Effect of High-fat/High-sugar Diet on Food Reward Signaling

In this randomized, single-blinded basic research study, healthy normal-weight human participants are exposed to a high-fat/high-sugar (HF/HS) snack or a low-fat/low-sugar (LF/LS) snack twice a day for eight weeks in addition to their regular diet. All participants are tested at baseline, after 4 weeks and after 8 weeks of dietary intervention. At all time points the investigators acquire the following parameters: * Body weight and composition, * Blood parameters to control for metabolic changes, * Visual analog scales (hunger, satiety, tiredness, etc.), * Fat and sugar concentration preference, * Functional Magnetic Resonance Imaging (fMRI) during a learning and a gustatory perception task. The investigators hypothesize that the habitual consumption of a small HF/HS snack will reduce the preference for low-fat concentrations and will have an impact on brain response to the anticipation and consumption of palatable food. Moreover, the investigators hypothesize, that HF/HS diet will have an impact neuronal encoding of learning independent of food cues. The investigators expect these alterations independent of body weight gain suggesting a direct effect of HF/HS diet on neuronal circuits.