EAL

AWM: High Calcium (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether inclusion of low-fat dairy products into the diets of obese African-American adults would result in reductions in body fat with preservation or increase of lean body mass in the absence of caloric restriction, and to determine whether a dairy-rich diet would accelerate the fat loss induced by energy restriction in obese African-American adults.

Inclusion Criteria:

Otherwise healthy obese African-American adults. All subjects had initial BMI of 30 - 40, a low calcium (<600 mg/day) and low dairy (<1 serving/day) diet as determined by FFQ and diet history at study entry, no more than 3 kg weight change over preceding 12 weeks, and no recent (4 weeks) changes in exercise intensity or frequency.

Exclusion Criteria:

Subjects excluded if they required the use of oral antidiabetic agents or insulin, used obesity pharmacotherapeutic agents and/or herbal or other preparations intended for use in obesity or weight management, 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 described.

Design

Randomized Controlled Trial.

Blinding used (if applicable)

Not used.

Intervention (if applicable)

Weight maintenance trial with low calcium (500 mg/day)/low dairy (<1 serving/day) or high dairy (1200 mg Ca/day with 3 dairy servings) for 24 weeks. Weight loss trial with low or high dairy diets in addition to a 500 calorie deficit.

Statistical Analysis

Data for each study phase assessed with MANOVA using SAS-PC software to facilitate evaluation of both the repeated-measures and independent group comparisons. Only subjects who completed the entire study were included in the data analysis.

Data Collection Summary:

Timing of Measurements

Phase 1: 2 week lead-in period to establish stable baseline of dietary and physiological measures followed by 24-week maintenance intervention. Phase 2: 2 week lead-in period followed by 24 week weight loss intervention.

Dependent Variables

Body weight measured weekly using calibrated scale and height measured with wall-mounted stadiometer, with subjects wearing street clothes with no shoes, outerwear or accessories.
Waist circumference measured weekly in standing position, with measurements obtained midway between lateral lower rib margin and the iliac crest. Measurements taken mid-exhalation and the average of 2 readings recorded
Body fat measured at beginning of study and at weeks 12 and 24 using DXA
Regional fat measured using DXA
Blood pressure measured with subjects seated in an upright position in a chair for at least 5 minutes with the arm supported at heart level. Blood pressure measured using appropriately sized cuff and standard, calibrated sphygmomanometer.
Circulating insulin, glucose, and lipids (triglycerides and total and HDL cholesterol) were measured in the fasting state at baseline, and weeks 12 and 24. Plasma glucose measured using glucose oxidase method, and insulin and leptin levels determined using radioimmunoassay.

Independent Variables

Dietary interventions: subjects were provided individual instruction, counseling, and assessment from the study dietitian regarding dietary adherence and the development and reinforcement of strategies for continued success. Diets were monitored weekly. Energy needs calculated using WHO equations and through baseline dietary assessments. Diets constructed to provide average US levels of macronutrients and fiber - 35% kcals from fat, 49% kcals from carbohydrate, 16% kcals from protein, 8 - 12 g/day fiber.

Control Variables

Description of Actual Data Sample:

Initial N: 39 subjects in weight maintenance trial. 36 subjects in weight loss trial.

Attrition (final N): 34 subjects in weight maintenance trial (23 females, 11 males), 29 subjects in weight loss trial (25 females, 4 males). Those who did not complete the study did not exhibit significant differences in any of the baseline characteristics compared with those who completed. Reasons for drop out included scheduling conflicts, dissatisfaction with weight loss, and reluctance to comply with caloric restriction.

Age: Maintenance trial: Low dairy - 41.3 +/- 2.7 years, High dairy - 42.5 +/- 2.6 years. Weight loss trial: Low dairy - 41.7 +/- 2.7 years, High dairy - 41.7 +/- 2.9 years.

Ethnicity: African-American

Other relevant demographics: Not mentioned.

Anthropometrics: Not mentioned.

Location: Tennessee

Summary of Results:

	Maintenance Phase - Low Dairy	Maintenance Phase - High Dairy	Weight Loss Phase - Low Dairy	Weight Loss Phase - High Dairy
Calcium intake (mg/day)	458 +/- 96	1124 +/- 53	468 +/- 23	1037 +/- 27
Energy intake (kcal/day)	1843 +/- 98	1982 +/- 124	1278 +/- 84	1491 +/- 62
% Energy from fat	33 +/- 4	34 +/- 3	30 +/- 2	31 +/- 2
% Energy from protein	17 +/- 2	17 +/- 1	17 +/- 1	18 +/- 2
% Energy from carbohydrate	50 +/- 3	49 +/- 5	53 +/- 3	51 +/- 2

Other Findings

In the weight maintenance trial, body weight remained stable for both groups throughout the maintenance study (total weight change of 0.2 +/- 0.5 kg for low dairy, 0.4 +/- 0.6 kg for high dairy).

In the weight maintenance trial, the high dairy diet resulted in decreases in total body fat (2.16 kg, p < 0.01), trunk fat (1.03 kg, p < 0.01), insulin (18.7 pM, p < 0.04) and blood pressure (6.8 mm Hg systolic, p < 0.01; 4.25 mm Hg diastolic, p < 0.01) and an increase in lean mass (1.08 kg, p < 0.04), whereas there were no significant changes in the low dairy group.

In the weight loss trial, although both diets produced significant weight and fat loss, weight and fat loss on the high dairy diet were ~2-fold higher (p < 0.01) and loss of lean body mass was markedly reduced (p < 0.001) compared with the low dairy diet. There was also a greater decrease in waist circumference in the high dairy group (p < 0.05).

Author Conclusion:

This study suggests that 3 servings of dairy foods per day produce signficant reductions in total and central adiposity in obese African-American adults - an outcome achieved without weight loss or caloric restriction. We also found that dairy foods accelerate loss of weight and total and central adipose tissue mass secondary to energy restriction.

Funding Source:

Reviewer Comments:

Subject recruitment and population not well defined.

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?		???
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	No
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	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