A controlled trial of protein enrichment of meal replacements for weight reduction with retention of lean body mass.

Abstract

While high protein diets have been shown to improve satiety and retention of lean body mass (LBM), this study was designed to determine effects of a protein-enriched meal replacement (MR) on weight loss and LBM retention by comparison to an isocaloric carbohydrate-enriched MR within customized diet plans utilizing MR to achieve high protein or standard protein intakes.
Single blind, placebo-controlled, randomized outpatient weight loss trial in 100 obese men and women comparing two isocaloric meal plans utilizing a standard MR to which was added supplementary protein or carbohydrate powder. MR was used twice daily (one meal, one snack). One additional meal was included in the meal plan designed to achieve individualized protein intakes of either 1) 2.2 g protein/kg of LBM per day [high protein diet (HP)] or 2) 1.1 g protein/kg LBM/day standard protein diet (SP). LBM was determined using bioelectrical impedance analysis (BIA). Body weight, body composition, and lipid profiles were measured at baseline and 12 weeks.
Eighty-five subjects completed the study. Both HP and SP MR were well tolerated, with no adverse effects. There were no differences in weight loss at 12 weeks (-4.19 +/- 0.5 kg for HP group and -3.72 +/- 0.7 kg for SP group, p > 0.1). Subjects in the HP group lost significantly more fat weight than the SP group (HP = -1.65 +/- 0.63 kg; SP = -0.64 +/- 0.79 kg, P = 0.05) as estimated by BIA. There were no significant differences in lipids nor fasting blood glucose between groups, but within the HP group a significant decrease in cholesterol and LDL cholesterol was noted at 12 weeks. This was not seen in the SP group.
Higher protein MR within a higher protein diet resulted in similar overall weight loss as the standard protein MR plan over 12 weeks. However, there was significantly more fat loss in the HP group but no significant difference in lean body mass. In this trial, subject compliance with both the standard and protein-enriched MR strategy for weight loss may have obscured any effect of increased protein on weight loss demonstrated in prior weight loss studies using whole food diets.

Full text

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BioMed Central
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Nutrition Journal
Open Access
Research
A controlled trial of protein enrichment of meal replacements for
weight reduction with retention of lean body mass
Leo Treyzon1, Steve Chen1, Kurt Hong1, Eric Yan1, Catherine L Carpenter1,
Gail Thames1, Susan Bowerman1, He-Jing Wang2, Robert Elashoff2 and
Zhaoping Li*1
Address: 1UCLA Center for Human Nutrition, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, USA and
2Department of Biomathematics, David Geffen School of Medicine at UCLA, Los Angeles, USA
Email: Leo Treyzon - ltreyzon@mednet.ucla.edu; Steve Chen - schen@mednet.ucla.edu; Kurt Hong - kurthong@mednet.ucla.edu;
Eric Yan - eyan@mednet.ucla.edu; Catherine L Carpenter - ccarpenter@mednet.ucla.edu; Gail Thames - gthames@mednet.ucla.edu;
Susan Bowerman - sbowerman@mednet.ucla.edu; He-Jing Wang - wangh@ucla.edu; Robert Elashoff - relashof@biomath.medsch.ucla.edu;
Zhaoping Li* - zli@mednet.ucla.edu
* Corresponding author
Abstract
Background: While high protein diets have been shown to improve satiety and retention of lean body
mass (LBM), this study was designed to determine effects of a protein-enriched meal replacement (MR)
on weight loss and LBM retention by comparison to an isocaloric carbohydrate-enriched MR within
customized diet plans utilizing MR to achieve high protein or standard protein intakes.
Methods: Single blind, placebo-controlled, randomized outpatient weight loss trial in 100 obese men and
women comparing two isocaloric meal plans utilizing a standard MR to which was added supplementary
protein or carbohydrate powder. MR was used twice daily (one meal, one snack). One additional meal was
included in the meal plan designed to achieve individualized protein intakes of either 1) 2.2 g protein/kg of
LBM per day [high protein diet (HP)] or 2) 1.1 g protein/kg LBM/day standard protein diet (SP). LBM was
determined using bioelectrical impedance analysis (BIA). Body weight, body composition, and lipid profiles
were measured at baseline and 12 weeks.
Results: Eighty-five subjects completed the study. Both HP and SP MR were well tolerated, with no
adverse effects. There were no differences in weight loss at 12 weeks (-4.19 ± 0.5 kg for HP group and -
3.72 ± 0.7 kg for SP group, p > 0.1). Subjects in the HP group lost significantly more fat weight than the SP
group (HP = -1.65 ± 0.63 kg; SP = -0.64 ± 0.79 kg, P = 0.05) as estimated by BIA. There were no significant
differences in lipids nor fasting blood glucose between groups, but within the HP group a significant
decrease in cholesterol and LDL cholesterol was noted at 12 weeks. This was not seen in the SP group.
Conclusion: Higher protein MR within a higher protein diet resulted in similar overall weight loss as the
standard protein MR plan over 12 weeks. However, there was significantly more fat loss in the HP group
but no significant difference in lean body mass. In this trial, subject compliance with both the standard and
protein-enriched MR strategy for weight loss may have obscured any effect of increased protein on weight
loss demonstrated in prior weight loss studies using whole food diets.
Published: 27 August 2008
Nutrition Journal 2008, 7:23doi:10.1186/1475-2891-7-23
Received: 30 August 2007
Accepted: 27 August 2008
This article is available from: http://www.nutritionj.com/content/7/1/23
© 2008 Treyzon et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Background
Meal replacement shakes represent an important strategy
in combating the worldwide epidemic of obesity due to
their simplicity and convenience [1]. Meal replacement
shakes have been studied extensively for both medical
and public health efforts to combat obesity [2-4].
A number of studies have suggested that protein is the
most important macronutrient mediating satiety and
leads to increased weight loss with retention of lean
body mass. Single meals with increased protein to carbo-
hydrate ratios have also been shown to increase satiety
and decrease food intake [5,6], resulting in both
improved weight loss and improved maintenance of
weight loss [7-9]. Meal replacement simplifies the weight
loss regimens by replacing one or two meals a day with
a product of defined nutrient and calorie content. MR
leads to increased weight losses over twelve weeks com-
pared to simply restricting favorite food intakes, and
weight losses have been maintained for up to five years
using MR [10]
An increase in dietary protein content has been proposed
to be effective for body weight regulation through effects
on satiety, thermogenesis and substrate partitioning. Pro-
tein has specific effects on satiety hormones, including
PYY 3–36 [11]. When protein replaces carbohydrate
within a low-fat diet, reduced insulinemic and glycemic
responses have been observed resulting in increased fat
oxidation [12]
The present study was designed to test the hypothesis that
simply increasing the protein content of a meal replace-
ment (MR) within a high protein diet without the knowl-
edge of the participant would result in increased weight
loss and improved retention of lean body mass in the
absence of a resistance exercise program by comparison to
standard MR within a standard protein diet. To test the
hypothesis, a soy and whey protein powder was used to
enrich a standard MR shake in one arm compared to a car-
bohydrate "placebo" powder added to the same MR shake
in the other arm. This novel approach has not been tested
previously to our knowledge. To minimize variations
based on body composition, the diets were also adjusted
so that each subject was instructed to follow a diet which
provided either 2.2 gm/kg lean body mass protein in the
high protein (HP) group or 1.1 gm protein/kg lean body
mass in the standard protein (SP) group. Patients received
dietary instruction at baseline, and met with the dietitian
at weeks 2, 4 and 8 to assess general compliance and to
provide additional supplies of the MR products. There-
fore, this study examines the effectiveness of protein
enrichment of MR in a realistic outpatient setting on
weight loss and retention of lean body mass.
Methods
Subjects were recruited by public advertisement. Subjects
over 30 years of age with a body mass index (BMI)
between 27 to 40 kg/m2, and in good health by history,
physical examination, and basic laboratory screening
(complete blood count, serum chemistries, liver panel,
and lipid panel) were selected for study. Subjects with
type 2 diabetes or glucose intolerance were excluded as
were individuals who regularly drank more than one alco-
holic beverage daily,
One hundred men and women who met the selection cri-
teria were randomly assigned to either the HP or SP treat-
ment. This was a single-blinded study. The protein
powder jars were labeled as either A or B, depending on
their protein content. Subjects were randomized in a 1:1
manner to either HP or SP diet for 12 weeks using a com-
puterized random proportion model. Diet plans were
individualized per subject. Caloric intake to achieve
weight loss was based on a 500 Kcal deficit of the partici-
pants' estimated resting metabolic rate as determined by
body composition analysis by bioelectrical impedance.
Participants in the HP group received a diet plan that pro-
vided 2.2 grams of protein per kg of LBM while the diet for
the SP group provided 1.1 grams of protein per kg of LBM.
The meal energy macronutrient composition in the HP
group was approximately 30% protein, 30% fat, and 40%
carbohydrate. The macronutrient composition in the SP
diet was approximately 15% protein, 30% fat, and 55%
carbohydrate. Both groups received the same isocaloric
MR (Formula 1, Herbalife Intl., Los Angeles) with either a
protein supplement for the HP group (Performance Pro-
tein Powder, Herbalife Intl., Los Angeles) or with a similar
tasting carbohydrate placebo for SP group. Two MR and
two meals were eaten daily.
Instructions were provided for preparation of the MR and
subjects were advised to consume one MR as a meal and
the other as snack. All subjects were given individualized
menu plans that incorporated the two MR (one meal and
one snack) and included two all-food meals. All partici-
pants met individually with a registered dietitian at base-
line for dietary instruction, and at 2, 4, and 8 weeks to
assess compliance.
Participants were weighed and protein powder meal
replacement products were dispensed at each visit to
ensure compliance. Subjects were given general advice for
increasing their activity level with a goal of 30 minutes of
aerobic exercise per day, but no heavy resistance exercise.
Body weight and composition
Subjects were weighed at each visit (Detecto-Medic;
Deteco-Scales; Brooklyn, NY) while wearing no shoes and

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after an overnight fast. Height was measured with a stadi-
ometer (Detecto-Medic; Deteco-Scales; Brooklyn, NY) at
week 0. BMI was calculated as weight (kg)/height squared
(m). Body composition was determined by bioelectrical
impedance analysis (BIA) (310e Bioimpedance analyzer;
Biodynamics; Seattle, WA) and was performed at 0 and 12
weeks.
Biochemistry
Fasting blood samples were collected at weeks 0, 4, 8, and
12 for measurement of lipid profiles, blood glucose and
liver function tests.
Statistical analysis
Weight loss was the primary outcome and the data were
analyzed according to intention to treat allocation utiliz-
ing SAS version 9 (Cary, North Carolina) in the Depart-
ment of Biostatistics.
Patient characteristics and baseline measurements of the
two study groups were compared using t-test (for numer-
ical variables) or Chi-square test (for categorical variables)
to evaluate quality of the randomization.
Standard t-tests were used to compare weight losses
between the two arms. In addition, to assess weight loss
within each treatment arm, paired t-tests were conducted
comparing baseline and 12 week weight for each subject.
All data except baseline characteristics are presented as
means +/- standard error of the mean (SEM). A univariate
analysis of variance was used to assess differences between
treatment and outcome variables. Since the distributions
of change in fat weight and percentage change in fat
weight were not normal, signed rank test was used for test-
ing change from baseline within each group. The Wil-
coxon rank sum test was used for comparing the change
between the two groups. Multivariate analysis was per-
formed to compare the difference between the two diet
groups using general linear model. Square root transfor-
mation was applied before the multivariate analysis was
performed.
Results
100 obese men and women were randomly assigned to
either a HP or SP MR diet plan. Fifteen subjects withdrew
from the study within the first week after randomization
due to noncompliance with the meal plan (6 in the HP
group and 9 in the SP group). All other subjects com-
pleted the 12-week study. Subject characteristics in the
two treatment arms at baseline were not significantly dif-
ferent (Table 1). Mean age was 49.4 ± 1.1 years. Mean BMI
at baseline was 33.8 ± 0.53 for HP group and 32.6 ± 0.58
kg/m2 for SP group.
Weight loss
Subjects were weighed at baseline, and at 2, 4, 8 and 12
weeks. Baseline body weight was not significantly differ-
ent between these two groups. Both groups lost significant
amount of weight at 12 weeks (-4.19 ± 0.5 kg for HP
group and -3.72 ± 0.7 kg for SP group, p < 0.0001 for both
groups). (Figure 1) After controlling for baseline weight,
gender, and time period, there was no significant differ-
ence between the two treatment groups. For both dietary
groups, BMI was significantly lower at 12 weeks (HP = -
1.50 ± 0.58; SP = -1.13 ± 0.24). There were no significant
differences in BMI changes between the two dietary
groups (Table 2).
Waist circumference
Change in waist circumference (cm) at 12 weeks was sig-
nificant in both treatment groups (HP = -6.7 ± 1.1; SP = -
5.1 ± 0.8 p < 0.0001). No significant differences in change
in waist circumference at any time period were observed
between diets (table 2).
Fat mass by BIA
Subjects in the HP group lost a significant amount of fat
at 12 weeks (from 35.2 ± 1.0 kg to 33.6 ± 1.2 kg, p <
Table 1: Patient characteristics at baseline
HP (N = 45)SP (N = 42)Total (N = 87)HP vs. SP
Gender
F
M
Age
Mean ± SE
Median, range
Race
Asian
Black
Caucasian
Hispanic
Other
Unknown
34 (76%)
11 (24%)
27 (64%)
15 (36%)
61 (70%)
26 (30%)
NS
49.2 ± 1.8
47.0, 28–69
49.7 ± 1.4
49.5, 30–65
49.4 ± 1.1
49.0, 28–69
NS
4 (9%)
9 (20%)
25 (55%)
4 (9%)
0
3(7%)
1 (2%)
7 (17%)
30 (72%)
2 (5%)
1 (2%)
1 (2%)
5 (6%)
16 (18%)
55 (63%)
6 (7%)
1 (1%)
4(5%)
NS

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0.0001) but not the SP group (32.3 ± 1.3 kg to 31.7 ± 1.0
kg, p > 0.05). Subjects in the HP group lost significantly
more fat weight than the SP group (HP = -1.65 ± 0.63; SP
= -0.64 ± 0.79 kg p = 0.05) (Figure 2, table 2).
Fat-free mass by BIA
At 12 weeks, the two dietary groups had significantly
decreased lean body weight (kg) (HP = -2.78.1 ± 0.62; SP
= -4.06 ± 1.74, p < 0.0001). No significant differences
were observed between the dietary groups (table 2).
Cholesterol, HDL, LDL, triglyceride, and glucose
At 12 weeks, there were significant reductions in choles-
terol and LDL levels (mg/dL) for the HP group (choles-
terol -13.2 ± 5.3, p < 0.05; LDL -7.47 ± 3.38, p < 0.05) but
not for the SP group (cholesterol -7.02 ± 4.3 p > 0.05; -
9.17 + 5.65, p > 0.05). The difference between the two
groups was not significant. There were no significant
changes from baseline, nor between dietary groups in
serum HDL and triglyceride levels. Similarly, fasting
blood glucose levels did not change significantly from
baseline for either group at 12 weeks. (Table 3)
Discussion
Protein-enriched meal replacements within a higher pro-
tein diet resulted in no greater overall weight loss than the
standard protein MR plan over 12 weeks. In this trial, the
amounts of weight lost were typical for meal replacement
studies done previously [10]. However, the expected
effects on increased weight loss resulting from a high pro-
tein diet were not seen in this study. There are two possi-
ble reasons for the observed similarities in overall weight
loss. First, the subjects in the SP group may have eaten
foods outside their recommended meal plans which
increased protein intake enough to compensate for the
difference in protein contents of the MR. Second, the use
of MR may have been the major influence on the weight
loss by simplifying their weight loss efforts so that the
power of the MR intervention may have obscured the dif-
ference between the weight loss of subjects using protein-
enriched MR shakes by comparison to standard MR [13].
The purpose of the study was to test the real world impact
of simply enriching MR with more protein. Based on our
Change of fat mass by BIA from baseline at 12 weeks
Figure 2
Change of fat mass by BIA from baseline at 12 weeks.
** p < 0.001 compared with base line fat mass. Blank bar rep-
resents the high protein group and the shaded bar represents
the standard protein group.
Table 2: Change of BMI, waist circumference, fat mass, and fat fee mass at 12 weeks
BMI ((kg/m2)Waist Circumference (cm) Fat Mass (kg) Fat Free Mass (kg)
HPSP HPSPHP SPHP SP
Baseline
12 weeks
33.77 ± 0.53
32.13 ± 0.54
32.66 ± 0.58
31.11 ± 0.56
104.2 ± 1.8
98.8 ± 1.6
101.7 ± 2.0
97.3 ± 2.0
35.2 ± 1.0
33.6 ± 1.2*
32.3 ± 1.3
31.7 ± 1.0
58.3 ± 1.6
55.6 ± 1.4
60.0 ± 1.9
55.9 ± 1.7
*p < 0.0001 compare 12 weeks vs. baseline
Weight change from baseline at 12 weeks
Figure 1
Weight change from baseline at 12 weeks. * p < 0.05
compared with base line body weight. Blank bar represents
the high protein group, the shaded bar represents the stand-
ard protein group.

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results, it appears that compliance is a much more impor-
tant factor in the MR regimen than protein content.
Protein enrichment of MR did appear to lead to increased
retention of lean body mass based on bioelectrical imped-
ance analysis. In this study, greater retention of lean body
mass was suggested by the observation of increased fat
loss at similar weight losses. Fat loss is determined by sub-
tracting the lean body mass determined based on body
water content from the total body weight at baseline com-
pared to 12 weeks. The fat loss was significant both
between groups and in individuals over time. Loss of lean
mass was not different since the variability in fat free mass
between subjects increased the variability of this measure-
ment, reducing our power to see any difference. The
observation we made at 12 weeks using bioelectrical
impedance will require confirmation in longer-term stud-
ies where changes in body composition are more marked
and in which additional methods for determining body
composition are used. A recent meta-analysis of 87 short-
term diet studies where protein and carbohydrate content
was varied found that a protein intake of greater than 1.05
g/kg of actual body weight was associated with 0.6 kg
additional fat-free mass retention compared with diets
with protein intakes ≤1.05 g/kg [14]. Both meal plans in
this study had protein greater than this cut point and the
effects seen may be blunted by the relatively high protein
in the SP group.
In future studies, it may also be desirable to combine
protein enrichment of MR with resistance exercise to
demonstrate significant differences in the retention of
lean body mass during weight loss due to protein enrich-
ment of MR. Evans and co-workers have shown that
healthy free-living elderly men and women accommo-
date to the Recommended Dietary Allowance (RDA) for
protein of 0.8 grams/kilogram/day with a continued
decrease in urinary nitrogen excretion and reduced mus-
cle mass. Increased dietary protein intake (up to 1.6 g
protein/kg/day) may also enhance the hypertrophic
response to resistance exercise that would enhance
weight loss maintenance [15].
Conclusion
In summary, both the HP and SP diets resulted in the
expected weight loss typical of an MR diet plan at 12
weeks. Both diets were well tolerated, sustainable, and did
not result in any adverse effects. While typical results for
outpatient trials of MR were observed in both arms,
greater compliance with the MR diet plan may be neces-
sary to obtain an improved sense of the contribution of
protein enrichment of MR to lean body mass retention
during weight loss. Finally, future studies may be more
successful if they include a comparison of standard MR
and protein-enriched of MR weight reduction regimens
combined with heavy resistance exercise to maintain or
increase lean body mass.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
All authors read and approved the final manuscript. LT
participated in the conduct of the study, the analysis of the
data, and drafted the manuscript. SC participated in the
conduct of the study. KH participated in the conduct of
the study. EY participated in the conduct of the study. CLC
participated in the study design and statistical analysis. GT
participated in the study coordination. HW participated
in the statistical analysis. RE participated in the statistical
analysis. ZL conceived of the study, participated in its
design and coordination, and drafted the manuscript.
Acknowledgements
This study was supported through an unrestricted gift from Herbalife Inter-
national, Los Angeles, California. LT was supported by NIH Training Grant
No. DK0718033. SC, KH, and EY were supported by NIH Training Grant
No.T32 DK 07688.
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