Do increase portion size effect how much we eat?

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November 11, 2012 by yuiweng

It is no secret that portion size, as well as weight and waistline, is expanding in United States and worldwide. Restaurant meals of all kinds have gotten larger with an emphasis on getting more food for the money. Average portion sizes have grown so much over the past 20 years that sometimes the plate arrives and there’s enough food for two or even three people on it. But how does this portion size race get started in the very beginning?  For restaurant owners, larger portion size can both promote sales and maintain the rotation of food ingredient for freshness. It will only cause a slightly increase in ingredient investment, and consumers perceive it as great value and are willing to pay more money for the supersize meals. No stakeholders in food industry, so as consumers, have the incentive to control portion size and results in the skyrocket portion expansion.

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However, the rise of portion sizes is not limited to restaurants alone. Bags of snack foods or soft drinks in vending machines and the grocery store are offered in larger and larger sizes that contain multiple servings while a 1-ounce bag of snack food or an 8-ounce soft drink, which are the recommended single serving sizes, are very difficult to find. Some people argue that the increase in food portion does not necessarily related to adverse health outcome. From the weight management section of Dietary Guidelines for Americans 2005, stating that there are no empirical studies to show a causal relationship between increased portion sizes and obesity, but there are short-term studies showing that controlling portion sizes helps limit calorie intake, particularly when eating high-calorie foods.

In an ideal world, serving sizes and nutrient information on nutrition labels or calorie labeling on menu items will help consumers make smart choice and have better portion control. It obviously does not work very well in real world settings. Studies show that often people are unable to tell the differences in portion size when offered different sizes on different days. The characteristics of people (gender, age, body weight, level of education) cause differences in the way they estimate portion size, and error in estimating becomes greater as portions increase.

As public health nutrition researchers and practitioners, there are still many questions waiting for us to answer. For example, there have been no long-term studies published that determine the impact of portion size on energy balance or weight maintenance. There have been no published intervention studies on portion size and weight control, such as those that would train people to recognize appropriate serving sizes and incorporate that knowledge into their eating behavior. Hopefully by answering these questions, we can raise public awareness of portion distortion and end the vicious portion expanding cycle.

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