Canadian Politics from Canada's Centre

Sunday, January 29, 2006

Portion Sizes and Obesity: Variables

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Here's something I've been promising for ages, and which finally works. summaries of the variables analyzed in the studies, which were part of the research my partner and I did on portion sizes and obesity. I keep reading more and more research on the topic, without seeing anything being done, so I'm going to look into writing some solutions to the problem. Some will be policy, but I think we need to fight fire with fire here. Hershey is bigger and better, so perhaps we need to advertise that hershey's made us bigger too. And it's not all roses, like when Garfield said: "there's more of me to love." Anyways, here's the info on portion size study variables. At the end is a bit of the goals my partner and I had set for our own research.


Introduction

In recent decades, the types of food we eat, along with portion sizes, have been brought to the fore of the popular conscience. For example, throughout North America, young children are presented with the ever-so-popular food pyramid as a guide to proper eating.

That said, one wonders what people believe about their own eating habits, specifically in terms of portion size, and foods eaten. Researching this in a college setting would be of great interest, due to the common perception that post-secondary students’ eating habits are poor. Of course, the scientific method does not accept such generalizations without valid proof. Research having shown that portion sizes have been growing since the 1970s, it would be worthwhile to find out whether college students contribute to this trend, and whether or not they are aware that they do, if that be the case.

Previous Findings

Variable 1: portion size

Statistically speaking, according to Cook, Goldman, Mickle, Mitchell and Smiciklas-Wright (2003), portion sizes grew for one third of foods examined. Young and Nestle (2002) discovered the same trend in regards to meals bought ready for consumption outside the home. For example, portion sizes of candy bars today are much larger than they were years ago. Levitsky and Youn (2004) found that when presented with large portion sizes, undergraduate students ate more than when they made up their own portion sizes from food taken from a buffet. Fraser, Sharar, Shai and Vardi (2003) found that people over the age of 65 ate smaller portions than people between the ages of 35 and 65.

Variable 2: age

Cook et al.’s research was extensive, and found that food consumption grew in all age groups covered, these groups being from 2 years of age and up. Fraser et al. found that portion sizes depended on age.

Variable 3: types of food eaten

Young and Nestle’s research focused on food consumed outside the home and from specific venues. Mainly, these were fast food outlets, family-oriented restaurants, and takeout places. Foods from these sorts of venues are similar, and Young and Nestle found that the portion sizes of these foods grew since the 1970s. Fraser and co., in carrying out their research, categorized the foods to be eaten, and found that older participants ate more salad, though less of everything else. Cook and his fellow researchers discovered that a majority of the types of foods grew in their consumption, though some did decline.

Variable 4: gender

None of the foods examined by Cook et al. were different over time for all age/sex groups studied. Some unique group-specific differences were found. For example, beer portion sizes for men 40-59 increased. Overall, important differences were generally in the same direction across groups, though, as mentioned above, some groups did not show change. Although it was not a major factor in their research, Fraser et al. made note of the differences in portion size for both men and women in both age groups. Levitsky and Youn noted the gender of their sample, but it was not a factor they considered.

The Present Study

Previously, researchers showed that portion sizes for a variety of food groups have been growing over time and generally speaking across both age and sex groups. Sex and age were noted to have an impact on quantities consumed and preferences for different foods. In other words, people are eating more than they used to, irrelevant of what’s on their plate. How much more and what their choice of food is will be affected by age and sex.

The purpose of this research, then, is to determine whether college students (e.g. youth 17-20) are aware of these trends in nutrition. More specifically, the present study will look at these students beliefs about their own eating habits. That means assessing their perceptions of how much they’re eating relative to their forebears, of what they’re eating relative to their forebears, and whether they know that their sex has a role in determining what food choices they make.

Non-random quota sampling will be used. The groups categorized by the quotas will be divided along gender lines and age. In order to carry out the quota sampling, a list will be obtained from the registrar’s office regarding students’ age and sex. Failing this, rough estimates will be obtained in a similar manner. If this too should fail, the research will use quotas of 50% for each gender, and 25% for ages 17-20, with subjects older than 20 being disregarded.

The method used to evaluate the sample’s perceptions will be a survey of no more than 50 questions. These will be comprised of multiple choice questions and short (2-3 lines max.) essay questions. In order to more easily obtain cooperation from our subjects, the survey will be designed to take no longer than 5 minutes.

A dual-pronged approach will be used. Blunt questions such as “On a scale of 1-5, do you believe portion sizes have been changing (5 being maximal growth, 3 being stability and 1 being a decline)?” will compose one third of the questions. The other two thirds will be more subtly worded, in order to avoid possible social-desirability issues.

Another issue in the selection and phrasing of this study’s questions will be assessing subject’s body image. This might be an extraneous variable. For instance, people considering themselves to be overweight might think they eat more, or eat unhealthy foods frequently. Similarly, someone with a healthy image of self might perhaps attribute that to their good eating habits. The questions in this section will of course be on the subtle side of things, given that people are taught that they should be happy with their self-image (at least by those authorities not selling a diet book).

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If you're interested in seeing my other posts on the subject, here they are.

Portion Sizes and Obesity - The Research ... a very long annotated bibliography. Rich in detail, but you'll need time.
Portion Sizes Linked to Obesity, Centrerion Tells Time - Time magazine published my letter on the issue. I guess some of what I'm writing makes sense. You can see the text they published.
Young and Nestle's study was looked at by my partner and I. Here's an abstract of their work.

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