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Abstract

BACKGROUND:Although several observational and experimental studies have investigated the effect of dairy consumption on weight and body composition, results are inconsistent.OBJECTIVE:This systematic review and meta-analysis was conducted to summarize the published evidence from randomized controlled clinical trials (RCTs) regarding the effect of dairy consumption on weight, body fat mass, lean mass and waist circumference (WC) in adults.DESIGN:PubMed, ISI Web of Science, SCOPUS, Science Direct and EMBASE were searched from January 1960 to October 2011 for relevant English and non-English publications. Sixteen studies were selected for the systematic review and fourteen studies were included in meta-analysis.RESULTS:Our search led to 14, 12, 6 and 8 eligible RCTs that had data on weight, body fat mass, lean mass and WC, respectively. Overall, mean difference for the effect of dairy on body weight was -0.61 kg (95% confidence interval (CI): -1.29, 0.07, P=0.08). Increased dairy intake resulted in 0.72 kg (95% CI: -1.29, -0.14, P=0.01) greater reduction in fat mass, 0.58 kg (95% CI: 0.18, 0.99, P<0.01) gain in lean mass and 2.19 cm (95% CI: -3.42, -0.96, P-value <0.001) further reduction in WC than that in controls. Subgroup analysis revealed that increasing dairy intake without energy restriction in both intervention and control groups does not significantly affect weight, body fat mass, lean mass and WC; consumption of high-dairy weight loss diets led to 1.29 kg (95% CI: -1.98, -0.6, P<0.001) greater weight loss, 1.11 kg (95% CI: -1.75, -0.47, P=0.001) greater reduction in body fat mass, 0.72 kg (95% CI: 0.12, 1.32, P=0.02) gain in body lean mass and 2.43 cm (95% CI: -3.42, -1.44, P<0.001) additional reduction in WC compared with controls.CONCLUSION:Increased dairy consumption without energy restriction might not lead to a significant change in weight or body composition; whereas inclusion of dairy products in energy-restricted weight loss diets significantly affects weight, body fat mass, lean mass and WC compared with that in the usual weight loss diets.International Journal of Obesity advance online publication, 17 January 2012; doi:10.1038/ijo.2011.269.
1
Effect of dairy consumption on weight and body composition in adults: a
systematic review and meta-analysis of randomized controlled clinical trials
Amin Salehi Abargouei1,2, Mohsen Janghorbani3, Mohammad Salehi-Marzijarani3,
Ahmad Esmaillzadeh1,2
1Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
2Department of Community Nutrition, School of Nutrition and Food Science, Isfahan
University of Medical Sciences, Isfahan, Iran
2 Department of Epidemiology and Biostatistics, School of Public Health, Isfahan University
of Medical Sciences, Isfahan, Iran
Running title: Dairy intake, weight and body composition
Correspondence to:
Ahmad Esmaillzadeh, PhD
Department of Community Nutrition
School of Nutrition and Food Science
Isfahan University of Medical Sciences
PO Box 81745
Isfahan,
Iran
Phone: +98 311 792-2791
Fax: +98 311 6682509
Email: esmaillzadeh@hlth.mui.ac.ir
Word count: 7443
Number of tables: 2
Number of figures: 5
Conflicts of interest:
ASA, MJ, MSM and AE declared no personal or financial conflicts of interest.
2
ABSTRACT ١
Background: Although several observational and experimental studies have investigated the ٢
effect of dairy consumption on weight and body composition, results are inconsistent. ٣
Objective: This systematic review and meta-analysis is conducted to summarize the ٤
published evidence from randomized controlled clinical trials (RCTs) regarding the effect of ٥
dairy consumption on weight, body fat mass, lean mass and waist circumference (WC) in ٦
adults. ٧
Design: PubMed, ISI Web of Science, SCOPUS, Science Direct and EMBASE were ٨
searched from January 1960 to October 2011 for relevant English and non-English ٩
publications. Sixrteen studies were selected for the systematic review and fourteen studies ١٠
were included in meta-analysis. ١١
Results: Our search led to 14, 12, 6 and 8 eligible RCTs which had data on weight, body fat ١٢
mass, lean mass and WC, respectively. Overall Mean difference for the effect of dairy on ١٣
body weight was -0.61 kg (95% CI: -1.29, 0.07,
P
value=0.08). Increased dairy intake ١٤
resulted in 0.72 kg (95% CI: -1.29, -0.14,
P
value=0.01) more decrease in fat mass, 0.58 ١٥
(95% CI: 0.18, 0.99,
P
value<0.01) more increase in lean mass and 2.19 cm (95% CI: -3.42, -١٦
0.96,
P
value<0.001) more reduction in WC than that in controls. Subgroup analysis revealed ١٧
that increasing dairy intake without energy restriction in both intervention and control groups ١٨
dose not significantly affect weight, body fat mass, lean mass and WC; consumption of high-١٩
dairy weight loss diets caused 1.29 kg (95% CI: -1.98, -0.6,
P
<0.001) more weight loss, 1.11 ٢٠
kg (95% CI: -1.75, -0.47,
P
=0.001) decrease in body fat mass, 0.72 kg (95% CI: 0.12, 1.32, ٢١
P
=0.02) increase in body lean mass and 2.43 cm (95% CI: -3.42, -1.44,
P
<0.001) more ٢٢
reduction in WC compared to controls. ٢٣
Conclusion: Increased dairy consumption without energy restriction might not lead to a ٢٤
significant change in weight or body composition; while inclusion of dairy products in ٢٥
3
energy-restricted weight-loss diets significantly affects weight, body fat mass, lean mass and ٢٦
waist circumference compared to that in the usual weight loss diets. ٢٧
KEYWORDS: Dairy, weight, body fat mass, body lean mass, waist circumference, obesity, ٢٨
adiposity, clinical trials ٢٩
٣٠
4
INTRODUCTION ٣١
Obesity is an important public health problem worldwide, and its prevalence is increasing in ٣٢
both developed and developing countries 1. At least 2.8 million adults die each year as a ٣٣
result of being overweight or obese. Furthermore WHO fact sheet stated that diabetes (44%), ٣٤
ischemic heart disease (23%) and cancer burdens (7% and 41% based on type) are ٣٥
attributable to overweight and obesity 1. Obesity is now an epidemic worldwide 1 and the ٣٦
recent increase in its prevalence suggests a strong determinant role of environmental factors ٣٧
in its etiology 1, 2. ٣٨
Dairy consumption has been extensively studied for their possible roles in body weight ٣٩
regulation3. According to the report of International Dairy Federation (IDF), per capita ٤٠
consumption of dairy products is higher in western countries than that in non-western ٤١
countries4. On the other hand, prevalence of overweight and obesity is also higher in western ٤٢
populations as well5. Although several observational and experimental studies have ٤٣
investigated the association between dairy consumption and weight change, the role of dairy ٤٤
consumption in weight loss is still to be fully explored 3, 6. Available data are conflicting on ٤٥
the effect of dairy product consumption on weight loss3, 6, 7
.
The primary support for the ٤٦
negative association between dairy intake and obesity was originated from cross-sectional ٤٧
studies 3; and a meta-analysis did provide information on the inverse association of calcium ٤٨
intake (from dairy and other sources) with weight status in cross-sectional studies 3. These ٤٩
findings were not confirmed by cohort studies about the effect of dairy consumption 7; such ٥٠
that in a recent systematic review of cohort studies, 8 investigations -three in children 8-10 and ٥١
five in adults 11-15- showed a protective associations of dairy intake against weight gain and ٥٢
one reported a significant protective association only in adult males who were initially ٥٣
overweight 16; while seven studies reported no effect 16-22 and one reported an increased risk ٥٤
(among children) 23. Others have reported both a decreased and increased risk of incident ٥٥
obesity depending on the type of dairy intake15, 24. Due to the heterogeneity of cohort studies ٥٦
5
as well as inconsistent exposure and outcome measures, no meta-analysis has been done on ٥٧
their findings. ٥٨
Well-designed clinical trials are the best way for assessing the effect of dairy intake on ٥٩
weight and body composition. It has been postulated that dairy consumption affects weight ٦٠
control, but findings from RCTs have been conflicting. Several studies have suggested the ٦١
beneficial effects of dairy consumption on weight loss25-29. For instance, consumption of a ٦٢
dairy-rich (3 servings/d) weight loss diet has been resulted in a 5 kg additional weight loss ٦٣
compared with the conventional weight loss diet27. However, several RCTs have failed to ٦٤
reach significant conclusions27, 30-32, and still some others have even documented their ٦٥
significant effects of weight gain 33-35. ٦٦
Although the effect of dairy consumption on body weight and composition has been reviewed ٦٧
extensively 3, 6, 36-38, we are aware of no meta-analysis of RCTs in this regard. Inconsistent ٦٨
results from RCTs might be explained by different study designs, dose and duration of ٦٩
intervention, variety of age groups and gender. An advantage of meta-analysis to narrative ٧٠
reviews is the potential to yield less biased summaries of the published findings. Therefore, ٧١
the goal of this report was to conduct a systematic review and if possible a meta-analysis of ٧٢
published RCTs to summarize the evidence on the effect of dairy consumption on body ٧٣
weight and composition and to identify possible sources of heterogeneity between studies. ٧٤
RESEARCH DESIGN AND METHODS ٧٥
Search Strategy: We searched for relevant English and non-English publications by using ٧٦
the online databases of PubMed, ISI Web of Science, SCOPUS, Science Direct and ٧٧
EMBASE for the period from January 1960 to October 2011. We also contacted experts in ٧٨
the field and searched reference lists of the published papers. The key words used in our ٧٩
search strategy were selected from Medical Subject Headings (MeSH) database and were ٨٠
included as: dairy or calcium or milk or yogurt and obese or obesity or ٨١
6
overweight or fat mass or adiposity or adipose or weight or body mass index or ٨٢
BMI or waist circumference or WC. ٨٣
Eligibility Criteria: To be included in the meta-analysis, a published study had to meet the ٨٤
following criteria: (1) original article; (2) randomized controlled trial; (3) adult human ٨٥
population; and (4) dairy or one of natural dairy products as the main independent variable. ٨٦
When there were multiple publications from the same population or cohort, only data from ٨٧
the most recent report were included. Information on study design, participant characteristics, ٨٨
measurement of weight change and randomization was extracted independently by two ٨٩
reviewers (ASA and AE). Discrepancies were resolved by discussion. A total of 18 ٩٠
randomized controlled trials were considered for inclusion in this systematic review and ٩١
meta-analysis25-35, 39-45. ٩٢
Excluded studies: Eligible studies were read more carefully by ASA and AE for any ٩٣
methodological difference. We found that two papers33, 41 that administered energy ٩٤
restriction, had confined the energy intake into a defined certain value in both intervention ٩٥
and control groups while other studies restricted the energy intake of participants to the ٩٦
amount of 500 kcal less than their computed daily energy requirement. Because restriction of ٩٧
energy to fixed values can directly affect weight change33, 41, we preferred not to include the ٩٨
results of these 2 studies in the systematic review and meta-analysis; however, findings from ٩٩
the maintenance phase of study done by Zemel et al41 were included in our systematic review. ١٠٠
Besides restriction of energy intake to a fixed value, these two studies had some other distinct ١٠١
features. The study by Bowen et al33 has compared high-dairy diet with a high-protein diet, ١٠٢
while those we included in the meta-analysis have used high-dairy diet versus diets with the ١٠٣
same amount of protein. Another RCT done by Zemel et al41 was a two phase RCT which ١٠٤
had 3 months of energy restriction to a 1200-1500 kcal/day and a 6-mo maintenance phase. ١٠٥
Zemel et al41 in their study had an intervention on physical activity, and they could not ١٠٦
practically raise total intake of dairy and calcium (dairy consumption in intervention group: ١٠٧
7
1.2 servings/d vs. 1.1 serving/d for controls). Therefore, we excluded these two papers from ١٠٨
the meta-analysis. Further readings also revealed that a study by Eagan et al 42 was an ١٠٩
analysis of one year follow up of another intervention done by Gunther et al 32; therefore this ١١٠
study was removed too. One study35 had not presented data needed for meta-analysis. We ١١١
included findings of this study in our systematic review but not in meta-analysis. These ١١٢
exclusions remained fourteen studies [4 papers that assessed the effects of high-dairy diets ١١٣
(without energy restriction) 30-32, 34 , 9 papers that assessed the effects of high dairy weight ١١٤
loss diets (with energy restriction)25, 26, 28, 29, 39, 40, 43-45 and one study with two phases (with ١١٥
and without restriction)27] for meta-analysis. All mentioned papers had data on weight, ١١٦
twelve papers had data on fat mass 25-32, 39, 43-45, six studies reported data for lean mass 26-28, 30,
١١٧
32, 45 and eight papers contained data for waist circumference25-28, 31, 40, 43, 45. ١١٨
Data Extraction: We extracted data on publication (the first author's last name, year of ١١٩
publication, and country of population studied), number of individuals in intervention and ١٢٠
control groups, duration of intervention, age, gender, and mean and standard deviation (SD) ١٢١
of change in weight, fat mass, lean mass and waist circumference (WC). Two studies had not ١٢٢
reported mean and standard deviation (SD) of weight change34, 35, 40, but presented means at ١٢٣
baseline and after intervention. We calculated mean difference for these studies by the use of ١٢٤
post intervention data and included these papers in our meta-analysis. Another study by ١٢٥
Baran et al 35 that had not reported mean and standard deviation (SD) of weight change was ١٢٦
included in the systematic review but not in meta-analysis. One of the above-mentioned ١٢٧
studies that was done by Barr et al34 had reported their results in men and women separately. ١٢٨
Therefore, we included the findings of this study as two separate studies in the meta-١٢٩
analysis34. Two studies had not reported standard deviation of mean changes in ١٣٠
anthropometric measures but reported
P
value for comparison of means between intervention ١٣١
and control groups27, 30. Therefore, we computed the standard deviation for these studies and ١٣٢
used them in the meta-analysis. For five studies26-29, 45 that had reported standard error (SE) ١٣٣
8
of the mean, we calculated standard deviations (SD). One recently published study had not ١٣٤
reported mean change for weight, fat mass and waist circumference, therefore we took these ١٣٥
data by contacting authors 45. ١٣٦
Statistical Analysis: The mean difference and standard deviation (SD) of changes in ١٣٧
anthropometric measures (including weight, fat mass, lean mass and WC) was used for the ١٣٨
meta-analysis. Summary mean estimates with their corresponding SDs were derived by the ١٣٩
method of DerSimonian and Laird 46 by using random effects model, which incorporates ١٤٠
between-study variability. Meta-regression and subgroup analyses were performed to check ١٤١
for specific source of heterogeneity. Between subgroup heterogeneity was evaluated using ١٤٢
fixed effect model. Statistical heterogeneity between studies was evaluated with Cochran's Q ١٤٣
test 47. Sensitivity analysis was used to explore the extent to which inferences might depend ١٤٤
on a particular study or group of studies. Publication bias was assessed by visual inspection of ١٤٥
funnel plots 48. In these funnel plots, the difference in mean change of weight and other ١٤٦
indices were displayed against the inverse of the square of the standard error (a measure of ١٤٧
the precision of the studies). Formal statistical assessment of funnel plot asymmetry was done ١٤٨
with Egger's regression asymmetry test and adjusted rank correlation test49. Reported
P
١٤٩
values are from the intercept of the regression analysis, which provides a measure of ١٥٠
asymmetry. In addition, Begg's adjusted rank correlation test was used49 . Statistical analyses ١٥١
were carried out by the use of Stata, version 11.2 (Stata Corp, College Station, TX).
P
values ١٥٢
that were less than 0.05 were considered statistically significant. ١٥٣
RESULTS ١٥٤
Totally, for the 14 studies included in the meta-analysis, 883 adults aged 18-85 years had ١٥٥
been enrolled. Our preliminary analysis indicated slightly greater weight loss among those ١٥٦
with high dairy intake compared with those with low dairy intake [-0.61 kg (95% CI: -1.29, ١٥٧
0.07,
P
=0.08)]. However, there was a significant heterogeneity between studies (
P
= 0.04) ١٥٨
(Fig. 1). To find the source of variation, we categorized the studies into two major groups: ١٥٩
9
those that administered energy restriction (almost 500 kcal/day less than the estimated energy ١٦٠
requirement) for both intervention and control groups 25, 26, 28, 29, 39, 40, 43-45 , and those that did ١٦١
not used an energy restriction 30-32, 34. One study 27 that had two phases of energy restriction ١٦٢
and weight maintenance (without energy restriction) was considered in both categories. ١٦٣
Characteristics of RCTs (without energy restriction) included in systematic review are ١٦٤
presented in Table 1. Two out of 7 papers in this category had no reported data on weight ١٦٥
change and its standard deviation; therefore we did not include them in meta-analysis35, 41. ١٦٦
For 5 studies included in meta-analysis, participants age ranged between 18 and 85 years. ١٦٧
Duration of intervention varied between 21 and 48 weeks. In these studies, increasing ١٦٨
calcium intake of 400 to 850 mg/d via dairy products in intervention group was compared ١٦٩
with control subjects who had maintained their habitual diet. None of these individual studies ١٧٠
found a statistically significant effect of dairy consumption on weight. Among a total of 453 ١٧١
subjects, the pooled standard difference in mean weight change was 0.33 kg (95% CI: -0.35, ١٧٢
1.00,
P
= 0.34) (Fig. 1). No heterogeneity was found between studies included in this ١٧٣
subgroup (
P
= 0.67). ١٧٤
Characteristics of 9 RCTs that administered high-dairy weight loss diets (with energy ١٧٥
restriction) and included in this systematic review are presented in Table 2. Participants age ١٧٦
in these studies ranged between 18 and 70 years. Duration of intervention varied between 8 to ١٧٧
48 weeks. In these RCTs additional calcium intake of 550-1000 mg/d via dairy products in ١٧٨
intervention group was compared with control subjects who consumed 290-800 mg calcium ١٧٩
daily. Total energy intake had been restricted to a 500 kcal less than the requirement for both ١٨٠
groups. Among a total of 430 subjects, the pooled mean difference in mean weight change ١٨١
was -1.29 kg (95% CI: -1.98, -0.6,
P
<0.001) (Fig. 1). Heterogeneity was not significant ١٨٢
between studies (
P
=0.33). ١٨٣
Meta-analysis on 12 eligible studies 25-32, 39, 43-45 that presented data on fat mass showed that ١٨٤
among a total of 638 adults aged 18-70 years, the pooled estimated standard difference was ١٨٥
10
-0.72 kg (95% CI: -1.29, -0.14,
P
=0.01) with a significant between-study heterogeneity ١٨٦
(
P
=0.007) (Fig. 2). Subgroup analysis based on energy restriction demonstrated that for 9 ١٨٧
RCTs with energy restriction25-29, 39, 43-45, the pooled standard difference in means among a ١٨٨
total of 331 subjects was -1.11 kg (95% CI: -1.75, -0.47,
P
=0.001). No significant ١٨٩
heterogeneity was found (
P
=0.33). When we considered data from 4 RCTs27, 30-32 that did not ١٩٠
administered energy restriction, we observed that among a total of 253 subjects, the pooled ١٩١
standard difference in means was -0.16 kg (95% CI: -0.97, 0.66,
P
= 0.71) with a significant ١٩٢
between-study heterogeneity (
P
=0.02). We could not find the source of this heterogeneity ١٩٣
even after further subgroup analyses based on sex and age group and meta-regression. ١٩٤
We found a significant effect of dairy intake on increasing lean body mass in the whole ١٩٥
dataset 26-28, 30, 32, 45 (the pooled estimated standard difference: 0.58 kg; 95% CI: 0.18, 0.99, ١٩٦
P
<0.01; P for heterogeneity=0.07); subgroup analysis based on energy restriction showed that ١٩٧
the effect is significant for 4 RCTs26-28, 45 that administered energy restriction 0.72 kg (95% ١٩٨
CI: 0.12, 1.32,
P
=0.02, P for heterogeneity=0.06) and not significant for 3 RCTs27, 30, 32 ١٩٩
without energy restriction 0.35 kg (95% CI: -0.15, 0.86,
P
=0.17, P for heterogeneity=0.29) ٢٠٠
(Fig. 3). ٢٠١
Eight studies25-28, 31, 40, 43, 45 had reported data on waist circumference (WC). For all studies ٢٠٢
combined, we found the pooled estimated standard difference of -2.19 cm (95% CI: -3.42, -٢٠٣
0.96,
P
<0.001, P for heterogeneity=0.03) (Fig. 4). When the subgroup analysis was ٢٠٤
performed based on energy restriction, we observed that for 7 RCTs25-28, 40, 43, 45 that ٢٠٥
administered energy restriction in a total of 289 subjects, high dairy intake has been resulted ٢٠٦
in a greater reduction in WC compared with that in control group (the pooled standard ٢٠٧
difference in means: -2.43 cm; 95% CI: -3.42, -1.44,
P
<0.001, P for heterogeneity=0.60). ٢٠٨
Such finding was not obtained for 2 RCTs27, 31 that had not administered energy restriction (-٢٠٩
2.68 cm; 95% CI: -8.02, 2.66,
P
=0.32, P for heterogeneity=0.01). ٢١٠
11
In a sensitivity analysis, we found that the effect of dairy foods on body weight and fat mass ٢١١
was not substantially modified by the result of a certain study. However, due to the small ٢١٢
number of non energy restricted studies that presented data for WC and lean mass, excluding ٢١٣
each study could change the overall effect size. We did not find any evidence of publication ٢١٤
bias for studies assessing dairys effect on weight (
P
=0.68, Eggers test) and lean body mass ٢١٥
(P=0.32), although a slight asymmetry was seen in beggs funnel plot (Fig. 5). With regard to ٢١٦
body fat and WC, we reached a significant publication bias by funnel plot and Eggers test ٢١٧
(
P
=0.03 and
P
=0.01, respectively); however, this was not verified by Begg and Mazumdar ٢١٨
test (
P
=0.47 and
P
=0.28, respectively). ٢١٩
DISCUSSION ٢٢٠
We found that increasing dairy consumption to about recommended daily intakes in adults, ٢٢١
who do not follow any calorie-restricted diet, would not affect weight, fat mass, lean body ٢٢٢
mass and waist circumference. However, consumption of high-dairy calorie-restricted diets ٢٢٣
might result in a greater weight loss and higher reduction of waist circumference and fat mass ٢٢٤
compared with the conventional calorie-restricted diets. Our findings indicated that increased ٢٢٥
dairy intake might lead to gaining lean body mass. To the best of our knowledge, this is the ٢٢٦
first meta-analysis of RCTs assessing the effect of dairy intake on weight and body ٢٢٧
composition. ٢٢٨
It must be kept in mind that we could not include two papers35, 41 that met our inclusion ٢٢٩
criteria but lacked required data about weight change. Baran et al35 found that increased dairy ٢٣٠
intake would result in weight gain compared with the controls; however as the main endpoint ٢٣١
of the study was not weight change, they did not perform further analysis on weight change ٢٣٢
difference. Zemel et al41 showed no difference in weight between high-dairy group and ٢٣٣
controls. In both above-mentioned studies35, 41 as well as in another study done by Barr et ٢٣٤
al34, total energy intake was significantly increased due to the inclusion of dairy products in ٢٣٥
the diet. This was not the case for 4 other studies27, 30-32 that administered dairy products ٢٣٦
12
without energy restriction. Therefore, one might conclude that dairy consumption (without ٢٣٧
calorie-restriction) would result in a significant weight gain and increased body fat mass and ٢٣٨
WC due to increased energy intake. However, with the findings of all such studies combined, ٢٣٩
we did not find any evidence supporting this hypothesis. In contrast, our findings confirm the ٢٤٠
suggestions made by recent narrative reviews on the effect of dairy consumption on weight ٢٤١
change3, 6. Dougkas et al 3 expressed that majority of studies found no significant weight gain ٢٤٢
by dairy consumption when energy intake was not restricted. The same conclusion was also ٢٤٣
reached by Lanou and Barnard 6 when they reviewed studies that used dairy or calcium ٢٤٤
supplements as an intervention. ٢٤٥
We found that inclusion of dairy products in weight loss diets might accelerate weight ٢٤٦
reduction. The amount of dairy products used in published papers was equivalent to the ٢٤٧
provision of 550-1000 mg additional calcium for overweight or obese subjects as compared ٢٤٨
with the consumption of 200-800 mg calcium in the control group. Our findings also ٢٤٩
demonstrated that consumption of high-dairy weight loss diets would result in a greater ٢٥٠
reduction in fat mass and waist circumference and increase in Lean body mass. These results ٢٥١
indicate that dairy consumption would help people losing weight from fat compartment of the ٢٥٢
body, particularly from abdominal adipose tissue, which has been reported as a main ٢٥٣
determinant of cardiovascular risk factors50. ٢٥٤
Narrative reviews that considered the effect of increasing dairy intake along with energy ٢٥٥
restriction have reached conflicting findings. For instance, Dougkas et al 3 found five RCTs ٢٥٦
with energy restriction in their review and reported that 3 studies showed no evidence 33, 43, 44 ٢٥٧
while two studies 27, 28 found significant effect of increasing dairy consumption along with ٢٥٨
weight-loss diets on weight reduction. However, the search methodology used by Dougkas et ٢٥٩
al 3 seems to be incomplete because we found eleven studies that assessed the effect of dairy-٢٦٠
rich weight-loss diets on weight change25-29, 33, 39-41, 43, 44 . These studies had some ٢٦١
inconsistencies in their method of intervention which can affect the interpretation of their ٢٦٢
13
results. Two of the mentioned studies restricted total energy intake of their subjects to a fixed ٢٦٣
calorie33, 41 (i.e. 1200-1400 kcal/day); others administered an energy intake of 500 kcal less ٢٦٤
than subjects requirements. ٢٦٥
Several underlying mechanisms for the effect of dairy products on body weight and ٢٦٦
composition are proposed. It has been suggested that calcium supplementation can affect ٢٦٧
adipocyte lipid metabolism, fat oxidation, fatty acid absorption and postprandial fat ٢٦٨
metabolism. Furthermore there are some findings that suggest dairy constituents other than ٢٦٩
calcium, like conjugated linoleic acid, medium chain fatty acids and proteins may play a role. ٢٧٠
Evidence about the effect of dairy on appetite regulation is accumulating recently and some ٢٧١
of its constituents like dairy protein, calcium and fat have been proposed for this kind of ٢٧٢
effect. All these possible underlying mechanisms have been extensively reviewed and ٢٧٣
discussed by Dougkas et al 3. Despite these mechanisms, we found the beneficial effects of ٢٧٤
dairy only in energy-restricted studies. Therefore, it might be hypothesized that appetite- ٢٧٥
lowering effects of dairy work more efficiently along with energy restricted diets. This ٢٧٦
hypothesis remains to be examined in future studies. ٢٧٧
Majority of cross-sectional studies about the relationship between dairy consumption and ٢٧٨
body weight, composition or abdominal fat accumulation in adults found a significant inverse ٢٧٩
association 51-59. Some studies failed to find any relationship 53, 60, 61 and one study showed ٢٨٠
inconsistent results based on kind of dairy product 62. Cross-sectional studies cannot reach a ٢٨١
casual relationship; therefore, to detect a causal relationship one would need to look at cohort ٢٨٢
studies. Findings from cohort studies on the association of dairy intake and weight change are ٢٨٣
inconclusive7. So far, many RCTs have been published worldwide about the effect of ٢٨٤
increasing dairy consumption on weight change and body composition. This makes meta-٢٨٥
analysis of their results possible. RCTs are the most appropriate study designs to show casual ٢٨٦
effects and meta-analysis on their results can be resulted in a more reliable conclusions. ٢٨٧
14
It must be kept in mind that some RCTs included in the current meta-analysis had small ٢٨٨
sample sizes. Furthermore, the duration of follow-up for studies administered dairy intake ٢٨٩
with energy restriction was short; such that only few investigations had followed the ٢٩٠
participants for more than 12 weeks. In addition, most published papers were from US and ٢٩١
limited data are available from other countries, particularly from non-western populations. ٢٩٢
As our findings, particularly those for body composition indicators (fat mass, lean body mass ٢٩٣
and WC) are based on a limited number of RCTs, further investigations are required to come ٢٩٤
to a better understanding. ٢٩٥
In conclusion, our systematic review and meta-analysis on RCTs indicated that increasing ٢٩٦
dairy consumption without energy restriction might not lead to a significant change in weight ٢٩٧
and body composition; while inclusion of dairy products in weight-loss energy-restricted ٢٩٨
diets would result in a greater reduction of weight, fat mass and waist circumference and ٢٩٩
increase in Lean body mass compared with the conventional weight loss diets. ٣٠٠
٣٠١
٣٠٢
٣٠٣
٣٠٤
15
ACKNOWLEDGEMENT ٣٠٥
ASA and AE contributed in conception, design, statistical analyses, data interpretation and ٣٠٦
manuscript drafting. MJ and MSM contributed in data analysis. All authors contributed in the ٣٠٧
approval of the final manuscript for submission. ٣٠٨
CONFLICTS OF INTEREST ٣٠٩
ASA, MJ, MSM and AE declared no personal or financial conflicts of interest. ٣١٠
٣١١
16
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21
Table 1. Randomized controlled trials (without energy restriction) eligible to include in the systematic review ٥٤٩
Author Subjects
and
gender
Country Age
range
(y)
Duration
(wk)
Intervention Calcium intake (mg/d) Variables
presented
Result
intervention
a
control
a
Palacios et al,
2011 30
13 F/ 3
M
Puerto
Rico
22-50 21 4 daily
servings of
dairy
products
1337 ± 380 463± 325 Mean (SD)
weight, fat and
lean mass at
baseline and after
intervention
High dairy diet
alone did not
affect body
composition.
Wennersberg
et al, 2009 31
76
F/37M
Finland,
Norway
and
Sweden
30-65 24 3-5 portions
of dairy
products
daily
1145±425 625±259 Mean (SD)
change in weight,
fat mass and WC
Body composition
was not different
between groups.
Zemel et al,
200841
244
adults
USA 19-65 24 3
servings/day
from dairy
products
1325±254 579±166 Not reported No difference
when unadjusted.
Low dairy group
gained more
weight, BMI and
trunk fat in the
university of
Tenessee.
Zemel et al,
2005 27
23 F/11
M
USA 26-55 24 3 servings of
dairy
products
daily
1124±53 458±96 Mean (SD)
change in weight,
mean change and
P
value for fat
mass, lean mass
and WC
Not significant
change in weight
but significant
change in fat
mass, lean mass
and WC
22
Gunther et al,
2005 32
90 F USA 18-30 48 1300-1400
mg Ca/d
from dairy
1131.29 ±
337.2
742.4±321.
5
Mean (SD)
change in weight,
fat and lean mass
Increased dairy
intake did not
affect weigh, fat
and lean mass
Barr et al,
2000 34
129 F/71
M
Canada 55-85 12 3 servings of
fluid milk
Females:
1404± 296
Males:
1556±400
Females:
654±218
Males:
745±222
Mean (SD)
weight at baseline
and after
intervention
Milk group
gained more
weight than
controls
Baran et al,
1990 35
37 F USA 30-42 144 Increased
dietary intake
of calcium by
an average of
610 mg/d via
fluid milk
2163±583 1850±334 Mean change in
weight. SD or
P
value was not
provided
Milk group
gained more
weight than
controls.
a Mean ± standard deviation (SD); WC: waist circumference ٥٥٠
٥٥١
٥٥٢
٥٥٣
٥٥٤
٥٥٥
٥٥٦
٥٥٧
٥٥٨
23
Table 2. Randomized controlled trials (with energy restriction) eligible to include in the systematic review ٥٥٩
Author Subjects
and
gender
Country Age
range
(y)
Duration
(wk)
Intervention Calcium intake (mg/d) Variables
presented
Result
intervention
a
control
a
Van Loan et
al, 201139
71 adults USA 20-50 12 4 servings
of dairy
products per
day
1288.4 ± 94.6 434.6 ±
56.6
Mean (SD)
change in weight
and body fat
Increased dairy
intake led to
greater weight
and fat loss
Smilowitz et
al, 201140
36 F/ 9
M
USA 18-35 12 3-4 daily
servings of
dairy
products
1244.8 ± 108 449.0 ±
69.7
Mean (SD) for
weight and WC at
baseline and after
intervention
Percent change of
anthropometric
measurements
was not different
between groups
Josse et al,
201145
54 F Canada 19-45 16 3-4daily
servings of
dairy
products
1200 ± 19 299 ± 22 Mean (SD)change
in weight, fat
mass, lean mass
and WC
Percent change of
anthropometric
measurements
was not different
between groups
Fagih et al,
2010 25
42 F Iran 20-50 8 3 servings of
low fat milk
1302± 107.56 495.46±163
.87
Mean (SD)
change in weight,
fat mass and WC
Subjects in milk
group lost more
weight, fat mass
and WC than
controls
Zemel et al,
2009 26
49 adults USA 18-35 12 3 daily
servings of
dairy
products
1400 500 Mean (SE)
change in weight,
fat mass, lean
mass and WC
Dairy-rich diet
augmented weight
loss by targeting
fat compartment
24
Zemel et al,
2005 27
25 F/ 4
M
USA 26-55 24 3 daily
servings of
dairy
products
1037±27 468±23 Mean and
P
value
for change in
weight, fat mass,
lean mass and
WC
Subjects in dairy
group lost more
weight, fat mass
and WC and less
lean mass than
controls
Zemel et al,
2005 28
27 F, 7
M
USA 18-50 12 6 ounce
servings of
fat free
yogurt
1077±22 495 ± 28 Mean (SE)
change in weight,
fat mass, lean
mass and WC
Subjects in dairy
group lost more
weight, fat mass
and WC and less
lean mass than
controls
Thompson et
al, 2005 43
36 adults USA 25-70 48 4 servings of
dairy
products
1387.4 ± 152.9 799.6±
166.5
Mean (SD)
change in weight,
fat mass and WC
Mean changes in
weight, fat mass
and WC was not
different between
groups.
Harvey-
Berino et al,
2005 44
48 adults USA 18-60 48 3-4 servings
of dairy
1239 ± 355 574 ± 157 Mean (SD)
change in weight
and body fat
Change in weight
and body fat was
not different
between groups
Zemel et al,
2004 29
22 adults USA 18-60 12 3 daily
servings of
dairy
products
1137 ± 164 430 ± 94 Mean (SE)
change in weight
and body fat,
mean change in
WC was
presented only in
figure and data
was not shown
Mean loss of
weight, fat mass
and WC was
significantly
higher in the dairy
group.
25
a Mean ± standard deviation (SD); WC: waist circumference ٥٦٠
26
Legend to Figures ٥٦١
٥٦٢
Fig. 1. Forest plot of randomized controlled trials illustrating weighted mean difference in ٥٦٣
weight change between dairy-supplemented and control groups for all eligible studies as well ٥٦٤
as for subgroup analysis based on energy restriction. For all studies combined, slightly ٥٦٥
greater weight loss was seen among those with high dairy intake compared with those with ٥٦٦
low dairy intake (P for heterogeneity= 0.04,
Q
test, I-square=41.2% and Tau-square=0.64). ٥٦٧
Meta-analysis of studies that administered high dairy intake without energy-restriction ٥٦٨
showed no significant effect of dairy intake on weight change (P for heterogeneity= 0.67,
Q
٥٦٩
test, I-square=0.0% and Tau-square=0.0). For studies that administered energy-restriction, we ٥٧٠
found the significant effect of dairy intake on weight loss (P for heterogeneity= 0.32,
Q
test, ٥٧١
I-square=12.5% and Tau-square=0.15). ٥٧٢
٥٧٣
Fig 2. Forest plot of randomized controlled trials illustrating weighted mean difference in fat ٥٧٤
mass between dairy-supplemented and control groups for all eligible studies as well as for ٥٧٥
subgroup analysis based on energy restriction. For all eligible studies combined, the ٥٧٦
significant effect of dairy intake on reducing fat mass was observed (P for heterogeneity< ٥٧٧
0.01,
Q
test, I-square=56.1% and Tau-square=0.51). For 7 RCTs with energy restriction, the ٥٧٨
effect was also significant (P for heterogeneity= 0.33,
Q
test, I-square=12.0% and Tau-٥٧٩
square=0.11). However, data from 4 RCTs, that did not administered energy restriction, ٥٨٠
indicated no significant effect of dairy intake on body fat mass (P for heterogeneity= 0.02,
Q
٥٨١
test, I-square=70.7% and Tau-square=0.46). ٥٨٢
٥٨٣
Fig 3. Forest plot of randomized controlled trials illustrating weighted mean difference in ٥٨٤
Lean body mass between dairy-supplemented and control groups for all eligible studies as ٥٨٥
well as for subgroup analysis based on energy restriction. For all studies combined, the ٥٨٦
significant effect of dairy consumption on WC was seen (P for heterogeneity= 0.07,
Q
test, I-٥٨٧
27
square=48.9% and Tau-square=0.13). For 4 RCTs that administered energy restriction, high ٥٨٨
dairy intake has been resulted in a greater reduction in WC compared with that in control ٥٨٩
group (P for heterogeneity= 0.06,
Q
test, I-square=59.7% and Tau-square=0.21). Such ٥٩٠
finding was not obtained for 3 RCTs that had not administered energy restriction (P for ٥٩١
heterogeneity= 0.29,
Q
test, I-square=19.5% and Tau-square=0.05). ٥٩٢
Fig 4. Forest plot of randomized controlled trials illustrating weighted mean difference in ٥٩٣
waist circumference (WC) between dairy-supplemented and control groups for all eligible ٥٩٤
studies as well as for subgroup analysis based on energy restriction. For all studies combined, ٥٩٥
the significant effect of dairy consumption on WC was seen (P for heterogeneity= 0.03,
Q
٥٩٦
test, I-square=53.4% and Tau-square=1.63). For 6 RCTs that administered energy restriction, ٥٩٧
high dairy intake has been resulted in a greater reduction in WC compared with that in ٥٩٨
control group (P for heterogeneity= 0.60,
Q
test, I-square=0.0% and Tau-square=0.0). Such ٥٩٩
finding was not obtained for 2 RCTs that had not administered energy restriction (P for ٦٠٠
heterogeneity= 0.01,
Q
test, I-square=84.7% and Tau-square=12.8). ٦٠١
Fig 5. Beggs funnel plots (with pseudo 95% CIs) of the difference in means (DMs) versus ٦٠٢
the SEs (standard errors) of the MDs (mean differences) for studies that assessed the effect of ٦٠٣
dairy intake on weight (A), fat mass (B), Lean body mass (C) and waist circumference (D). ٦٠٤
The horizontal line shows the pooled DMs calculated with the DerSimonian and Laird ٦٠٥
random-effects model. We did not find any evidence of publication bias for studies assessing ٦٠٦
dairys effect on weight and lean body mass. With regard to body fat and WC, we reached a ٦٠٧
significant publication bias by funnel plot; however, this was not verified by Begg and ٦٠٨
Mazumdar test. ٦٠٩
٦١٠
٦١١
٦١٢
٦١٣
28
Fig 1. ٦١٤
٦١٥
٦١٦
29
Fig 2. ٦١٧
٦١٨
٦١٩
30
Fig 4. ٦٢٠
٦٢١
٦٢٢
٦٢٣
٦٢٤
٦٢٥
٦٢٦
31
Fig 5. ٦٢٧
٦٢٨
٦٢٩
٦٣٠
32
Fig 3. ٦٣١
٦٣٢
٦٣٣
33
٦٣٤
34
٦٣٥
٦٣٦
٦٣٧
... Several meta-analyses have focused on the effect of total dairy on body weight [39][40][41][42][43][44][45]. A marginal weight reduction ranging from 0.6 to 1.2 kg was reported in some metaanalyses in which dairy supplementation was implemented within the context of an energy-restricted diet [40,44,45], whereas a neutral effect or a marginal weight increaseranging from 0.36 to 0.60 kg-was shown by studies where dairy supplementation was not associated with energy restriction (Supplemental Table S1) [40,43,44]. ...
... Several meta-analyses have focused on the effect of total dairy on body weight [39][40][41][42][43][44][45]. A marginal weight reduction ranging from 0.6 to 1.2 kg was reported in some metaanalyses in which dairy supplementation was implemented within the context of an energy-restricted diet [40,44,45], whereas a neutral effect or a marginal weight increaseranging from 0.36 to 0.60 kg-was shown by studies where dairy supplementation was not associated with energy restriction (Supplemental Table S1) [40,43,44]. The effect of low-fat or full-fat dairy foods on body weight was explored by Benatar et al. [43] in a meta-analysis showing a statistically significant increase for either low-fat or full-fat dairy products in the context of a dietary regimen without energy restriction. ...
... Several meta-analyses have focused on the effect of total dairy on body weight [39][40][41][42][43][44][45]. A marginal weight reduction ranging from 0.6 to 1.2 kg was reported in some metaanalyses in which dairy supplementation was implemented within the context of an energy-restricted diet [40,44,45], whereas a neutral effect or a marginal weight increaseranging from 0.36 to 0.60 kg-was shown by studies where dairy supplementation was not associated with energy restriction (Supplemental Table S1) [40,43,44]. The effect of low-fat or full-fat dairy foods on body weight was explored by Benatar et al. [43] in a meta-analysis showing a statistically significant increase for either low-fat or full-fat dairy products in the context of a dietary regimen without energy restriction. ...
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Limited consumption of dairy foods and use of low-fat products is recommended for cardiovascular (CV) prevention; however, other features besides fat content modulate their metabolic effects. We analyze updated evidence on the relationship of different dairy products (low/full-fat dairy, milk, cheese, yogurt) with CVD by reviewing meta-analyses of cohort studies and individual prospective cohort studies with CV hard endpoints (CVD/CHD incidence/mortality), together with meta-analyses of randomized controlled trials exploring the effect of dairy on major CV risk factors. The analyses provide evidence that moderate dairy consumption (up to 200 g/day, globally) has no detrimental effects on CV health and that their effect depends more on the food type (cheese, yogurt, milk) than on the fat content. These data expand current knowledge and may inform revision of current guidelines for CVD prevention.
... Additionally, the highest category of total dairy intake was significantly associated with a reduced risk of abdominal obesity and risk of overweight compared to the lowest intake [299]. Four meta-analyses [288,[300][301][302] compiled data of randomized controlled trials concerning the impact of dairy intake on body weight and body composition. Three of them suggest that an increased dairy intake may have a modest beneficial effect on body weight, fat mass and lean body mass when combined with an energy-reduced diet. ...
... Three of them suggest that an increased dairy intake may have a modest beneficial effect on body weight, fat mass and lean body mass when combined with an energy-reduced diet. No effect of dairy products intake was found when diet was not energy reduced [300][301][302]. The fourth meta-analysis reported a modest weight gain with increased intake of either whole or low-fat dairy food [288]. ...
Technical Report
Given the limited amount of current evidence linking total water intake to health outcomes, further data would be needed to guide evidence-based recommendations on water intake. In particular, scientific evidence on the levels of long-term water intake needed to reduce the risk of common chronic diseases is currently limited.
... In contrast to previous studies, we observed no significant difference in the true digestibility among all groups. This discrepancy occurred because the Similarly, previous studies revealed that milk could improve body composition by increasing lean mass [30,31]. We hypothesized that muscle lean mass would increase as the whey proteins proportion increases, because it was reported that whey proteins promote muscle protein synthesis compared to casein [10,14,32]. ...
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This study investigated the effects of the casein to whey proteins (CW) ratio in milk on body composition, muscle strength, and endurance exercise capacity in rats. Thirty rats were assigned into five groups, and each treatment was administered for eight weeks: (1) control (isocaloric lactose supplementation), (2) CW8:2 (regular milk), (3) CW6:4, (4) CW5:5, and (5) nitrogen-free (lactose). The milk concentration was converted from a human equivalent dose (400 mL/60 kg body weight/day). All the milk-administered groups showed significantly greater growth performance, including body weight and weight gain compared to the isocaloric lactose control (p < 0.05). However, different CW ratios in milk had no effect on growth performance. Additionally, body composition, i.e., lean body mass and adiposity, was not affected by the CW ratio. Interestingly, CW6:4 and CW5:5 had significantly higher plasma branched-chain amino acids concentrations than control and CW8:2 (p < 0.05). In addition, CW5:5 showed significantly increased grip strength by 12–24% and time to exhaustion by 8–62% compared to the other groups (p < 0.05), indicating that the higher whey proteins ratio improved physical performance. We concluded that whey proteins-fortified milk enhances muscle strength and endurance exercise capacity without altering lean mass in rats.
... Milk is very important during growth periods, especially when growth occurs rapidly, for instance, in adolescence [20]. Since, young adults continue to grow in early adulthood, accurate knowledge and health benefit about milk will lead them to increase their milk consumption. ...
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Backgrounds: Milk well- known important source of human nutrition and contain considerable amounts of macro and micronutrients and have enormous health benefit. This study was performed to determine the nutritional knowledge and health benefit knowledge of diary and dairy products consumption among medical students at Benghazi university. Methodology: This a cross section study comprised of 541 students from branches of medical faculties in which 290 female and 251 male. Data were collected by using a semi-constructed questionnaire. Data was analysis by either mean ± SD or frequencies and percentages according to the natural of data. Chi-square test was used at α< 0.05. Results: The result of present work revealed that milk was consumed by one serving a day (53%) (P< 0.05), and among types of milks, whole fat milk significantly consumed (P< 0.05). Our result also shown that dairy products were highly consumed by one serving/day. Furthermore, 65.2 % of the students drink milk with tea (P=0.000). Nutrition knowledge of milk and dairy products reported that students have good knowledge score for nutritional knowledge questions and poor knowledge scores for questions related to health benefit with exception question on oral health (P< 0.05). Even though, the nutritional status of the students reveals that they fall under normal weight categories. However there were abnormal low levels of Hb, vitamin D have been found and abnormal high levels of calcium among male students. Conclusion Dairy consumption among students was relatively higher with good nutritional knowledge of dairy and dairy products consumptions and poor knowledge regarding health benefit. The result of this study suggested that nutritional education program might be in great importance of dairy and dairy product knowledge and benefit. The data of this study needed to be validated in large samples.
... As it was mentioned before, high dairy intake by overweight/obese subjects (low dairy consumers) following a weight maintenance diet for 24 weeks did not change body weight but caused a significant reduction in total body fat and an increase in lean mass (Zemel et al., 2005). Two meta-analyses have concluded that dairy consumption in situations without energy restriction neither leads to gain nor to loss of body weight (Abargouei et al., 2012;Chen et al., 2012). Beneficial effects on body composition were not observed in the present study, probably due to the smaller duration of the intervention. ...
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Hunger-reducing effects and beneficial changes in gastrointestinal hormones have been reported, in overweight/obese individuals consuming dairy while yogurt takes pride of place due to its unique structure and composition. Although the contribution of yogurt to metabolic regulation has received growing attention, the research studies which examine its role on appetite are limited, especially regarding type 2 diabetes mellitus (T2DM) patients. The aim of the present study was to investigate the effects of non-fat, conventional yogurt consumption on appetite hormone responses of T2DM patients following a non-energy-restricted diet. Overweight subjects participated in a 12-week dietary intervention including 2 meals/day (2 × 200 g) of yogurt. At the beginning and the end of the intervention, a mixed meal tolerance test assessing the postprandial response of glucose, insulin, ghrelin, glucagon-like peptide-1 (GLP-1), and peptide-YY (PYY) was performed. Subjective appetite ratings were also evaluated. Area under the curve for glucose, insulin, ghrelin, GLP-1, and PYY responses did not differ after the 12-week intervention with yogurt (p > .05) as well as for subjective appetite ratings (p > .05). No significant differences were indicated at specific time points in any of the examined parameters. Regular consumption of non-fat, conventional yogurt for 12-week duration does not affect appetite hormone responses in overweight patients with T2DM following a non-energy-restricted diet.
... The analyses in this review are limited to the effects of higher dietary protein on body weight changes because studies investigating potential effects on changes in body composition are scarce. Differences in efficacy may be observed dependent on whether the effects on body weight or fat mass changes are evaluated, which is indicated in the meta-analyses by Chen et al. and Abargouei et al. [75,76]. A more beneficial effect of higher intakes of dietary protein may thus be evident if changes in fat mass are taken into consideration. ...
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The primary aim was to systematically review the current evidence investigating if dietary interventions rich in protein lead to improved body weight management in adults with excessive body weight. The secondary aim was to investigate potential modifying effects of phenotyping. A systematic literature search in PubMed, Web of Science, and Cochrane Library identified 375 randomized controlled trials with 43 unique trials meeting the inclusion criteria. The Cochrane collaboration tool was used for a thorough risk of bias assessment. Based on 37 studies evaluating effects of dietary protein on body weight, the participants with increased protein intake (ranging from 18–59 energy percentage [E%]) were found to reduce body weight by 1.6 (1.2; 2.0) kg (mean [95% confidence interval]) compared to controls (isocaloric interventions with energy reduction introduced in certain studies). Individuals with prediabetes were found to benefit more from a diet high in protein compared to individuals with normoglycemia, as did individuals without the obesity risk allele (AA genotype) compared to individuals with the obesity risk alleles (AG and GG genotypes). Thus, diets rich in protein would seem to have a moderate beneficial effect on body weight management.
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This study aimed to determine total weight loss percent (%TWL) and the contributing factors in 100 patients post-bariatric surgery. Self-reported anthropometric measurement, 13 dietary behaviors, lifestyle, sociodemographic, and bariatric surgery–related data were collected from the participants via telephone. The results revealed a %TWL mean of 29.00% ± 10.30%. %TWL was significantly associated with exercise, preoperative body mass index, locality type, and intake of dairy products (P < .05). Significant positive changes in dietary behaviors were reported postsurgically (P < .001). This study highlights the role of exercise and diet as part of overall post–bariatric surgical care.
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Background: Weight management is the key to prevent and treat the adverse consequences of overweight and obesity. The aim of this study was to compare the effect of consuming milk and pistachio snacks on anthropometric indices in overweight or obese women. Methods: In this randomized crossover trial, 60 overweight or obese women with a mean age of 24 ± 4.2 years were randomly divided into two groups. Women in the milk group received 200 mL/day low-fat milk while women in the other group received 30 g/day pistachio for 4 weeks. After a 6-day washout period, the participants received a similar intervention in a crossover manner. Results: Out of the total 60 participants, 52 completed the study. At the end of the study, the weight of women in the milk group significantly decreased (70.8 ± 8.4 vs. 69.9 ± 8.3, P value = 0.001). No statistically significant changes were observed in the weight of participants in the pistachio group (70.3 ± 8.4 vs. 70.6 ± 8.3, P value = 0.06). Further analyses showed a slightly significant beneficial effect on waist circumference (WC) (P-value =0.068) and body mass index (BMI) in the milk group P value = 0.01). Conclusions: Based on the observed positive effects of milk intake on weight loss in this crossover study, milk consumption may be considered an appropriate snack in weight loss programs in overweight or obese women.
Chapter
Aging is one of the key contributors to a broad spectrum of chronic diseases. Reactive oxygen species (ROS) increase oxidative stress in cells and thus induces inflammatory cascades. The antioxidant defense systems are declined during aging. Antioxidant controls the oxidative radical process by suppressing the formation of free radicals and interrupting the propagation and initiation of free radicals through several mechanisms. Considering the crucial roles of oxidative stress in age-related diseases, the manipulation of ROS levels would represent a useful option to delay age-related diseases and attenuate associated symptoms. Numerous compounds with antioxidant activity have demonstrated their potential to alleviate age-related diseases; however, mixed results are yielded. Therefore, this chapter discussed the potential of dietary antioxidants against age-related diseases. We also explored on how dietary choices dampen or exacerbate the inflammation and metabolic disorders. Collectively, this information may shed light on the discovery for potential intervention, and thus promoting healthy longevity.
Chapter
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Objective: Funnel plots (plots of effect estimates against sample size) may be useful to detect bias in meta-analyses that were later contradicted by large trials. We examined whether a simple test of asymmetry of funnel plots predicts discordance of results when meta-analyses are compared to large trials, and we assessed the prevalence of bias in published meta-analyses. Design: Medline search to identify pairs consisting of a meta-analysis and a single large trial (concordance of results was assumed if effects were in the same direction and the meta-analytic estimate was within 30
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ABSTRACT: Insufficient calcium intake has been proposed to cause unbalanced energy partitioning leading to obesity. However, weight loss interventions including dietary calcium or dairy product consumption have not reported changes in lipid metabolism measured by the plasma lipidome. The objective of this study was to determine the relationships between dairy product or supplemental calcium intake with changes in the plasma lipidome and body composition during energy restriction. A secondary objective of this study was to explore the relationships among calculated macronutrient composition of the energy restricted diet to changes in the plasma lipidome, and body composition during energy restriction. Overweight adults (n = 61) were randomized into one of three intervention groups including a deficit of 500kcal/d: 1) placebo; 2) 900 mg/d calcium supplement; and 3) 3-4 servings of dairy products/d plus a placebo supplement. Plasma fatty acid methyl esters of cholesterol ester, diacylglycerol, free fatty acids, lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamine and triacylglycerol were quantified by capillary gas chromatography. After adjustments for energy and protein (g/d) intake, there was no significant effect of treatment on changes in weight, waist circumference or body composition. Plasma lipidome did not differ among dietary treatment groups. Stepwise regression identified correlations between reported intake of monounsaturated fat (% of energy) and changes in % lean mass (r = -0.44, P < 0.01) and % body fat (r = 0.48, P < 0.001). Polyunsaturated fat intake was associated with the % change in waist circumference (r = 0.44, P < 0.01). Dietary saturated fat was not associated with any changes in anthropometrics or the plasma lipidome. Dairy product consumption or calcium supplementation during energy restriction over the course of 12 weeks did not affect plasma lipids. Independent of calcium and dairy product consumption, short-term energy restriction altered body composition. Reported dietary fat composition of energy restricted diets was associated with the degree of change in body composition in these overweight and obese individuals.
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Background. Research on dairy foods to enhance weight and fat loss when incorporated into a modest weight loss diet has had mixed results. Objective. A 15-week controlled feeding study to determine if dairy foods enhance central fat and weight loss when incorporated in a modest energy restricted diet of overweight and obese adults. Design. A 3-week run-in to establish energy needs; a 12-week 500 kcal/d energy reduction with 71 low-dairy-consuming overweight and obese adults randomly assigned to diets: ≤1 serving dairy/d (low dairy, LD) or ≤4 servings dairy/d (adequate dairy, AD). All foods were weighed and provided by the metabolic kitchen. Weight, fat, intra-abdominal adipose tissue (IAAT), subcutaneous adipose tissue (SAT) macrophage number, SAT inflammatory gene expression, and circulating cytokines were measured. Results. No diet differences were observed in weight, fat, or IAAT loss; nor SAT mRNA expression of inflammation, circulating cytokines, fasting lipids, glucose, or insulin. There was a significant increase (P = 0.02) in serum 25-hydroxyvitamin D in the AD group. Conclusion. Whether increased dairy intake during weight loss results in greater weight and fat loss for individuals with metabolic syndrome deserves investigation. Assessment of appetite, hunger, and satiety with followup on weight regain should be considered.
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Weight loss can have substantial health benefits for overweight or obese persons; however, the ratio of fat:lean tissue loss may be more important. We aimed to determine how daily exercise (resistance and/or aerobic) and a hypoenergetic diet varying in protein and calcium content from dairy foods would affect the composition of weight lost in otherwise healthy, premenopausal, overweight, and obese women. Ninety participants were randomized to 3 groups (n = 30/group): high protein, high dairy (HPHD), adequate protein, medium dairy (APMD), and adequate protein, low dairy (APLD) differing in the quantity of total dietary protein and dairy food-source protein consumed: 30 and 15%, 15 and 7.5%, or 15 and <2% of energy, respectively. Body composition was measured by DXA at 0, 8, and 16 wk and MRI (n = 39) to assess visceral adipose tissue (VAT) volume at 0 and 16 wk. All groups lost body weight (P < 0.05) and fat (P < 0.01); however, fat loss during wk 8-16 was greater in the HPHD group than in the APMD and APLD groups (P < 0.05). The HPHD group gained lean tissue with a greater increase during 8-16 wk than the APMD group, which maintained lean mass and the APLD group, which lost lean mass (P < 0.05). The HPHD group also lost more VAT as assessed by MRI (P < 0.05) and trunk fat as assessed by DXA (P < 0.005) than the APLD group. The reduction in VAT in all groups was correlated with intakes of calcium (r = 0.40; P < 0.05) and protein (r = 0.32; P < 0.05). Therefore, diet- and exercise-induced weight loss with higher protein and increased dairy product intakes promotes more favorable body composition changes in women characterized by greater total and visceral fat loss and lean mass gain.
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Few studies exist regarding the effects of the Dietary Approaches to Stop Hypertension (DASH) diet on novel cardiovascular risk factors among type 2 diabetic patients. We evaluated the effects of the DASH eating pattern on C-reactive protein (CRP) level, coagulation abnormalities, and hepatic function tests in type 2 diabetic patients. In this randomized, crossover clinical trial, 31 type 2 diabetic patients consumed a control diet or the DASH diet for 8 wk. The DASH diet was rich in fruits, vegetables, whole grains, and low-fat dairy products and low in saturated fat, total fat, cholesterol, refined grains, and sweets, with a total of 2400 mg/d sodium. The control diet was a standard diet for diabetic patients. There was a 4-wk washout between the 2 trial phases. The main outcome measures were CRP level, coagulation indices, and hepatic function tests. The mean percent change for plasma CRP level was -26.9 ± 3.5% after the DASH diet period and -5.1 ± 3.8% after the control diet period (P = 0.02). Decreases in both alanine aminotransferase and aspartate aminotransferase levels were greater after consuming the DASH diet compared with the control diet (-14.8 ± 3.0% vs -6.6 ± 3.4%; P = 0.001; -29.4 ± 3.7% vs -5.9 ± 1.4%; P = 0.001, respectively). The decrease in the plasma fibrinogen level during the DASH diet period (-11.4 ± 3.6%) was greater than that during the control diet (0.5 ± 3.4%) (P = 0.03). Among diabetic patients, the DASH diet can play an important role in reducing inflammation, plasma levels of fibrinogen, and liver aminotransferases. Future longer term studies are recommended.
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Background: Previous results suggested that increased intake of dairy calcium is associated with reduced weight and fat mass. Objective: The purpose of this study was to determine whether long-term increases in consumption of dairy calcium alter body weight and fat mass in young, healthy women. Design: We used a randomized, 1-y intervention for dairy calcium. Subjects were 155 young (aged 18–30 y), healthy, normal-weight women with intake of dietary calcium < 800 mg/d and energy intake ≤ 2200 kcal/d. Women were randomly assigned to 1 of 3 groups: 1) control: continue established dietary intake; 2) medium dairy: substitute dairy products to achieve intake of calcium of ≈1000–1100 mg/d and maintain isocaloric intake; 3) high dairy: substitute dairy products to achieve intake of calcium of 1300–1400 mg/d and maintain isocaloric intake. The main outcome measures were 1-y changes in body weight (in kg) and fat mass (in kg). One hundred thirty-five women completed the trial. Results: Mean intakes of calcium during the intervention were 742.4 ± 321.5, 1026.4 ± 311.3, and 1131.29 ± 337.2 mg/d for the control, medium-dairy, and high-dairy groups, respectively (P < 0.0001). No significant differences were observed in the mean 1-y change in body weight between the control, medium-dairy, and high-dairy groups (0.8 ± 2.8, 0.7 ± 3.0, and 1.5 ± 4.1 kg, respectively; P = 0.45). No significant differences were observed in the mean 1-y change in fat mass between the control, medium-dairy, and high-dairy groups (−0.5 ± 2.5, 0.3 ± 2.7, and 0.5 ± 3.5 kg, respectively; P = 0.26). Conclusion: Increased intake of dairy products does not alter body weight or fat mass in young, healthy women over 1 y.
Article
Background: Although previous studies showed some benefits from dairy consumption with respect to obesity and insulin resistance syndrome, epidemiologic data on the association between dairy intakes and metabolic syndrome are sparse. Objective: The objective was to evaluate the relation between dairy consumption and metabolic syndrome in Tehranian adults. Design: Dairy consumption and features of metabolic syndrome were assessed in a population-based cross-sectional study of 827 subjects (357 men and 470 women) aged 18–74 y. Metabolic syndrome was defined according to guidelines of the Adult Treatment Panel III. Multivariate logistic regression adjusted for lifestyle and nutritional confounders was used in 4 models. Results: Mean (±SD) consumption of milk, yogurt, and cheese was 0.7 ± 0.2, 1.06 ± 0.6, and 0.9 ± 0.3 servings/d, respectively. Subjects in the highest quartile of dairy consumption had lower odds of having enlarged waist circumference [odds ratio (OR) by quartile: 1, 0.89, 0.74, 0.63; P for trend < 0.001], hypertension (OR by quartile: 1, 0.88, 0.79, 0.71; P for trend < 0.02), and metabolic syndrome (OR by quartile: 1, 0.83, 0.74, 0.69; P for trend < 0.02). The values of ORs became weaker after further adjustment for calcium intake. Conclusion: Dairy consumption is inversely associated with the risk of having metabolic syndrome. It seems that this relation is somewhat attributed to calcium.
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