MNT: Weight Management (2015)
Citation:
Thomson CA, Stopeck AT, Bea JW, Cussler E, Nardi E, Frey G, Thompson PA. Changes in body weight and metabolic indexes in overweight breast cancer survivors enrolled in a randomized trial of low-fat vs. reduced-carbohydrate diets. Nutr Cancer. 2010; 62 (8): 1,142-1,152.
PubMed ID: 21058203Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:

Research Purpose:
To evaluate the changes in weight, body composition and metabolic parameters among overweight or obese breast cancer survivors enrolled in either a low-carbohydrate or low-fat six-month dietary counseling program.
Inclusion Criteria:
- Post-menopausal women
- Age 50 years to 60 years
- Breast cancer survivor: Diagnosed with Stage I or II invasive, estrogen receptor positive breast cancer and had completed treatment within the previous four years
- Overweight or obese: BMI, 25kg/m2 to 35kg/m2
- No recent history of significant weight loss or enrollment in a commercial weight loss program during the previous 12 months
- No current medically prescribed diet therapy
- Normal renal and hepatic function
- No history of diabetes or significant cardiovascular disease
- Currently receiving hormonal suppression therapy.
Exclusion Criteria:
Not described.
Description of Study Protocol:
Recruitment
Individuals meeting eligibility requirement were recruited between May 2006 and January 2007 from the Arizona Cancer Center.
Design
- Study participants were randomized 1:1 to one of two calorie-restricted diets: A low-fat diet or a modified Atkins/reduced-carbohydrate diet
- The duration of the study was 24 weeks
- Body composition and metabolic parameters were evaluated every six weeks.
Intervention
Diet
- Subjects were assigned to one of two diet arms: A low-fat diet or a reduced-carbohydrate diet
- In both arms, calorie requirements were individualized to induce a one-pound- to 1.5-pound-per-week weight loss in both diets. Subjects were instructed to follow the diet for a period of six months
- Low fat diet: 55% to 60% carbohydrate, 15% to 20% protein, 25% fat
- Reduced carbohydrate diet: 35% carbohydrate, 25% to 30% protein and 35% to 40% fat. Subjects randomized to this diet arm were instructed to reduce carbohydrates to less than 30g per day during the first two weeks, then gradually increase carbohydrate intake until the 35% carbohydrate goal was achieved.
Dietary counseling
- Subjects received 24 weeks of dietary counseling by a registered dietitian
- The counseling began with a 45-minute, clinic-based, face-to-face session. They met with the dietitian weekly for a period of six weeks.
- Standardized educational materials, including dietary goals, sample menus, tips for behavior change and macronutrient logs, were provided to each participant.
Statistical Analysis
- Descriptive statistics were calculated for demographic, clinical, dietary, anthropometric and metabolic data for the 40 study participants included in the analysis
- Descriptive statistics were used to compare demographic characteristics of completers vs. non-completers
- Baseline carried forward rules were applied for any missing follow-up data
- Student's T-tests were used to assess changes in dietary intake, body weight, body composition and metabolic factors over time and between dietary arms, controlling for baseline values
- P for trend was also assessed using repeated measures of analysis of variance (ANOVA) for measures that were evaluated more than twice during the trial
- Statistics significance was set at P=0.05 for within-subject changes and P=0.1 for diet group comparisons.
Data Collection Summary:
Timing of Measurements
- Body weight, height, waist and hip circumference were measured at baseline, six weeks, 12 weeks, 18 weeks and 24 weeks
- Body composition, resting energy expenditure, dietary intake and physical activity were assessed at baseline and at 24 weeks
- Fasting glucose, insulin, HbA1c and lipid panels were measured at baseline, six weeks, 12 weeks, 18 weeks and 24 weeks
- High-sensitivity C-reactive protein (hsCRP) was assessed at baseline, 18 weeks and 24 weeks.
Dependent Variables
- Weight
- BMI
- Waist circumference
- Waist-to-hip ratio
- Body fat: Assessed using whole body Dual-energy X-Ray Absorptiometry (DXA) using a Lunar DPX-IQ whole body densitometer
- Appendicular lean mass: Assessed using whole body DXA
- Resting energy expenditure: Measured by the respiratory gas exchange method using MedGem portable indirect calorimeter under standard conditions
- Systolic blood pressure
- Diastolic blood pressure
- Glucose
- Glycated hemoglobin
- Insulin
- Homeostasis model assessment (HOMA)
- Quantitative insulin-sensitivity check index (QUICKI)
- Total cholesterol
- LDL-cholesterol
- HDL-cholesterol
- Total-to-HDL-cholesterol ratio
- Triglycerides
- C-reactive protein (assessed using an automated turbidimetry analyzer).
Independent Variables
Low-fat diet or reduced carbohydrate diet.
Control Variables
No control variables for assessment, but control measures were employed to minimize bias.- Standardized dietary counseling protocol: The same dietitian delivered all dietary counseling
- Counseling frequency and behavioral methods were similar across diet groups. Only content related to macronutrient goals differed between arms.
- 24-hour recall was completed at each counseling session to assess adherence to target diet.
Description of Actual Data Sample:
Initial N
40 (40 female, no males).Attrition (Final N)
- 32 participants (80%) completed the trial: 19 subjects (90.5%) in the Low Carbohydrate Group and 13 subjects (68.4%) in the Low Fat Group
- Baseline carried-forward rules were applied for any missing follow-up data.
Age
Mean: 56.2±9.4 years.Ethnicity
- White: 82.5%
- Hispanic origin: 10%
- Other: 17.5%.
Other Relevant Demographics
- 3.7±3.4 years since diagnosis
- 65% with college degree
- 45.0% sedentary
- 90% currently non-smokers
- 65% low to moderate smokers.
Anthropometrics
- Weight: 84.1±12.3kg
- BMI: 31.8±4.3kg/m2
- Waist: 99.8±10.5cm
- Waist-to-hip ratio: 0.9±0.1
- Fat percentage: 47.2±5.2%
- Appendicular lean mass: 17.5±2.2kg.
Location
Tucson, AZ.Summary of Results:
Key Findings
- Both diet arms demonstrated significant reductions in body weight, body fat and waist circumference, but the difference between study groups was not significant.
- Weight change: -5.9±4.1kg in the low-carbohydrate diet (P<0.001) and -6.3±5.6kg in the low-fat diet (P<0.001)
- Body fat change: -2.4±1.6% in the low-carbohydrate diet (P<0.001) and -2.5±3.2% in the low-fat diet (P=0.003)
- Waist circumference change: -5.3±4.4cm in the low-carbohydrate diet (P<0.001) and -6.1±7.4cm in the low-fat diet (P=0.007).
- Both diet arms also demonstrated significant reductions in appendicular lean mass [0.8+0.9kg in the low-carbohydrate diet (P<0.001) and 0.6+0.8kg in the low-fat diet (P=0.008)], but the difference between study groups was not significant
- Fasting insulin, HbA1c and HOMA were significantly reduced, regardless of diet assignment
- Insulin change: -3.5±6.8mcU per ml, P=0.002
- HbA1c change: -0.1±0.3%, P=0.006
- HOMA change: -0.9±1.8%, P=0.002.
- Total cholesterol-to-HDL cholesterol ratio was improved in both groups (-0.3±0.5, P=0.08 in the low-carbohydrate diet; -0.1±0.5, P=0.83 in the low-fat diet; P for trend, 0.03)
- Triglycerides were significantly reduced in the Low-Carbohydrate Diet Group (-31.1±36.6mg per dL, P=0.01), but not in the Low-Fat Diet Group
- C-reactive protein was reduced in both groups (-0.4±1.7, P=0.06 in the low-carbohydrate diet; -0.4±1.6, P=0.10 in the low-fat diet), although the overall change was not statistically significant and was not different by diet arm
- Systolic blood pressure tended to decrease over the course of the study, but predominantly in the low-fat diet (-8.6±16.3mmHg, P=0.02 compared to -0.8±14.1 mmHg, P=0.80)
- Resting energy expenditure was reduced in both groups but the difference was not significant.
Author Conclusion:
Regardless of macronutrient composition, overweight breast cancer survivors who are provided regular diet counseling on an energy-restricted diet by registered dietitians can achieve significant weight loss.
Funding Source:
University/Hospital: | University of Arizona Cancer Center | ||
Not-for-profit |
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Reviewer Comments:
- It was unclear whether counseling was six weeks or six months. Page 1,143, second column, first paragraph states subjects met with dietitian for a period of six weeks, but the rest of the article indicates six months or 24 weeks.
- Small sample size
- Differential drop-out across study groups: Subjects in the Low Carbohydrate Group were more likely to complete the trial
- Reliance on self-reported diet to estimate adherence
- It is not possible to evaluate intervention responsiveness based on adjuvant hormone therapy
- There was a broad range of years since diagnosis among participants, which may have influenced weight loss, body composition and metabolic response to intervention.
Quality Criteria Checklist: Primary Research
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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) | Yes | |
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? | Yes | |
5.1. | In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? | Yes | |
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.) | Yes | |
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? | N/A | |
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? | Yes | |
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? | N/A | |
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? | Yes | |
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 | |