The following questions are based on the study by Ladabaum et al. (2014).
1. (a) Is this study based on a cross-sectional survey design, a cohort study design, or a randomised controlled trial design?
(b) Participants were grouped into three levels of leisure-time physical activity: ideal, intermediate, and none. What type of measurement scale is this?
(c) Anthropometric measures included height, weight and waist circumference. What type of measurement scales were used to measure (i) height (in cm) and (ii) weight (in kg)?
(iii) The researchers measured waist circumference (in cm) and then stated that “Abdominal obesity was defined based on a waist circumference of >88 cm for women and >102 cm for men”. What type of measurement scale was “abdominal obesity”?
(d) The authors state that “While height, weight and waist circumference are measured, caloric intake and physical activity are self-reported, and we analyzed caloric intake on 24-hour recall. Caloric intake may be under-reported and physical activity overestimated.” Why might caloric intake be under-reported and physical activity over-reported? Is this a form of measurement error or measurement bias? (Briefly explain the reason for your answer).
(e) In Table 1, the proportion of the population of women aged 18 years and older who were obese (based on BMI) in 1988-1994 was reported as: 24.9 (23.1-26.8). Briefly explain what these three figures mean. Your answer should include completing the following sentence: “The 95% confidence limit (23.1-26.8) means that……”
(f) In Table 1, the proportion of the population of women aged 18 years and older who were obese (based on BMI) in 2009-2010 was reported as: 35.4 (33.6-37.3). By comparing data for 1988-1994 [in Q1(e)] with the data for 2009-2010, has there been a statistically significant change in the proportion of the population of women aged 18 years and older who were obese between these two time periods? Briefly explain your answer, using percentages who are obese and 95% confidence intervals.
(g) In the Results section the authors state that “Compared to the previous year, the odds ratio for being categorized as obese in any given year was 1.026 (95% CI, 1.019-1.033) for women [aged 18 years and older].” Based on this finding, was there a statistically
significant change in the likelihood of being obese from one year to the following year? Briefly explain how you used this data to come to your conclusion. Include in your answer, what an odds ratio of 1.026 means.
(h) Implications for practice:
(i) The authors state that “Our findings do not support the popular notion that the rise in obesity in the U.S. can be attributed primarily to sustained increases over time in the average daily caloric intake of Americans.” What evidence (from Table 2) supports this statement? Include in your answer whether or not there has been a statistically significant change in “Mean energy intake in kcal/day (95% CI)” between 1988-1994 and 2009-2010 for women in the age range 18 years and older, and how you decided this –
use either the kcal/day (95% CI) data or the APC (Annual Percentage Change) data.
(ii) Drawing on the wider body of research evidence (in the Discussion section), do the authors conclude that energy intake has had little impact on changes in levels of obesity? What evidence (from the wider body of research) do the authors cite to back up their statement?
(iii) Based on the study findings and the additional research findings referred to in the Discussion, would you recommend that programs aimed at reducing overweight and obesity should promote increased physical activity, reduced caloric intake or both?
These questions are based on the study by Metzgar et al. (2015).
2. (a) What was the study aim? (Please write this in your own words).
(b) What reasons did the authors give for exploring both weight loss and weight loss maintenance?
(c) What data collection method was used? Why is this data collection method appropriate for addressing the study aim?
(d) In the data analysis, the researchers identified nine major themes (Table 3):
1. Weight loss journey
2. Accountability and support
3. Planning ahead, mindfulness and awareness
4. Nutrition education
5. Portion control
8. Total lifestyle change
9. Eating patterns and snacking
If you were responsible for the coding analysis, identify the key theme into which you would code each of the following participants’ comments1.
To save on words, just write the key theme and the letter that identifies the comment - you do not have to write out the comments. Reading the results section of the journal article will assist in making your coding decisions; and if in doubt about a coding decision, opt for the theme that you consider to be closest to the participant’s comment.
A. “I make myself do a menu plan each week, and make sure I only buy what’s on my list.”
B. “No-one else in the family seems to care about their weight, so they think I’m a bit strange.”
C. “I went out and bought a whole new dinner set with smaller plates.”
D. “I feel as if I’ve been on a yo-yo diet for most of my life.”
E. “I kept on reminding myself that I wasn’t on a diet, I was just living my life differently.”
F. “I kept reminding myself that the occasional slip-up was okay - I didn’t beat up on myself when I didn’t do all the things I wanted to.”
(e) Based on the study findings, briefly describe, in your own words, four things that future weight loss and weight loss maintenance programs could do to achieve sustained weight loss for women.
The following questions are based on the study by Foster-Schubert et al. (2012).
3. (a) Identify the study design used by Foster-Schubert et al. (2012). Based on this study design, are the study findings likely to have good internal validity? Briefly explain the reasons for your answer. Based on the sample used in the study, is this study likely to have good external validity? Briefly explain the reasons for your answers.
1 These participant comments have been made up for the purposes of this assignment.
(b) In the Results section, the authors stated that “With the exception of percent fat intake in the diet estimated by FFQ, there were no statistically significant differences in any demographic or lifestyle variables between the study groups at baseline.”
What element of the study design is likely to have contributed to this finding, and why is this considered a strength of the study design used?
(c) What was the independent study variable? What was the primary dependent study variable?
(d) Based on the outcome measure of ‘waist circumference’ (cm) in Table 2, which intervention group had the greatest percentage change (% Δ) in waist circumference between baseline and 12-month follow-up? Name the group and the percentage change. For this group, what was the p-value for the change from baseline to 12- month follow-up for this intervention group compared to the control group? Does this p-value indicate a statistically significant difference between this intervention group compared to the control group? (Briefly explain the reason for your answer, in terms of how p-values are interpreted).
(e) Based on the overall pattern of changes in various measures of body weight and adiposity, which intervention group resulted in the greatest changes? (There is no need to include data in your answer to this question).
4. Suppose you are a Policy Officer in the Population Health Division of the Commonwealth Department of Health. You are required to write a policy brief for the Health Minister that summarises the key findings from the three studies in this assignment related to the three questions above, and concludes with a recommendation for future action. You must include in-text citations for the study findings you refer to, but there is no need to include the actual data – just provide a very brief summary of what the key findings were.
Your recommendation might be for a more comprehensive review of the evidence, further research, or the introduction of programs or policies to improve healthy eating and/or physical activity. If, so, include a specific example (eg based on the evidence youhave reviewed, what should be included in a more comprehensive review, what further research is required, or what programs or policies should be implemented)?