International Journal of Sport Nutrition and Exercise Metabolism, 2009, 19, 18-33
© 2009 Human Kinetics, Inc.
Changes in Body Composition
With Yogurt Consumption
During Resistance Training in Women
Kimberly M. White, Stephanie J. Bauer, Kristopher K. Hartz,
and Monika Baldridge
Introduction: Resistance training is an effective method to decrease body fat (BF)
and increase fat-free mass (FFM) and fat oxidation (FO). Dairy foods containing
calcium and vitamin D might enhance these benefits. This study investigated the combined effects of habitual yogurt consumption and resistance training on body composition and metabolism. Methods: Untrained women (N = 35) participated in an 8-wk
resistance-training program. The yogurt group (Y) consumed 3 servings of yogurt
containing vitamin D per day, and the control groups maintained their baseline lowdairy-calcium diet. Postexercise, Y consumed 1 of the 3 servings/d fat-free yogurt, the
protein group consumed an isocaloric product without calcium or vitamin D, and the
carbohydrate group consumed an isocaloric product without protein. Strength, body
composition, fasted resting metabolic rate (RMR) and FO, and serum 25-hydroxyvitamin D were measured before and after training. Results: Calories (kcal · kg–1 · d–1)
and protein (g · kg–1 · d–1) significantly increased from baseline for Y. FFM increased
(main effect p = .002) and %BF decreased (main effect .02) for all groups with training, but Group  Time interactions were not observed. RMR and FO did not change
with training for any group. Conclusion: Habitual consumption of yogurt during
resistance training did not augment changes in body composition compared with a
low-dairy diet. Y decreased %BF as a result of training, however, even with increased
calorie consumption.
Keywords: dairy, muscle mass, body fat, strength
Optimal body composition, achieved via both diet and exercise, is important
for both athletic performance and health. Thus, methods to improve body composition—specifically, decreasing fat mass (FM) while also increasing fat-free mass
(FFM)—are attractive to athletes, as well as individuals concerned with health
outcomes such as preventing and treating obesity, sarcopenia, and osteoporosis
(Winett & Carpinelli, 2001). Resistance training is one such method to achieve
these alterations in body composition, as well as increase strength (Winett &
Carpinelli).
The authors are with the Div. of Health Sciences, Carroll College, Waukesha, WI.
18
Yogurt, Resistance Training, and Body Composition 19
Consuming dairy products such as milk or yogurt during a resistance-training
program might further enhance the benefits of training on body composition. Milk
and yogurt provide protein and carbohydrate, necessary macronutrients to maximize the anabolic response to resistance exercise (Tipton et al., 2001). When consumed after a bout of resistance exercise, fluid milk has been shown to acutely
increase muscle protein synthesis (Elliot, Cree, Sanford, Wolfe, & Tipton, 2006;
Wilkinson et al., 2007). When applied to training, chronic postexercise consumption of milk during a resistance-training program has been found to increase FFM
and decrease FM compared with both isoenergetic soy protein and carbohydrateonly beverages (Hartman et al., 2007). Similar training studies in young men have
observed trends to an increase in lean mass compared with carbohydrate (Rankin
et al., 2004) or soy protein (Phillips, Hartman, & Wilkinson, 2005).
Milk and some yogurts contain both calcium and vitamin D. These micronutrients might further enhance the benefits of resistance exercise because of their
associations with fat oxidation (FO; Cummings, James, & Soares, 2006; Gunther,
Lyle, et al., 2005; Melanson, Donahoo, Dong, Ida, & Zemel, 2005; Melanson et
al., 2003; Teegarden et al., 2008), body fat (Eagan, Lyle, Gunther, Peacock, &
Teegarden, 2006; Zemel, Richards, Mathis, et al., 2005; Zemel, Richards, Milstead, & Campbell 2005; Zemel, Thompson, Milstead, Morris, & Campbell,
2004), and muscle mass and strength (Bischoff et al., 2003; Sato, Iwamoto,
Kanoko, & Satoh, 2005). Some interventions to increase dietary calcium, from
both dairy and supplemental sources, have resulted in decreased body fat with
energy restriction (Zemel, Richards, Mathis, et al., 2005; Zemel, Richards, Milstead, & Campbell 2005; Zemel et al., 2004) and energy maintenance (Eagan et al.;
Zemel, Richards, Milstead, & Campbell, 2005), independent of weight loss. The
mechanism for reduction of fat mass via calcium intake might be the result of
increased postprandial whole-body FO in humans at rest (Cummings et al.;
Gunther, Lyle, et al., 2005; Melanson et al., 2003; Melanson et al., 2005, Teegarden et al.). Although not all studies have found calcium intake to increase postprandial FO (Boon et al., 2005; Jacobsen, Lorenzen, Toubro, Krog-Mikkelsen, &
Astrup, 2005), there is enough evidence to suggest that dietary calcium from dairy
and supplemental sources might play a role in the utilization of fat for energy.
Maintenance of adequate vitamin D status might affect muscle mass. In trials
conducted with vitamin-D-deficient participants given at least 800 IU/day of ergocalciferol or cholecalciferol, the two forms of dietary vitamin D, supplementation
was found to increase muscle mass, strength, and functional ability in older adults
(Bischoff et al., 2003; Sato et al., 2005). To date, only one study has examined the
combination of vitamin D supplementation and strength training on physical performance and muscle strength in vitamin-D-deficient older adults (Bunout et al.,
2006). After 9 months of supplementation with 400 IU/day vitamin D and twiceweekly training sessions, muscle mass and strength were not different than in
controls. No studies have examined the impact of vitamin D from dairy sources on
muscle mass and strength with a higher volume of resistance training in young
adults.
To date, no studies have been conducted to investigate dairy-food consumption with resistance training in women. Furthermore, incorporation of the recommended amount of dairy foods into the daily diet during a resistance-training
20 White et al.
program in addition to postexercise supplementation has not been investigated.
Therefore, the objective of this study was to determine whether habitual consumption of yogurt fortified with vitamin D during an 8-week resistance-training program would result in greater increases in FFM and decreases in FM than in a
low-dairy control diet. Because milk fortification can vary and amount consumed
per serving is more variable over the course of the day, a specific brand of yogurt
fortified with vitamin D was used as the dairy source in this study.
Participants and Methods
Study Design
The intervention group was counseled to incorporate three cartons of yogurt per
day into their usual diet; the control groups maintained their baseline habitual
low-dairy-calcium diet. Because timing of protein and carbohydrate intake immediately after resistance training has been found to enhance muscle hypertrophy
(Tipton et al., 2001), postexercise food consumption was also controlled. The
yogurt group consumed one fat-free yogurt serving immediately after each training session. Similar to other investigations of postexercise dairy consumption
during resistance training, a carbohydrate-only postexercise group was used
(Rankin et al., 2004; Hartman et al., 2007). The habitual low-dairy-calcium groups
consumed isocaloric, commercial, nondairy sports-nutrition products, one
matched to yogurt for carbohydrate and protein content, the other with carbohydrate only. Neither product contained calcium or vitamin D. Therefore, after meeting compliance criteria participants were randomly assigned to one of three experimental groups: yogurt (Y), low habitual dairy calcium with a carbohydrate and
protein postexercise supplement (PRO), and low habitual dairy calcium with a
carbohydrate-only postexercise supplement (CHO).
Participants
Untrained women (n = 45, age 18–35) were recruited from the Carroll College
community. Inclusion criteria included baseline habitual low-calcium (≤800 mg/
day total) and low-dairy (≤1serving/day) diet, weight stable (less than ±5% change
in body weight) for at least 3 months, participation in aerobic activity ≤5 hr/week,
and no involvement in a formal weight-training program for at least 3 months.
Participants were asked to maintain their baseline level of activity and kept exercise logs for the duration of the study. Exclusion criteria included high blood
pressure (>140/90 mm Hg), lactose intolerance or allergies to dairy foods, current
participation in a weight-loss program, use of over-the-counter diet aids, lactation
or pregnancy, digestive or metabolic diseases, diabetes, history of an eating disorder, use of medication that might interfere with calcium absorption, self-reported
exposure to sunlight greater than 30 min/day, or use of a tanning bed in the previous 3 months. Calcium intake was initially assessed via a food-frequency questionnaire (Legowski et al., 2001), and participants completed the Physical Activity
Readiness Questionnaire (PAR-Q). All protocols were approved by the Carroll
College institutional review board, and participants gave informed consent before
commencement of the study.
Yogurt, Resistance Training, and Body Composition 21
Training Sessions
All resistance-exercise sessions took place in the Carroll College weight room.
Participants were expected to complete three weight-training sessions per week
for 8 weeks under the supervision of trainers and log their progress. Exercises
included chest press, latissimus pull-down, overhead press, biceps curl, triceps
extension, crunch, leg press, hamstring curl, and quadriceps extension. To ensure
proper progression, the exercise prescription was based on the Daily Adjustable
Progressive Resistance Exercise (DAPRE) system (Knight, 1985).
For each training session, participants reported to the weight room in the
morning after an overnight fast. On arrival, all participants consumed 12 oz of a
commercial sports drink and then began their training session. Immediately after
the resistance-training session, participants in the Y group consumed one 6-oz
carton of Yoplait light yogurt (100 calories, 19 g carbohydrate, 5 g protein, 200 mg
calcium, 80 IU vitamin D; General Mills, Minneapolis, MN). The milk protein in
yogurt is approximately 80% casein and 20% whey protein. The PRO group consumed one packet of Accel Gel (90 calories, 20 g carbohydrate, 5 g protein; PacificHealth Laboratories, Inc., Matawan, NJ) with whey as the protein source, and
the CHO group consumed one packet of Clif Shot gel (100 calories, 25 g carbohydrate, 0 g protein; Clif Bar Inc., Berkley, CA). A nutritional comparison of
these different treatments is shown in Table 1. Postworkout meals were provided
to the participants.
Diet
Participants randomized into the PRO and CHO groups were counseled by a registered dietitian to maintain their usual low-dairy-calcium diet and calorie intake
for the duration of the study. Those in the Y group were counseled to incorporate
three 6-oz cartons of Yoplait yogurt (light or original) into their usual diet to maintain energy balance, along with one calcium-fortified food source. This protocol
was designed to provide approximately 1,000 mg of total calcium and 120 IU of
vitamin D. On workout days, the postworkout yogurt counted as one of the total
for that day.
Table 1 Nutritional Comparison of the Postexercise Supplements
by Group
Brand name
Calories (kcal)
Carbohydrate (g)
Protein (g)
Fat (g)
Calcium (mg)
Vitamin D (IU)
Y: Yoplait light
100
19
5
0
200
80
PRO: Accel Gel
90
20
5
0
0
0
CHO: Clif Shot
100
25
0
0
0
0
Note. Y = habitual yogurt group (3 servings per day); PRO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate plus protein; CHO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate.
22 White et al.
Assessments
Assessments were conducted immediately before and after the 8-week training
protocol.
Strength. Following protocols established by the American College of Sports
Medicine (2005), a 1-repetition maximum (1-RM) test was conducted for chest
and leg presses.
Predicted 1-RM values were determined from the DAPRE protocol (Knight,
1985) for the latissimus pull-down, overhead press, biceps curl, triceps extension,
hamstring curl, and quadriceps extension. Following the approach of Rankin et al.
(2004), an overall strength score was determined as the total 1-RM for all eight
exercises.
Energy Expenditure. Participants reported to the laboratory after an overnight
fast before and after the 8-week training session. On arrival at the laboratory, they
rested quietly for 10 min. Resting metabolic rate (RMR) was measured for 10 min
using a MAX-1 metabolic cart (Physiodyne, Pittsburg, PA), of which the last 5
min of data were averaged (Compher, Frankenfield, Keim, & Roth-Yousey, 2006).
From a review of the literature, Compher et al. found this protocol to be accurate
to measure RMR. FO was calculated using the equations of Jequier, Acheson, and
Schutz (1987).
Body Composition. After RMR measurement, fasted body weight was measured on a digital scale. Two-compartment body composition was assessed via
hydrodensitometry (Exertech, La Crescent, MN).
Biochemical Measurements. 25-Hydroxyvitmain D (25OHD) concentration
was measured in serum obtained from blood samples at baseline and after the
8-week training program via a 25OHD radioimmunoassay (DiaSorin Corp., Stillwater, MN). All samples were assayed in duplicate with the appropriate 25OHD
standards. The intra-assay coefficient of variation derived from replicate aliquots
was <5%.
Diet. All participants completed 3-day food records during baseline and Weeks
4 and 8, which were analyzed using the NutriBase 6.09 diet-analysis system
(CyberSoft, Phoenix, AZ). These food records were used to assess total calories,
carbohydrate, protein, calcium, and vitamin D, as well as total dairy servings.
Compliance
Predetermined compliance criteria were completion of 19 out of 21 training sessions, consumption of the prescribed amount of calcium (<800 mg/day for the
PRO and CHO control groups, ≥1,000 mg/day yogurt group), and consumption of
at least 19 of the prescribed 21 weekly servings of yogurt for the Y group. Each
week, participants in the Y group were required to turn in the lids from their
yogurt cartons, as well as a scorecard of their yogurt and calcium-fortified food
servings. Compliance was also monitored by analysis of 3-day food records at 4
and 8 weeks.
Yogurt, Resistance Training, and Body Composition 23
Statistics
All 25OHD radioimmunoassay (RIA) data were spline-transformed before analysis. Statistical analysis was done using SPSS (version 15.0.1). Descriptive data
and change scores from baseline by group were analyzed using one-way analysis
of variance (ANOVA). A two-way repeated-measures ANOVA was used to analyze changes in body composition from pretraining to posttraining. Covariate
analyses for baseline weight (kg), calorie consumption during training (kcal · kg–1
· day–1), and protein intake during training (g · kg–1 · day–1) were conducted for
body-composition outcome variables. Conservative post hoc tests were performed
when applicable using the least-significant-difference method. Normality and
equality of variances were also tested. Outliers were removed from the analyses
when values were found to be more than 2 SDs from the group mean. Cohen’s
effect size was calculated for changes in body-composition measurements (small
effect = .2, medium effect = .5, large effect = .8). When no significant treatment
effects were observed, Pearson’s correlations were used to investigate relationships independent of treatment group. We set p < .05 as statistically significant for
all analyses. Values are presented as M ± SD.
Results
Participants
All participants included in the study reported consuming ≤1 serving/day of dairy
food and 800 mg/day calcium via a food-frequency questionnaire (Legowski et
al., 2001). Of the 45 participants recruited for the study, 42 completed it. One
woman dropped out because of a family situation, 1 decided the time commitment
was too great, and 1 woman injured her ankle (unrelated to the study) and could
not complete any of the lower body exercises. Based on the predetermined criteria, 35 participants successfully completed the study under compliance (Y n = 12,
PRO n = 12, CHO n = 11). The reasons for noncompliance were not completing
enough training sessions (n = 2) and not consuming the appropriate amount of
calcium during training, based on group assignment (n = 5). Baseline descriptive
information is presented in Table 2.
Habitual Diet
Diet information is presented in Table 3. At baseline, no differences were found
between groups for calorie or protein intake, expressed as total grams of protein
or adjusted for body weight. During the training period, Y increased their calorie
intake by 267.4 ± 321.4 kcal/day from baseline (p = .003), resulting in significantly greater calorie intake during the training period than both PRO and CHO.
When analyzed per kilogram of body weight, calorie intake was elevated during
training compared with baseline for Y (+3.6 ± 5.2 kcal · kg–1 · day–1), but the
groups were not different during training (Table 3; p = .5). A similar pattern was
observed for protein. Protein intake increased from baseline for Y when expressed
as total grams and when adjusted for body weight (p = .04). Group differences in
24 White et al.
Table 2 Baseline Descriptive Characteristics and Body
Composition Pre- and PostTraining, M ± SD
Age (years)
Height (in.)
Weight (kg)
pre
post
Y (n = 12)
PRO (n = 12)
CHO (n = 11)
20.9 ± 2.2
65.1 ± 2.2
18.8 ± 1.1
65.3 ± 1.5
19.3 ± 1.1
63.7 ± 2.6
70.8 ± 11.0a
71.9 ± 11.4
61.7 ± 7.3b
62.8 ± 7.7
63.6 ± 6.3ab
63.6 ± 6.1
n = 10
Fat-free mass (kg)
pre
post
Fat mass (kg)
pre
post
% Body fat
pre
post
47.0 ± 3.9#
49.0 ± 4.1*a
42.7 ± 5.5
44.2 ± 5.3*b
42.7 ± 5.5
44.6 ± 4.1*b
23.8 ± 8.5
22.9 ± 8.2
18.1 ± 5.2
17.9 ± 4.5
19.9 ± 5.1
19.0 ± 5.0
32.8 ± 7.2
31.0 ± 6.6*
29.6 ± 6.2
28.7 ± 4.4*
31.0 ± 6.0
29.6 ± 5.8*
Note. Y = habitual yogurt group (3 servings per day); PRO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate plus protein; CHO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate. Different superscript letters indicate different mean
values (p ≤ .05).
#Trend to a difference at baseline compared with PRO (p = .09). *Significantly different from baseline
(p ≤ .05).
protein intake during training were only found for total gram consumption (Y >
PRO = CHO; p = .001), not when adjusted for body weight (Table 3; p = .1). Calcium and vitamin D consumption, determined from the average of 3-day food
records at Weeks 4 and 8, was above the recommended daily allowance for Y
(Table 4). PRO and CHO maintained their low-calcium/vitamin D diet and were
significantly lower than Y during training.
Body Composition
Y had significantly higher body weight at baseline (Table 2) than PRO, but not
CHO (p = .03). There was a trend to a main effect of time to increase weight with
training in all groups (p = .07), with Y greater than PRO but not CHO (Table 2).
Protein and calorie intake during training were not significant covariates.
For body-fat measurements, two outliers in the change of body fat from baseline were found in the PRO group and removed from analyses. The changes in FM
for these participants were +9.86 kg and –7.40 kg, both of which were greater than
2 SD from the group mean. Body fat (expressed as FM [g] or %BF) was not different between groups pre- or posttraining (Table 2). By repeated-measures
ANOVA, a main effect of time was observed for the decrease in %BF for all
Yogurt, Resistance Training, and Body Composition 25
Table 3 Diet Information by Group Pretraining and During Training, M ± SD
Calories (kcal/day)
pre
during
Calories (kcal · kg–1 · day–1)
pre
during
Protein (g/day)
pre
during
Protein (g · kg–1 · day–1)
pre
during
Y (n = 12)
PRO (n = 12)
CHO (n = 11)
1,545.6 ± 472.6
1,813.0 ± 356.1*a
1,611.7 ± 157.8
1,494.1 ± 210.7b
1,603.1 ± 420.7
1,466.0 ± 366.9b
22.1 ± 7.1
26.2 ± 6.6*
26.4 ± 3.8
24.7 ± 5.3
25.5 ± 7.5
23.2 ± 6.1
62.7 ± 21.5
77.0 ± 12.8*a
55.1 ± 15.2
59.2 ± 11.1b
56.1 ± 18.8
55.6 ± 14.5b
0.9 ± 0.3
1.1 ± 0.2*
0.9 ± 0.2
1.0 ± 0.2
0.9 ± 0.3
0.9 ± 0.3
Note. Y = habitual yogurt group (3 servings per day); PRO = low habitual dairy calcium (≤1 dairy serving per
day), postexercise carbohydrate plus protein; CHO = low habitual dairy calcium (≤1 dairy serving per day),
postexercise carbohydrate. From 3-day food records in the week before training (pre) and the average of 3-day
food records from weeks 4 and 8 of training (during). Different superscript letters indicate different mean values
(p < .05).
*Significantly different from baseline (p < .05).
Table 4 Calcium and Vitamin D Consumption During Training,
M ± SD
Calcium (mg)
Vitamin D (IU)
Y (n = 12)
PRO (n = 12)
CHO (n = 11)
1,338.79 ±
329.67 ± 55.44a*
547.54 ±
51.67 ± 41.70b
433.15 ± 134.24b
37.36 ± 25.75b
159.64*a
39.79b
Note. Y = habitual yogurt group (3 servings per day); PRO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate plus protein; CHO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate. Different superscript letters indicate different mean
values (p = .0001).
*Significantly different from baseline (p < .05).
groups (p = .02), but a Group  Time interaction was not observed (p = .7; Figure
1). The decreases in %BF from pre- to posttraining were –1.84% ± 0.54%, 0.90%
± 1.19%, and 1.38% ± 1.08% for the Y, PRO, and CHO groups, respectively. The
decreases in FM from pre- to posttraining were –0.94, –0.19, and –0.85 kg for the
Y, PRO, and CHO groups, respectively. Calorie and protein consumption during
training, as well as baseline body weight, were not significant covariates. A correlation was not observed between calcium intake during training and the change
from baseline in %BF or FM.
The two outliers found in PRO for body fat were also found for the change in
FFM from baseline and removed from analyses. The changes in FFM for these
participants were –10.95 kg and +9.59 kg, both of which were greater than 2 SD
26 White et al.
Figure 1 — Mean (± SE) percentage body fat (%BF) before (Pre) and after (Post) an
8-week resistance-training program by group and change (∆) in %BF from baseline: Yogurt
(Y, n = 12); low habitual dairy calcium, postexercise carbohydrate plus protein (PRO, n =
10); and low habitual dairy calcium, postexercise carbohydrate (CHO, n = 11). Data analyzed by two-way repeated-measures ANOVA. *Significantly lower than baseline (main
effect of time p = .02), Group  Time interaction p = .7. The change from baseline was
analyzed by one-way ANOVA.
from the group mean and were likely a result of measurement error. At baseline,
Y tended to have greater FFM than PRO (p = .09) but not CHO (Table 2). A main
effect of time was observed for the increase in FFM for all groups with training (p
= .002); however, there was not a Group  Time interaction (p = .5; Figure 2). The
increases in FFM from pre- to posttraining were +2.03 ± 0.71, 1.42 ± 0.8, and 0.87
± 0.65 kg, for the Y, PRO, and CHO groups, respectively. Although ANOVA did
not show group differences for the increase from baseline (p = .5), Cohen’s effect
sizes for the change in FFM with training between Y and CHO was .52 (medium
effect) and between Y and PRO was .25 (small effect). Calorie and protein consumption during training, as well as baseline body weight, were not significant
covariates in any analyses. A correlation was not observed between vitamin D
intake during training and the change in FFM from baseline.
Yogurt, Resistance Training, and Body Composition 27
Figure 2 — Mean (± SE) fat-free mass (FFM) before (Pre) and after (Post) an 8-week
resistance-training program by group and change (∆) in FFM from baseline: Yogurt (Y, n =
12); low habitual dairy calcium, postexercise carbohydrate plus protein (PRO, n = 10); and
low habitual dairy calcium, postexercise carbohydrate (CHO, n = 11). Data analyzed by
two-way repeated-measures ANOVA. *Significantly higher than baseline (main effect of
time p = .002), Group  Time interaction p = .5. The change from baseline was analyzed
by one-way ANOVA.
Strength
Baseline 1-RM values were not different between groups. All groups significantly
increased chest- and leg-press 1-RM from baseline (main effect p < .01), but the
increase was not different between the three groups. Using the strength score as
an indication of total-body strength gains, overall strength increased in all groups
from baseline (main effect p < .0001), and a group effect was also observed (p =
.03). Post hoc testing revealed that the increase in total overall strength was greater
in Y than in PRO, but no differences were found between CHO and Y or PRO (Y
+354.8 ± 103.6 lb, n = 12; PRO +268.9 ± 113.7 lb, n = 12; CHO +342.2 ± 119.0
lb). The increase in FFM with training was not a significant covariate and did not
alter the results.
28 White et al.
Fat Oxidation and RMR
Because of problems with the metabolic cart on two occasions, data for 1 participant each in the Y and PRO groups could not be used in this analysis. At baseline,
no group differences were observed in resting FO (g · kg–1 · min–1) or RMR (kcal
· kg–1 · day–1). A main effect of time was not observed with training (Table 5).
Similar results were found when FO and RMR were analyzed at baseline and after
training per kilogram of FFM. Pretraining RMR was positively correlated to baseline FFM (R = .55, p = .001). Similarly, posttraining RMR was positively correlated with posttraining FFM (R = .49, p = .004).
Serum 25OHD
A time effect was observed for the decrease in serum 25OHD from pretraining
(October) to posttraining (December), but decreases were not different between
groups (Table 6).
Discussion
In the current study, women who consumed three cartons per day of yogurt fortified with vitamin D while participating in a resistance-training program did not
show greater changes in body composition than those who followed a low-dairy
diet. All participants did, however, significantly increase FFM and decrease %BF.
This result is encouraging because the women in the yogurt group increased calorie (kcal · kg–1 · day–1) and protein (g · kg–1 · d–1) consumption from baseline and
were still able to lose body fat with training.
A limitation of this study is that the baseline randomization did not result in
equivalent groups in terms of body weight. This difference might influence the
results; however, although the Y group began with a higher baseline body weight
than the PRO group and trended to a higher FFM, this group was able to significantly further increase FFM with training, similar to the PRO and CHO groups.
Although the increase was not significantly different between groups, the yogurt
Table 5 Pre- and Posttraining Values for Fasting Resting Metabolic
Rate (RMR) and Fat Oxidation, M ± SD
·
RMR (kcal ·
pre
post
Fat oxidation (g · kg–1 · min–1)
pre
post
kg–1
Y (n = 11)
PRO (n = 11)
CHO (n = 11)
22.2 ± 3.8
22.4 ± 3.3
23.1 ± 3.7
23.5 ± 2.5
20.2 ± 2.6
20.9 ± 3.4
0.02 ± 0.04
0.02 ± 0.02
0.03 ± 0.04
0.03 ± 0.03
0.01 ± 0.03
0.02 ± 0.03
min–1)
Note. Y = habitual yogurt group (3 servings per day); PRO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate plus protein; CHO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate.
Yogurt, Resistance Training, and Body Composition 29
Table 6 Pre- and Posttraining Values for Serum 25OHD (ng/ml),
M ± SD
Pretraining
Posttraining
Y (n = 12)
PRO (n = 9)
CHO (n = 8)
86.81 ± 40.22
33.05 ± 22.83*
97.07 ± 52.31
37.87 ± 23.84*
81.04 ± 29.61
31.85 ± 19.78*
Note. Y = habitual yogurt group (3 servings per day); PRO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate plus protein; CHO = low habitual dairy calcium (≤1 dairy
serving per day), postexercise carbohydrate.
*Significantly different from baseline (p < .00001).
consumers gained 2.03 kg FFM, resulting in a medium effect size compared with
CHO and small effect size compared with PRO.
Postexercise protein alone likely does not explain the larger effect size for the
increase in FFM for Y versus CHO in this protocol because the amount of protein
provided postexercise (5 g) is considerably less than the recommendation of 0.4
g/kg for strength training (Andrews, MacLean, & Riechman, 2006). The results of
this study are similar to those of studies that examined the effect of postexercise
milk consumption on body composition in men. Rankin et al. (2004) compared
postexercise chocolate milk consumption (0.21 g/kg protein, on average ~16 g)
with an isoenergetic carbohydrate-only beverage during a 10-week resistancetraining program in untrained men (n = 19). Although the increase in FFM was not
significant by group, a trend was found toward a greater increase with the chocolate milk treatment. In the current study, ~15 g of protein from yogurt were consumed throughout the day, rather than entirely after the exercise bout. Future work
should include a comparison of postexercise and habitual dairy-food consumption
during a training program.
Although several studies have not found dietary calcium to decrease body
weight or fat (Gunther, Legowski, et al., 2005; Harvey-Berino, Gold, Lauber, &
Starinski, 2005; Lorenzen, Molgaard, Michaelsen, & Astrup, 2006; Shapses,
Heshka, & Heymsfield, 2004), decreases in body fat are an expected result of
resistance training (Winett & Carpinelli, 2001). To our knowledge, no studies
have been conducted to specifically examine the ability of dietary calcium to promote decreases in body fat during a resistance-training program. During a training
program of longer duration and higher intensity than the current protocol (5 days/
week, 12 weeks), Hartman et al. (2007) observed greater decreases in FM in
untrained men (n = 56) who consumed fat-free milk postexercise than in those
who consumed isoenergetic soy or carbohydrate-only beverages. Habitual calcium intake was not reported. In our 8-week, 3 days/week training study, body fat
decreased in all groups. Similar to the studies that have not found calcium to
decrease body fat without calorie restriction, these data do not suggest that calcium might augment decreases in body fat usually found with resistance training
compared with a low-calcium diet. It is encouraging, however, that the yogurt
group lost ~0.9 kg of FM (~1.8% body fat) even when increasing calories by ~267
kcal/day. Perhaps a longer training program in combination with calorie maintenance is needed to observe a benefit of habitual dairy consumption on body fat
during a resistance-training program.
30 White et al.
All women recruited for this study were low-dairy-calcium consumers at
baseline. The low-dairy-calcium groups were asked to maintain this baseline diet;
therefore, no change was expected in their calorie consumption during the training period. The women randomized to the yogurt group were counseled by a
registered dietitian to replace approximately 300 kcal/day of foods they were consuming at baseline with yogurt. Postexercise nutrition provided to the women was
nominal (300 kcal/week) and the same for all groups. Another limitation of this
study is that the yogurt consumers did not successfully substitute yogurt into their
diet for similar nondairy foods. As a result, total protein and calorie intake during
the training program was increased compared with baseline (~14 g protein, ~267
kcal), although calorie (kcal · kg–1 · day–1) and protein intake (g/kg) during the
study were not statistically different between groups. In a study designed to examine variable habitual protein consumption with standard postexercise protein supplementation (0.4 g/kg) during a 12-week resistance-training program in older
adults, Andrews et al. (2006) did not find an association between habitual protein
intake and increases in lean mass in men (n = 22, 64.3 ± 3.1 years) and women
(n = 30, 63.6 ± 2.8 years). Rozenek, Ward, Long, and Garhammer (2002) observed
that once protein needs are met for an individual, calorie consumption has the
greatest effect on gains in FFM during an 8-week resistance-training program. In
statistical analyses, adjusting for neither protein nor calorie intake resulted in a
statistically significant increase in FFM in the yogurt group.
It was hypothesized that vitamin D intake from yogurt to meet the recommended daily allowance would maintain vitamin D status and influence increases
in FFM with training. Vitamin D status is determined by measuring the circulating
form of the hormone 25OHD (Holick, 2005). Vitamin D insufficiency is defined
as <10 ng/ml, and the normal range is 10–15 ng/ml, although experts now suggest
that 30 ng/ml is necessary for multiple health outcomes (Holick). All the women
in the current study were well above the sufficient values at baseline (~88 ng/ml),
and all groups significantly decreased serum 25OHD from baseline to the currently proposed level of 30 ng/ml. A decrease from October (baseline) to December (posttraining) is not unexpected, but it was expected that the yogurt group
would maintain or at least exhibit less of a decrease in their vitamin D status as
they consumed just over the recommended amount of dietary vitamin D. A possible explanation is that the current adequate intake is not sufficient to maintain
vitamin D levels through the winter months.
RMR did not increase as a result of the training program in any group, even
with the increase in FFM, although FFM was correlated to RMR at baseline and
posttraining. These results are similar to those of other studies in which increases
in FFM without increases in RMR were reported (Broeder, Burrhus, Svanevik, &
Wilmore, 1992; Rankin et al., 2004), although some protocols of 10 and 24 weeks
did report an increase in RMR with resistance training in young men (Dolezal &
Potteiger, 1998; Lemmer et al., 2001). The reason for the discrepancy in results is
unclear. In data from cross-sectional studies, FFM is related to RMR (Alpert,
2007; LaForgia et al., 2004); however, the outcomes are not as clear using longitudinal data (Alpert), such as from a training protocol.
Resistance training has also been found to increase FO (Treuth, Hunter,
Weinsier, & Kell, 1995). Therefore, it was surprising that FO did not increase in
any group as a result of training. Furthermore, it was hypothesized that the high-
Yogurt, Resistance Training, and Body Composition 31
dairy-calcium diet would increase the ability to oxidize fat. This has been found
in both acute settings (Cummings et al., 2006) and after adaptation periods similar
to the length of this protocol (Teegarden et al., 2008). In all these studies, however, postprandial, not fasting, FO was increased with the calcium intervention.
Future work should include measuring postprandial in addition to resting changes
in metabolism.
In summary, habitual consumption of yogurt fortified with vitamin D during
a resistance-training program did not augment changes in body composition compared with a low-dairy diet. The resistance-training program did result in decreased
body fat and increased FFM in all participants. It is encouraging that even with the
addition of calories to their diet, the group of yogurt consumers lost significant
body fat as a result of this protocol. Future work should examine the use of dairy
foods for nutritional support during a resistance-training program to alter body
composition during energy maintenance or deficit.
Acknowledgments
This work was funded by the General Mills Bell Institute of Health and Nutrition,
Minneapolis, MN. The authors are also thankful to Ms. Lynn Peterson, MS; Colleen
Kristbaum, RD; Dr. Reinhold Hutz at the University of Wisconsin-Milwaukee; and the
Carroll College Exercise Science practicum students. The principal investigator, Dr.
Kimberly White, would like to thank Kristopher Hartz for his role as co-PI, Stephanie
Bauer for running this study, and Dr. Monika Baldridge for her work with the blood draws
and analyses. The results of this study do not constitute endorsement by the authors.
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