Abstract
Food intake influences human cognition, olfaction, hunger, and food craving. However, little research has been done in this field to elucidate the effects of different nutrients. Thus, the goal of our study was to investigate the effects of oral ingestion of different nutrient solutions on olfactory, cognitive, metabolic and psychophysical function. Twenty healthy men participated in our study employing a double-blind, cross-over, repeated measurement design. Participants were tested on four different study days. Each day participants received, in randomized order, one of three isocaloric (protein, carbohydrate or fat 600 kcal, 1,500 mL) solutions or a placebo. Olfactory and cognitive tests (monitoring only) were conducted three times, i.e., 60 min before the beginning of nutrient intake, following oral ingestion of the solution and 60, and 240 min after. Psychophysical and metabolic function tests (active grehlin, desacyl ghrelin, insulin, glucagon, glucose, triglyceride, urea) were performed 7 times on each examination day (observation period: −60 min, 0 = solution intake, +60, +120, +180, +240, and +300 min). Ratings of hunger and food craving significantly differed over the observation period with lowest ratings following application of the protein solution. Highest ratings of craving were found following placebo intake. We further observed a significant positive correlation of active grehlin with hunger and fat, protein and sweets craving for each nutrient solution. Active grehlin significantly correlated with carbohydrate craving for carbohydrate and fat solution and with vegetable craving for fat solution only. Hunger hormone levels, hunger and food craving ratings demonstrated that the hierarchical order that appears in satiating efficiencies of isovolumetric-isocaloric ingested macronutrients is protein > fat > carbohydrate. Our study reveals that the type of nutrient exerts a significant influence on metabolic parameters, hunger and food craving.
Highlights
Food intake is controlled by short-acting and long-acting regulatory mechanisms
Post-hoc analyses demonstrated that vegetable craving was significantly higher regarding placebo intake compared to protein intake (p ≤ 0.05)
Active grehlin significantly correlated with carbohydrate craving for carbohydrate and fat solution and with vegetable craving for fat solution only
Summary
Food intake is controlled by short-acting and long-acting regulatory mechanisms. The aim of the long-acting regulation is to control fat resources to maintain body weight (Wilding, 2002). The stomach and the small intestine expand, which can be measured by mechanosensors (Gekle et al, 2010) These sensors send information about the gastrointestinal expansion to the nucleus tractus solitarii, which inhibits the hunger center (Berthoud and Neuhuber, 2000). The researchers reported that the presence of the balloon in the stomach was associated with a significant decrease in ghrelin secretion, despite the concomitant weight loss. Another isovolumetric gastric distension study by Wijlens et al (2016) showed that a high caloric gastric infusion increased satiety and reduced subsequent energy intake compared to an isovolumetric low caloric gastric infusion.
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