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Sports Med 2006; 36 (3): 239-262
R
EVIEW
A
RTICLE
0112-1642/06/0003-0239/$39.95/0
2006 Adis Data Information BV. All rights reserved.
The Role of Diet and Exercise for the
Maintenance of Fat-Free Mass and
Resting Metabolic Rate During
Weight Loss
Petra Stiegler and Adam Cunliffe
Department of Human and Health Sciences, University of Westminster, London, UK
Contents
Abstract ....................................................................................239
1. Diet Intervention Studies ..................................................................241
1.1 Dietary Energy Restriction and Resting Metabolic Rate (RMR) ............................241
1.2 High-Carbohydrate, Low-Fat Diets .....................................................242
1.3 High-Protein Diets ....................................................................244
2. Exercise Intervention Studies ..............................................................246
2.1 Exercise and RMR ....................................................................246
2.2 Aerobic Exercise .....................................................................246
2.3 Resistance Exercise and Combined Aerobic and Resistance Exercise .....................249
3. Combined Diet and Exercise Intervention Studies ...........................................250
3.1 Dietary Energy Restriction and Aerobic Exercise .........................................250
3.2 Dietary Energy Restriction and Resistance Exercise ......................................254
3.3 Dietary Energy Restriction Combined with Aerobic and Resistance Exercise ...............255
4. Conclusion ..............................................................................257
The incidence of obesity is increasing rapidly. Research efforts for effective
Abstract
treatment strategies still focus on diet and exercise programmes, the individual
components of which have been investigated in intervention trials in order to
determine the most effective recommendations for sustained changes in
bodyweight. The foremost objective of a weight-loss trial has to be the reduction
in body fat leading to a decrease in risk factors for metabolic syndrome. However,
a concomitant decline in lean tissue can frequently be observed. Given that
fat-free mass (FFM) represents a key determinant of the magnitude of resting
metabolic rate (RMR), it follows that a decrease in lean tissue could hinder the
progress of weight loss. Therefore, with respect to long-term effectiveness of
weight-loss programmes, the loss of fat mass while maintaining FFM and RMR
seems desirable.
240 Stiegler & Cunliffe
Diet intervention studies suggest spontaneous losses in bodyweight following
low-fat diets, and current data on a reduction of the carbohydrate-to-protein ratio
of the diet show promising outcomes. Exercise training is associated with an
increase in energy expenditure, thus promoting changes in body composition and
bodyweight while keeping dietary intake constant. The advantages of strength
training may have greater implications than initially proposed with respect to
decreasing percentage body fat and sustaining FFM. Research to date suggests
that the addition of exercise programmes to dietary restriction can promote more
favourable changes in body composition than diet or physical activity on its own.
Moreover, recent research indicates that the macronutrient content of the
energy-restricted diet may influence body compositional alterations following
exercise regimens. Protein emerges as an important factor for the maintenance of
or increase in FFM induced by exercise training. Changes in RMR can only partly
be accounted for by alterations in respiring tissues, and other yet-undefined
mechanisms have to be explored. These outcomes provide the scientific rationale
to justify further randomised intervention trials on the synergies between diet and
exercise approaches to yield favourable modifications in body composition.
The prevalence of obesity has risen enormously tion.
[11]
Over the past 2 decades, numerous interven-
over the past few decades. According to the World tion studies have examined strategies for the preven-
Health Report 2002,
[1]
obesity has increased 3-fold tion and treatment of obesity. Diet and exercise are
in some parts of North America, Eastern Europe, the still the key variables for both men and women to
Middle East, the Pacific Islands, Australasia and imbalance the energy equation in the direction of
China since 1980. Defined by a body mass index weight loss. An abundance of studies provide evi-
>30 kg/m
2
,
[2]
obesity has been associated with many dence of successful bodyweight reductions follow-
diseases, including some forms of cancer,
[3]
type 2 ing dietary restriction and physical activity.
[12-15]
diabetes mellitus,
[4]
stroke,
[5]
coronary heart disease, However, in terms of the magnitude of change,
hypertension, dyslipidaemia, gallbladder disease, reductions in bodyweight are often below expecta-
sleep apnoea
[6]
and osteoarthritis.
[7]
tions.
[16-18]
Moreover, the majority of people are not
able to maintain the achieved losses and, over the
Factors underlying this epidemic are complex.
long term, weight regain is usually the case.
[19-21]
Although genetic susceptibility may play a role in
the development of excessive adiposity,
[8,9]
diet fac-
The reasons for the limited long-term effective-
tors, such as the availability of energy-dense food,
ness of conventional treatment strategies are di-
and the widespread reduction in physical activity
verse. The failure of changing lifestyle habits with
clearly make critical contributions.
[10]
Morbidity and
respect to dietary intake and regular physical activi-
mortality associated with obesity are substantial, but
ty during follow-up is well established.
[22,23]
While
can be effectively reduced following weight reduc-
behavioural issues are certainly the cornerstones,
tion.
weight maintenance appears to be antagonised by a
As early as 1975, a multi-factorial approach was reduction in resting metabolic rate (RMR). As the
used for the treatment of obesity, including dietary largest component of daily energy expenditure,
modification, exercise, psychotherapy and medica- RMR comprises approximately 60–70%. Fat-free
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Diet and Exercise During Weight Loss 241
mass (FFM) is the main factor that accounts for the vention studies, exercise intervention studies and
magnitude of resting metabolism.
[24-27]
As a hetero- studies that have investigated the combined effects
geneous compartment, FFM consists of highly met- of diet and exercise for the treatment of obesity. The
abolically active muscle and organs and low- article covers well controlled, randomised clinical
metabolic rate tissues such as bone and connective trials conducted in subjects with at least a minor
tissue.
[28] 1
Therefore, any diet or exercise interven- degree of over-fatness or overweight and where data
tions, which are capable of maintaining FFM or at on body compositional changes were provided. The
least attenuating its decline following weight loss, efficacy of the identified investigations was com-
could have significant effects on total energy bal- pared in terms of changes in bodyweight, fat mass,
ance. The residual variation in RMR seems to be FFM and RMR. As only a limited number of re-
related to a diversity of physiological parameters, search reports assessed energy expenditure, missing
such as thyroid hormones, leptin levels and sympa- data on RMR were not considered a criterion for
thetic nervous system activity. exclusion of the study. This article will conclude
with an evaluation of treatment strategies for obesi-
The foremost objective of a weight-loss trial has
ty, based on diet and exercise programmes and
to be the reduction in fat mass leading to a decrease
directions for future research will be discussed.
in risk factors for metabolic syndrome. However, an
accompanying loss in FFM can frequently be ob-
1. Diet Intervention Studies
served. Both with regard to a reduction in risk
factors and long-term weight maintenance the con-
tent of adipose tissue in the weight lost has to be
1.1 Dietary Energy Restriction and Resting
maximised, thus preserving FFM. It appears that
Metabolic Rate (RMR)
some dietary regimens induce a higher loss in FFM
than others, with the macronutrient composition and RMR is the energy expended by the active cell
the energy content of the diets having a major im- mass to maintain normal body functions at rest.
pact on the composition of the bodyweight lost.
[29,30]
There is evidence that RMR is largely dependent on
Another means by which a decline in bodyweight FFM.
[36-38]
Several intrinsic factors, which are be-
can be achieved while favourably modifying body yond the control of the individual, seem to account
composition with the maintenance of FFM is for the residual variation in RMR, including age,
through physical activity.
[31-33]
The ability of exer- sex, thyroid status
[39]
and genetic factors.
[40]
cise programmes to achieve these goals depends on
It is a well known fact that weight loss induced
the prescribed type and magnitude of exercise.
by dietary restriction is accompanied by a decline in
Therefore, as numerous studies show, a reduction in
RMR. A decrease in FFM mass most certainly has
RMR does not necessarily accompany a loss in FFM
considerable contribution to this effect
[41]
(figure 1).
and alterations in RMR might occur independent of
Concomitant neuroendocrine disturbances, such as
changes in muscle tissue.
[34,35]
Some studies have
alterations in leptin level,
[42,43]
thyroid status
[44]
and
reported that a low RMR is a determinant of weight
sympathetic nervous system activity
[45]
may further
gain, thus attenuating the decline in RMR is desira-
contribute to the decrease in RMR. This raises the
ble.
question as to whether the composition of the diet
Accordingly, the purpose of this review is to can modify physiological adaptations to energy re-
document recent (1990–2005) results of diet inter- striction, thus blunting the fall in RMR. The reduc-
1 Throughout this article, the terms ‘fat-free mass’ and ‘lean body mass’ are used interchangeably.
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
242 Stiegler & Cunliffe
and RMR has received little attention to date, sever-
al intervention studies have included those variables
in their outcome measurements.
1.2 High-Carbohydrate, Low-Fat Diets
There has been extensive research in the macro-
nutrient composition of the diet and its effect on
bodyweight reduction (table I). One popular ap-
proach within studies for the treatment of over-
weight entails altering the CHO to fat ratio in the
diet. The CARMEN (Carbohydrate Ratio Manage-
ment in European National diets) study, the largest
and most recent multicentre trial, tested the impact
of complex versus simple CHO in an ad libitum, fat-
reduced (by 10% of total energy) regimen in 398
Energy
expenditure
Energy
expenditure
FM
Pre-intervention
state
Post-intervention
state
FM
FFM
RMR
Energy deficit
Bodyweight
RMR
FFM
Bodyweight
Fig. 1. Theoretical impact of energy restriction on fat mass (FM),
fat-free mass (FFM) and resting metabolic rate (RMR). Energy
deficit over a prolonged period of time induces a reduction in
bodyweight, which is based on a decrease in FM and, possibly,
FFM. These body compositional changes might be associated with
a decline in RMR.
overweight individuals. After 6 months, a signifi-
cant reduction in bodyweight and fat mass was
tion of adipose tissue during weight loss induces an
observed on both diets while sustaining FFM.
[12]
associated decline in the secretion of leptin.
[46]
This was further investigated in 45 overweight fe-
Changes in leptin level have been shown to predict
males. Similar to the CARMEN study, a low-fat,
changes in RMR. However, a positive association is
high-CHO diet led to a spontaneous decline in
still noticeable after adjusting for body composi-
bodyweight, which was independent of the gly-
tion,
[42]
indicating an effect of leptin on RMR inde-
caemic index of the foods consumed.
[51]
Therefore,
pendent of fat mass. Therefore, the maintenance of
the removal of a substantial amount of fat from the
leptin appears to be desirable for weight stability in
diet leads to a spontaneous decline in bodyweight.
the post-obese state.
[47]
There is some evidence for a
As shown in several other studies, the mechanism
positive association between carbohydrate (CHO)
appears to be due to the concomitant energy reduc-
consumption and leptin concentration during energy
tion.
[51-54]
Although some studies advocate the con-
restriction,
[48]
suggesting an impact of the macronu-
sumption of foods with a low glycaemic index, this
trient content of the diet on energy expenditure.
was not confirmed in the two above-mentioned stud-
In order to prevent the decline in RMR, sus- ies.
[12,51]
In a recent review on high-CHO diets and
taining FFM emerges as an important aim. Studies energy balance, Brand-Miller et al.
[55]
claimed that
reveal that a protein intake sufficient to prevent foods that promote a high glycaemic response, such
negative nitrogen balance might be of great impor- as potatoes, breads and low-fat cereal products, tend
tance to lessen the decline in muscle mass
[49]
and to favour body fat gain. Another approach was ex-
energy expenditure (24-hour energy expenditure plored by randomly assigning 40 overweight wo-
and sleeping metabolic rate).
[50]
Thus, it is apparent men to an ad libitum, low-CHO diet or an energy-
that various factors associated with dietary composi- restricted, low-fat diet. After 4 months, the loss in
tion can modify the physiological adaptations to bodyweight and fat mass was greater in the low-
energy restriction. Although the potential effect of CHO group and reductions in FFM and RMR were
the macronutrient intake on the maintenance of FFM recorded. These results could not be accounted for
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Diet and Exercise During Weight Loss 243
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
Table I. Diet intervention studies
Study Dietary intervention Subjects BMI Duration ∆ Bodyweight ∆ Fat mass ∆ FFM ∆ RMR
(kg/m
2
) (wk) (%) (%) (%) (%)
Saris et al.
[12]
CC: ad lib, low-fat, high complex 389 30.4 26 SC:
–
1.0
a
SC:
–
3.8
a
NS
CHO
SC: ad lib, low-fat, high simple F, M CC:
–
2.0
a
CC:
–
5.3
a
CHO
C: control M C: NS
b
C: NS
b
N: seasonal control group
Brehm et al.
[56]
LC: ad lib, low CHO (20 g/day) 40 F 33.2 16 LC:
–
16.3
a
LC:
–
6.7 LC:
–
6.8
a
LC:
–
5.9
LF: 30% fat, 55% CHO LF:
–
8.7
b
LF:
–
2.3 LF:
–
10.8
b
LF:
–
5.5
Sloth et al.
[51]
HGI: <30% fat, high GI 45 F 27.6 10 HGI:
–
1.6 HGI:
–
1.3
–
1.6
LGI: <30% fat, low GI LGI:
–
3.5 LGI:
–
3.5
Skov et al.
[57]
C: control diet (40% fat) 50 F, 15 M 30.4 26 HP:
–
10.0
a
HP:
–
26.7
a
HP: ad lib, 30% fat, 25% PRO HC:
–
5.6
b
HC:
–
14.1
b
HC: ad lib, 30% fat, 12% PRO
Baba et al.
[58]
80% of RMR, 30% fat 13 M 35.8 4 HP:
–
7.3
a
–
6.7
–
6.1 HP:
–
5.9
a
HP: 45% PRO HI HC:
–
5.7
b
HC:
–
17.4
b
HC: 12% PRO
Torbay et al.
[35]
80% of RMR, 30% fat 14 HI 35.1 4 HPHI:
–
7.3
a
–
15.7 NS HPHI:
–
5.9
a
HP: 45% PRO 13 NI NI:
–
5.9
b
NI:
–
4.0
a
,
c
HC: 12% PRO M HCHI:
–
5.7
b
HCHI:
–
17.5
b
,
d
NI:
–
6.6 NI:
–
18.1
c
,
b
Farnsworth et al.
[30]
70% TEE, 4wk E balance (30% 14 M 34.0 12
–
8.5
–
17.3
–
2.5
fat):
HP: 27% PRO 43 F
SP: 16% PRO
Luscombe-Marsh et 70% of TEE, 4wk E balance 32 F 34.0 12
–
9.5
–
13.2
–
5.9
–
4.0
al.
[59]
HP: 29% fat, 34% PRO 15 M
SP: 45% fat, 18% PRO HI
Luscombe et al.
[60]
70% TEE, 4wk E balance (30% 10 M 34.1 12
–
8.4
–
16.5
–
3.0
–
8.8
fat)
HP: 27% PRO 26 F
SP: 16% PRO HI
Continued next pag
e
244 Stiegler & Cunliffe
by changes in components of energy expenditure or
intake through 3-day food records and most likely
represent underreporting.
[56]
Thus, although a low-
fat diet seems to induce a spontaneous loss in body
fat, this may be accompanied by reductions in FFM.
In addition, the current opinion on the impact of the
type of CHO on weight loss seems inconclusive.
1.3 High-Protein Diets
Recently, renewed interest was shown in whether
replacing some dietary CHO with protein may
favourably affect bodyweight and body composition
during energy restriction. Addressing this question,
Skov et al.
[57]
randomly assigned 60 overweight
subjects to a control diet or an ad libitum low-fat
diet, which was either high in protein or CHO. After
6 months, a clinically relevant loss of bodyweight
(
–
8.7 vs
–
5.0kg, p = 0.0002) and fat mass (
–
7.6 vs
–
4.3kg, p < 0.0001) was achieved on both low-fat
diets, which was greater in the high-protein than the
high-CHO group. The study design allowed the
participants to collect the foods from a shop set up
by the researchers. Therefore, between-group differ-
ences, such as a limited variety of foods shown to
influence bodyweight,
[61]
may have biased the re-
sults. However, the observed tendency was con-
firmed by a well controlled study in 24 overweight
women. The investigators examined the effects of
low-fat meals with CHO/protein ratios of 3.5 and
1.4. After 10 weeks, declines in bodyweight and fat
mass were similar across groups, but the participants
in the high-protein group achieved an elevated fat/
lean tissue loss (p < 0.05).
[29]
Moreover, a study in
13 hyperinsulinaemic obese men with normal fast-
ing plasma glucose levels showed similar effects
after 4 weeks on a hypo-energetic diet. A high intake
of protein was associated with 28% more weight
loss (
–
8.3 vs
–
6.0kg, p < 0.05) than the isocaloric
consumption of a diet high in CHO. It is possible
that this effect is partly derived from a significantly
greater loss of total body water in the high-protein
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
Table I. Contd
Study Dietary intervention Subjects BMI Duration ∆ Bodyweight ∆ Fat mass ∆ FFM ∆ RMR
(kg/m
2
) (wk) (%) (%) (%) (%)
Layman et al.
[29]
<1700 kcal/day 24 F 30.3 10
–
8.4
–
13.3 NS
HP: 30% PRO, 41% CHO
HC: 16% PRO, 58% CHO
a Significantly different from b, c and d at p < 0.05.
b Significantly different from a, c and d at p < 0.05.
c Significantly different from a, b and d at p < 0.05.
d Significantly different from a, b and c at p < 0.05.
ad lib = ad libitum; BMI = body mass index; C = control group; CC = diet high in complex carbohydrates; CHO = carbohydrate; E = energy; F = females; FFM = fat-free mass; GI =
glycaemic index; HC = high-carbohydrate diet; HCHI = high-carbohydrate diet, hyperinsulinaemic; HGI = high GI; HI = hyperinsulinaemic; HP = high-protein diet; HPHI = high-
protein diet, hyperinsulinaemic; LC = low-carbohydrate diet; LF = low-fat diet; LGI = low GI; M = males; N = no intervention; NI = normoinsulinaemic; NS = not statistically significant
(p > 0.05); PRO = protein; RMR = resting metabolic rate; SC = diet high in simple carbohydrates; SP = standard protein diet; TEE = total energy expenditure; ∆ = change.
The Role of Diet and Exercise During Weight Loss 245
compared with the high-CHO group.
[58]
In subjects ther CHO or fat may make some contribution. This
with normal insulin levels following the same proto- effect may also account for the reduced fall in
col, no major differences have been detected. How- 24-hour energy expenditure when maintaining the
ever, despite the comparable decline in lean tissue, protein content of an energy-restricted diet.
[50]
Fur-
the high-protein diet was superior to the high-CHO thermore, compared with high-protein diets, hormo-
diet in maintaining RMR (p < 0.05),
[35]
in both nal responses associated with high-CHO diets may
hyperinsulinaemic and normoinsulinaemic partici- induce a series of physiological events favouring
pants.
[35]
catabolism of FFM. A rise in insulin following a
high intake of CHO promotes the uptake of glucose
In contrast, a study in 57 overweight subjects
and triacylglycerol in the liver and adipose tissue,
with slightly elevated insulin levels (>12 mU/L)
reduces glycogenolysis and lipolysis, thus sup-
failed to show an association between the protein
pressing the post-absorptive appearance of glucose
content of the diet and weight reduction after 12
and fatty acid. This triggers the release of counter-
weeks of energy restriction and 4 weeks of energy
regulatory hormones inducing catabolism of lean
balance. The results, however, indicated a preserva-
mass. Following the intake of a meal high in protein,
tion of lean mass during weight loss in the 43 female
less reliance on peripheral insulin actions and a
subjects (p = 0.02). The authors pointed out that the
delayed postprandial rate of disposal for amino acids
lack of an effect in the 14 male subjects may be due
appear to stabilise the glycaemic environment
[65]
to the small number participating in the study and a
and may conserve lean tissue. Moreover, the meta-
reported protein intake, which was sufficient to pre-
bolic role of leucine and the branched-chain amino
vent proteolysis in women, but not in men.
[30]
A
acids for muscle protein synthesis seems consistent
similar reduction in RMR was observed after the
with the conservation of FFM on high-protein di-
two diets, presumably in a subgroup (36 subjects) of
ets.
[65]
the above-mentioned study.
[60]
In a recent study
investigating energy restricted diets high in protein In one study, high-protein diets were investigated
or monounsaturated fat, no differences with respect under ad libitum conditions.
[57]
Subjects were re-
to body composition and RMR were found.
[59]
quired to cut out foods high in CHO. A greater
reduction in caloric intake due to the limitation in
The studies reviewed in this section indicate that
food choice rather than an effect of macronutrient
replacing some dietary CHO with protein might
composition may have facilitated the observed loss
favourably affect body compositional changes dur-
of bodyweight. This theory is supported by the
ing energy restriction compared with fat-restricted,
finding that the variety of sweets, snacks and CHO
high-CHO diets. The explanation for these observa-
consumed is positively associated with body fat-
tions, however, remains unclear. It is well estab-
ness.
[66]
Furthermore, more subtle aspects of palat-
lished that the utilisation of ingested nutrients for
ability of foods high in protein cannot be discounted.
energy is inversely related to the thermogenesis of
Nevertheless, several studies suggest that protein
food, a phenomenon associated with the energy cost
promotes satiety and reduces appetite when com-
of nutrient absorption, processing and storage.
[62]
pared with fat and CHO
[29,67-71]
and only a small
This loss of energy is highest for protein consisting
number oppose this view.
[72,73]
of 25–30% of the ingested energy, followed by CHO
with 6–8% and fat with only 2–3%.
[63,64]
Therefore, Therefore, in the light of recent data, high-protein
a higher thermogenic response following the intake hypocaloric diets may facilitate weight loss for over-
of protein compared with isocaloric preloads of ei- weight subjects while more lean tissue (and there-
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
246 Stiegler & Cunliffe
fore RMR) might be preserved. Moreover, a diet ing body fat. As importantly, weight loss due to
high in protein was superior to conventional diets in exercise may be associated with a retention of lean
improving insulin sensitivity
[29,58,74,75]
and no delete- body mass. Although weight reduction following
rious effects on blood pressure,
[74]
total cholesterol, physical activity is mainly brought about by the
triglycerides
[29,30,58,74,75]
and bone turnover
[30,57]
have energy expended during the exercise bout, addition-
been reported. However, according to Eisenstein et al mechanisms may increase resting metabolism,
al.
[76]
detrimental impacts on bone health and renal thus further promoting energy imbalances. Given
disease can not be discounted as dietary protein the association between lean tissue and RMR, the
increases urinary calcium excretion. Evidence from most apparent impact of exercise training on resting
a study conducted by Kerstetter et al.
[77]
weighs metabolism is the ability to initiate skeletal muscle
against this hypothesis, as 80% of the protein-in- growth.
[79]
In addition, increases in energy expendi-
duced calciuria was compensated for by increased ture during the post-exercise recovery period (ex-
intestinal absorption of dietary calcium. In addition, cess post-exercise oxygen consumption) may induce
when substituting foods high in protein (e.g. dairy a short-term rise in metabolic rate for >24 hours.
[80]
products and nuts) for highly refined foods in the However, as recently reviewed, this effect might
grain and starch groups (e.g. bread, rice, cereals and only be noticeable following medium- to high-inten-
pasta) potential adverse effects of a high intake of sity exercise.
[81]
Despite a more rapid return to base-
protein may be reduced by other nutrients found in line levels in trained individuals,
[82,83]
regular exer-
the protein source (e.g. high amounts of calcium in cise bouts may promote small elevations in
milk or high potassium levels of legumes).
[78]
RMR.
[84,85]
Further mechanisms, by which exercise
may increase metabolic rate, have yet to be fully
Based on the evidence noted in this section, the
elucidated, but may include uncoupled respira-
frequently recommended high-CHO, low-fat diets
tion,
[86,87]
protein turnover
[88]
and sympathetic ner-
have not always been associated with the greatest
vous system activity.
[89]
Therefore, the theoretical
loss in bodyweight. Complex and as yet incomplete-
effects of physical activity on changes in body com-
ly understood physiological processes associated
position are apparent. Nonetheless, with regard to
with a high intake of protein seem to facilitate
RMR, the literature to date is still inconclusive, as
reductions in body fat, with less declines in FFM
exercise training has also been associated with re-
and RMR. However, evidence is still scarce and
ductions in RMR.
[90,91]
As will be seen, the out-
further examinations are needed in order to clarify
comes of exercise intervention studies with respect
the relative merits of diets high in protein.
to body compositional alterations seem to be related
2. Exercise Intervention Studies
to the type of exercise, with intensity, frequency and
duration of the exercise bouts as limiting factors.
2.1 Exercise and RMR
2.2 Aerobic Exercise
Controlled trials on the effects of an increased
physical activity level as the primary intervention The design of exercise intervention studies varies
without diet modification provide the best way to in terms of the mode, frequency, intensity and dura-
determine exercise effects on weight, body compo- tion of exercise. Whereas total energy requirements
sition and RMR. An increase in physical activity rely on absolute exercise intensity, relative exercise
without changing energy intake can successfully intensity determines the contribution of fat and CHO
promote negative energy balance, thereby decreas- as fuels. It is well established that fat is the predomi-
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Diet and Exercise During Weight Loss 247
nant source of energy during physical activity at low 16-month supervised trial with 31 men and 43 wo-
men. Aerobic exercise on 5 days a week significant-
to moderate intensities (<50% maximum oxygen
ly decreased bodyweight (
–
2.9kg) and fat mass
consumption [
˙
VO
2max
]). A progressive decline of
(
–
4.8kg) in men. Interestingly, despite the consider-
fat oxidation in favour of CHO occurs with increas-
able amount of exercise performed, there were no
ing intensities (>50%
˙
VO
2max
).
[92]
As oxygen sup-
body compositional changes from baseline in the
ply to the muscles is not sufficient at these intensi-
female participants, but the control group gained a
ties due to the limited capacity of the heart and
significant amount of weight (p < 0.05).
[96,97]
Thus,
lungs, glucose is used as the only fuel that can be
the results of these studies show small, but signifi-
oxidised anaerobically.
[93]
Despite the relative de-
cant, reductions in body fat.
cline in fat oxidation with higher exercise intensi-
ties, the absolute quantity of fat oxidised may aug-
To determine, whether the intensity of exercise
ment as the amount of work performed increases.
alters outcomes with respect to bodyweight and
Thus, with the aim of utilisation of lipid stores and a
composition, Grediagin et al.
[99]
randomly assigned
high caloric expenditure, high-intensity exercise
12 untrained, moderately overweight women to ei-
might seem more beneficial. However, in the light
ther a high-intensity or a low-intensity exercise
of a low aerobic fitness and a bodily condition not
group. After 12 weeks of four-times weekly tread-
capable of high-intensity training in overweight and
mill training (with a duration designed to expend
obese patients, investigations into physical activity
300 kcal), no statistically significant differences
as a weight-loss tool have traditionally been based
were detected between the groups. In accordance, a
on low- to moderate-intensity exercise.
study set up by van Aggel-Leijssen et al.,
[34]
with a
similar design including a control group, failed to
van Aggel-Leijssen et al.
[94]
conducted a study in
show an effect on body composition. Twenty-four
21 pre-menopausal women with either lower- or
obese male volunteers trained according to a cycle
upper-body obesity (table II). All participants with
instead of a treadmill test protocol on only three
lower-body obesity were assigned to 12 weeks of a
occasions per week. Furthermore, RMR was slightly
low-intensity cycling programme and the women
lower after the 12-week intervention following the
with upper-body obesity were randomly divided
high-intensity training (
–
179 kcal/day, p < 0.05).
into an exercising and a control group. The study
outcomes failed to demonstrate any changes in body
The impact of exercise frequency and duration
composition and RMR across the groups. The same
was assessed in 22 sedentary, moderately obese
exercise modality was examined in the HERITAGE
females, who were randomly assigned to a continu-
Family Study,
[95]
a highly controlled multicentre
ous exercise group or an intermittent exercise group.
clinical trial, with a study population of 557 subjects
After 18 months, reductions in body fat (
–
2.1kg, p <
of various races and ages. The 20-week training
0.05) and weight (
–
1.5kg, p < 0.05) were only seen
programme consisted of exercise sessions on 3 days
in the continuous exercise group, whereas FFM was
per week with increasing intensity. The results sug-
unchanged in both.
[100]
Disparity in outcomes for
gested small, but statistically significant, reductions
weight loss may have been a consequence of differ-
in total body mass and fat mass and an increase in
ences in total weekly energy expenditure between
FFM, with no changes in RMR. In women,
the groups. To further investigate this, Sykes et
bodyweight did not change as the loss of fat mass
al.
[101]
conducted a study in 30 overweight Sin-
equalled the gain in FFM. This was further investi-
gaporean women, who exercised at moderate inten-
gated in the Midwest Exercise Trial, a randomised sity on 2 and 5 days a week, respectively, with total
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
248 Stiegler & Cunliffe
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
Table II. Exercise intervention studies
Study Exercise intervention Subjects BMI Duration ∆ Bodyweight ∆ Fat ∆ FFM ∆ RMR
(kg/m
2
) (wk) (%) mass (%) (%)
van Aggel-Leijssen et al.
[94]
UB + LB: cycling, 40%
˙
VO
2max
3 d/wk, EE = 13 F UB 32.7 12 NS NS NS NS
~250 kcal/d 8 F LB
UB-C: no intervention
Wilmore et al.
[95,98]
Cycling from 55%
˙
VO
2max
30 min to 75% 299 F 25.4 20 M:
–
0.5 M:
–
4.8
a
+0.9 NS
˙
VO
2max
50 min 3 d/wk 258 M F: NS F:
–
2.3
b
Donnelly et al.
[96]
and E: aerobic (primarily walking), from 55% to 70% 43 F 29.4 69 M:
–
5.1 M:
–
11.1 NS
Kirk et al.
[97]
˙
VO
2max
20–45 min/d 5 d/wk 31 M F: NS
a
F: NS
a
C: no intervention C: +3.6
b
C: +7.1
b
Grediagin et al.
[99]
LI: 50%
˙
VO
2max
4 d/wk, EE = 300 kcal/d 12 F 25.0 12
–
1.3
–
1.1
–
3.0
HI: 80%
˙
VO
2max
4 d/wk, EE = 300 kcal/d
van Aggel-Leijssen et al.
[34]
LI: 40%
˙
VO
2max
3 d/wk, EE ≈350 kcal/d 24 F 31.8 12 NS NS NS HI:
–
7.8
HI: 70%
˙
VO
2max
3 d/wk, EE ≈350 kcal/d LI: NS
C: no intervention
Donnelly et al.
[100]
CONT: walking 60–75%
˙
VO
2max
30 min 3 d/wk 22 F 31.2 78 CONT:
–
1.8 CONT: NS
I: walking 2 × 15 min 5 d/wk I: NS
–
6.2
a
I: NS
b
Sykes et al.
[101]
E1: treadmill + cycling 400 kcal 5 d/wk 30 F 23.8 8
–
3.1
–
4.2 NS
E2: treadmill + cycling 1000 kcal 2 d/wk
Schmitz et al.
[102]
R: resistance 50 min 2 d/wk 60 F 26.6 15 NS R:
–
3.9
a
R: +2.3
a
C: no intervention C: NS
b
C: NS
b
Cullinen and Caldwell
[103]
R: resistance 45 min 2 d/wk 30 F 23.0 12 NS R:
–
8.1 R: +4.5 NS
C: no intervention C: NS C: NS
Byrne and Wilmore
[104]
R: resistance 4 d/wk 19 F 27.0 20 NS NS +4.0 R: +3.0
RW: resistance 4 d/wk + walking 20–40 min RW:
–
3.8
3 d/wk
C: no intervention
a Significantly different from b at p < 0.05.
b Significantly different from a at p < 0.05.
BMI = body mass index; C = control group; CONT = continuous exercise group; E = exercise group; E1 = exercise group one; E2 = exercise group two; EE = energy expenditure; F
= females; FFM = fat-free mass; HI = high-intensity exercise; I = intermittent exercise group; LB = lower-body obesity; LI = low-intensity exercise; M = males; NS = not statistically
significant (p > 0.05); R = resistance exercise group; RMR = resting metabolic rate; RW = resistance exercise and walking group; UB = upper-body obesity; UB-C = upper-body
obesity control group;
˙
VO
2max
= maximal oxygen consumption; ∆ = change.
The Role of Diet and Exercise During Weight Loss 249
energy expenditure being the same. After 8 weeks, a were in those individuals that did a combination of
significant loss of bodyweight and body fat indicat-
resistance training and walking exercise, for whom
ed beneficial effects regardless of the training fre-
RMR declined (
–
53 kcal/day), despite an increase in
quency.
lean body mass. The authors suggested that the
In summary, prolonged, sub-maximal exercise
reduction in RMR was a result of heat acclimation as
may result in a small decline in bodyweight and fat
average monthly temperatures increased from the
mass. However, the magnitude of the change ap-
pre- to the post-training periods. Speakman and
pears to be less than expected and several exercise
Selman
[106]
discussed in a recent review a down-
protocols failed to reduce body fat. The impact of
regulation of uncoupling-protein 3 in muscle, en-
exercise intensity on FFM and RMR warrants fur-
hancing mechanical efficacy during physical activi-
ther evaluation.
ty, as a possible reason for a decline in RMR.
In summary, considering the amount of physical
2.3 Resistance Exercise and Combined
activity prescribed in the above-mentioned exercise
Aerobic and Resistance Exercise
intervention studies, the magnitude of the changes in
each of the variables was relatively small. With
The relatively small muscle mass usually used
respect to those studies that included measurements
during resistance exercise creates lower metabolic
of energy expenditure of the exercise bouts, theoret-
demands than aerobic exercise. Therefore, strength
ical losses in body fat could be calculated before-
training was considered to provide only minimal
hand. The observed reductions were frequently be-
stimulus to reduce body fat. However, as an impor-
low the expectations, and some exercise program-
tant benefit of resistance exercise, Walberg
[105]
re-
mes failed to induce changes.
[16,34]
This raises the
ported in her review preliminary evidence that sug-
question of whether a compensation for the energy
gests weight training in favour of aerobic exercise to
deficits has occurred, either as a compensatory rise
preserve or increase FFM and RMR, while decreas-
in food intake, a decrease in spontaneous physical
ing body fat. Referring to experimental data, in a
activity, or both. Whereas some studies dispute a
recent study in 60 women aged between 30 and 50
reduction in spontaneous physical activity
[107]
and
years, 15 weeks of supervised strength training on 2
an increase in energy intake,
[108-110]
other studies
days per week resulted in a small but significant
provided strong evidence for at least partial compen-
increase in FFM (+0.89kg) and a similar loss in fat
satory trends with respect to habitual daily activi-
mass (
–
0.98kg) when compared with a control
ties
[111]
and caloric consumption.
[112]
Some interest-
group. These body compositional changes were
ing patterns emerged from a recent study showing
maintained over 6 months through an unsupervised
that negative energy balance is compensated for
programme.
[102]
To investigate whether a combina-
more readily than surfeits and that this compensa-
tion of resistance training and walking was more
tion is more marked for changes in energy expendi-
beneficial than resistance exercise on its own, Byrne
ture, i.e. decreases in nonexercise activity, than in
and Wilmore
[104]
set up a study in 19 moderately
energy intake.
[113]
Thus, in free-living populations,
obese women. After 20 weeks, measurements of
this may be a key factor counteracting the expected
body composition indicated an increase in lean body
weight reduction. Furthermore, a less successful
mass in both exercise groups compared with a sed-
pattern of weight loss in women than in men has
entary control group, which was associated with an
been reported in two studies.
[95,96]
An increase in
elevation in RMR (+44 kcal/day) in the strength-
energy intake may have provoked these results.
trained subjects. The most striking results, however,
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
250 Stiegler & Cunliffe
With a high rate of restraint eaters,
[112,114]
dieting many recent studies support the beneficial role of a
women are more likely to allow for a greater food combination of the two.
intake when exercise has been performed.
[115]
How-
ever, this notion remains controversial.
[110]
Some
3.1 Dietary Energy Restriction and
data also lend credence to the idea that abdominal
Aerobic Exercise
adipose tissue, which is more pronounced in men, is
Over the past few decades, the focus of activity
better mobilised than gluteal adipose tissue as, for
programmes for obesity treatment has been on aero-
example, fat oxidation during exercise was only
bic exercise and the potential of this exercise type to
elevated in upper-body obese women when com-
improve outcomes has been repeatedly evaluated in
pared with participants with lower body obesity.
[94]
diet-exercise intervention studies (table III).
Nevertheless, there is insufficient evidence to gener-
As physical activity has been shown to promote
alise sex differences with respect to a loss in fat
favourable changes in body composition, the con-
mass induced by physical activity.
cept tested in some studies was as to whether exer-
The implications of the findings of strength train-
cise training may be a substitute for dietary restric-
ing for changes in body composition underline its
tion. Addressing this question, Frey-Hewitt et al.
[116]
potential to increase FFM and this requires further
randomly assigned 121 overweight men to 1 year of
evaluation.
energy restriction or engagement in walking/jogging
In summary, for exercise to be successful at
when compared with a control group. Although the
reducing body fat and increasing FFM, a considera-
reduction in bodyweight and fat mass in the dieters
ble number of regular exercise bouts need to be
was greater (p < 0.01) than in the exercise group,
performed. Regarding long-term effects of exercise
exercise training was superior to dieting with respect
on bodyweight and body composition, data are
to the maintenance of FFM. In the dieting subjects,
scarce and additional obesity intervention program-
FFM declined by 1.2kg and both absolute RMR
mes are required. However, considerable controver-
(
–
149 kcal/day) and RMR per kilogram FFM (
–
1.68
sy remains about the degree of the influence of
kcal/kg FFM) decreased (p < 0.05). An even more
exercise on RMR. While one study reported an
striking result was found in a 3-month study, with a
increase in RMR following strength training,
[104]
reduction in RMR (
–
247 kcal/day) after a hypo-
most studies reported no changes
[95]
and a decline in
caloric diet and an increase (202 kcal/day) following
RMR was detected in two intervention groups.
[34,104]
jogging on 3–5 days per week. When both groups
Thus, although exercise has the ability to increase
were evaluated simultaneously, alterations in RMR
FFM, an increase in RMR does not necessarily
were related to the changes in FFM. As the loss of
result.
fat mass differed significantly between the groups, it
was pointed out that exercise alone might not bring
3. Combined Diet and Exercise
about the desired changes in bodyweight.
[33]
Several
Intervention Studies
investigations have focused on the role of exercise
for body compositional changes when added to a
Inducing negative energy balance is the most hypocaloric diet. In an investigation in 20 obese
important aim of weight-loss programmes. Physical women, assigned to a very low-energy diet alone or
activity in conjunction with dietary energy restric- combined with modest exercise sessions, a greater
tion has been promoted as an important component reduction of fat mass (p < 0.05) was observed fol-
of successful weight-loss regimens. The results of lowing the exercise treatment, whereas declines in
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Diet and Exercise During Weight Loss 251
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
Table III. Diet and exercise intervention studies
Study Dietary restriction Exercise Subjects BMI Duration ∆ Bodyweight ∆ Fat mass ∆ FFM ∆ RMR
(kg/m
2
) (wk) (%) (%) (%) (%)
Frey-Hewitt D:
–
300 to
–
500 kcal/d D, C: no exercise 121 M 27.3% BF 52 D:
–
7.1
a
D:
–
21.6
a
D:
–
1.7
a
D:
–
8.1
a
et al.
[116]
E: no dietary restriction E: jogged 25 min 3 d/wk to 50 E:
–
4.3
b
E:
–
16.3
a
E: NS
b
E: NS
b
C: no dietary restriction min 5 d/wk C: NS
c
C: NS
b
C: NS
bc
C: NS
b
Schwartz et D: 1200 kcal/d D: no exercise 31 M 29.4% BF 13 D:
–
12.9
a
D:
–
29.8
a
D:
–
5.8
a
D:
–
8.1
a
al.
[33]
E: no dietary restriction E: walking/jogging 70–85% E:
–
2.3b E:
–
9.5
b
E: NS
b
E: +6.7
b
HRR 40 min 3–5 d/wk
Kempen et Wk 1–4: formula, 478 kcal/d D: no exercise 20 F 32.0 8
–
9.1% D:
–
14.9
a
D, DE: SMR:
–
10
al.
[111]
Wk 5–8: formula + food, 956 DE: aerobic 90 min 3 d/wk DE:
–
20.5
b
–
2.8
kcal/d
Hays et C: no dietary restriction C: no exercise 20 F, 14 M 30.9 12 D:
–
3.6
a
C: NS
b
In the
al.
[117]
D, DE: ad lib, 18% fat, 63% D: no exercise DE:
–
5.8
a
D:
–
2.2
a
thigh: NS
CHO DE: aerobic 45 min 4 d/wk C: NS
b
DE:
–
3.5
a
Utter et C: no dietary restriction C: no exercise 91 F 33.0 12 C, E: NS
b
C, E: NS
b
NS
al.
[18]
E: no dietary restriction D: no exercise D, DE:
–
8.8
a
D, DE:
–
17.6
a
D, DE: 1200–1300 kcal/d DE, E: walking 60–80%
HR
max
45 min 5 d/wk
van Aggel- Wk 1–6: formula, 500 kcal/d DE: cycling, walking, aqua 40 M 32.3 10
–
14.6
–
35.9
–
3.5
Leijssen et Wk 7–10: formula + self- jogging 40%
˙
VO
2max
, 60 min
al.
[16]
selected foods 4 d/wk
D: no exercise
Brill et al.
[17]
1200–1400 kcal/d, <35g fat/ D: no exercise 56 F 34.0 12
–
5.8
–
9.4
–
3.3
d, ad lib high-fibre, low-fat, DE1: walking 30 min 5 d/wk
low-calorie foods DE2: walking 60 min 5 d/wk
Okura et Approx. 1130 kcal/d D: no exercise 90 F 29.3 14 D:
–
10.8
a
D:
–
18.7
a
FFM +
al.
[118]
DW: walking 30 min 7 d/wk DW:
–
12.8 DW:
–
24.6
b
BFM:
DA: aerobic dance 45 min 3 DA:
–
7.2
b
DA:
–
29.3
b
D:
–
5.2
a
d/wk, DW:
–
6.2
b
EE = 1050 kcal/wk DA:
–
3.8
b
Continued next pag
e
252 Stiegler & Cunliffe
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
Table III. Contd
Study Dietary restriction Exercise Subjects BMI Duration ∆ Bodyweight ∆ Fat mass ∆ FFM ∆ RMR
(kg/m
2
) (wk) (%) (%) (%) (%)
Racette et ~75% of RMR, LF, LC: no exercise 23 F 34.1 12 LC:
–
11.6
a
–
7.9
–
2.2
–
129
al.
[119]
compensated for EE of LFE, LCE: aerobic 60–65% LF:
–
8.6
b
LFE, LCE > LF, kcal/d
exercise
˙
VO
2max
45 min 3 d/wk LFE, LCE: 11.3 LC
LF, LFE: 60% CHO, 15% fat LF, LC: 8.9
LC, LCE: 25% CHO, 50%
fat
Gornall and 812 kcal/day D: no exercise 20 F 28.8 4
–
6.6
–
11.2
–
2.9
–
8.8
Villani
[120]
DR: resistance 55 min 3 d/wk
Doi et al.
[121]
C:
–
17% of EI Light resistance 25 min 7 d/ 17 M 25.9 12 C, S:
–
5.5
–
14.2 C:
–
2.1 S: +8.1
S:
–
17% of EI + PRO wk S: NS C: NS
Demling and D: 80% of TEE D: no exercise 38 M 27% BF 12
–
2.6 D:
–
10.4
a
D: +0.6
a
DeSanti
[49]
DRC: 80% of TEE + casein DRC: resistance 4 d/wk DRC:
–
39.5
b
DRC:
DRW: 80% of TEE + whey DRW: resistance 4 d/wk DRW:
–
22.5
b
+5.1
b
DRW:
+2.6
b
Rice et
–
1000 kcal/d, fat <30% D: no exercise 29 M 32.7 16
–
12.0
–
27.4 D:
–
7.0
a
al.
[122]
DA: 50–85% HR
max
19–60 DA: NS
b
min 5 d/wk DR: NS
b
DR: resistance 30 min 3 d/wk
Janssen et
–
1000 kcal/d, fat <30% D: no exercise 38 F 33.6 16
–
11.3
–
20.9 D:
–
4.8
al.
[123]
DA: aerobic 5 d/wk DA, DR:
DR: resistance 3 d/wk NS
Geliebter et 70% of RMR D: no exercise 40 F, 25 M 41.1% BF 8
–
9.2
–
16.9 D:
–
4.7
a
–
6.9
al.
[124]
DA: cycling 30 min 3 d/wk DA:
–
4.0
a
DR: resistance 60 min 3 d/wk DR:
–
1.9
b
Bryner et 800 kcal/d liquid formula, D: walking, biking or stair 17 F, 3M 35.4 12 D:
–
19.3
a
–
31.8 D:
–
8.0 D:
–
13.4
a
al.
[125]
40% protein, 49% CHO climbing 1h 4 d/wk DR:
–
14.7
b
DR: NS DR: +3.6
b
DR: resistance 3 d/wk
Continued next pag
e
The Role of Diet and Exercise During Weight Loss 253
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
Table III. Contd
Study Dietary restriction Exercise Subjects BMI Duration ∆ Bodyweight ∆ Fat mass ∆ FFM ∆ RMR
(kg/m
2
) (wk) (%) (%) (%) (%)
Marks et C: no dietary restriction D: no exercise 44 F 29.4 20 C: 2.0
a
C: +2.2
a
NS
al.
[126]
D, DA, DR, DAR: ~1237 DA: cycling D, DA, DR, D, DA, DR,
kcal/d DR: resistance DAR: 5.2
b
DAR:
–
13.3
b
DAR: both, 30 min 3 d/wk
Wadden et 900–925 kcal/d (+ formula) D: no exercise 128 F 36.4 48
–
15.7
–
28.2
–
5.2
–
2.6
al.
[127]
Wk 18–19: + normal foods DA: aerobic (stepping)
Wk 20: 1250 kcal/d DR: resistance
Wk 22–48: 1500 kcal/d DAR: both, 20–40 min 3 d/wk
Kraemer et D, DA, DAR: ~1200 kcal/d C: no exercise 31 F 28.6 12
–
8.9 Approx.
–
23 NS NS
al.
[128]
C: no dietary restriction D: no exercise
DA: aerobic 3 d/wk
DAR: aerobic + resistance
30–50 min 3 d/wk
Svendsen et C: no dietary restriction C: no exercise 118 F 29.7 12 C: NS C: NS C: NS
b
C: NS
a
al.
[129]
D and DE: formula 1000 D: no exercise D, DE:
–
12.6 D:
–
24.3
b
D:
–
2.6
a
DE: +11.5
b
kcal/d DE: aerobic + resistance DE:
–
30.1
a
DE: NS
b
D: NS
1–1.5h 3 d/wk
Schlundt et LF: ad lib, high CHO Exercise 5 d/wk 49 M + F 31.8 10–20 LF:
–
5.3
a
LF:
–
7.8
a
–
2.5
–
5.5
al.
[53]
Lkcal: low-fat, low-calorie Lkcal:
–
9.0
b
Lkcal:
–
17.0
b
a Significantly different from b and c at p < 0.05.
b Significantly different from a and c at p < 0.05.
c Significantly different from a and b at p < 0.05.
ad lib = ad libitum; approx. = approximately; BF = body fat; BFM = bone-free mass; BMI = body mass index; C = control group; CHO = carbohydrate; D = diet group; DA = diet and
aerobic exercise group; DAR = group following diet in combination with aerobic and resistance exercise; DE = diet and exercise group; DE1 = diet and exercise group one; DE2 =
diet and exercise group two; DR = diet and resistance exercise group; DRC = diet and resistance exercise group receiving casein supplement; DRW = diet and resistance exercise
group receiving whey supplement; DW = diet and walking exercise group; E = exercise group; EE = energy expenditure; EI = energy intake; F = females; FFM = fat-free mass;
HR
max
= maximum heart rate; HRR = heart rate reserve; LC = low-carbohydrate diet group; LCE = low-carbohydrate diet and exercise group; LF = low-fat diet group; LFE = low-fat
diet and exercise group; Lkcal = low-calorie diet group; M = males; NS = not statistically significant (p > 0.05); PRO = protein; RMR = resting metabolic rate; S = diet group
receiving protein supplement; SMR = sleeping metabolic rate; TEE = total energy expenditure;
˙
VO
2max
= maximal oxygen consumption; ∆ = change.
254 Stiegler & Cunliffe
FFM and sleeping metabolic rate were similar In summary, weight loss, and specifically fat
across groups.
[111]
loss, may be promoted by aerobic exercise alone and
during decreased energy intake, with a potential
In contrast to the above-mentioned outcomes,
attenuation of the depletion of FFM being of major
other investigators have been unable to confirm an
benefit. However, engagement in a considerable
increased fat loss induced by exercise training. In 91
amount of physical activity of at least moderate
obese women, brisk walking on its own, or as a diet
intensity is recommended, when exercise is per-
(1200–1500 kcal/day) plus exercise treatment
formed as a strategy to lessen body fat. The addition
showed no major impact on body mass and fat loss
of aerobic exercise during the reducing diet proved
when compared with a diet-only and a control
to be effective in preserving FFM in some studies.
group.
[18]
These findings were confirmed in a recent
Changes in RMR did not necessarily appear to be
investigation by van Aggel-Leijssen et al.
[16]
follow-
attributable to changes in lean tissue mass.
ing a similar protocol in 40 obese men.
Some recent studies used an experimental ap-
3.2 Dietary Energy Restriction and
proach to delineate the relationship between exer-
Resistance Exercise
cise intensity and duration on bodyweight modifica-
tion during caloric restriction. Brill et al.
[17]
failed to
Recent findings have revealed a new perspective
show a positive effect of daily walking for 30 or 60
on physical activity as part of obesity intervention.
minutes with regard to alterations in body composi-
Resistance training shows promise as a means of
tion over a diet-only intervention in 56 overweight
losing bodyweight, while increasing or maintaining
women. However, the results of Okura et al.
[118]
muscle mass. With respect to lean body mass as a
oppose these findings. Daily walking for 30 minutes
major factor influencing RMR,
[106]
it is important to
was found to be associated with a greater decline in
look closely at the impact of strength training on a
fat mass (
–
6.6kg) over diet modification alone
successful pattern of weight reduction. A recent
(
–
5.0kg). A third group performed aerobic dance.
study investigating the effect of resistance exercise
This approach was superior to walking, due to a
on weight loss when added to a very-low calorie diet
greater loss of fat mass (
–
8.0kg) and the preserva-
(812 kcal/day) failed to indicate a suppressed de-
tion of fat- and bone-free mass.
cline in FFM and RMR after 4 weeks of interven-
tion.
[120]
It is likely that 40g of protein per day,
To assess both the effects of macronutrient com-
provided during severe energy restriction, was not
position and aerobic exercise on body composition,
sufficient to limit losses of skeletal muscle mass.
23 obese women were randomly assigned to an
Dietary protein is necessary to synthesise skeletal
energy restrictive diet either low in fat or CHO and
muscle and an increased intake may enhance nitro-
aerobic exercise or no exercise intervention in a 2 ×
gen retention and muscle hypertrophy. Therefore
2 factorial design. After 12 weeks, the decrease in
protein supplements are frequently used by strength
bodyweight was higher in the low-CHO group and
athletes to allow for accumulation and maintenance
the loss in fat mass tended to be enhanced following
of lean tissue.
[130]
exercise training despite food intake being adjusted
to the energy costs of the exercise sessions. No Doi et al.
[131]
investigated whether the ingestion
protective effect of exercise on RMR was found and of a protein supplement could prevent losses of FFM
RMR values decreased (
–
129 kcal/day) in all groups and, as a result, reductions in RMR in 17 overweight
to values lower than predicted from reductions in men participating in a 12-week weight-reduction
FFM.
[119]
programme that consisted of both mild energy re-
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Diet and Exercise During Weight Loss 255
striction (
–
17% of energy intake) and resistance of RMR) when compared with aerobic exercise in
exercise. The findings showed an increase in RMR
moderately obese subjects. These findings are in
expressed per kilogram bodyweight following the
agreement with those in a study of 20 subjects by
supplement intake, whereas the increase was not
Bryner et al.
[125]
that incorporated progressive inten-
significant (p = 0.07) when RMR was adjusted for
sive resistance training of high-volume and aerobic
changes in FFM. Recent research has also demon-
exercise of various modalities in conjunction with a
strated that the type of protein can markedly affect
very low-calorie diet. However, Geliebter et al.
[124]
body compositional changes induced by a hypo-
were unable to show a blunting in the decline in
caloric diet (80% of total daily energy expenditure)
RMR associated with a significant preservation of
plus resistance training. When a casein protein hy-
lean tissue following resistance exercise. Bryner et
drolysate was used, gains in lean mass were doubled
al.
[125]
showed impressive results with a decrease in
(+4.1 vs +2.0kg) with a greater reduction in fat mass
lean body mass (
–
4.1kg) and RMR (
–
211 kcal/day)
(
–
7.0 vs
–
4.2kg) compared with a whey protein
in the group performing aerobic exercise, which was
hydrolysate.
[49]
Weight loss was similar across
not found when strength training was prescribed.
groups (
–
2.5kg) and in the diet control group, this
These outcomes could be explained by the high
was only from body fat (
–
2.5kg) with no change in
protein content of the diet of approximately 80 g/
FFM.
day. Given the above-mentioned studies, convincing
data in support of either aerobic or resistance train-
3.3 Dietary Energy Restriction Combined
ing for weight loss and maintenance of muscle mass
with Aerobic and Resistance Exercise
are rare, but there was a tendency for a preservation
of lean tissue and RMR following strength exercise.
In the light of potential positive impacts of both
Several studies have examined whether a combi-
aerobic and strength programmes on body composi-
nation of the two exercise modalities may contribute
tion, some recent data provide insight into whether
to a more successful pattern of weight loss. Marks et
the effects are comparable. Rice et al.
[122]
randomly
al.
[126]
investigated the effect of a hypocaloric diet
assigned 29 obese men to one of three 16-week
alone and together with resistance training, cycling
treatments, which consisted of a hypocaloric diet
or a combination of resistance training and cycling
alone or in combination with resistance exercise or
in a 20-week study in 44 overweight, inactive wo-
aerobic exercise, respectively. Whereas the reduc-
men. Mean reductions in fat mass and bodyweight
tions in weight (
–
12.4kg) and total adipose tissue
were comparable in the exercise groups to those
(
–
9.7kg) were not significantly different between
achieved by the diet controls and minimal changes
the three groups, skeletal muscle was only preserved
were observed in the non-diet control group. No
after the exercise training, independent of the mode,
major differences in FFM were detected from base-
compared with the diet-only group (
–
2.5kg). In wo-
line and between the groups. Nevertheless, only the
men following the same protocol, the effect of exer-
combination of diet, resistance training and aerobic
cise on maintaining lean body mass was less
exercise significantly lowered percentage body fat
clear.
[123]
In this study, the recorded changes in body
(
–
4.6%). Following a similar study design, Wadden
composition were comparable between the two ex-
et al.
[127]
failed to illustrate any positive impact of
ercise groups. In contrast, earlier work by Geliebter
exercise (strength training alone, aerobic training
et al.
[124]
demonstrated that only strength training
alone and as a combination) on body composition in
significantly attenuated the loss of lean tissue ac-
120 obese women when added to dietary restriction.
companying an energy-reduced formula diet (70%
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
256 Stiegler & Cunliffe
For participants in the aerobic condition, the reduc- than did subjects consuming a low-fat, ad libitum
tion in RMR was significantly blunted in week 24,
CHO diet. However, the authors pointed out that
but not at the end of the 48-week study period when
these results were related to a more reduced energy
compared with the strength condition. These results
intake in the low-calorie group.
[53]
are in accordance with those of Kraemer et al.,
[128]
From the above-mentioned studies it becomes
who examined the effects of diet alone and diet
clear that a combination of modest caloric restriction
combined with endurance exercise or endurance
and physical training of different modes is prefera-
plus heavy-resistance exercise in 31 overweight wo-
ble over dietary modification alone to induce fa-
men. After 12 weeks, similar reductions in body
vourable changes in body composition accompany-
mass (between
–
6.2 and
–
7.0kg) were demonstrated
ing weight loss. However, the reduction in
across the three treatment conditions, but without
bodyweight and the changes in body composition
changes in FFM and RMR.
induced by exercise training seem in many cases to
However, in another 12-week study in 118 over-
be less than expected, and several studies failed to
weight postmenopausal women, the addition of
report significant benefits of exercise. The lack of an
combined aerobic and resistance exercise to an ener-
impact of exercise training on body composition
gy-restrictive diet (1000 kcal/day) led to a greater
may be the prescribed amount of exercise not being
reduction in body fat (
–
9.6 vs
–
7.8kg) and a preser-
sufficient with respect to the frequency and duration
vation of FFM in the exercising group compared
of the exercise bout and from the investigated stud-
with the diet-alone treatment. Furthermore, an in-
ies, no clear line of evidence seems to emerge in
crease in RMR per kilogram bodyweight reached
terms of the minimum amount of exercise required
statistical significance in the diet-plus-exercise
for successful outcomes. In addition, to date no
group when compared with the control group.
[129]
intervention studies in overweight subjects have
However, this would not be surprising given that the
been done providing insight into the long-term ef-
decrease in bodyweight consisted of fat, not lean
fects of exercise programmes. Nevertheless, several
mass. From these studies in overweight and obese
lines of evidence suggest that resistance exercise
populations, it seems obvious that exercise training
may be preferable in terms of preserving FFM over
can reduce the loss in FFM during energy restric-
aerobic training and this type of exercise should be
tion. Another study showed that an individualised,
explored, especially in patients that did not succeed
more concentrated exercise protocol offers better
with aerobic exercise programmes. In addition, al-
overall results in terms of physical fitness and moti-
though training at higher intensities seemed to pro-
vation to subsequent physical activity (despite simi-
duce better results, long-term compliance needs to
lar results in terms of weight reduction).
[132]
be evaluated and constant monitoring of the exercis-
ing patient has to be ensured. With respect to the
Only one study has addressed the question as to
energy-restricted diet, there seems to be evidence
whether the effectiveness of a physical activity pro-
for protein intake as a limiting factor for mainte-
gramme with respect to changes in body composi-
nance and/or augmentation of FFM. Furthermore,
tion depends on the type of the prescribed, energy-
although only well controlled studies have been
restricted diet. In a 16- to 20-week programme with
included in this review, compensatory behaviour,
at least five exercise sessions per week, 60 subjects
such as reductions in non-exercise physical activity
consuming a low-calorie diet lost significantly more
and increases in food intake cannot be completely
weight, with a greater decline in body fat (
–
6.6 vs
ruled out in free-living subjects. A discrepancy be-
–
2.7kg) [and similar reductions in FFM and RMR],
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
The Role of Diet and Exercise During Weight Loss 257
tween self-reported and actual energy intake and Therefore, the juxtaposition of the energy restriction
and exercise treatment adds a layer of considerable
self-reported and actual physical activity in obese
complexity to measuring and understanding the re-
subjects is well established,
[133]
with the degree of
sponses recorded in RMR. Furthermore, the time of
under-/over-reporting being related to bodyweight.
measuring of RMR relative to the termination of the
As several studies required the subjects to keep daily
last exercise bout is important, because long-term
diet records for the duration of the study, while
excess post-exercise oxygen consumption events
regular dietary advice was provided,
[121,123,128,134]
in-
may last for up to 36–48 hours.
[106,139,140]
Hence,
accuracies of dietary histories may also have biased
there is no clear evidence for the alteration of RMR
some study outcomes. Moreover, although all the
by exercise. However, dietary restriction results in
assessed studies had recruited subjects with at least a
loss of lean tissue; the findings of several studies
minor degree of over-fatness, body fat of partici-
have demonstrated that the reduction in RMR can be
pants differed between studies. This appears to be
blunted via physical activity, specifically resistance
important, as a role of the body fat content for
exercise.
[33,120,127]
changes in body composition induced by nutrition
Apart from changes in body composition, exer-
and exercise has been reported. Forbes
[135]
provided
cise has been shown to increase insulin sensitivi-
evidence that lean body mass was a function of body
ty,
[122,141-143]
cardiovascular fitness
[128]
and fat oxida-
fat. Thus, the loss of FFM per unit of weight loss
tion.
[16,144,145]
In addition, abdominal fat can be re-
will be higher in those subjects with a lower initial
duced independent of significant changes in body
relative body fat content. These differences could
composition.
[146]
Moreover, increases in lifestyle ac-
confound the results when comparing studies with
tivity may also be promoted
[147]
and exercise is
participants with different body fatness.
associated with improvements in mood.
[124]
There-
Another purpose of this review was to compare
fore (for a successful study outcome), exercise train-
intervention studies with respect to changes in
ing appears to be a beneficial if not substantial
RMR. However, only a few studies have examined
addition to diet modification.
RMR and these have produced equivocal findings.
Despite the well known association between FFM
4. Conclusion
and RMR, an offset in the decline in FFM following
weight loss appears not to necessarily parallel a
A rapidly growing body of evidence supports the
reduction in RMR and vice versa. A possible expla-
opinion that dietary recommendations beyond the
nation is that length and intensity of the exercise
generally advised reduction in fat intake should be
programme were not sufficient to cause a continued
considered for weight loss and long-term weight
disruption of metabolism or a growth of lean tissue.
sustenance. Several studies lend credence to the idea
Metabolically active compounds include FFM and
that diets high in fibre and with a low glycaemic
internal organs. Small changes in FFM my not be
index are successful at producing and, more impor-
sufficient to impact RMR. On the other hand, exer-
tantly, maintaining weight loss, which is due to a
cise training may influence RMR independent of
reduction in energy intake and hormonal responses
changes in body composition.
[136-138]
Increases in
associated with a blunted rise in blood glucose.
protein turnover associated with resistance training
Furthermore, potential benefits of diets high in pro-
regimens may contribute to elevations of metabolic
tein (between 25% and 30% of total energy intake)
rate.
[130]
However, the negative energy balance in-
are emerging, although scientific data with respect
duced by dietary limitation may offset this effect.
to enhanced losses of fat mass and sustained muscle
2006 Adis Data Information BV. All rights reserved. Sports Med 2006; 36 (3)
258 Stiegler & Cunliffe
tissue are still inconclusive. Long-term interven- Acknowledgements
tions are required to clarify these issues.
Support for the preparation of this manuscript was provid-
Evaluation of both aerobic and strength training
ed by the School of Biosciences, University of Westminster.
The authors have no conflicts of interest that are directly
for treatment of overweight indicates that higher
relevant to the content of this review.
intensities may bring about more favourable
changes in body composition. However, this may be
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Human and Health Sciences, School of Biosciences, Univer-
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specific vs individualized exercise training protocols on aero-
bic anaerobic and strength performance in severely obese E-mail: stieglp@wmin.ac.uk
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