Discussion Question 2
Aside from a larger sample size, how could the
study be redesigned to overcome some of the listed limitations?
posted by Julie @ 7:21 PM
29 comments
ISU Dietetic Internship Journal Club
Objective: To become familiar with current scientific literature on a variety of nutrition topics and to gain experience in gathering, organizing, critically evaluating, presenting and facilitating group discussion of the literature and the implications to practice.
29 Comments:
As mentioned in the article, the sample size needed to be bigger and more diverse. It needed to include males, other races and ethnicities, less educated individuals, and lower-income individuals.
The study would also need to set up its weighing frequency differently to determine results for those who weighed themselves less than five days per week. There would need to be separate groups for those who weighed themselves four days per week, three days per week, two days per week, and one day per week (weekly) to determine if weighing at these frequencies made any significant small changes in dietary behaviors.
Also, because individuals had to self-weigh, not all of them completed this task. It would be important for researchers of the study to set up times that individuals had to come in to be weighed so there would be 100% participation.
A limitation of the study was the homogeneity of the sample utilized. Most of the participants were female, Caucasian, and had a college education. The study could be redesigned with a more variable sample. The sample could include more male participants. Men and women have different hormones that can impact their ability to lose weight. Also, more participants with varying races could be included in the study. Genetics and lifestyle factors of different races could impact weight loss. Also, the education level of participants could have impacted the results, and more participants with less than a college education could be included in the study. The study also utilized mostly middle-aged participants, so it would be interesting to discover whether similar results would occur with younger participants. Making these changes to the sample may make the results more generalizable to the United States’ population.
There was also a limitation with participants’ frequency of weighing themselves. Participants who weighed themselves five days or less per week were lumped together in one group. There is a big difference between weighing yourself five days per week or weighing yourself one day per week. Therefore, the study could be redesigned to establish more specific differences in frequency of weighing. Participants should indicate if they weighed themselves five days per week, four days per week, three days per week, etc. This could provide more data about weighing frequency and its association with weight loss.
As the majority of the participants were college-educated, middle-aged Caucasian females, the study was limited in participant variety. Another limitation was the categorization of the frequency of weigh-ins. By grouping weighing frequency of 5days/week through 1day/week together, the researchers limited specificity in their analysis.
If redesigned, the study should include a greater variety of subjects, including males and females, younger and older, as many ethnicities as possible, and individuals with higher and lower education levels. The researchers should also redesign the weighing frequency measures to be more specific: either creating specific numbers of weigh-ins per week or creating smaller ranges (5-4days/week, 3-2 days/week, etc.).
Additionally, I agree with Janelle's comment that the study could be redesigned to include a better way of ensuring subject participation in weigh-ins. For example, the researchers could randomly assign participants a weekly number of weigh-ins that they would adhere to during the study. Then the participants would be grouped by frequency of weighings, which may provide a clearer correlation between weight loss success and number of weighings per week.
I don't think this study focused enough on the behaviors of the participants. Sure, we know that those who weighed themselves daily lost more weight, but there were no statistical differences in calorie intake, activity or behavioral strategies. Besides weighing themselves daily, what was the intervention group doing differently in order to lose weight? I think understanding the factors that led to weight loss is more important than the weight loss itself. Sure, it's great that this group was able to lose weight in 6 months, but is this sustainable? Did they adopt some unhealthy habits? I think this study just presents a lot more questions and I'm not sure I'd be ready to adopt this strategy with my own clients.
I think it would be interesting to focus on the different demographics and lifestyles, which would make this a much larger study. I'd be curious to see if people who work more or less have different outcomes in weightloss whether or not they weight themselves everyday. I would be interested to see what these people are eating or whether or not they're exercising and how much. Maybe people who weigh themselves more are more likely to be mindful of what they're doing. I also think breaking it down by age would be helpful to see if it has a different impact on different age groups. Possibly, the research could look into the time of day the participants are weighing themselves and see if there's a difference there. I heard the most accurate weight is the one in the morning after a long night of fasting but I don't know how accurate that is.
I like Susan's question of whether or not they adopted unhealthy habits due to every day weights or if they've come out jus fine and have been able to maintain it. I also agree with Carrie that the number of days apart would be interesting to see whether or not a 2day weigh or 3 day weigh would make a difference too.
2) A larger samples size may help accomplish this, but the most evident limitation in my mind is the lack of diversity in gender, ethnicity, and education level. Women are generally more concerned with losing weight than men. A curvier physique is more of the norm in some ethnicities. Finally education level has associations with higher inclusion of health behaviors. Within each of these demographic categories, different groups and individuals will respond in different ways with varying levels of motivation. To apply this study’s conclusions to a general population would be inappropriate.
I fully agree with the concerns expressed in the statement “self-weighing frequency may be a proxy for intervention adherence.” To more effectively isolate relationships between outcomes and self-weighing frequency, study participants could be randomly assigned to weigh a specific number of days per week (i.e. control group, information only, 1 day, 3 days, 5 days, or 7 days). All experimental groups would receive the same informational education. This would help eliminate confounding from level of adherence assuming effective randomization. From here, each group could be examined to more accurately assess the relationship between adherence to specified weighing protocol and level of adoption of weight management strategies.
Another sampling approach may be to stratify the sample by level of motivation for weight loss. If there was a way to assess level of satisfaction with current weight and body shape/size as well as attitude toward weight loss, we may better be able to understand the “human” element in this whole equation. This would likely require a more labor intensive research protocol though. So much goes into the issue of weight management; it is hard to disentangle emotional, behavioral, and attitudinal factors.
In response to Janelle's suggestion. I agree with having separate groups for number of days per week. Having the participants come in to a facility to be weighed would place a huge and uneven time burden on the participants though. I could see participant drop out being a big problem if then had to come in and weigh every day of the week for a 6 month or more intervention. I also agree with Susan and Tina's suggestions to go more in depth with data collection to see what else could potentially be contributing to weight loss or lack there of.
Beyond the homogeneity of the sample, I think an additional limitation of the study is long term maintenance of the weight loss. Is there a significant difference between the intervention and control groups after the six month period for long-term weight maintenance? Is there a slower rate of weight re-gain for one of the groups? I think there are many follow-up questions that need to be addressed.
In addition, for the control group that received the delayed, modified intervention, no data was collected other than their weight after the intervention. Since focus of the data collection was focused on the initial intervention group alone, how can the researchers be certain of the frequency that control group subjects participated in self-weighing? I do not believe this confounding variable was addressed.
I am very interested in some of the suggestions others are making in regards to the weight loss data collection methods. Specifically, Tina brought up recording the time of the daily weighing, which I certainly think may affect the final outcome. Would AM or PM weight checks affect the final result? I also agree with Caroline in splitting up the participants into discrete groups for weight check frequencies per week. There are certainly a number of variables that could be isolated and investigated.
As many have already stated, a larger sample size would possibly enhance the quality of the results. Additionally, as the authors stated, "Finally, our sample was predominantly female, white, and college educated. As such, it is not possible for us to infer whether similar findings would be found with a different population." A more diverse sample would also help to overcome some limitations. I'd also be interested to see how these results would differ by education status with a larger, more diverse, set of education levels. Would a larger sample of those of a lower education (and possibly lower SES) have different results compared to the college educated group? Along those same lines, I think that asking about income (household and/or individual) could help to overcome some limitations. Income plays a definite role in our goals with anything, and it'd be interesting to see if those with a higher reported income were able to lose weight more effectively (possibly due to ability to afford certain types of food, gym memberships etc.) than those with lower reported income.
Like Caroline said, it's problematic that participants who weighed themselves five days per week or less were lumped into one group. I also believe that the study could be redesigned to include the effect of weighing one,two, three, four, five, six, or seven days per week (or less than weekly) compared to the current procedure of seven days per week (everyday) versus five days per week (less than daily).
To run meaningful statistical analysis on data that focuses on more specific differences in weighing frequency, a larger sample would be needed too, so the study would have to be a larger in scope. By recruiting a larger sample, hopefully a more diverse group would be included. The researchers would have to recruit participants who aren't white college educated females.
I also agree with Emma that the researchers could redesign the study with smaller ranges (which would also take more participants, some of whom would have to not be as compliant and/or instructed to weigh themselves less...like once per week etc.) It wouldn't necessarily have to be one, two, three etc. days per week (that may cause some very low expected cell counts for chi-square analysis...Fisher's exact testing anyone??). They could always do an everyday (seven days per week), 5-6 days, 3-4, 1-2, 0 (less than weekly) type of breakdown and run analysis on those groups. In my mind, that would be a good middle ground and would allow the researchers to understand more about "whether weighing on fewer than 5 days per week (eg, weekly or less than weekly) produces smaller weight losses and fewer behavior changes compared with weighing 5 days."
Gina, I agree that asking participants to come in and weigh a given number of times per week may be a burden and also may cause undue dropout rates. One of the great things about technology is that we've made research much easier on the participants. Along those same lines, going into a research facility to weigh is not what the participants will be doing once they are done with the study...they will be weighing themselves from the comfort of their own home and tracking their results (if they choose to do so, of course). So, if we want to try and ensure that study participants continue to adhere to healthy weighing (and other lifestyle) behaviors post-study (to keep the weight off...as some of you mentioned), I think it's important that they self-regulate their weighing from their own home, because that is realistic.
I agree with Susan's suggestion that behaviors need to be studied more in depth. I would like to know the other factors that correlate with the group that weighed themselves daily and were able to lose weight. Also, the follow-up after 6 months or years after would be interesting. This may only work short term and may be ineffective for the future weight loss or weight maintenance strategies. Finding a diverse group and categorizing it appropriately is a common problem in research and they need to take a different approach. Intervention and education may be a way to acquire better participation. Giving the participants the responsibility of weighing themselves makes it less reliable evidence, especially if they do not adhere to their weighing in schedule.
What jumps out at me is that only overweight individuals were included. This does fall under the category of too small of sample size probably, but I think it would be better to compare outcomes to those who have a healthy body weight and their daily weighing habits.
As majority of the other responders have said, the sample was made up of mostly female, Caucasian individuals who were highly educated. I think that if the sample size was not only larger, but more varied by age, gender, ethnicity, economical status, and educational status. This would provide the researchers with greater variance in the results. Several of these variables, such as gender, age, ethnicity, all play a role in the individuals overall ability to lose weight and the rate at which the weight is lost. This alone may change the results of the study.
Additionally, as Susan mentioned, the study did not focus much on the specific behaviors of the individuals. It didn't include much information on their usual dietary habits and how/if they changed during the study and the amount of calories they were consuming daily.
I also agree with what many others have said about the definitions of the variables need to be more specifically defined. For example, how often they weighed themselves. If the study could be redone, I would suggest 3 groups: those who weigh themselves daily, those who weigh themselves weekly, and those who weigh themselves monthly. This would give the researchers much more clearly defined results.
As mentioned others above, the sample needs to be more diverse in addition to increasing the size of it. They can overcome the limitation by taking samples from certain areas of the country with no specifications on education. For example, they have 100 participants from an East Coast state, 100 participants from a West Coast state, and 100 participants from a Midwest state. It could add diversity to the sample population as well as provide results more generalizable to the general public.
The categories for weigh-in frequencies need to be more specific since weighing in five days per week could produce completely different results from individuals who weigh themselves once a week. It could provide more accurate and specific results for the association between weigh-in frequency and weight loss.
It would be interesting to see whether people from lower-socioeconomic statuses would experience less of an effect from daily weigh-ins due to limitations on what they can eat, and the time they can contribute to exercising.
Jessica brings up a great point about this study using only overweight individuals. Would the results have been different for obese individuals?
I think healthy individuals would likely adopt unhealthy behaviors if they were to weigh themselves everyday. It would be interesting to see the outcomes of daily weigh-ins on healthy individuals, but they also do not have much of a purpose in weighing themselves everyday if they are already at a healthy weight. Doing so may just result in an unhealthy obsession with the number on the scale.
I agree with Susan that a second study would really benefit from more focus on other behaviors aside from the weighing. And I also like Gina's recommendation to try to get a better understanding of motivation for weight loss and the that plays in this. There are a lot of different ways to make this better in the future.
Self-reported always gives way for larger error. Other exercise needs to be factored in, for example, weight bearing exercises, and there should be a control for increased muscle mass versus loss of fat mass. Females have different perceptions than males about body image, therefore more males should have been included and a wider variety of races. Different levels of overweight individuals could have been compared to each other as well.
Vivian, Jessica, and those who mentioned only overweight individuals, the study could need to confound for the rate of weight loss and the composition. For instance, the water that is lost first and quickly before a person plateaus would depend on the amount of muscle and fat mass they had prior to beginning the weigh-ins. Everyone has different body compositions and the lack heterogeneity in just this small aspect would make a huge difference in outcomes.
A larger study with a more diverse population would improve the limitations related to sample size and lack of sample diversity (population was mostly female, white and college-educated). Distributing this larger, more diverse population into groups with a wider variety of weighing frequencies would provide the researchers with more information about differences between variations of weighing frequencies, such as daily vs. 5 days per week, 3 days per week, once per week or less than once per week.
I wondered if the lessons that were given to the intervention group may have affected the outcome? It seems like the lessons should either be given to both groups or neither.
In addition to a larger sample size, the article listed several limitations. One of the limitations was that the study did not include a randomized comparison of daily weighing vs. less than daily weighing. I would have liked to have seen a study ideally with three groups: daily weighing, one day per week weighing, and no weighing at all. This would have been better for comparison purposes. Another limitation was that the questionnaire examined weight control strategies by individual item. It would have been more effective if they could have somehow grouped factors together to get a better view of the habits in combination with one another. Finally, the lack of diversity in the population should be noted. The sample was mostly female, white, and college educated. Perhaps a sample of males at the same age would have had completely opposite results. Increasing the diversity or even doing a comparison between two groups would give a clearer picture of the role self-weighing has in weight loss.
Another limitation of this study besides the sample size was the additional education the intervention group received. The study said that the intervention group received email messages that included behavior- related weight control lessons based on the topics from the gold standard weight loss trials and other internet based trials. The group that received the delayed intervention and was blinded to the focus of weighing did not receive these emails during the trial. I think that behavior- related weight control lessons could have a very large impact on someone trying to lose weight and therefore the weight loss results the researchers found in this study could be due to the lessons rather than the daily weighing.
I agree with Gina that all experimental groups should receive the same educational information to ensure that the weight loss seen in the study was due to the frequent weighing rather than the additional education intervention group received.
I also agree with Susan that it is more important to learn what the intervention group was doing to lose weight rather than how much weight each group lost. Jumping to the conclusion that the intervention group lost weight because of the frequent weighing is not right when other factors could have contributed to the weight loss such as education or increased physical activity.
As the authors and the majority of others have mentioned, there needed to be a more equal distribution of males and females as a part of a larger sample size. I feel that this was one of biggest limitations to the study. Men and women undoubtedly have different attitudes, perceptions, and physiological responses to weight loss. Also the inclusion of a more diverse ethnic population would help to increase the validity from these research findings and translate into a more effective study.
Gina also brought up a very interesting point as well about including the assessment of satisfaction, motivation, and attitudes toward weight loss as an aspect to include within the study. To add to that, I think that it would be interesting to see an additional qualitative research aspect to this study and create more of a mixed-methods approach to weight loss to determine overall outcomes from daily weighing.
I also agree with Charity that the lack of emphasis upon exercise and physical activity is a clear limitation of this study as well. The type of exercise being performed could have a significant impact upon an individual’s body composition and overall weight loss outcomes. I think that it would be interesting to add body composition testing into the study, once at baseline and once after the 6 month intervention for added measures.
Like many others have said, I think the sample was too homogenous. This study would be more applicable if the sample would have been more diverse. I think Susan made a great point that the study should have focused more on the behaviors of the participants. It could be that the people who weighed themselves daily could have been successful with other weight loss interventions, and may be those individuals who did not weigh themselves daily did not have the strong motivation or desire to make life changes.
I think the fact that the the daily weighing group received additional education through emails for the daily weighing group is a very important part of this study. Without having both groups receiving those emails, it's difficult to say that the greater weight loss was a result of the daily weighing rather than the actual emailed lessons and tailored feedback. This study should be replicated with both groups or neither group receiving those emails to see if the daily weighing group still had greater weight loss.
I also agree with John that having an equal distribution of men and women would be important as well because, as he stated, men and women approach weight loss very differently, and have different perceptions.
When evaluating the limitations one of the major limitations is that it was not a randomized comparison between those who weighed less to those that weighed everyday. If this study were to be replicated it would be crucial to do a randomized comparison because while the statistics are interesting it could be that those who weighed themselves less did not adhere to the intervention as closely to those who weighed everyday.
I also agree with Abby that the sample was too similar. While this research gave us more insight on weight loss techniques for adult white educated females seeing if the same results occurred in males and different ethnic groups would be useful.
I think that redesigning the study to include behavioral dietary patterns as Susan mentioned would be beneficial. Weight loss is definitely a psychological issue that involves many lifestyle and behavioral changes. I think this could greatly affect outcomes.
As Carly and Sammy mentioned as well, I think that the education aspect of the study is very overlooked. Individuals who received education on what to do are going to be more likely to lose weight than those who do not. It is another factor or variable that could have caused the weight loss, rather than the actual weighing frequency itself.
John had a good point about exercise/physical activity and it's affect on the weight loss outcome. He suggested testing body composition, and I think in addition to that, tracking the amount and type of exercise might be useful.
Arthur mentioned a good point about self-regulation for the subjects as a method of tracking weight loss.
Having the participants come into a facility to weigh themselves may be an additional factor driving their weight loss. I feel that if the subjects think someone is accountable for actually weighing them, they are more likely to adhere to healthier habits such as more exercise or eating healthier. So self-weighing seems to be a more realistic approach that can produce results generalizable to the public whom are actually doing self weigh-ins rather than going to a facility to be weighed.
And Charity made a great point in response to my earlier comment. I think if similar studies were to be conducted on different body compositions, they should do so separately. Like she mentioned, different body compositions will respond differently to the same interventions.
Post a Comment
<< Home