AWM: Nutrient Adequacy and Caloric Restriction (2013)

Study Design:
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Quality Rating:
Research Purpose:
To compare, under field conditions, meal replacements with a structured weight-reduction diet in overweight/obese Australians with raised triglycerides, in the absence of personal professional support.
Inclusion Criteria:
Subjects were included if aged 20 - 65 years, BMI 27 - 40, displayed a fasting triglyceride level > 2.0 mmol/L, had no abnormality of clinical significance on medical history, had no history of metabolic disease, and if female, were not pregnant or breast feeding.
Exclusion Criteria:
Subjects were excluded if they suffered from type 1 or type 2 diabetes, reported a history of heavy alcohol consumption (>5 drinks/day) and were unable to cease alcohol consumption for the duration of the study, had widely fluctuating exercise patterns, reported frequent dining out (>2 times per week and unable to cease), reported an inability to prepare meals or meet diet requirements, had a history of extended absences due to travel or other commitments, or were unable to comprehend or cope with study requirements.
Description of Study Protocol:


Not described.


Randomized parallel design with minimum intervention.

Blinding used (if applicable)

Not blinded.

Intervention (if applicable)

Randomized to either meal replacement group or control group.  Both underwent a 6000 +/- 50 kJ/day intervention for 3 months (stage 1) and a further 3 months (stage 2) for a planned weight loss of 6 - 12 kg.  Groups were provided oral and written information.  The control group was provided with shopping vouchers and followed a low fat, low energy diet.  The meal replacement group was supplied with Slim Fast products for 2 meals (1800 kJ) and consumed a low-fat evening meal.  Free Slim Fast products and shopping vouchers were provided.

Statistical Analysis

Repeated measures ANOVA was calculated with the treatment period as the within-subject factor and with the diet as the between-subject factor.  Age, baseline triglyceride, BMI and change in weight between periods were inserted into the model as covariates where appropriate.  Student's t test was used to compare means for within-group paired samples and between-group independent samples.  Data are presented as means +/- SEM unless stated otherwise.

Data Collection Summary:

Timing of Measurements

Clients were weighed every 2 weeks and received structured supervision without professional dietary input.  Subjects returned 3 day weighed food records at 4 week intervals.  Venous blood samples taken at weeks 0, 4, 8 and 12 (stage 1) and week 24 (stage 2) for serum folate, plasma carotenoids and plasma homocysteine.  Nutrition quality of life questionnaire was used to assess attitudes to treatment at the end of stages 1 and 2.

Dependent Variables

  • Serum triglycerides concentrations measured by using Cobas-Bio clinical analyzer and enzymatic in vitro test kits
  • Plasma folate and homocysteine measured by Institute Medical Veterinary Sciences
  • Carotenoids measured as described by Khachik et al or Noakes et al

Independent Variables

  • Dietary intervention:  control or meal replacement assignment.  Compliance was assessed through 3 day weighed food records.  Blood biomarkers were used to assess fruit/vegetable intake. 

Control Variables


Description of Actual Data Sample:

Initial N: 300 subjects were screened.  66 matched subjects were selected and blocked into 2 groups of 33 each.

Attrition (final N):  55 subjects completed stage 1 (3 months), 17 men and 9 women in the meal replacement group, 15 men and 14 women in the control group.  7 withdrew from the meal replacement group, 4 in the control group.  Most withdrawals occurred due to changes in personal circumstance rather than dislike of either diet.  42 subjects completed stage 2, 19 in the meal replacement group and 23 in the control group.

Age:  Meal replacement group:  mean age 49.3 +/- 8.8 years, control group:  mean age 47.1 +/- 10.3 years. 

Ethnicity:  Not mentioned.

Other relevant demographics: Meal replacement group:  mean BMI 31.8 +/- 2.8, control group:  mean BMI 33.2 +/- 3.1.

Anthropometrics Subjects in each group were matched for age, gender, triglycerides, and BMI.

Location: Australia


Summary of Results:

Other Findings

Energy intake and energy distribution did not differ between treatments at 3 or 6 months.  3 day mean intake for the meal replacement group was 6026 kJ, 20.1% kcals from protein, 22.7% kcals from fat, 57.2% kcals from carbohydrate, and 24.4 g fiber.  3 day mean intake for the control group was 6047 kJ, 21.5% kcals from protein, 16.8% kcals from fat, 61.7% kcals from carbohydrate, and 27.8 g fiber.

Dietary fiber intake was significantly lower in the meal replacement group than the control group at both 3 months (23.2 +/- 0.8 g vs 28.7 +/- 1.5 g, P < 0.01) and 6 months (23.3 +/- 1.0 g vs 28.2 +/- 1.6 g, P < 0.02).   

Weight loss was 6.0 +/- 4.2 kg (6.3%) for the meal replacement group and 6.6 +/- 3.4 kg (6.9%) in the control group after 3 months (both P < 0.001 from baseline), and 9.0 +/- 6.9 kg (9.4%) for the meal replacement group and 9.2 +/- 5.1 kg (9.3%) for the control group (both P < 0.001 from baseline - different over time within but not between treatments).  No significant difference in weight change between the meal replacement group and controls was observed at baseline, 3 months or 6 months.  There was no interaction between gender, BMI, age, and treatment with the amount of weight lost. 

Serum folate and plasma beta-carotene were higher in the meal replacement group, but the differences between groups were not statistically significant.  Serum folate levels increased from baseline (27.1 +/- 1.4 nmol/L) to 6 months (31.3 +/- 0.8 nmol/L, P = 0.007).  Beta-carotene levels increased significantly in the meal replacement group by 32% at 3 months and 41% at 6 months (P < 0.001).

Plasma homocysteine fell in both groups (4% in control group, 8% in meal replacement group, P < 0.005).

Calcium, magnesium and zinc were higher in the meal replacement group (P < 0.001), as well as iron (P < 0.01).

The meal replacement group scored significantly higher on poststudy questionnaire for ease of dining out than the control group (P < 0.01).  The meal replacement group also found the diet strategy easier to comply with, scoring significantly higher on questions related to understanding of food amounts (P < 0.05) and complying with food amounts ( P < 0.05) than the control group.  For the meal replacement group, 42% of respondents found the intervention better than other dietary strategies, and 12% would continue using it. 

Author Conclusion:
In conclusion, in this minimally controlled study in Australian adults, meal replacements were as effective a strategy for weight loss as a conventional diet, maintained over both a 3 and 6 month period.  The nutritional adequacy of the meal replacement program was equal to (except for dietary fiber) and in the case of some micronutrients, superior to the conventional diet.  Participants found meal replacement easy to comply with and found it easier to dine out on this plan.  This may facilitate longer-term compliance with a weight loss program and suggests that the program is nutritionally sound if applied appropriately.
Funding Source:
Government: Health Sciences & Nutrition, Commonwealth Scientific & Industrial Research Organisation (CSIRO),
Unilever Australia, Slim-Fast Nutrition Institute
Food Company:
Reviewer Comments:
Subjects in each group were matched.  Dietary compliance assessed through weighing food and blood biomarkers.
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) 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? 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.) No
  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? Yes
  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)? N/A
  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