MNT: Weight Management (2015)
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: 21058203
- 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.
Individuals meeting eligibility requirement were recruited between May 2006 and January 2007 from the Arizona Cancer Center.
- 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.
- 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.
- 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.
- 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.
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.
- 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
- Glycated hemoglobin
- Homeostasis model assessment (HOMA)
- Quantitative insulin-sensitivity check index (QUICKI)
- Total cholesterol
- Total-to-HDL-cholesterol ratio
- C-reactive protein (assessed using an automated turbidimetry analyzer).
Low-fat diet or reduced carbohydrate diet.
Control VariablesNo 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.
Initial N40 (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.
AgeMean: 56.2±9.4 years.
- 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.
- 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.
- 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.
|University/Hospital:||University of Arizona Cancer Center|
- 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
|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|
|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|