Obesity is one of the most important risk factors for the development of diabetes, and diet plays a central role in this context. Numerous diets are available today; however, there is increasing evidence that not only the amount of calories is decisive for their effects, but also the composition of the diet. In particular, carbohydrate restriction seems to have beneficial effects on the development of diabetes, although the exact mechanisms are unclear. This project investigates how a carbohydrate-reduced diet changes the human metabolism. In particular, its effects on liver fat, abdominal fat, insulin resistance and the intestinal flora will be investigated. Moreover, we investigate the effects of carbohydrate restriction on the immune metabolism. The combination of state-of-the-art metabolic measurement methods with techniques from basic research enables comprehensive findings that should directly benefit people with obesity. In this way, the development of diabetes can be reduced or prevented by means of personalized diets.