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1 Center for Sports Medicine, 2 Department of Kinesiology, and 3 Noll Physiological Research Center, The Pennsylvania State University, University Park, Pennsylvania 16802
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
FOOTNOTES
REFERENCES
ABSTRACT 
Kraemer, William J., Jeff S. Volek, Kristine L. Clark, Scott
E. Gordon, Thomas Incledon, Susan M. Puhl, N. Travis Triplett-McBride, Jeffrey M. McBride, Margot Putukian, and Wayne J. Sebastianelli. Physiological adaptations to a weight-loss dietary regimen and
exercise programs in women. J. Appl.
Physiol. 83(1): 270-279, 1997.
Thirty-one women
(mean age 35.4 ± 8.5 yr) who were overweight were matched and
randomly placed into either a control group (Con; n = 6), a diet-only group (D;
n = 8), a diet+aerobic endurance exercise training group (DE; n = 9),
or a diet+aerobic endurance exercise training+strength training group
(DES; n = 8). After 12 wk, the three
dietary groups demonstrated a significant
(P 
0.05) reduction in body mass,
%body fat, and fat mass. No differences were observed in the magnitude
of loss among groups, in fat-free mass, or in resting metabolic rate.
The DE and DES groups increased maximal oxygen consumption, and the DES
group demonstrated increases in maximal strength. Weight loss resulted
in a similar reduction in total serum cholesterol, low-density
lipoprotein cholesterol, and high-density lipoprotein cholesterol among
dietary groups. These data indicate that weight loss during moderate
caloric restriction is not altered by inclusion of aerobic or
aerobic+resistance exercise, but diet in conjunction with training can
induce remarkable adaptations in aerobic capacity and muscular strength
despite significant reductions in body mass.
body composition; strength training; lipoproteins; endurance
training; hormones
INTRODUCTION ONE OF THE GOALS of Healthy People 2000: National
Health Promotion and Disease Prevention Objectives is to reduce
overweight to a prevalence of no more than 20% among people aged 20 yr
and older (37). Data obtained from the 1988-1991 National Health and Nutrition Examination Survey (NHANES III) (5) showed that the
number of US adult women classified as overweight has risen to 35%
compared with 25% reported from NHANES II (1976-1980) (31). No
efficacious practical therapeutic solution has yet been identified addressing the increasing prevalence of overweight. Therefore, an
increased understanding of dietary and exercise strategies used to
promote the loss of body mass and maintenance of a healthy weight is
needed if these weight-loss goals are to be realized by the year 2000.
Physical activity in conjunction with moderate dietary energy
restriction and behavior modification has been promoted as an important
component of a successful weight-loss regimen (7, 40). The results of
many studies support the beneficial role of combined diet and exercise
in accelerating weight loss (18, 22, 38), preserving fat-free mass (2,
15, 17, 23, 42, 43) and resting metabolic rate (RMR) (33, 36), and improving serum lipoprotein (19, 22, 38) and triglyceride (22) status.
However, results of several studies also indicate that exercise in
conjunction with food restriction provides no additional benefits in
these parameters (9, 39, 52). Furthermore, studies evaluating the
impact of high-intensity resistance exercise on body composition and
other physiological adaptations during weight loss have reported
inconsistent findings (3, 11, 12, 36, 43, 46). For example, conflicting
results concerning the impact of dietary restriction combined with
resistance training on lean body mass have been reported. Ross et al.
(43) demonstrated that lean tissue is preserved, whereas Donnelly et
al. (11) reported no advantages of a resistance training regimen to
maintenance of lean body mass. The inconsistencies reported in previous
diet/exercise studies may reflect differences in several important
program design components, such as severity of the dietary energy
restriction, nutritional composition and nutrient adequacy of the diet,
mode and intensity of the exercise programs, dietary and exercise
compliance, and total duration of the study. Thus the influence of
exercise, but more specifically resistance training, in a dietary
program directed at weight loss remains unclear.
Another limitation with regard to research examining the physiological
effects associated with various forms of weight loss is that few
studies have simultaneously reported data on body composition, exercise
performance (muscular stength, endurance, power), metabolic rate, and
blood lipid profiles, and no studies have examined all of these
variables in response to resistance training. The outcome of a specific
weight-loss program must be judged in terms of all of these variables
to make comparisons among various programs. For example, a weight-loss
program may improve body composition to a greater degree but have a
negative impact on blood cholesterol compared with another weight-loss program. Because blood lipid measurements have been strongly correlated with coronary heart disease risk status, these become very informative in the selection of an optimal weight-loss strategy.
We hypothesized that a weight-loss diet/exercise regimen
(i.e., high-fiber moderate caloric restriction combined with
individually prescribed high-intensity endurance and resistance
training programs performed over 12 wk) would have a positive influence
on body composition, serum lipid profiles, and physical performance
measurements compared with a treatment with diet alone. Therefore, the
primary purpose of this study was to examine the effects of diet alone and diet combined with endurance training and diet combined with endurance and resistance training on physiological and performance adaptations in overweight adult women.
METHODS
120% of desirable weight, defined as the midpoint of the range of
weights for a medium-frame woman on the basis of the 1983 Metropolitan
Height and Weight Tables, or a body mass index 27). Women were
matched according to body mass index and randomly placed into one of
four groups that included a control group (Con; n = 6), which just performed the
testing, maintained body weight, and normal activities; a diet group
(D; n = 8), which maintained normal
activities while reducing calories for weight loss; a diet group that
performed an aerobic endurance exercise training program 3 days/wk (DE;
n = 9); and a diet group that
performed an aerobic endurance exercise training program combined with
a strength training program 3 days/wk (DES;
n = 8). Each woman was menstruating
normally (i.e., every 29-36 days), as calculated according to
methods previously described in detail, and testing was performed in
the same phase of the menstrual cycle (27). The experimental testing
took place before the program and after experimental familiarization,
at 6 wk, and after 12 wk. Descriptive data for the experimental groups are presented in Table 1. No significant
differences in any of the listed variables were observed among the
groups at the beginning of the study.
Table 1.
Descriptive data of experimental groups
Variable
Con
D
DE
DES
n
6
8
9
8
Age, yr
31.0 ± 9.6
34.6 ± 10.2
35.6 ± 8.5
36.5 ± 7.6
Height, m
1.7 ± 6.9
1.6 ± 7.1
1.7 ± 6.8
1.6 ± 13.1
Body mass, kg
77.9 ± 12.1
71.4 ± 12.3
77.7 ± 12.2
76.1 ± 13.0
Body mass index
28.2 ± 4.0
27.3 ± 3.1
28.3 ± 4.2
30.5 ± 5.1
Body fat, %
37.4 ± 6.8
38.0 ± 5.5
39.3 ± 4.1
35.0 ± 6.7
Fat-free mass, kg
48.3 ± 5.5
43.8 ± 5.3
47.1 ± 7.6
49.0 ± 5.8
Fat mass, kg
29.6 ± 9.2
27.6 ± 7.8
30.6 ± 6.3
27.2 ± 8.8
Values are means ± SD; n = no. of subjects. Con, control
group; D, diet-only group; DE, diet + endurance exercise group; DES, diet + endurance exercise + strength training group.
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80°C until analyses were performed. Serum glucose, blood urea nitrogen (BUN), total cholesterol, and high-density lipoprotein (HDL) cholesterol and triglyceride concentrations were determined via spectrophotometry (Novaspec II,
Pharmacia Biochrom, Cambridge, UK), and testosterone and cortisol concentrations were determined by using standard
radioimmunoassay procedures. Serum glucose was assayed in duplicate by
using an enzymatic (hexokinase) technique at an absorbance of 340 nm
(Sigma Diagnostics, St. Louis, MO). Total cholesterol, HDL cholesterol, tryglycerides, and BUN were enzymatically determined in duplicate by
using commercially available kits (Sigma Diagnostics). Low-density lipoprotein (LDL) cholesterol concentrations were calculated according to the method of Friedewald et al. (14). Serum testosterone and
cortisol concentrations were assayed by using solid-phase 125I single-antibody
radioimmunoassays (Diagnostic Products, Los Angeles, CA) with detection
limits of 0.14 and 5.5 nmol/l, respectively. Immunoreactivity was
measured with an LKB 1272 Clini-gamma automatic gamma counter with an
online data-reduction system (Pharmacia Wallac, Wallac Oy, Finland).
Intra- and interassay variances for all assays were <5 and <10%,
respectively.
Statistical analyses.
Comparisons between values obtained at baseline, week
6, and week 12 within
each group and between groups at each time point were made by using a
two-way analysis of variance. In the presence of a significant
F-value, post hoc comparisons of means
were provided by Fisher's least significant differences test.
Statistical power calculations demonstrated power ranges in this
investigation from 0.75 to 0.78. The relationship between changes in
selected variables was made by using simple regression. The level of
significance was P 0.05.
RESULTS
Table 3 shows the estimated daily nutrient intake for the three dietary groups. There were no significant differences among groups in any of the examined nutritional variables. Mean energy intake in the three dietary groups was 1,194 kcal/day. Greater than 70% of the total energy was composed of carbohydrate, and <15% was composed of fat. Mean dietary fiber was >28 g/day.
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Figure 1 shows the changes in body
composition over the 12-wk program in the three intervention groups. No
changes were observed in the control group. A significant reduction in
body mass was observed at 6 wk in all intervention groups. At
week 12, all three dietary groups (D,
DE, and DES) significantly reduced body mass by 6.2, 6.8,
and 7.0 kg, respectively (Fig.
1A). In the D and DE groups, body
mass at week 12 was significantly
decreased relative to their week 6 values. Significant reductions in percent body fat (Fig.
1B) and fat mass (Fig.
1C) were observed at
week 6 in the D and DE groups and by
week 12 in the DES group.
Additionally, the DE and DES groups demonstrated a significant decrease
in percent body fat and fat mass at week
12 relative to their week
6 values. At week 12,
the D, DE, and DES groups significantly reduced percent body fat by
5.8, 8.0, and 4.3%, respectively. No significant changes were observed in fat-free mass over the 12 wk in any of the
groups (Fig. 1D). There were no
differences in the magnitude of changes in body mass, percent body fat,
fat mass, and fat-free mass among groups.
, Diet-only
group (D); 
, diet+endurance group (DE); 
,
diet+endurance+strength group (DES). Significantly different
(P 0.05) from corresponding value
at baseline : a D group,
b DE group,
c DES group. Significantly
different (P 0.05) from
corresponding value at week 6:
d D group,
e DE group,
f DES group.
The results of the 1-RM strength testing in the bench press and squat
exercise are shown in Table 4. No changes
were observed in the Con, D, or DE groups. The DES group demonstrated
significant increases in the 1-RM bench press and squat at
week 6, with continued improvement at
week 12 (+14% in the bench press and
+25% in the squat). Maximal oxygen consumption, expressed
relative to body mass
(ml · kg
1 · min1),
improved significantly in the DE (+25%) and DES (+28%) groups at week 12, but not in the Con or D
groups (Table 5). When expressed in
absolute terms (l/min), maximal oxygen consumption in the DES group
significantly increased by 15% and in the DE group by 10% (P = 0.12). There were no changes in
Wingate anaerobic power performances in the Con, D, and DES groups
after 6 or 12 wk. However, at 6 wk the D group demonstrated a
significant increase in peak power (+25%). There was no significant
difference in RMR when expressed as kilocalories per day or
kilocalories per kilogram of fat-free mass in any group at
week 12; however, the DES group
demonstrated a lower respiratory exchange ratio at
week 12 (Table
6). Because it has been suggested that
dividing RMR by fat-free mass is inappropriate as the intercept of the
relationship does not intersect zero (41), Fig.
2 illustrates the relationship between RMR
and fat-free mass at baseline and week
12 in the D (Fig.
2A), DE (Fig.
2B), and DES (Fig.
2C) groups.
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) and at week 12 () in
D (A), DE
(B), and DES (C) groups.
A: y = 943.48 + 12.08x,
r = 0.65 (baseline);
y = 710.42 + 15.61x,
r = 0.28 (week
12). B:
y = 442.74 + 23.00x,
r = 0.89, P 0.05 (baseline);
y = 88.574 + 29.77x,
r = 0.79, P 0.05 (week 12). C:
y = 1091.35 + 7.66x,
r = 0.25 (baseline);
y = 417.55 + 19.02x,
r = 0.63 (week
12).
Serum triglyceride, glucose, BUN, and cortisol and testosterone
concentrations are presented in Table 7.
There were no significant changes observed for serum triglycerides,
glucose, BUN, and testosterone in any group. Cortisol concentrations
were not affected in any group, except for significantly higher levels
at 6 and 12 wk for the DE group. Percent changes in serum
concentrations of total cholesterol, HDL cholesterol, and LDL
cholesterol are shown in Fig. 3. Total
serum cholesterol, HDL cholesterol, and LDL cholesterol at
week 12 were significantly reduced,
when all dietary groups are combined. However, the decrease in total
cholesterol was only significant in the DE (31.9 ± 10.4 mg/dl) and DES (36.8 ± 30.3 mg/dl) groups but not in the D
group (25.6 ± 26.2 mg/dl). HDL cholesterol was significantly
reduced in the D (9.7 ± 8.6 mg/dl) and DES (9.4 ± 6.1 mg/dl) groups at week 12 but not
in the DE group (4.9 ± 6.9 mg/dl). Although the D, DE, and
DES groups all demonstrated a decrease in LDL cholesterol at 12 wk
(17.7 ± 20.2, 23.0 ± 24.6, and 26.6 ± 31.2 mg/dl, respectively) only results in the DE group
were statistically significant. There were no differences in the
magnitude of changes in any of the serum measurements among groups.
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0.05.
Significant correlations were observed between changes in several of the measured variables when combined among groups (Table 8). The strongest relationship with change in body mass was total cholesterol (Fig. 4) and LDL cholesterol. The change in body mass accounted for 60% of the variation in total cholesterol and 48% of the variance in LDL cholesterol.
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, Individual data points.
r2 = 0.60;
P 0.05.
DISCUSSION
Many investigations have examined the physiological effects associated with diet-induced and diet plus exercise-induced weight loss. A variety of physiological effects have been examined, including assessment of body composition, exercise performance, RMR, and serum lipid profile. However, few studies have looked at all these physiological effects simultaneously, and no studies have examined all these variables in response to heavy-resistance exercise. Thus, because of methodological differences among studies, the clinical (i.e., risk for coronary heart disease) and functional (i.e., muscular strength and aerobic capacity) significance of a particular weight-loss regimen may not be known and must be interpolated from other studies. In this study, we report several important findings related to the effects of diet alone and diet combined with endurance exercise or endurance plus heavy-resistance exercise on 1) body composition, 2) aerobic capacity, 3) muscular strength, 4) muscular power, 5) RMR, 6) serum lipids and lipoprotein fractions, and 7) anabolic and catabolic hormone responses in overweight adult women.
Surprisingly, all dietary groups experienced similar reductions in body
mass (6.2, 6.8, and 7.0 kg for D, DE, and DES
groups, respectively) and body composition (5.8, 8.0, and
4.3% in D, DE, and DES groups, respectively), whereas fat-free
mass remained relatively constant (0.1, +1.4, and 1.7 kg
in D, DE, and DES groups, respectively) over the 12-wk period. Our
findings of no difference in the magnitude of loss in total body mass,
percent fat, and fat mass among dietary groups is in agreement with the results of Ballor and Poehlman (2), who reported in a meta-analysis of
46 studies that exercise training does not influence the loss in body
mass, percent fat, or fat mass compared with dietary restriction without exercise. However, the data from the meta-analysis did show
that exercise training reduces the percentage of body mass lost as
fat-free mass during weight-loss regimens (2). In contrast, our data
showed no loss in fat-free mass and no difference among groups. In
support of our findings on fat-free mass, a number of studies using
various methods of body composition such as magnetic resonance imaging
(42, 43), hydrostatic weighing (3, 34), and bioelectric impedance (38)
have also reported that the loss in fat-free mass is not only
attenuated but maintained or increased when exercise is added to
dietary restriction.
The retention of fat-free mass in the D group was unexpected because
dietary restriction without exercise has been shown to result in
reductions of both fat mass and fat-free mass (see Ref. 15 for review).
The mechanism(s) that mediate this observation remains unclear. It is
possible that the high-fiber nature of the diet resulted in an enhanced
insulin sensivity and lower insulin levels (i.e., by reduction of the
glycemic response of meals) throughout the day. The role of dietary
fiber and insulin in obesity is discussed in detail by Ullrich and
Albrink (51). Lower insulin concentrations may release the normal
inhibitory action of insulin on the synthesis of adenosine
3
,5-cyclic monophosphate, thereby inhibiting lipogenic
enzymes (e.g., acetyl-CoA carboxylase, pyruvate dehydrogenase, glycerol
phosphate transferase) and stimulating lipolytic enzymes (e.g.,
hormone-sensitve lipase). This scenario may have created an environment
in the body enabling subjects to preferentially mobilize adipose tissue
stores as opposed to skeletal muscle. We have no data on the insulin
responses or enzyme activities of the subjects in this study. Future
studies may concentrate on these potential mechanisms in the context of
preservation of fat-free mass during weight loss. Alternatively, the
less severe caloric restriction, moderate rate of weight loss,
repletion of vitamin and mineral intakes to recommended daily
allowance levels, and/or individualized programs
of nutritional intervention may have also contributed to our findings.
Strength increases were observed in the bench press and squat exercise in the group that participated in the resistance training program. The highest gains were made in the first 6 wk, with continued improvement by 12 wk of training. Little attention has been given to performance changes with nutritionally sound weight-loss programs. Furthermore, most resistance exercise training programs have not utilized the higher intensities of exercise, nor have they varied the program over time (i.e., periodized training). These data demonstrate that with proper exercise prescription and a sound weight-loss program, despite the reduction in body mass, positive adaptational responses can be achieved with a periodized heavy resistance training program on strength performance. The benefit of adding exercise comes from the fact that the functional capacity is improved. Also, changes occur in the actual composition and density of the muscle and nerve tissue quality (e.g., type of myosin heavy chains, type of muscle enzymes, nervous system changes, nerve branches, more neurotransmitters, and so on) when an exercise program is added to the weight-loss protocol (10, 45). In fact, an increase in the cross-sectional area of both type I (~22%) and type II (~28%) muscle fibers has been demonstrated in subjects despite severe dietary restriction (~800 kcal/day) and large-scale weight loss (~15 kg) if resistance training is performed (12).
As expected, both groups that performed aerobic conditioning demonstrated a significant increase in maximal oxygen consumption expressed per kilogram body mass at 6 and 12 wk. The fact that both DE and DES groups increased maximal oxygen consumption by 10 and 15%, respectively, after 12 wk when expressed in absolute terms (l/min) suggests that the increase is a true enhancement of cardiovascular and respiratory endurance capacity and not an artifact of standardizing maximal oxygen consumption by body mass. The reason for the slightly greater increase in maximal oxygen consumption in the DES group relative to the DE group is unclear. This enhanced aerobic training response in the DES group may reflect additional benefits of increased volume of exercise, as shown by Donnelly et al. (12) in subjects who participated in both endurance and weight training. Alternatively, greater leg strength may have allowed the DES group to run longer on the treadmill, thus contributing to the increase in maximal oxygen consumption. In support of this finding, Hickson et al. (20, 21) have also reported similar benefits in endurance capacity when resistance training is performed in addition to the endurance training program.
No statistically significant changes were observed over the 12-wk training program in anaerobic power performance. The mechanisms responsible for enhancing fast-velocity strength changes have been shown to be different from those that mediate slow-velocity strength changes (28). Thus the lack of improvement in the power component of performance is most likely attributable to the fact that neither the weight training nor the cycle exercise used in the endurance training was specifically designed with power development in mind. Nevertheless, no reductions in power performance were observed in any of the groups despite significant reductions in body mass.
The fact that all dietary groups demonstrated a remarkable retention of fat-free mass is also supported in part by the findings in our analysis of RMR. The RMR data, expressed as kilocalories per day or kilocalories per kilogram fat-free mass, were not different after 12 wk in any of the diet groups. When RMR is expressed relative to fat-free mass, larger subjects tend to have lower values because of an overestimate of their metabolically active mass compared with smaller subjects (41). Thus it has been suggested to regress RMR across fat-free mass and compare the regression lines before and after weight loss (Fig. 2; see also Ref. 41). The only significant regression lines were obtained at baseline and in the DE group after 12 wk. Furthermore, the change in fat-free mass was not significantly correlated with the change in RMR, which is in agreement with the findings of a meta-analysis on the effects of diet and exercise on metabolic rate (49). The lower respiratory exchange ratio (CO2 production divided by O2 consumption) in the DES group at week 12 may indicate a proportionally greater utilization of fat at rest. Increased utilization of fat may be a metabolic adaptation reflecting the increased volume of exercise performed by this group.
When all diet groups are considered, there was a significant decrease in total serum cholesterol, LDL cholesterol, and HDL cholesterol. The significant correlation (r = 0.77) between the change in body mass and the change in total cholesterol would indicate that the greatest reductions in serum cholesterol are achieved in those individuals who reduce body mass to the greatest extent. The reductions in total serum cholesterol and LDL cholesterol are consistent with a number of studies investigating the impact of weight loss on serum lipids (19, 22, 38). Examination of the literature on HDL cholesterol would predict that this lipoprotein fraction should either increase or remain unchanged in women engaged in regular vigorous exercise (see Ref. 48 for review) and possibly decrease after weight reduction if body mass has not stabilized (8, 50). Because subjects in this study may still have been losing body mass at week 12, firm conclusions regarding the potential response of HDL should be made with caution. Although exercise typically increases HDL, a few studies have shown that dietary restriction in conjunction with exercise results in a small reduction in HDL cholesterol in women (4, 19). The fact that HDL cholesterol was reduced despite a high activity level in this study may be due to the low-fat, high-carbohydrate nature of the diet or the low dietary cholesterol intake of the subjects (13, 47). Mensink and Katan (35) have shown that a high-fiber diet rich in complex carbohydrates resulted in a significant reduction in HDL cholesterol and an increase in serum triglycerides compared with a high-fiber diet rich in olive oil (higher in fat), which resulted in a specific fall in non-HDL cholesterol while leaving HDL cholesterol and triglyceride values unchanged. Furthermore, a marked reduction in dietary fat and isocaloric increase in carbohydrate has been shown to result in a decrease in HDL cholesterol and an increase in triglyceride concentrations (30). Thus data from this study and others (6, 32) might suggest that reducing total fat per se may not be the best way to prevent coronary heart disease because a low HDL cholesterol level is associated with an increase in the risk of coronary heart disease (16).
The lack of a response in serum testosterone concentrations is consistent with the findings of Staron et al. (45), who reported a significant increase in testosterone in men, but not women, engaged in progressive resistance exercise. The DES group demonstrated a slight increase in serum cortisol (+10%), whereas the DE group showed a significant elevation (+51%) after 12 wk of training. Kraemer et al. (26) reported a similar increase in resting cortisol concentrations after a 10-wk program of either sprint interval or sprint interval combined with endurance training in men and women. The attenuation in cortisol response in the DES group relative to the DE group may indicate a protective effect of resistance training (i.e., weight training provides an anabolic stimulus that counteracts the catabolic response of endurance training). This has been shown in a previous study in men (29).
In summary, these data indicate that moderate dietary restriction alone has the same effect on the magnitude and composition of body mass alterations, serum lipid profile, RMR, and muscular power production as dietary restriction combined with exercise in overweight women. However, diet in conjunction with endurance and high-intensity resistance exercise significantly improves maximal oxygen consumption and maximal (1-RM) strength despite a significant reduction in body mass. Thus exercise, especially high-intensity resistance exercise, is an important component for weight management programs because it improves functional capacity and quality of life.
ACKNOWLEDGEMENTS
We thank a dedicated group of subjects, who made this project possible. Also, we especially thank Kathy Buhl and Laura Gerace for technical assistance in body composition measurement and Brenda Sinclair for contributions related to nutritional aspects of the study. Last, we are fortunate to have a great staff at the Center for Sports Medicine and the Noll Physiological Research Center and thank all of them for help in data collection and nutritional support.
FOOTNOTES
Address for reprint requests: W. J. Kraemer, Center for Sports Medicine, 146 REC Bldg., The Pennsylvania State Univ., University Park, PA 16802.
Received 24 July 1996; accepted in final form 17 March 1997.
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