Individual variations in eating rate and oral processing behaviours and their association with energy intake and appetite in older adults (≥ 65 years old)

Oral processing behaviours (OPBs) have been repeatedly associated with energy intake and appetite in younger adults; however, in older adults, these associations remain poorly understood. Older adults often experience ageing-related physiological decline, which can affect food oral manipulation and intake. This study investigated individual variations in OPBs and their association with energy intake and appetite in healthy older adults. Eighty-eight participants (44 males, mean age 73.7 SD 5.3 years) attended one visit after an overnight fast. A fixed-portion breakfast was provided and consumed in full, while consumption was video-recorded to quantify OPBs (chews, bites, swallows, chews per bite, bite size, eating rate, meal duration). Self-reported appetite was assessed using visual analogue scales (VAS). Meal energy intake was measured using an ad libitum lunch. A weighed food diary was used for the rest of the day to record food and drink intake. Generally, eating rate was negatively correlated with OPBs frequency and duration (p < 0.001). OPBs differed between genders and eating rate subgroups. From the postprandial self-reported appetite ratings, in faster compared to slower eaters, "prospective intake" was rated higher, indicating greater perceived appetite. Faster eating rate at the ad libitum meal was significantly and independently associated with greater energy intake (p < 0.001), when accounting for age, gender, BMI, lunch liking and pre-lunch appetite ratings. This study highlights the link between eating rate and energy intake in older adults and provides insights for future interventions, especially when energy intake needs to be increased in frail older adults.