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Effects of Dietary Macronutrient Content on the Sensation of Fullness

By AnalyzeDirect Staff, last updated March 17, 2016

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Nutrition factsThe feeling of fullness experienced after food intake is given by gastric distension, which is sensed by mechanoreceptor neurons in the stomach and later relayed, via the vagus nerve, to sites in the central nervous system that mediate ingestive behavior. Satiation is, therefore, affected by the volume of food ingested, but changes in gastric relaxation alone are not sufficient to explain the dynamics of this event.

In fact, previous studies have shown that the macronutrient composition of a meal – protein, fat, and carbohydrate percentage – also affects satiety.

Researchers from the University of Nottingham decided to gain insight into the relationship between gastric volume changes and sensation of postprandial fullness after test meals high in fat or high in carbohydrate.

Each of the 13 subjects included in the study was provided, on two separate occasions, with either one of the two test meals. Participants were scanned to obtain baseline images of the stomach and underwent serial postprandial MRI scans for 4.5 h. Immediately after every scan, volunteers’ fullness score were collected.

Measurements of gastric volumes were obtained from the MRI scans using Analyze software by manually tracing regions of interest on each slice and summing across the slices to determine the total gastric volume. The use of non-invasive MRI technology provided unlimited strength and novel contribution to the study through a direct measurement of gastric relaxation and contraction.

Fullness was assessed on a 100-mm visual analogue scale, asking the participants to indicate a position along a continuous line between two end-points. As such an assessment is clearly highly subjective, this scale is of most value when looking at changes within individuals. In fact, clinical relevance of sensation is very often not related to absolute values, which can be very different between subjects, but more closely to mean changes from baseline in fullness score.

When considering how much a change from baseline in gastric volume impacted on the sensation of satiety, results showed that subjects experienced a greater degree of satiety at any gastric volume for the high-fat compared with the high-carbohydrate meal. Indeed, high fat meals increase visceral sensitivity: lipid digestion triggers the duodenum to release the peptide hormone cholecystokinin, which enhances the sense of satiety.

Unfortunately, although these results indicate that dietary intervention may help control digestive sensations, it is important to recognize and understand that high-fat foods are usually higher in calories than high-carbohydrate ones, and often extremely palatable. Therefore, these issues highlight the complex interplay of hedonic and physiological signaling that drives food (over)consumption.

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