Zimmerman Annie R, Ferriday Danielle, Davies Sarah R, Martin Ashley A, Rogers Peter J, Mason Alice, Brunstrom Jeffrey M
Nutrition and Behaviour Unit, School of Experimental Psychology, University of Bristol, UK.
Nutrition and Behaviour Unit, School of Experimental Psychology, University of Bristol, UK.
Appetite. 2017 Sep 1;116:284-290. doi: 10.1016/j.appet.2017.05.019. Epub 2017 May 10.
'Dietary' delay discounting is typically framed as a trade-off between immediate rewards and long-term health concerns. Our contention is that prospective thinking also occurs over shorter periods, and is engaged to select portion sizes based on the interval between meals (inter-meal interval; IMI). We sought to assess the extent to which the length of an IMI influences portion-size selection. We predicted that delay discounters would show 'IMI insensitivity' (relative lack of concern about hunger or fullness between meals). In particular, we were interested in participants' sensitivity to an uncertain IMI. We hypothesized that when meal times were uncertain, delay discounters would be less responsive and select smaller portion sizes. Participants (N = 90) selected portion sizes for lunch. In different trials, they were told to expect dinner at 5pm, 9pm, and either 5pm or 9pm (uncertain IMI). Individual differences in future-orientation were measured using a monetary delay-discounting task. Participants chose larger portions when the IMI was longer (p < 0.001). When the IMI was uncertain, delay-discounting participants chose smaller portions than the average portion chosen in the certain IMIs (p < 0.05). Furthermore, monetary discounting mediated a relationship between BMI and smaller portion selection in uncertainty (p < 0.05). This is the first study to report an association between delay discounting and IMI insensitivity. We reason that delay discounters selected smaller portions because they were less sensitive to the uncertain IMI, and overlooked concerns about potential future hunger. These findings are important because they illustrate that differences in discounting are expressed in short-term portion-size decisions and suggest that IMI insensitivity increases when meal timings are uncertain. Further research is needed to confirm whether these findings generalise to other populations.
“饮食方面的”延迟折扣通常被视为即时奖励与长期健康问题之间的权衡。我们的观点是，前瞻性思维也会在较短时期内出现，并且会根据用餐间隔时间（餐间间隔；IMI）来选择食物分量。我们试图评估IMI的时长对食物分量选择的影响程度。我们预测，延迟折扣者会表现出“IMI不敏感”（相对而言不太在意餐间的饥饿或饱腹感）。具体而言，我们对参与者对不确定IMI的敏感性感兴趣。我们假设，当用餐时间不确定时，延迟折扣者的反应会较小，并选择较小的食物分量。参与者（N = 90）为午餐选择食物分量。在不同的试验中，他们被告知预计晚餐时间分别为下午5点、晚上9点，以及下午5点或晚上9点（不确定IMI）。使用货币延迟折扣任务来测量未来导向的个体差异。当IMI较长时，参与者选择的食物分量更大（p < 0.001）。当IMI不确定时，延迟折扣参与者选择的食物分量比在确定IMI情况下选择的平均分量小（p < 0.05）。此外，货币折扣在BMI与不确定情况下较小食物分量选择之间起到了中介作用（p < 0.05）。这是第一项报告延迟折扣与IMI不敏感之间关联的研究。我们推断，延迟折扣者选择较小的食物分量是因为他们对不确定的IMI不太敏感，并且忽略了对未来潜在饥饿的担忧。这些发现很重要，因为它们表明折扣方面的差异在短期食物分量决策中有所体现，并且表明当用餐时间不确定时，IMI不敏感会增加。需要进一步研究来确认这些发现是否适用于其他人群。
