EAL

DF: Obesity (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the effect of a high-dairy diet (four servings per day, including two of liquid milk) on weight loss, body fat, trunk fat, waist and hip circumference, fasting lipids, fasting and two-hour post-prandial glucose and insulin levels, high-sensitivity C-reactive protein (hs-CRP) and leptin levels in obese adults
To determine whether this effect is enhanced by a high-fiber (from whole grains, fruits and vegetables), low-glycemic index (foods over 100GI discouraged) diet.

Inclusion Criteria:

Men and women
Ages 25 to 70
Obese: BMI, 30 to 40
Stable weight over the previous six months.

Exclusion Criteria:

Lactose intolerance
Pregnancy
History of eating disorder
Calcium supplement use (and unwilling or unable to discontinue for study duration)
Weight loss or diabetes medication use
Antidepressant agent use associated with weight gain
Digestive disorders that prohibit following a high-fiber diet.

Description of Study Protocol:

Recruitment

Posters placed near employee elevators in clinic and hospital
Recruitment from October 2001 to April 2002.

Design

Randomized clinical trial.

Blinding Used

None, although participants were assigned to groups by someone otherwise uninvolved in study
RDs who enrolled participants and administered diets nor participants were blinded.

Intervention

After a two-week maintenance run-in phase, during which the participants kept daily food records and exercise logs that were reviewed by the RD once a week (average calcium intake, 932mg; average fiber intake, 16.2g), they were randomized to any of the three following diets for 48 weeks:

Control diet, moderate in dairy and fiber (Diet One): 30% fat, 20% protein, 50% carbohydrate
- 500kcal deficit from estimated energy expenditure (BEE x 40% AF; calculated using Harris-Benedict, using actual weight)
- Average calcium and fiber intake
- Two servings of dairy per day
- Meal plan based on their calorie level, using American Diabetes Association exchanges
- Participants instructed to do moderate exercise for at least 30 minutes, four times per week
- Daily food diary and exercise log, reviewed with an RD once a week (those who adhered to diet only seen by RD every two weeks during second half of study period)
- RD administered educational materials for weight loss
- Harris-Benedict recalculated at 12, 24 and 36 weeks and subjects were given new caloric goals for weight loss
- If less than six pounds were lost, caloric intake was decreased by 200 calories from HB equation.
Diet Two (high-dairy): Same as control diet, except for amount of dairy
- Four servings of dairy per day, including at least two from liquid milk.
Diet Three (high-dairy/high-fiber/lower GI): Same as control diet, except for amount of dairy, amount of fiber and GI
- Four servings dairy per day, including at least two from liquid milk
- Increased fiber from whole grains, fruits and vegetables
- Low-GI foods (foods with GI over 100 strongly discouraged).

Randomization by computer generated algorithm, stratified by sex.

Statistical Analysis

Distributions characterized by percentages, means and SDs
Wilcoxon rank sum test used to determine pre- and post-treatment participant differences
Kruskal-Wallis test used to determine group differences
Non-parametric tests used because many factors measured were highly skewed
Intention-to-treat analysis with last available value carried forward
Completer's analysis
Adherer's analysis (75% or more as determined by RDs)
80% power.

Data Collection Summary:

Timing of Measurements

Oral glucose and insulin tolerance tests: Twice at beginning and twice at end of study
Fasting lipids, hs-CRP, homocysteine and leptin: Measured twice at the beginning and twice at 48 weeks
Weight and waist-to-hip ratio: Determined twice at beginning, at 12, 24 and 36 weeks and twice at 48 weeks
REE (indirect calorimetry) and body fat (DXA scan): Measured at the beginning, 24 and 48 weeks
Average measure used when measurement was taken twice
Food diaries analyzed (two weekdays and one weekend day): Weeks 11, 23, 35, 47.

Dependent Variables

Weight (kg) and BMI
Body fat/trunk fat: Measured by DXA scan
Waist-to-hip ratio
- Waist circumference (cm): Measured at umbilicus
- Hip circumference (cm): Measured at widest part of hip/buttocks with tape measure parallel to floor.
Fasting lipids
- Cholesterol (mM)
- Triglycerides (mM)
- HDL-C (mM)
- LDL-C (mM).
Fasting glucose (mM) and insulin (pM): Oral glucose and insulin tolerance tests (using 75g glucose load)
Hs-CRP (mg per L)
Leptin (ng per mL): Measured by Human Leptin double antibody radioimmunoassay kit
Two-hour glucose (mM) and insulin (pM).

Independent Variables

Dairy
Dietary fiber
Low-GI foods.

Control Variables

Age
Sex
Exercise
Caloric intake.

Description of Actual Data Sample:

Initial N: 90 (13 males, 77 females)
Attrition (final N): 72.

Age

25 years to 70 years
Average age at baseline
- Control diet: 42±8.8
- High-dairy diet: 41.2±9.3
- High-fiber/high-dairy diet: 41.1±8.6.

Ethnicity

Unknown.

Other Relevant Demographics

Recruitment posters placed near employee elevators in clinic or hospital, so participants were likely clinic employees.

Anthropometrics

Obese subjects [average BMI, 35±3.1 (control diet); 35±3.2 (high-dairy diet); 34.5±3 (high-fiber/high-dairy diet)]
No significant differences in weight, BMI, waist-to-hip ratio between groups.

Location

Mayo Clinic, Rochester, MN.

Summary of Results:

Calcium Intake, Fiber Intake, Macronutrient Intake

Calcium intake significantly lower in standard diet group
Fiber intake higher and high-GI food intake lower in high-dairy/high-fiber/low-GI group
Significant differences among groups in macronutrient intake
- High-fiber group (Group Three) had higher carbohydrate and lower fat intake.
No significant difference in exercise minutes among groups
No significant difference in number of days food intake recorded among groups
Similar results (no significant difference among groups) when intention-to-treat and adherer's analysis was used.

Weight Loss

Significant and comparable between three groups
9% weight loss using intention-to-treat (completers, 11%; adherers, 12%)
- Most weight loss occurred in the first 24 weeks.
Among completers, the high-dairy group lost a mean of 1.8kg more than the standard diet group (95% CI=-2.0kg to 5.6kg) and high-fiber/high-dairy group lost a mean of 0.5kg more than standard diet group (-3.7kg to 4.8 kg)
- CI narrower at 24 weeks: -2.8kg to 2.7kg and -2.8kg to 3.1kg, respectively.
No significant difference in weight loss between groups, using intention-to-treat analysis.

Fat Loss and Trunk Fat Loss, Waist and Hip Circumference, Waist-to-Hip Ratio

Significant fat loss and trunk fat loss in all three groups
No significant differences between groups in body fat loss, trunk fat loss or change in waist and hip circumference, using any of the methods of analysis.

Fasting Lipids, Glucose, Insulin, Leptin, hs-CRP

Each group showed significant increase in HDL-C and significant reductions in LDL-C
Each group showed significant decrease in fasting glucose, fasting insulin, leptin and hs-CRP
No significant differences found between groups for the above measures
No differences among groups in change in two-hour glucose or two-hour insulin
Intention-to-treat analysis or analyzing high adherers-only did not change these results.

Other Findings

No significant adverse events
No significant difference in caloric intake among the three groups, among completers. Among adherent subjects, there was a greater difference between prescribed calories and reported calories, although weight loss was similar even with the greater reported calorie deficit.
Of the 72 who completed study, 53 were compliant more than 75% of the time.

Author Conclusion:

A calorie-reduced diet, high in dairy, whether or not also high in fiber and lower in GI, did not enhance weight loss relative to a calorie-reduced, moderate-dairy diet in obese adults.

Funding Source:

Industry:

Naional Diary Council

Commodity Group:

Reviewer Comments:

Well-described study design
Small number of males included.

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.)	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?	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)?	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?	No
	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