Food delivers energy, nutrients and a pleasurable experience. Slow eating and prolonged oro-sensory exposure to food during consumption can enhance the processes that promote satiation. This systematic review and meta-analysis investigated the effects of oral processing on subjective measures of appetite (hunger, desire to eat) and objectively measured food intake. The aim was to investigate the influence of oral processing characteristics, specifically "chewing" and "lubrication", on "appetite" and "food intake". A literature search of six databases (Cochrane library, PubMed, Medline, Food Science and Technology Abstracts, Web of Science, Scopus), yielded 12161 articles which were reduced to a set of 40 articles using pre-specified inclusion and exclusion criteria. A further two articles were excluded from the meta-analysis due to missing relevant data. From the remaining 38 papers, detailing 40 unique studies with 70 subgroups, raw data were extracted for meta-analysis (food intake n = 65, hunger n = 22 and desire to eat ratings n = 15) and analyzed using random effects modelling. Oral processing parameters, such as number of chews, eating rate and texture manipulation, appeared to influence food intake markedly but appetite ratings to a lesser extent. Meta-analysis confirmed a significant effect of the direct and indirect aspects of oral processing that were related to chewing on both self-reported hunger (-0.20 effect size, 95% confidence interval CI: -0.30, -0.11), and food intake (-0.28 effect size, 95% CI: -0.36, -0.19). Although lubrication is an important aspect of oral processing, few studies on its effects on appetite have been conducted. Future experiments using standardized approaches should provide a clearer understanding of the role of oral processing, including both chewing and lubrication, in promoting satiety.

As overeating, overweight and obesity remain public health concerns, it is crucial to design satiety-enhancing foods that suppress appetite and lower snack intake. Existing research identifies oro-sensory targets to promote satiation and satiety within the “satiety cascade” yet it remains unclear as to whether it is ‘chewing’ or ‘oral lubrication’ that might amplify satiation signals.Here we have combined techniques from experimental psychology, food material science and mechanical engineering to measure the role of chewing and lubrication using novel, model foods as preloads on subjective appetite and intake of a salty snack. Three mint flavoured hydrogels were engineered to vary in their texture (fracture stress) and lubrication (inverse of friction coefficient) properties, and a control group received a mint tea. Results showed that snack intake was suppressed by 32% after eating the low chewing/high lubricating preload as compared to the high chewing/low lubricating preload (p<0.05). No other significant effects were found for snack intake. Hunger ratings decreased from t1 to t3 (p<0.05), however differences between conditions were subtle and not significant. Thus, this proof-of-concept study demonstrates that manipulating oral lubrication is a promising new construct to reduce snack intake that merits future research in the oro-sensory satiety domain.