Whole-grain rye foods: effects on appetite and metabolism

Abstract: Overweight, obesity and associated diet-related chronic diseases are increasing worldwide. Diet constitutes a modifiable risk factor for these conditions. Whole-grain consumption has been associated with health benefits, e.g. decreased risk of weight gain, diabetes and cardiovascular disease. Furthermore, whole-grain rye foods, rich in dietary fibres, have upon consumption shown increased satiety and lower postprandial glycaemia and insulinaemia compared with refined wheat. The overall aim of the present thesis was to investigate how appetite and postprandial glycaemia and insulinaemia were affected by consumption of whole-grain rye porridge and crisp bread compared with isocaloric refined wheat bread, served as part of complete breakfasts. Effects of replacing part of the rye in whole-grain rye porridge with inulin and wheat gluten were evaluated on appetite, food intake, gut fermentation, postprandial glucose, insulin and GLP-1 during 8 h after intake. The effect of daily consumption of whole-grain rye porridge for three weeks was evaluated on appetite, food intake, gut fermentation and gut passage time during 8-12 h after intake. Moreover, the impact of unfermented and yeast-fermented whole-grain rye crisp bread on appetite, postprandial glucose and insulin responses was evaluated during 4 h after intake. Whole-grain rye porridge reduced appetite during 4 h after intake compared with refined wheat bread, even after three weeks of daily consumption. The satiating effect of whole-grain rye porridge did not increase with added inulin and wheat gluten. The extensive gut fermentation of whole-grain rye porridge 4-8 h after intake was related to a lower second meal glucose response, but not to appetite, and no differences were observed in postprandial insulin and GLP-1 responses compared with refined wheat bread. Whole-grain rye crisp bread reduced appetite and postprandial insulin response during 4 h after intake compared with refined wheat crisp bread, with no differences in postprandial glucose, and the effect was larger for unfermented whole-grain rye crisp bread. To conclude, whole-grain rye porridge and crisp bread have beneficial effects on appetite regulation and metabolic responses. Including whole-grain rye foods as part of a healthy diet may contribute to appetite control and decrease the risk of diet-related chronic diseases.