Visual food cues decrease blood glucose and glucoregulatory hormones following an oral glucose tolerance test in...

Previous experiments of our group have demonstrated that preprandial processing of food cues attenuates postprandial blood glucose excursions. Here we systematically re-evaluated the glucose-lowering effect of visual food cues by submitting 40 healthy fasted men (20 normal-weight men, mean age 24.8 ± 3.7 years, BMI 21.9 ± 0.3 kg/m²; 20 obese men, 26.8 ± 4.2 years, 34.3 ± 1.3 kg/m²) to an oral glucose tolerance test (OGTT) following exposure to pictures of high-calorie food items versus neutral items. OGTT-related changes in blood concentrations of glucose and relevant glucoregulatory hormones including GLP-1 were assessed and analyzed according to the oral minimal model. Independent of body weight, food-cue compared to neutral stimulus presentation reduced postprandial concentrations of glucose (p = 0.041), insulin (p = 0.026) and C-peptide (p = 0.007); accordingly, oral minimal model analyses yielded a food-cue induced decrease of dynamic-phase insulin secretion (p = 0.036). We also observed a trend towards lower GLP-1 levels directly after food cue stimulation in both body weight groups (p = 0.057), as well as a trend towards decreased heart rate (p = 0.093) and significantly decreased diastolic blood pressure (p = 0.019). While we did not detect indicators of an early rise in insulin levels in terms of a 'cephalic phase insulin response', our findings support the assumption that preprandial processing of food cues exerts marked effect on postprandial glucose regulation, with possible contributions of changes in GLP-1. The mechanisms linking food cue exposure and glucoregulatory improvements should be investigated in greater detail, to potentially open new treatment options for metabolic dysfunctions.