Sensory Responses in Nutrition and Energy Balance : Role of Texture, Taste, and Smell in Eating Behavior

Billions of people, almost 40% of the world’s population, are either overweight or underweight, which is a direct consequence of the food environment. In more and more countries in the world, people are overweight in a large part due to the obesogenic food environment. The obesogenic food environment leads to an overconsumption of energy; it is obvious that sensory characteristics of food have a tremendous impact on food choice and intake. The chapter deals with the effects of texture, taste, and smell on intake. The effect of texture on energy intake is dramatic. Liquid and soft foods are consumed at much higher rates compared to more harder foods. The energy intake rate of energy dense liquids (like sugar sweetened beverages) and soft solids (like cake, sausage roll, minced meatball) is in the range of 150-450 kcal/min, quickly leading to overconsumption of energy. Liquid and soft solid calories are not well sensed by the sense of taste, due to their short oro-sensory exposure time per kcal ingested. Various recent studies show that across the food supplies in Australia, Malaysia, the Netherlands, and the USA, sweetness, umami, saltiness, and fat sensation intensities relate to concentrations of carbohydrates, protein salt, and fat in food. So, taste serves as nutrient sensing system, and this sensing system contributes to satiation. The role of smell is different. Retronasal smell sensations coming through flavors within foods do not have an impact on satiation; odors in the environment may lead to sensory specific appetites. In summary, sensory signals from foods have a large impact on energy intake, and designing foods in an optimal way leads to a higher satiating efficiency per kcal, while maintaining palatability. In this way we can make the healthy choice the happy choice

Functional MRI and sensory perception of food

Nowadays, human brain activity in response to complex paradigms can be extensively mapped. Though introduced relatively recently, functional magnetic resonance imaging (fMRI) based on blood-oxygen-level-dependent contrast has developed dramatically. It is a noninvasive and exploratory approach which provides in a relatively direct way a differentiated measure of each processing step within the brain, the complete network giving access to cognitive mechanisms. Compared with the other functional imaging methods, fMRI offers high spatial and temporal resolution, and so can detail cognitive tasks both in space and in time by following the time course of the operations. This review deals with how this detailed breakdown is achieved. A further aim is to show how and why fMRI can be used to study sensory perceptions that might, at first sight, seem hard to address by this method, namely perceptions during eating. The processing of stimuli from food by the brain is one determinant of food representation, but also of food liking and wanting, which in turn control appetite, and ultimately food intake. Food consumption also activates the reward system, which thus helps to control food intake. fMRI experiments conducted with human subjects have largely helped to gain a fuller understanding of these intricate brain processes. Among the sensations triggered by food, visual, olfactory, gustatory, and somatosensory cues are the most salient. Accordingly, we focus here on these sensory systems and on the integration of the two senses necessary to produce flavor perception: namely olfaction and gustation