Nutrition and Behaviour Unit, School of Experimental Psychology, University of Bristol, Bristol, UK.
The University of Western Australia, WA, Australia.
Int J Obes (Lond). 2018 Apr;42(4):905-910. doi: 10.1038/ijo.2017.275. Epub 2017 Nov 16.
Obesity is related to a tendency to discount the future. Information regarding inter-meal interval (IMI) allows meal planning. We sought to assess how obese, overweight and lean people select portion sizes based on the length of an IMI. We hypothesised that individuals with a high body mass index (BMI) would discount information about the IMI. In addition, we investigated how reduced sensitivity to IMIs relates to monetary temporal discounting.
Participants (lean, n=35; overweight, n=31; obese, n=22) selected lunchtime portion sizes in response to information about the timings of their next meal. In seven trials, the time of the IMI was systematically manipulated, ranging from 'right now' to '8 h'. Participants then completed a monetary temporal discounting task. BMI was included as a continuous measure. For each participant, we conducted a linear regression of portion size on IMI to yield a gradient that reflected reduced sensitivity to future meal timings.
As expected, participants selected larger portion sizes in response to a long IMI. Consistent with our hypothesis, individuals with a high BMI discounted information about the IMI (β=-3.49, P=0.015; confidence interval (CI) 6.29 to -0.70). Monetary discounting also negatively predicted BMI (β=-8.1, P=0.003; CI=-13.43 to -2.77), but did not correlate with IMI sensitivity (P>0.05).
These results are the first to demonstrate that temporal discounting operates in planning from one meal to the next, and is more prevalent in obese and overweight, relative to lean individuals. Participants with a high BMI discounted concerns about potential future fullness and hunger in the IMI. Our observations might begin to explain associations between obesity and irregular meal timings or help to form the basis for a targeted intervention that promotes future thinking in meal planning.
肥胖与对未来的低估倾向有关。关于两餐之间间隔时间（IMI）的信息可以帮助进行用餐计划。我们试图评估肥胖、超重和正常体重的人如何根据 IMI 的长度选择食物份量。我们假设高体重指数（BMI）的个体将对 IMI 信息进行折扣。此外，我们还研究了对 IMI 的敏感性降低与货币时间折扣之间的关系。
参与者（正常体重，n=35；超重，n=31；肥胖，n=22）根据下一顿饭的时间信息选择午餐份量。在七次试验中，系统地操纵 IMI 时间，范围从“现在”到“8 小时”。然后，参与者完成了货币时间折扣任务。BMI 作为连续变量纳入。对于每个参与者，我们对部分大小与 IMI 的线性回归生成一个梯度，反映对未来用餐时间的敏感性降低。
正如预期的那样，参与者选择了更大的份量来响应较长的 IMI。与我们的假设一致，BMI 较高的个体对 IMI 信息进行了折扣（β=-3.49，P=0.015；置信区间（CI）6.29 至-0.70）。货币折扣也与 BMI 呈负相关（β=-8.1，P=0.003；CI=-13.43 至-2.77），但与 IMI 敏感性无关（P>0.05）。
这些结果是首次证明时间折扣在从一顿饭到下一顿饭的计划中起作用，并且在肥胖和超重人群中比正常体重个体更为普遍。BMI 较高的参与者对 IMI 中潜在的未来饱腹感和饥饿感进行了折扣。我们的观察结果可能开始解释肥胖与不规律的用餐时间之间的关联，或有助于为促进未来计划用餐的有针对性干预措施提供基础。
