Results of a randomized controlled trial evaluating the effect of increasing package size on usage volume of peanut butter in older adults

Background: Portion and package sizes of foods generally influence energy intake in children and adults. However, little is known about this effect in older adults. This study aimed to determine the effect of increasing package size on usage volume of peanut butter in older adults. Furthermore, it is investigated whether older women and men, different age groups (< 65, 65-80, and 80 +), and non-overweight (BMI < 25), overweight (BMI. 25) and obese (BMI > 30) older adults had different responses to variation in package size. Methods: A randomized controlled trial among 205 older adults was conducted wherein participants were randomized to either the small (350 g) (n = 103) or the large (1000 g) (n = 102) package size condition. Linear regression analyses were used to determine the association between package size condition and usage volume of peanut butter on a slice of bread. Interactions of sex, age groups and BMI categories with package size were tested to investigate differences in responses to variation in package size. Results: Older adults spread on average 12.4 g (SD = 4.3) of peanut butter on a slice of bread when exposed to a small jar of peanut butter and 12.6 g (SD = 4.4) when exposed to a large jar of peanut butter (B = 0.15; 95%CI = 1.04 to 1.35). Interactions between sex, age groups or BMI categories with package size condition were not statistically significant. Conclusions: Increased package size has no effect on usage volume of peanut butter among older adults. Older women and men, different age groups within older adults, and normal-weight, overweight and obese older adults do not respond differently to variation in package size of spreads.