Abstract
Food cues affect hunger and nutritional choices. Omnipresent stimulation with palatable food contributes to the epidemics of obesity. The objective of the study was to investigate the impact of food cues on appetite-related hormones and to assess the functionality of the secreted hormones on macronutrient uptake in healthy subjects. Additionally, we aimed at verifying differences in the response of total and active ghrelin to stimulation with food pictures and to a meal followed by the stimulation. We were also interested in the identification of factors contributing to response to food cues. We recruited healthy, non-obese participants for two independent cross-over studies. During the first study, the subjects were presented random non-food pictures on the first day and pictures of foods on the second day of the study. Throughout the second study, following the picture session, the participants were additionally asked to drink a milkshake. Concentrations of blood glucose, triglycerides and hunger-related hormones were measured. The results showed that concentrations of several hormones measured in the blood are interdependent. In the case of ghrelin and gastric inhibitory peptide (GIP) as well as ghrelin and glucagon-like peptide-1 (GLP-1), this co-occurrence relies on the visual cues. Regulation of total ghrelin concentration following food stimulation is highly individual and responders showed upregulated total ghrelin, while the concentration of active ghrelin decreases following a meal. Protein content and colour intensity of food pictures reversely correlated with participants' rating of the pictures. We conclude that observation of food pictures influences the concentration of several appetite-related hormones. The close link of visual clues to physiological responses is likely of clinical relevance. Additionally, the protein content of displayed foods and green colour intensity in pictures may serve as a predictor of subjective attractiveness of the presented meal.
Highlights
Most food consumption in western populations happens for reasons other than energy shortage, suggesting that a significant proportion of food consumption is driven rather by pleasure than by a physiological need [1]
Food stimuli compared to the non-food objects resulted in statistically non-significant trends indicating increase in blood insulin (p = 0.05; d = 0.9; 95% CI: 4, 430; Fig 2D and S4 Table) and gastric inhibitory peptide (GIP) level (p = 0.07; d = 0.8; 95% CI: 39.7, 121.5; Fig 2E and S4 Table)
A linear correlation was measured between glucagon-like peptide-1 (GLP-1) and glucagon as well as Peptide YY (PYY) and glucagon across all measured time points (11:15 am, 11:30 am, 11:45 am), which was independent from the type of pictures shown (S2D–S2I Fig)
Summary
Most food consumption in western populations happens for reasons other than energy shortage, suggesting that a significant proportion of food consumption is driven rather by pleasure than by a physiological need [1]. Dietary behaviours and the drive to eat are undeniably powered by food-related cues. The number as well as the density of the food-related cues have been implicated in choices to consume food or restrain from it [2,3,4,5]. Food choices consumed as snacks besides main meals appeared to be more influenced by food-related cues than main meals and that internal and external cues, rather than hunger, are the most frequently recalled triggers of snacking behaviour. A response to a food-related stimulus seems to be linked to higher overall caloric intake and, to the development and maintenance of obesity and obesityrelated health problems [5, 9]. Understanding regulations that lead to weight gain on the level of unconscious processes as well as molecular mechanisms is of high importance
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