Blood and urine parameters * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Resting metabolic rate * Hand strength measurement * Documentation of safety * Continuous glucose measurement * Sampling of blood, urine, and saliva * Optional: Adipose tissue distribution by MRI measurement; parameters for physical strength, motor function and body static condition; 24h urine collection; fecal samples Step III - Weight maintenance intervention If weight loss is \> 4 kg after eight weeks, the participant is eligible for randomization into one of the following four weight maintenance intervention arms: Low carb - App-based group Low carb - Newsletter-based group Low fat - App-based group Low fat - Newsletter-based group Data collection V3A: * Anthropometry * Blood and urine parameters * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Documentation of safety * Sampling of blood and urine samples for further research questions, e.g. metabolic profile (to be confirmed) * Optional: 24h urine collection Data collection V3B: * Anthropometry * Blood parameters * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Documentation of safety * Sampling of blood samples for further research questions, e.g. metabolic profile (to be confirmed) Data collection V3C: * Anthropometry * Blood and urine parameters * Resting metabolic rate * Vital parameters * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Documentation of safety * Hand strength measurement * Sampling of blood, urine, and saliva * Optional: Adipose tissue distribution by MRI measurement; parameters for physical strength, motor function and body static condition; 24h urine collection; fecal samples Step IV - Follow-up During follow-up, all participants receive the same newsletters with nutritional information every 3 months (independent of weight maintenance intervention group). Further weight management is carried out by "self-help". Data collection V4: * Anthropometry * Vital parameters * Blood parameters ( * Clinical, lifestyle (nutrition, physical activity), psychological, environmental and social factors (questionnaires and protocols) * Resting metabolic rate * Sampling of blood