Portion Size Effects on Body Weight: Free Living Setting

描述（由申请人提供）：拟开展的研究对公共卫生具有极高的意义。超重和肥胖影响着大多数美国成年人以及越来越多的儿童和青少年。原因尚不清楚，但大多数科学家认为，这主要是由于食物环境促进了过量的能量摄入。大份量食物被认为是暴饮暴食的重要原因，而且在人们生活、工作和社交的几乎所有环境中都很普遍。高度控制的实验室研究提供了强有力的证据，证明大份量食物对增加能量摄入有短期影响，但尚未调查大份量食物对能量摄入或体重变化的长期影响。小份量食物对能量摄入或体重变化的潜在保护作用尚未得到评估。拟议的研究通过创建一个新的模型实验范式来测试自然环境中自由生活的人的分量大小的影响，从而弥合了从实验室到自然环境的关键差距。该研究解决了一个关键的公共卫生问题，即普遍的大份量是否会导致自由生活人群的体重过度增加，从而成为超重、肥胖和体重过度增加的潜在公共卫生风险。目前没有直接涉及这一重要公共卫生问题的数据。这项研究的目的是在六个月的时间里，在200名自由生活的成年人中，研究大份量和小份量对体重的影响。能量摄入的改变是第二个结果。分量大小和体重变化之间关系的潜在调节因子和中介因子将以探索性的方式进行研究。在六个月的时间里，参与者将被随机分配到四种研究条件中的一种：午餐份量为400千卡、800千卡或1600千卡，或者是不干预的对照组。在6个月的时间里，每周五天，每天提供一顿午餐。体重和能量摄入将在基线、1个月、3个月和6个月时进行测量。假设参与者在1600千卡的情况下相对于800千卡的情况下和相对于对照组会增加体重。

DESCRIPTION (provided by applicant): The proposed research is of extremely high significance for public health. Overweight and obesity affect the majority of US adults and a growing proportion of children and youth. The causes are not well understood, but are believed by most scientists to be largely due to a food environment that promotes excess energy intake. Large food portion sizes are thought to play a significant role in overeating, and are pervasive across virtually every setting in which people live, work and socialize. Highly controlled laboratory studies have provided strong evidence that large portion sizes have short-term effects to increase energy intake, but have not investigated the longer-term effects of large portion sizes on energy intake or body weight change. Small portion sizes have not been evaluated for their potential protective effects on energy intake or body weight change. The proposed research bridges a crucial gap from the laboratory to the naturalistic environment by creating a novel model experimental paradigm through which to test the effects of portion sizes in free-living people in the natural environment. The research addresses a critical public health question of whether the pervasive large portion sizes are contributing to excess weight gain among free-living people and are therefore a potent public health risk exposure for overweight, obesity and excess weight gain. No data currently exist that directly address this important public health question. The proposed study aims to examine the effects of large and small portion sizes on body weight over a six-month period among a free-living sample of 200 adults. Change in energy intake is a secondary outcome. Potential moderators and mediators of the association between portion size and body weight change will be examined in an exploratory manner. Participants will be randomized to one of four study conditions for a six-month period: Lunch meal portion size 400 kcal, 800 kcal or 1600 kcal or a no-intervention control group. Participants in the portion size lunch groups will be provided with one lunch meal daily 5 days per week for the six-month period. Body weight and energy intake will be measured at baseline, one, three and six months. It is hypothesized that participants will gain weight in the 1600 kcal portion size condition relative to the 800 kcal portion size condition and relative to the control group.