EAL

NCBS: Weight Loss and Weight Regain Expected After Procedure (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

This study attempted to determine the two-year morbidity of participants who had undergone Roux-en-Y gastric bypass surgery compared to two control groups who had not had bypass surgery.

Inclusion Criteria:

BMI greater than or equal to 40 or BMI greater than or equal to 35 with two of the following comorbidities: heart problems, sleep apnea, uncontrolled Type 2 diabetes, or weight induced physical problems that interfered with daily functioning.

Exclusion Criteria:

Previous gastric surgery for weight loss
Gastric or duodenal ulcers in the previous six months
Active cancer (except non-melanoma skin cancer within the past five years)
Myocardial infarction within the past six months
Abuse of alcohol or narcotics.

Description of Study Protocol:

Recruitment: Participants were recruited for participation in the study through the clinics of bariatric surgeons in Salt Lake city, Utah. The second control group was recruited from the data set called, Utah Health Family Tree Program which contains information about body weight.
Design: Case control study. The cases had the surgery. Control group 1 consisted of patients that wanted to have the surgery but were denied and Control group 2 consisted of patients who were eligible for the surgery, but did not wish to have the surgery.
Blinding used: None
Intervention: The Roux-en-Y bypass operation was performed in both open and laparoscopic approaches
Statistical analysis: Frequency data, percentages, prevalence information, means ± standard deviations.

Data Collection Summary:

Timing of measurements: Baseline and two-year examinations. The intent is to continue to follow the patients at the fifth and tenth year after the surgical procedure.
Dependent variables: weight loss, blood pressure, blood glucose, blood lipids
Independent variables: Surgical internvention.

Description of Actual Data Sample:

Initial N: 1156 participants (416 in the surgical group; 419 in control group 1; and 321 in control group 2)
Attrition (final N): The study is ongoing, but all the patients have been contacted for their two-year appointment date and over one-half of the total study population has returned for their exams
Age: 42-49 years of age for the group means with a range of 18 to 72 years
Ethnicity: Not stated
Other relevant demographics: 14 years of education in all three groups
Anthropometrics: The mean body weight was 274-295 pounds across the three groups or a BMI that varied from a mean of 43-47 with a range of 33 to 92 across the three groups
Location: Salt Lake City, Utah.

Summary of Results:

Weight loss: The observed group difference was statistically significant at 47kg ± 39kg, two years post-surgery, based on the 264 participants that had been retested at exam year two
Blood pressure: The observed group difference was statistically significant at 12 ± 18mm Hg for the blood pressure reading, two years post-surgery, based on the participants that had been retested at exam year two
Blood glucose: The observed group difference was statistically significant at 18 ± 31mg per dL for the blood glucose reading, two years post-surgery, based on the participants that had been retested at exam year two
Blood lipids: The observed group difference was statistically significant for cholesterol, triglycerides, and HDL-C, two years post-surgery, based on the participants that had been retested at exam year two.

Author Conclusion:

Baseline and two-year exams provide valuable information for comparison to future long-term follow-up data that will be collected at the fifth and tenth years on these subjects
The effectiveness of gastric bypass surgery in reducing morbidity and maintaining long-term weight loss is an open question and not resolved at this time.

Funding Source:

Government:

Food Standards Agency

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

This is an excellent study. The design is unique and unparalled in terms of two control groups: one seeking surgery, but denied and the other group eligible for surgery, but not interested in having the surgery.
When the fifth and tenth years of follow-up data become available, this study will provide meaningful answers to the questions posed regarding effectiveness and health consequences of having vs. not having the surgery.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		No
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	Yes
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	Yes
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes