EAL

AWM: High Calcium (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine if the utilization of a single dairy product (yogurt) in a highly structured diet would result in a comparable augmentation of weight and fat loss to that observed with a mixture of dairy products.

Inclusion Criteria:

Otherwise healthy obese adults aged 18 - 50 years. All subjects had an initial BMI of 30.0 - 39.9, a low-calcium diet (500 - 600 mg/day, as determined by food frequency and diet history) at study entry, had no more than 3 kg weight change over preceding 12 weeks and no recent (12 week) changes in exercise frequency or intensity.

Exclusion Criteria:

Patients excluded if they required use of oral antidiabetic agents or insulin, utilized obesity pharmacotherapeutic agents and/or herbal preparations intended for obesity management, utilized calcium supplements, reported adverse effects to dairy products, had a history of significant endocrine, hepatic or renal disease, were pregnant or lactating, or suffered any form of malabsorption syndrome.

Description of Study Protocol:

Recruitment

Not mentioned.

Design

Randomized Controlled Trial. Obese subjects were placed on balanced deficit (-500 kcal/day) diets and randomized to control or yogurt treatments for 12 weeks.

Blinding used (if applicable)

Not blinded.

Intervention (if applicable)

Balanced deficit diets (-500 kcal/day) defined as control (0-1 servings of dairy products/day and 400-500 mg Ca/day, as well as a sugar-free gelatin snack control food) or yogurt diet (three 6-oz servings of Yoplait Light each day and 1100 mg Ca/day). All calcium in both diets was from food sources. Dietary macronutrients and fiber were held constant at the US average (35% kcals from fat, 49% kcals from carbohydrates, 16% kcals from protein, fiber 8 - 12 g/day). Nutritional supplements not permitted. Caffeine intake maintained at constant level individualized for each patient.

Statistical Analysis

Data were assessed via multivariate MANOVA using SAS-PC software to facilitate evaluation of repeated measures and independent group comparisons. Only subjects who completed entire study were included in data analysis. All data presented as mean +/- s.e.m.

Data Collection Summary:

Timing of Measurements

2 week lead-in period to establish current caloric requirements and complete baseline dietary and physiological assessment. Dietary data reviewed weekly, as well as weight and waist circumference. Body fat, blood pressure and blood tests taken after 12 weeks of intervention.

Dependent Variables

Body weight measured with calibrated scale and height measured with a wall-mounted stadiometer with subjects in street clothes, no shoes
Waist circumference measured in standing position, with measurements obtained midway between lateral lower rib margin and iliac crest, taken mid-exhalation, the average of 2 measurements recorded
Total body fat mass and percent lean and fat mass assessed by DEXA
Blood pressure and heart rate taken with subject in seated position with standard calibrated sphygmomanometer, average of 2 readings reported
Plasma glucose determined using oxidase method and insulin via standard radioimmunoassay
Fasting lipid profile (triglycerides, total cholesterol, HDL and LDL cholesterol) assessed using standard clinical techniques, as well as circulating glycerol

Independent Variables

Dietary treatments: subjects were provided individual instruction, counseling and assessment from dietitian regarding dietary adherence and development and reinforcement of strategies for continued success. Diets monitored weekly, all subjects maintained complete diet diaries. Compliance assessed by weekly interview, review of diet diary and product return.

Control Variables

Description of Actual Data Sample:

Initial N: 38 otherwise healthy obese adults

Attrition (final N): 34 completed, 18 in yogurt group (13 female, 5 male) and 16 controls (14 female, 2 male). Of 4 subjects who withdrew, 3 were in control group and 1 in yogurt group. 3 left study due to scheduling conflicts, 1 left study due to relocation.

Age: Yogurt diet subjects: 39 +/- 10 years, controls: 42 +/- 6 years

Ethnicity: Not mentioned

Other relevant demographics: All subjects had initial BMI of 30.0 - 39.9

Anthropometrics: No significant differences between completers and noncompleters for any parameter studied

Location: Knoxville, TN

Summary of Results:

Other Findings

All participants lost body weight and body fat due to daily energy deficit. Participants on low calcium control diet lost 4.99 +/- 0.5 kg body weight, while those on yogurt diet lost 6.63 +/- 0.6 kg (P < 0.01).

Fat loss was markedly increased on the yogurt diet (-4.43 +/- 0.47 vs -2.75 +/- 0.73 kg in yogurt and control groups, P < 0.005).

There was a significant reduction in lean body mass on the control diet compared to the yogurt diet (-1968 +/- 212 g vs -1351 +/- 156 g, P < 0.05).

Trunk fat loss was augmented by 81% on the yogurt vs control diet (-3.158 vs -1.744, P < 0.001) and this was reflected in a markedly greater reduction in waist circumference (-3.99 +/- 0.48 vs -0.58 +/- 1.04 cm, P < 0.001).

Further, the fraction of fat lost from the trunk was higher on the yogurt diet vs control (P < 0.005).

Participants on the yogurt diet exhibited a significant increase in circulating glycerol (22.3%, P < 0.001), indicating an increase in lipolysis, while there was no significant change in circulating glycerol in participants on the control diet.

There were no significant effects of any of the diets on systolic pressure or circulating lipids, while patients on the yogurt diet exhibited a significant reduction in diastolic blood pressure (P < 0.01).

Author Conclusion:

In summary, isocaloric substitution of yogurt for other foods in the diet of obese adults results in a repartitioning of energy and body composition, resulting in reduction of body weight, total and central adiposity, and an improved metabolic profile during energy restriction. In vitro data obtained in human adipocytes suggest that the partially selective effect on central adiposity may result, in part, from reductions in adipocyte cortisol production secondary to suppression of calcitriol levels on the higher calcium diets.

Funding Source:

Industry:

National Dairy Council

Food Company:

Reviewer Comments:

Relied upon self-reported intake for compliance. Low dropout rate. Outpatient study - food not provided.

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?		???
	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.)	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?	???
	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