BACKGROUND Smaller portions may help to reduce energy intake. However, there may be a limit to the magnitude of the portion size reduction that can be made before consumers respond by increasing intake of other food immediately or at later meals. We tested the theoretical prediction that reductions to portion size would result in a significant reduction to daily energy intake when the resulting portion was visually perceived as 'normal' in size, but that a reduction resulting in a 'smaller than normal' portion size would cause immediate or later additional eating. METHODS Over three 5-day periods, daily energy intake was measured in a controlled laboratory study using a randomized crossover design (N = 30). The served portion size of the main meal component of lunch and dinner was manipulated in three conditions: 'large-normal' (747 kcal), 'small-normal' (543 kcal), and 'smaller than normal' (339 kcal). Perceived 'normality' of portion sizes was determined by two pilot studies. Ad libitum daily energy intake from all meals and snacks was measured. RESULTS Daily energy intake in the 'large-normal' condition was 2543 kcals. Daily energy intake was significantly lower in the 'small-normal' portion size condition (mean difference - 95 kcal/d, 95% CI [- 184, - 6], p = .04); and was also significantly lower in the 'smaller than normal' than the 'small-normal' condition (mean difference - 210 kcal/d, 95% CI [- 309, - 111], p < .001). Contrary to predictions, there was no evidence that the degree of additional food consumption observed was greater when portions were reduced past the point of appearing normal in size. CONCLUSIONS Reductions to the portion size of main-meal foods resulted in significant decreases in daily energy intake. Additional food consumption did not offset this effect, even when portions were reduced to the point that they were no longer perceived as being normal in size. TRIAL REGISTRATION Prospectively registered protocol and analysis plan: https://osf.io/natws/; retrospectively registered: https://clinicaltrials.gov/ct2/show/NCT03811210.

中文翻译：

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无论份量是否正常，减少主餐份量都会减少每日能量摄入：一项为期 5 天的交叉实验室实验。

背景技术较小的份量可能有助于减少能量摄入。然而，在消费者通过立即或稍后进餐增加其他食物的摄入量做出反应之前，可以减少份量的幅度可能是有限的。我们测试了理论预测，即当所得到的部分在视觉上被认为是“正常”大小时，减少份量将导致每日能量摄入量显着减少，但导致“小于正常”份量的减少会导致每日能量摄入量显着减少。立即或稍后额外进食。方法 在一项对照实验室研究中，使用随机交叉设计（N = 30）测量了三个为期 5 天的时期的每日能量摄入量。午餐和晚餐的主要膳食成分的份量在三种情况下进行控制：“正常大”（747 kcal）、“正常小”（543 kcal）和“比正常小”（339 kcal）。份量感知的“正常性”是通过两项试点研究确定的。测量所有膳食和零食的每日随意摄入的能量。结果“大正常”状态下每日能量摄入量为 2543 kcals。在“小正常”份量条件下，每日能量摄入量显着较低（平均差 - 95 kcal/d，95% CI [- 184, - 6]，p = .04）；并且在“小于正常”条件下也显着低于“小正常”条件（平均差 - 210 kcal/d，95% CI [- 309, - 111]，p < .001）。与预测相反，没有证据表明当份量减少到超过正常大小时，观察到的额外食物消耗程度会更大。结论 减少主餐食物的份量会导致每日能量摄入量显着减少。额外的食物消耗并不能抵消这种影响，即使份量减少到不再被认为是正常大小的程度。试用注册 前瞻性注册方案和分析计划：https://osf.io/natws/；回顾性注册：https://clinicaltrials.gov/ct2/show/NCT03811210。