MNT: Weight Management (2015)


Nijamkin MP, Campa A, Sosa J, Baum M, Himburg S, Johnson P. Comprehensive nutrition and lifestyle education improves weight loss and physical activity in Hispanic Americans following gastric bypass surgery: A randomized controlled trial. J Acad Nutr Diet. 2012 Mar; 112(3): 382-390.

PubMed ID: 22717198
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To implement and evaluate the influence of a comprehensive nutrition and lifestyle education intervention (six post-operative education sessions that incorporated behavior modification strategies into nutrition counseling) in comparison to a non-comprehensive minimal approach (printed guidelines on healthy eating and physical activity recommendations) on weight loss and physical activity in Hispanic American adults six to 12 months following Laparoscopic Roux-en-Y gastric bypass (RYGB).

Inclusion Criteria:
  • Hispanic Americans with morbid obesity
  • Recently had (six months ±6 weeks before recruitment) undergone laparoscopic RYGB surgery for reversing morbid obesity at the Palmetto General Hospital in Hialeah, FL
  • Must have been aged 18 years and older with English or Spanish proficiency
  • To have participants relatively homogeneous regarding bariatric diet knowledge, nutritional status and compliance, only those who attended at least five nutrition-counseling sessions with a registered dietitian (RD) were included.
Exclusion Criteria:
  • Non-ambulatory
  • Pregnancy
  • Anatomical problems following surgery that required re-operation
  • Medical problems such as kidney, adrenal or heart disease.
Description of Study Protocol:


  • From the Laparoscopic Institute of South Florida
  • Primary recruitment: Telephone calls and placing flyers in the waiting room
  • Secondary recruitment: The investigator, who was not involved in the patients’ usual care, extracted pre-operative information from patients’ records and contacted potential subjects inviting them to participate in this study
  • Potential participants were fully informed regarding the purpose of the study, frequency of assessments, intervention schedules, expectations and extent of their participation
  • Participants were not monetarily compensated for their time or transportation expenses
  • On average, 18 participants were enrolled each month.


Prospective, randomized controlled trial.

  • Immediately following the first assessment meeting with the investigator, participants were randomized into:
    • Comprehensive intervention group
    • Non-comprehensive (comparison) group.
  • Standard of care at the bariatric center:
    • Pre-surgical medical, nutrition and psychological evaluation
    • During first post-operative year:
      • Patients meet with the surgeon at two and six weeks and then every three months
      • Patients met with the RDs monthly for the first six months and every six months thereafter. The dietary treatment sought to facilitate weight loss by reducing the risk of nutritional deficiencies.
  • Study phases:
    • Assessment meetings with the investigator at six and 12 months following surgery (initial and final assessment, respectively) and an intervention
      • Initial (six-month) assessment with surgeon for monitoring nutritional deficiencies and co-morbidities (e.g., diabetes, hypertension and dyslipidemia) by laboratory tests 
      • All participants were reassessed at 12 months following surgery
      • Assessments included:
        • Self-reported forms on sociodemographic and medical information 
        • Patients’ medical records were also used to obtain pre-surgery measurements and to corroborate participants’ self-reported forms
        • Patient body weight was measured by a digital scale.

Comprehensive Intervention Group

  • Received a total of six nutrition and lifestyle education and behavioral–motivational sessions in groups of up to 12 participants in Spanish or English according to the participant’s language preference
  • Sessions were conducted every other week by an RD starting at seven months following surgery
  • Each session took place at the Laparoscopic Institute of South Florida and lasted approximately 90 minutes
  • Sessions were presented in lecture format with PowerPoint slides
  • Participants were able to ask questions during the presentation and group discussion was encouraged at the end of each session
  • Participants had the opportunity to complete any missed session before the final assessment and were allowed to receive printed materials for one, and only one, missed session
  • The purpose of the intervention was the promotion of dietary recommendations reinforced by practical behavior-modification strategies for dealing with emotional difficulties encountered in the pursuit of healthy lifestyles
  • All sessions stressed the need for adherence to lifelong supplementation with vitamins and minerals and the importance of physical activity in the post-operative bariatric life, along with a healthy diet
  • Before and after completion of each education session, participants were asked to complete a brief pre-session and post-session quiz to evaluate the knowledge acquired.
  • Intervention Session One:
    • Covered the daily meal planning guide and the maintenance diet
    • Recommendations for identifying and avoiding unhealthful foods
    • Tips to promote proper nutrition by controlling portion size
    • Establishing new routine eating habits
    • Using an exchange list for weight management
    • Session was based on the Dietary Guidelines for Americans 
    • Daily energy intake was limited to 1,000kcal to 1,400kcal
    • Minimum daily protein intake was 60g to 70g to preserve lean tissue and prevent nutritional deficiencies
    • Session emphasized information about the characteristics of typical Hispanic diets and the dietary changes that accompany the process of acculturation.
  • Intervention Session Two:
    • Designed to help sedentary individuals start a consistent exercise program
    • Helped recognize the reasons why physical activity is important for keeping weight off after bariatric surgery.
  • Intervention Sessions Three to Six:
    • Emotional support interventions
    • Behavior change strategies
    • Stress relief without food
    • Self-motivation
    • Relapse prevention
    • Increasing self-esteem
    • Overcoming obstacles to establish a consistent exercise program
    • Recognizing binge eating problems
    • Other motivational strategies.
  • After each education session, participants in the comprehensive intervention group were sent compliance reminders by e-mail and telephone calls
  • Reminders encouraged participants to stick to the bariatric diet and self-monitor their physical activity and dietary intake.

Non-comprehensive (Comparison) Group

  • Did not receive the comprehensive education sessions
  • Were provided brief printed guidelines for healthy eating and physical activity at the first assessment
  • Guidelines consisted of three pages of information and tips on nutrition, foods and beverages to avoid and how to make physical activity a habit
  • All the topics overlapped information provided in the comprehensive intervention
  • This group did not receive behavior modification strategies or have frequent contact with the investigator by telephone calls, e-mail messages and reminder messages
  • All participants were free to opt for additional counseling by an RD, psychologist or other professionals:
    • 45 participants (31.3%) opted for additional counseling by an RD
    • 15 participants (10.4%) opted for additional counseling by a psychologist
    • 88 participants (61.1%) visited a primary care physician or another professional.

Statistical Analysis

  • Sample size was calculated using PASS software for Windows two-sample T-test power analysis for clinical studies
    • Assuming a minimal relevant difference in excess weight loss between the two treatment groups of 5%, a sample of 130 individuals was calculated as necessary to provide the study with 80% power to detect a difference of this magnitude (P<0.05)
    • A dropout rate of 10% was estimated; thus, a sample of 144 individuals (intervention group N=72, comparison group N=72) was recruited.
  • Statistical analysis was performed using PASW for Windows (SPSS version 18.0, 2010, SPSS Inc, Chicago, IL):
    • All tests were two-sided with statistical significance set at P<0.05
    • Descriptive statistics (means±standard deviations or percentages) were used to characterize the population
    • Analyses of differences between groups for demographic and anthropometric variables were performed using independent samples T-tests for continuous variables and X2 tests for categorical variables
    • Changes in weight measures, physical activity time and energy expenditure and nutrient intakes were compared using paired-samples T-tests within each group and independent samples T-tests between groups
    • Intent-to-treat principle was applied for statistical analyses
    • The effectiveness of the comprehensive nutrition and lifestyle education intervention was assessed by differences in mean percent excess weight loss between groups from six to 12 months following surgery
    • Mann-Whitney analysis was used to assess the differences within and between groups in length and intensity of exercise.
Data Collection Summary:

Timing of Measurements

  • Study was conducted between November 2008 and April 2010
  • Outcomes were determined at the initial and final assessment points, at six and 12 months, respectively, after surgery.

Dependent Variables

  • Excess weight loss: Body weight measured by a digital scale
  • Physical activity changes over time: Assessed via questionnaire (Short Questionnaire to Assess Health Enhancing Physical Activity).

Independent Variables

  • Group assignment:
    • Comprehensive intervention
    • Comparison group.
  • Nutrition data collected by an RD
    • The 24-hour dietary recalls were completed at each of the assessment points
    • Nutrient intake was estimated using the Diet Analysis Plus (version 9.0, 2008, ESHA Research, Salem, OR)
    • To limit under-reporting of food intake, the U.S. Department of Agriculture five-step multiple path method was applied, inducing additional recall of the most often forgotten foods (i.e., sweets, snacks, cheeses, breads and beverages), emphasizing the amount of food eaten and the time and settings at which the food was eaten.

Control Variables

All surgical procedures were performed by the same surgeon using identical surgical techniques.

Description of Actual Data Sample:

Initial N


Attrition (Final N)

  • Assigned to comprehensive intervention: N=72
    • Only N=62 received the intervention
    • Did not receive allocated intervention (N=10):
      • Three family issues
      • Two transportation problem
      • Five other reasons.
    • Lost to follow-up (6.9%; N=5):
      • Three lost contact
      • Two moved.
    • Analyzed: N=72 Intention to treat analysis.
  • Assigned to comparison group: N=72:
    • All N=72 received the non-comprehensive guidelines
    • Lost to follow-up (8.3%; N=6):
      • Six lost contact.
    • Analyzed: N=72 Intention-to-treat analysis.


  Total (N=144) Comprehensive (N=72) Comparison (N=72)
  Mean ± Standard Deviation
Age (year) 44.5±13.5 44.2±12.6 44.8±14.4


Hispanic Americans (the sample represented primarily Cuban-born bi-lingual women).

Other Relevant Demographics

  Total (N=144) Comprehensive (N=72) Comparison (N=72) P-Value
  Mean ± Standard Deviation
Education (year) 13.7±2.7 14.0±2.8 13.4±2.6 0.200
Children (number) 1.6±1.3 1.8±1.4 0.4±1.3 0.136
  N (Percent)
Sex       0.371
120 (83.3) 62 (86.1) 58 (80.6)  
24 (16.7) 10 (13.9) 14 (19.4)  
Marital status       0.706
66 (45.8) 34 (47.2) 32 (44.4)  
38 (26.4) 21 (29.2) 17 (23.6)  
35 (24.3) 15 (20.8) 20 (27.8)  
5 (3.5) 2 (2.8) 3 (4.2)  
Nationality       0.257
71 (49.3) 38 (52.8) 33 (45.8)  
United States
38 (26.4) 21 (29.2) 17 (23.6)  
Puerto Rico
20 (13.9) 6 (8.3) 14 (19.4)  
15 (10.4) 7 (9.7) 8 (11.1)  
Language spoken       0.413
English and Spanish
75 (52.1) 39 (54.2) 36 (50.0)  
57 (39.6) 25 (34.7) 32 (44.4)  
12 (8.3) 7 (7.9) 5 (6.9)  
Occupation       0.053
Office administrator
40 (27.8) 13 (18.1) 27 (37.5)  
26 (18.1) 18 (25.0) 8 (11.1)  
33 (22.9) 14 (19.4) 19 (26.4)  
14 (9.7) 8 (11.1) 6 (8.3)  
11 (7.6) 6 (8.3) 5 (6.9)  
20 (13.9) 13 (18.1) 7 (9.7)  
Employment       0.149
82 (56.9) 46 (63.9) 36 (50.0)  
34 (23.6) 16 (22.2) 18 (25.0)  
21 (14.6) 9 (12.5) 12 (16.7)  
7 (4.9) 1 (1.4) 6 (8.3)  
Insurance       0.084
50 (34.7) 25 (34.7) 25 (34.7)  
Uninsured self-paid
43 (29.9) 25 (34.7) 18 (25.0)  
36 (25.0) 19 (26.4) 17 (23.6)  
15 (10.4) 3 (4.2) 12 (16.7)  
Smoking Habit       0.670
Never smoked
91 (63.2) 47 (65.3) 44 (61.1)  
Former smoker
29 (20.1) 15 (20.8) 14 (19.4)  
Current smoker
24 (16.7) 10 (13.9) 14 (19.4)  

P-values are two-sided for the comparison between comprehensive and comparison groups.


  Comprehensive (N=72) Comparison (N=72)
Weight (kg)
131.01±28.01 136.47±35.39
Body mass index 
48.98±8.48 36.51±7.03


The Laparoscopic Institute of South Florida (all participants had recent surgery at the Palmetto General Hospital in Hialeah, FL).

Summary of Results:

Key Findings

Comparison of Anthropometrics
  Within Groups Between Groups
  Comprehensive (N=72) Comparison (N=72) Comprehensive (N=72) Comparison (N=72) P-value
  Mean ± Standard Deviation
Weight (kg)     17.33±11.74 10.03±9.43 <0.001
131.01±28.01 136.47±35.39      
Six months
94.57±21.19 100.32±24.89      
12 months
77.24±19.21 90.29±21.93      
Body mass index   49.54±9.65 6.48±4.37 3.63±3.41 <0.001
48.98±8.48 36.51±7.03      
Six months
35.37±6.83 32.89±6.18      
12 months
Excess weight loss (kg)     17.33±11.74 10.03±9.43 <0.001
Six months
36.43±9.91 35.97±13.94      
12 months
53.76±15.35 46.00±18.87      
Excess weight loss (percent)     25.04±14.31 13.08±11.28 <0.001
Six months
54.56±12.90 50.68±12.89      
12 months
79.60±15.48 63.76±14.24      
Comparison of Physical Activity
  Within Groups Between Groups
  Comprehensive (N=67) Comparison (N=66) Comprehensive (N=67) Comparison (N=66) P-value
Frequency (percent)     5 (7.0) -4 (6.0) 0.131
Six months
50 (74.6) 48 (72.7)      
12 months
55 (82.1) 44 (66.7)      
0.302 0.503      
Intensity (MET-h)     8.85±14.9 1.35±12.5 0.002
Six months
11.83± 11.3 10.98±10.2      
12 months
20.68±18.0 12.33±13.6      
<0.001 0.386      
Frequency (days per week)     0.66±2.7 -0.02±2.8 0.159
Six months
3.22±2.4 3.18±2.3      
12 months
3.88±2.2 3.17±2.7      
0.052 0.965      
Time, minutes per week     13.66±46.7 -3.56±38.9 0.023
Six months
45.97±37.0 42.88±34.1      
12 months
59.63±48.1 39.32±33.7      
0.019 0.460      

Other Findings

  • Study participants:
    • There was a 57% response rate to in-person recruitment and 7.64% attrition rate at one year
    • Of 72 participants, 27 were randomly assigned to the comprehensive intervention group attended the entire program (37.5%)
    • Ten individuals attended five sessions (13.9%) and the rest attended four (9.7%), three (9.7%), two (8.3%) and one session (6.9%), respectively
    • The overall attendance rate to the comprehensive educational program was 64.4%
    • The median number of session attended was three
    • The first session on nutrition was the session with the highest attendance (76.4%)
    • The second session, which discussed the importance of physical activity in the post-operative bariatric life, had an attendance rate of 66.7%
    • The total attrition rate during the study was 13.9%.
  • Anthropometric outcomes:
    • Patients had a mean pre-operative excess body weight of 72.20± 27.81kg
    • Overall, participants lost an average of 52.62±12.99% of their excess body weight at six months
    • There were no significant differences in anthropometric characteristics between intervention and comparison group participants before surgery (pre-operative) and at six months after surgery (baseline assessment point)
    • Comprehensive group experienced significantly greater excess weight loss (25% vs. 13%; P<0.001) and significantly greater BMI reduction (6.48±4.37 vs. 3.63±3.41; P<0.001) than those in the comparison group who received non-comprehensive minimal approach (i.e., printed guidelines for healthy eating and physical activity recommendations)
    • At one year following surgery, comprehensive group participants lost 80% of their pre-operative excess weight, whereas comparison group participants lost 64% of their pre-operative excess weight (P<0.001).
  • Physical activity outcomes:
    • Six months post-surgery, approximately 74% of participants reported doing some type of physical activity
    • At one year, approximately 82% and 67% of the intervention and comparison group participants respectively stated that they regularly exercise
    • Walking was reported as the most frequent physical activity over time
    • Within groups, intervention group participants significantly increased their mean time (P=0.019) and intensity of exercise (P<0.001) from six months to 12 months after surgery
    • In contrast, comparison group participants did not significantly change their activity behavior during the study period (P>0.05)
    • Between groups, intervention group participants were significantly more involved in physical activity (+14 minutes per week vs. -4 minutes per week; P<0.001) than comparison group participants.
  • Dietary intake outcomes:
    • Between six and 12 months following surgery, mean total daily energy intake in both groups was slightly below the recommended guidelines for gastric bypass surgery, which is in the range of 1,000kcal to 1,400kcal for weight maintenance
    • Within both groups, the mean daily intake of protein was in the low range of the recommended for patients who have received gastric bypass, which is 60g to 105g based on a 1,000kcal to 1,400kcal diet
    • No significant differences in daily energy intake and number of meals between groups
    • Mean intake of protein in the comparison group was significantly lower than that of the intervention group (P=0.02).
Author Conclusion:
  • The comprehensive educational approach, which incorporated behavior change and motivation strategies into nutrition counseling, significantly increased weight loss and physical activity between six and 12 months following surgery
  • Further research studies should be performed in ethnically diverse samples to identify relevant socio-cultural parameters that may be associated with, or promote, a positive response to comprehensive nutrition and lifestyle education interventions following bariatric surgery.
Funding Source:
Other: not described
Reviewer Comments:
  • Funding source was not described
  • Although an attention-intervention effect might have occurred during the semi-annual data collection visits, the randomization should have reduced or eliminated it (Note: The paper does not detail how the randomization was done)
  • The nature of this intervention precluded the blinding of either participants or investigators, which might contribute to a placebo effect.
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? ???
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) ???
  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.) N/A
  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? Yes
  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? No
  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.) ???
  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? N/A
  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? No
  6.6. Were extra or unplanned treatments described? No
  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? No
  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)? No
  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? No
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? ???
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? ???