Portion Size & Energy Intake: A key nutritional concept we must now understand to address obesity

肥胖症的增加是由能量摄入的增加引起的，而一个关键的环境因素可能是造成这一现象的原因。在过去的三十年里，各种各样的食物的份量都增加了。这是一个令人担忧的原因，因为实验数据表明，人们“清空盘子”，吃了大部分的食物。到目前为止，我们有非常令人信服的急性实验室数据表明，份量可能是能量摄入的关键驱动因素;我们在一顿饭中提供的能量或食物份量影响我们消耗的能量。正因为如此，针对减少部分大小可能是解决肥胖的关键方法，最近委托的公共卫生报告支持这一观点。 然而，我们目前缺乏一个理论模型，能够1）解释为什么份量大小对能量摄入产生如此强烈的影响，2）确定我们可以减少份量大小的幅度，以促进可靠的长期减少能量摄入。这是一个主要的绊脚石，因为在我们确信利用份量将有助于解决肥胖问题之前，我们需要了解份量影响能量摄入的原因以及如何重新制定份量。最近的研究表明，减少份量的理论模型是至关重要的，因为如果没有，那么任何能量减少都可能被后来的补偿性饮食所抵消。 本研究的目的是开发和测试一个理论模型，以解释部分大小对能量摄入的影响，然后应用这些知识来测试我们如何减少部分大小，以促进可靠和持续的能量摄入减少。我们的理论模型建立在一个既定的框架，是基于这样的前提，即当与食物部分，个人作出简单的感知分类的部分是“正常”或不正常的大小。如果一部分被归类为“正常”，消费者可能会吃所提供的大部分食物。虽然这种感知分类在认知上是有效的，但相对较宽范围的部分大小似乎是“正常的”。我们预测，这会导致在这个“正常范围”内增加或减少份量对能量摄入产生显着影响。因此，我们提出的模型试图解释为什么份量大小可以对各种食物的摄入量产生如此强烈的影响，消费者仍然认为他们吃了一顿“正常”大小的饭。这项研究资助将实证检验我们提出的理论，并研究减少部分大小对能量平衡的影响。在这样做的过程中，这项工作汇集了食欲，健康心理学，视觉感知和公共卫生领域的专家，以了解份量和能量摄入。重要的是，我们的理论模型表明，很可能存在边界条件，这些边界条件决定了何时减少部分大小将不再对能量摄入产生可靠的影响。通过测试这些边界条件，我们将在一个独特的位置，以检查的大小部分大小减少所需的促进持续减少能量摄入。在这样做的过程中，我们将产生重要的知识，关于我们如何能够重新制定公共卫生利益的部分大小。到三年计划结束时，我们将测试为什么份量影响能量摄入的理论解释，并应用这些知识来测试是否有可能使用份量原则来促进能量摄入的持续减少。这些新的见解将与食品工业和公共卫生倡议直接相关，这些倡议旨在减少份量，以帮助解决广泛的肥胖问题。

Rises in obesity have been caused by increases in energy intake and a key environmental factor which may responsible for this is portion size. Over the last thirty years portion sizes for a wide variety of foods have increased. This is a cause for concern because experimental data shows that people 'clear their plate' and eat most of the food they are served. To date, we have very convincing acute laboratory data showing that portion size is likely to be a key driver of energy intake; the amount of energy we are served at a meal or provided in a food portion influences how much energy we consume. Because of this, targeting reductions to portion size could be a key approach to tackling obesity and recently commissioned public health reports support this view. However, we currently lack a theoretical model which is able to 1) explain why portion size exerts such a strong effect on energy intake and, 2) identify the magnitude of reductions to portion size we can make to promote reliable long-term reductions to energy intake. This is a major stumbling block because before we can be confident that exploiting portion size will help to tackle obesity, we need to understand why portion size influences energy intake and how to reformulate portion sizes. Recent research has shown that it is critical that reductions made to portion size are informed by a theoretical model, because if not, it is likely that any energy reductions made could be cancelled out by later compensatory eating. The aim of the present research is to develop and test a theoretical model to explain the effect that portion size has on energy intake, before applying this knowledge to test how we can reduce portion sizes to promote reliable and sustained reductions to energy intake. Our theoretical model builds on an established framework and is based on the premise that when presented with a food portion, individuals make a simple perceptual categorisation of the portion being either 'normal' or abnormal in size. If a portion is categorised as being 'normal' a consumer would be likely to eat the majority of the food provided. Although this kind of perceptual categorisation is cognitively efficient, a relatively wide range of portion sizes appear 'normal'. We predict that this causes any increases or decreases to portion sizes which sit inside this 'normal range' to have marked effects on energy intake. Thus, our proposed model attempts to explain why portion size can exert such a strong effect on intake for a variety of foods, with consumers still believing they have eaten a 'normal' sized meal. This research grant will empirically test our proposed theory and examine the effect of reducing portion size on energy balance. In doing so, this work brings together experts in the fields of appetite, health psychology, visual perception and public health, in order to understand portion size and energy intake. Critically, our theoretical model suggests that there are likely to be boundary conditions which determine when a decrease to portion size will cease to have a reliable effect on energy intake. By testing these boundary conditions we will be in a unique position to examine the size of portion size reductions required to promote a sustained decrease in energy intake. In doing so we will generate important knowledge about how we can go about reformulating portion sizes for public health benefit. By the end of the three year programme we will have tested a theoretical account of why portion size influences energy intake and applied this knowledge to test whether it is possible to use portion size principles to promote sustained reductions to energy intake. These novel insights will have direct relevance to the food industry and public health initiatives which aim to make reductions to portion size in order to help tackle the widespread obesity problem.