El entrenamiento a corto plazo HIIT y Fat max aumenta la aptitud aeróbica y metabólica en hombres con obesidad de clase II y III

Original Article
Obesity
CLINICAL TRIALS AND INVESTIGATIONS
Short-Term HIIT and Fatmax Training Increase Aerobic and
Metabolic Fitness in Men with Class II and III Obesity
Stefano Lanzi1,2, Franco Codecasa3, Mauro Cornacchia3, Sabrina Maestrini4, Paolo Capodaglio5, Amelia Brunani6,
Paolo Fanari3, Alberto Salvadori3, and Davide Malatesta1,2
Objective: To compare the effects of two different 2-week-long training modalities [continuous at the
intensity eliciting the maximal fat oxidation (Fatmax) versus high-intensity interval training (HIIT)] in men
with class II and III obesity.
Methods: Nineteen men with obesity (BMI 35 kg.m22) were assigned to Fatmax group (GFatmax) or to
HIIT group (GHIIT). Both groups performed eight cycling sessions matched for mechanical work. Aerobic
fitness and fat oxidation rates (FORs) during exercise were assessed prior and following the training.
Blood samples were drawn to determine hormones and plasma metabolites levels. Insulin resistance was
assessed by the homeostasis model assessment of insulin resistance (HOMA2-IR).
Results: Aerobic fitness and FORs during exercise were significantly increased in both groups after training (P 0.001). HOMA2-IR was significantly reduced only for GFatmax (P 0.001). Resting non-esterified
fatty acids (NEFA) and insulin decreased significantly only in GFatmax (P 0.002).
Conclusions: Two weeks of HIIT and Fatmax training are effective for the improvement of aerobic fitness
and FORs during exercise in these classes of obesity. The decreased levels of resting NEFA only in GFatmax may be involved in the decreased insulin resistance only in this group.
Obesity (2015) 23, 1987–1994. doi:10.1002/oby.21206
Introduction
Obesity is commonly associated with insulin resistance, which
seems to be linked with an impaired ability to oxidize lipids, particularly in class III obesity [body mass index (BMI): >40] (1). Exercise training is an effective strategy to improve insulin sensitivity
and to reduce the risk of type 2 diabetes (1). It has been suggested
that 8 (2) or 10 weeks (3) of training at the exercise intensity (Fatmax) eliciting maximal fat oxidation (MFO) may increase fat oxidation rates (FORs) during exercise and also muscle oxidative capacity
in men with overweight (BMI: 25-29.9) and class I obesity (BMI:
30-34.9). Recently, it has been shown that a shorter 4-week program
of Fatmax training may increase FORs during exercise and insulin
sensitivity in men with class I obesity (4). The effects of a Fatmax
training program of a shorter duration have never been investigated.
High-intensity interval training (HIIT) was reported to rapidly
induce adaptations that are linked to improved aerobic fitness and
health-related outcomes in sedentary individuals and individuals
with overweight/obesity (5-7). It was demonstrated that only 2 (8)
or 4 (9) weeks of Wingate-based HIIT was a sufficient stimulus to
_ 2max ) in men with overincrease the maximal oxygen uptake (VO
weight and class I obesity (8) and in women with overweight or
class I and II obesity (BMI: 35-39.9) (9). However, less evidence
has been found with regard to Wingate-based HIIT on increased
insulin sensitivity in individuals with obesity (10). Whyte et al. (8)
showed increased insulin sensitivity after 24 h, but not 72 h, after a
2-week Wingate-based HIIT. Skleryk et al. (11) recently showed no
significant metabolic or skeletal muscle adaptations after 2 weeks of
reduced-volume HIIT (10-s all-out sprints) in men with overweight
or class I and II obesity. To date, it seems that only an adapted
form of HIIT [10 3 60-s at 90% of the maximal heart rate (HRmax)
interspersed with 60-s recovery] for 2 weeks may simultaneously
increase the oxidative capacity of the muscle and insulin sensitivity in
sedentary individuals with overweight (12). Moreover, adapted HIIT
1
Institute of Sport Sciences University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland. Correspondence: Stefano Lanzi lanziste@
bluewin.ch 2 Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland 3 Pulmonary Rehabilitation
Department, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy 4 Molecular Biology Laboratory, San Giuseppe Hospital,
Istituto Auxologico Italiano Piancavallo, Verbania, Italy 5 Orthopaedic Rehabilitation Unit and Clinical Lab for Gait and Posture Analysis, San Giuseppe
Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy 6 Medicine Rehabilitation Department, San Giuseppe Hospital, Istituto Auxologico
Italiano Piancavallo, Verbania, Italy.
Disclosure: The authors declared no conflict of interest.
Author contributions: S.L., F.C., M.C., P.C., A.B., P.F., A.S., and D. M. designed the study. S.L., F.C., M.C., S.M., and P. F. performed the data collection. S.L., S.M.,
P.C., A.B., P.F., A.S., and D.M. contributed to the data analysis and interpretation. S.L. and D.M. wrote the manuscript, and all other authors were involved in the editing
process.
Clinical trial registration: ClinicalTrials.gov identifer NCT02254200.
Received: 11 December 2014; Accepted: 5 June 2015; Published online 3 September 2015. doi:10.1002/oby.21206
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Obesity | VOLUME 23 | NUMBER 10 | OCTOBER 2015
1987
Obesity
Exercise Training in Severe Obesity Lanzi et al.
_ 2peak
also leads to a greater early magnitude of improvement in VO
compared with training at a moderate intensity in this population
(13). In addition, the highest level of catecholamine secretion during
(14) and after (15) high-intensity exercise might also be related, in
part, to increased FORs during the post-exercise recovery period (16);
this, in turn, may lead to increased insulin sensitivity (1).
To our knowledge, no studies have compared the adapted HIIT with
a Fatmax training program that are both matched with respect to
mechanical work in men with class II and III obesity. This comparison would help determine the most appropriate short-term training
stimulus to improve aerobic fitness, FORs during exercise and insulin
resistance in relation to the adaptations of extra-muscular factors (hormones and plasma metabolites) that regulate fat metabolism. It has
been suggested that exercise training is an effective strategy recommended in the multidisciplinary medical and surgical management of
these classes of obesity (17). Exercise training can improve the lower
aerobic fitness, fat oxidation during exercise [metabolic fitness (18)]
and insulin resistance, that are characteristic of this population (1,17).
This study aimed to compare the effects of 2-week-long training
modalities (Fatmax vs. adapted HIIT), matched with respect to
mechanical work, on aerobic and metabolic fitness in men with class
II and III obesity. It was hypothesized that aerobic fitness, FORs
during exercise and insulin resistance would be improved to a
greater extent after adapted HIIT compared to Fatmax training.
Methods
Participants
Twenty men with obesity (BMI: 35; class II: n 5 7, class III:
n 5 13) were recruited as inpatients from the Istituto Auxologico Italiano, where they followed a 5-week lifestyle education program. This
program included diet (balanced diet corresponding to the basal metabolic rate which was prescribed by a nutritionist and applied during
the whole hospitalization), 30 min per day of recreational activities at
a low intensity (walking), and a psychological follow-up. In addition
to this program, the subjects performed a 2-week-long training program
that began approximately 15 days after their initial hospitalization.
Subjects with hypertension, impaired fasting glucose (>6.1 mmol.L21)
(19), type 2 diabetes, and abnormal electrocardiogram readings were
excluded. After pre-training test, subjects were assigned to two training groups [Fatmax group (GFatmax; n 5 10, class II: n 5 4, class III:
n 5 6); adapted HIIT group (GHIIT; n 5 10, class II: n 5 3, class III:
_ 2peak
n 5 7)] matched for age, BMI, both absolute and relative VO
values, and diet. For personal reasons, one subject dropped out of
the GHIIT; however, the characteristics of the two training groups
remained similar. The balanced diet and the macronutrient proportions
were similar between groups (Table 1). The study was approved by
the Ethics Review Committee of the institute. All subjects provided
written and voluntary informed consent before participation.
Maximal ramp incremental test.
The peak power output (PPOrwas determined by a maximal ramp incremental test to exhaustion on a cycle-ergometer (Ebike Basic BPlus, USA), as previously
described (20).
amp)
Pre-training test. The experimental trial was performed a minimum of 2 days after the maximal ramp incremental test and was
performed in the morning after 12-h overnight fast. The subjects
remained seated for 15 min on the cycle-ergometer and were connected to the metabolic system (rest). Thereafter, subjects performed
a maximal incremental test (Incr) to determine the whole-body fat
oxidation kinetics, Fatmax and CHO oxidation rates in the first phase
(IncrP1) and the maximal parameters in the second phase (IncrP2)
of the test. After a standardized 10-min warm-up at 20% PPOramp,
the PO increased by 10% PPOramp every 5 min until 70% PPOramp
was reached or until the respiratory exchange ratio (RER) reached
1.0 [IncrP1; adapted from Lanzi et al. (20)]. The HR and respiratory
values were averaged over the last minute of each stage. At this
point, the PO was increased by 15 W every minute until exhaustion
_ 2peak , PPOIncr, and HRmax (IncrP2). Blood samples
to determine VO
were drawn at rest and during the last 3 min of the last step of
IncrP1 to determine serum insulin and non-esterified fatty acids
(NEFA), plasma glycerol, epinephrine (E), norepinephrine (NE), glucose and lactate ([La-]) concentrations. According to Bordenave
et al. (21), we used long duration stages and, from our previous data
(20), we determined that 5-min duration was enough to reach a
steady-state in this population.
Exercise training.
The training intervention consisted of eight
cycling sessions spread over 14 days. For the GHIIT, each session
consisted of 10x60-s cycling intervals at workload eliciting 90%
HRmax interspersed with 60-s recovery at 50 W (22). Each session
included a 5-min warm-up and cool-down at 50 W, for a total of 30
min. To match both training groups with respect to mechanical work
during the exercise training session, for GFatmax each session consisted of 40-50 min of continuous exercise with an intensity that
corresponded to the individual Fatmax. The exercise sessions were
supervised and the HR of the subjects was continuously monitored
throughout the exercise session (Polar RS800, Finland). Subjects
were asked to rate their perceived exertion (RPE) during exercise
(GFatmax: each 10 min; GHIIT: at the end of each interval) using
Borg’s scale (0-10) and the average of the session was calculated.
The perceived enjoyment of the training sessions was assessed at
the end of each training session by an arbitrary scale that ranged
from 0 (not enjoyable at all) to 10 (very enjoyable) (22).
Post-training test. After the last training session (GFatmax:
3.9 6 0.4 days; GHIIT: 3.2 6 0.4 days, non-significant) subjects performed Incr, which was set at the same absolute workload as the pretraining test. Blood samples were collected at the same absolute workload as during the pre-training test (at rest and at the end of IncrP1Pre).
Data analysis and calculations
Experimental design
The 5-week lifestyle education program was planned as follow: (i)
during the first week subjects had clinical routine analysis; (ii) during
the second week subjects underwent the pre-training tests; (iii) during
the third and fourth week subjects performed the training program;
(iv) during the fifth week subjects underwent the post-training tests.
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Obesity | VOLUME 23 | NUMBER 10 | OCTOBER 2015
_ 2 , carbon dioxide production
VO
_
_
(VCO2 ) and ventilation (V E ) were measured continuously using a
breath-by-breath online system (Vmax 229, Sensor Medics, USA).
_ 2peak was defined as the highest 10-s mean value recorded
VO
before the subject’s volitional termination of Incr. PPOIncr and HRmax
were defined as the highest peak values reached during the test.
Gas exchange, PPO, and HR.
www.obesityjournal.org
Original Article
Obesity
CLINICAL TRIALS AND INVESTIGATIONS
TABLE 1 Effect of training on anthropometric measurements, aerobic fitness and whole-body fat oxidation kinetics in the
Fatmax training (GFatmax) and adapted high-intensity interval training (HIIT: GHIIT) groups
GFatmax (n 5 10)
PRE
Age, years
Height, m
Diet, kcal.day21
Dietary CHO, %
Dietary fat, %
Dietary protein, %
Body mass, kg
BMI, kg.m22
Fasting glucose, mmol.L21
Fasting insulin, mU.L21
HOMA2-IR, mmol.mU.L22
Fasting NEFA, mmol.L21
Exercise parameters
_ 2peak, mL.min21
VO
_ 2peak, mL.min21.kg21
VO
HRmax, bpm
PPOIncr, W
Whole-body fat oxidation
Resting FORs, g.min21
Resting FORs, mg.kg21.min21
MFO, g.min21
MFO, mg.kg21.min21
Fatmax, %PPOIncrPre
_ 2maxPre
Fatmax, %VO
Fatmax, %HR
Dilatation
Symmetry
Translation
GHIIT (n 5 9)
Significance
POST
PRE
POST
Group
Time
G3T
38.1 6 2.3
1.74 6 0.02
1970 6 56
55.8 6 0.3
23.7 6 0.5
20.5 6 0.3
124.1 6 4.5
40.9 6 1.1
5.3 6 0.1
28.7 6 3.0
3.6 6 0.4
1125.0 6 84.1
120.4 6 4.6
39.7 6 1.1
5.2 6 0.1
22.1 6 2.6§
2.8 6 0.3§
820.0 6 62.9§
34.9 6 3.4
1.76 6 0.03
2056 6 60
56.1 6 0.5
23.6 6 0.4
20.3 6 0.2
133.0 6 4.8
43.1 6 1.0
5.4 6 0.2
22.4 6 2.9
2.9 6 0.4
988.9 6 38.9
129.0 6 4.7
41.8 6 1.0
5.2 6 0.2
21.9 6 3.5
2.8 6 0.4
1028.9 6 101.1
NS
NS
NS
NS
NS
NS
0.001
0.001
NS
0.02
0.02
0.054
NS
NS
NS
0.04
0.04
0.02
2857 6 151
23.1 6 1.2
168 6 5
161 6 10
2983 6 166
24.9 6 1.2
172 6 5
179 6 12
3179 6 104
24.1 6 1.2
180 6 5
183 6 7
3439 6 119
26.9 6 1.2
179 6 4
213 6 9
NS
NS
NS
NS
0.001
0.001
NS
0.001
NS
NS
NS
NS
0.12 6 0.02
0.92 6 0.12
0.43 6 0.04
3.5 6 0.3
38.8 6 3.2
48.8 6 2.9
66.6 6 2.2
0.1 6 0.1
0.8 6 0.1
0.1 6 0.1
0.12 6 0.02
1.01 6 0.14
0.46 6 0.03
3.9 6 0.2
47.9 6 3.5
54.7 6 2.8
67.8 6 1.8
0.4 6 0.1
1.0 6 0.1
0.0 6 0.1
0.15 6 0.01
1.12 6 0.05
0.45 6 0.01
3.5 6 0.2
44.7 6 4.3
52.3 6 2.7
68.6 6 1.4
0.4 6 0.2
0.9 6 0.1
0.0 6 0.1
0.15 6 0.01
1.20 6 0.09
0.53 6 0.02
4.1 6 0.2
52.2 6 2.3
57.7 6 2.0
68.7 6 1.2
0.6 6 0.1
0.9 6 0.0
20.2 6 0.1
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
0.005
0.001
0.002
0.01
NS
0.004
NS
0.03
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
Values are the means 6 SE.
BMI: body mass index; CHO: carbohydrates; Fatmax: exercise training intensity at which the maximal fat oxidation rate (MFO) occurs; FORs: fat oxidation rates; HOMA2IR: homeostasis model assessment of insulin resistance; HRmax: maximal heart rate; NEFA: non-esterified fatty acids; PPOIncr: peak power output reached during the max_ 2peak : peak oxygen uptake.
imal incremental test (Incr); VO
§
P 0.05 for significant differences between the pre- and post-training conditions for GFatmax; NS: not significant; G 3 T: group 3 time interaction effect for two-way
repeated-measures ANOVA.
Indirect calorimetry. FORs and CHO oxidation rates were calculated with stoichiometric equations (23). The results of IncrP1
were used to calculate FORs over a wide range of exercise intensities. To model whole-body fat oxidation kinetics [% of the pretraining PPOIncr (PPOIncrPre)] and to determine Fatmax and MFO, the
SIN model (24), which includes three independent variables that
represent the main quantitative characteristics of the curve (dilatation, symmetry, translation), was used as previously described (20).
CHO oxidation rates (%PPOIncrPre) were calculated using a polynomial fitting curve.
Blood samples. The blood samples were collected through an
indwelling cannula inserted into the antecubital vein and plasma
hormones and metabolites concentrations were determined as
previously described (20). Insulin resistance was assessed by the
www.obesityjournal.org
updated homeostasis model assessment of insulin resistance
(HOMA2-IR) (25).
Statistical analysis
A three-way repeated-measures ANOVA (time 3 group 3 exercise
intensity) was performed to compare the RER, HR, V_ E , FORs and
CHO oxidation rates at each relative exercise intensity (%PPOIncrPre)
[time 3 group 3 exercise intensity (n 5 15; 10-80% PPOIncrPre)]
and to compare the plasma concentrations of metabolites and hormones [time 3 group 3 exercise intensity (n 5 2; rest-end of
IncrP1Pre)]. A two-way repeated-measures ANOVA (time 3 group)
was used to identify the differences in the average from all 15
stages for FORs, RER and CHO oxidation rates, in the variables of
the SIN model, Fatmax, MFO, peak parameters, HOMA2-IR and
anthropometric measures. The significance was determined with a ttest, with Bonferroni adjustment where appropriate, when ANOVA
Obesity | VOLUME 23 | NUMBER 10 | OCTOBER 2015
1989
Obesity
Exercise Training in Severe Obesity Lanzi et al.
TABLE 2 Descriptive characteristics of training programs in
the Fatmax training (GFatmax) and adapted high-intensity
interval training (HIIT: GHIIT) groups
Variable
GFatmax
(n 5 10)
GHIIT
(n 5 9)
90
Prescribed exercise intensity 66.6 6 2.2
during effort, %HRmax
69.7 6 1.4 89.5 6 1.1
Actual exercise intensity
during effort, %HRmax
Frequency, session/week
4
4
Time, min/session
42.0 6 1.3 30.0 6 0.0
Time, min/week
168 6 5
120 6 0
Adherence, %
100.0 6 0.0 98.6 6 1.4
Mechanical work, KJ
1274 6 102 1404 6 53
Perceived enjoyment
8.2 6 0.4
8.9 6 0.2
RPE
3.3 6 0.5
4.9 6 0.3
Significance
0.001
0.001
0.001
NS
NS
NS
0.009
Values are the means 6 SE.
Fatmax: exercise training intensity at which maximal fat oxidation rate occurs;
HRmax: maximal heart rate; RPE: rate of perceived exertion; NS: non-significant.
Adherence to training was calculated as a percentage by dividing the number of
the completed sessions by the total number of sessions.
revealed significant interaction effects. A t-test was also used to
compare the descriptive characteristics of the training programs.
When ANOVA revealed significant interaction effects, ANCOVA,
including pre-training values as co-variate, were assessed. Cohen’s d
values were used as an effect size (ES) index and were calculated to
examine the significance of the training improvements within each
group. Statistical significance was set at P 0.05.
Results
Anthropometric measurements and maximal
exercise parameters
These measurements are shown in Table 1. Before the training,
body mass, HRmax and PPOIncr were not different between groups.
In response to training, the body mass and BMI decreased signifi_ 2peak increased significantly in both
cantly in both groups. The VO
groups, with a large ES (d 5 0.82) for GHIIT and a small ES
(d 5 0.27) for GFatmax. The HRmax showed no significant differences
between groups, whereas the PPOIncr increased significantly in both
groups. For these variables, there was no significant time 3 group
interaction effect.
Characteristics of training
These measurements are shown in Table 2. Participants in GFatmax
exercised for a significantly greater duration but at significantly
lower exercise intensity than participants in GHIIT. The adherence to
the training program, mechanical work and average perceived enjoyment of the training sessions were similar in both groups. The average RPE during the training sessions was significantly higher for
GHIIT compared to GFatmax.
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Obesity | VOLUME 23 | NUMBER 10 | OCTOBER 2015
Gas exchange and whole-body substrate
oxidation (IncrP1)
Before the training, V_ E , RER, CHO oxidation rates, FORs, the wholebody fat oxidation kinetics (SIN variables, MFO and Fatmax) during
exercise, and resting FORs were not different between groups. In
response to training, resting FORs (Table 1) and V_ E during exercise
(data not shown) remained unchanged in both groups. RER during
exercise decreased significantly in both groups (time effect:
P 0.001, Figure 1A) and FORs during exercise increased significantly in both groups (time effect: P 0.001; Figures 1B and C).
CHO oxidation rates during exercise decreased significantly in both
groups (time effect: P 0.001; Figures 1E and F). For these variables,
there was no significant time 3 group 3 exercise intensity interaction
effect. When the average from all 15 stages was performed, FORs during exercise increased, whereas CHO oxidation rates and RER during
exercise decreased significantly in both groups after intervention
(time effect: P 0.001, data not shown). After the intervention,
whole-body fat oxidation kinetics during exercise were characterized
by similar symmetry and by a significantly greater dilatation and
right-shift translation in both groups (Table 1, Figure 1D). The MFO
increased significantly in both groups (Table 1), with a large ES
(d 5 1.49) for GHIIT and a small ES (d 5 0.32) for GFatmax. Fatmax
increased significantly in both groups (Table 1). For these variables,
there was no significant time 3 group interaction effect.
Plasma metabolite and hormonal
concentrations (IncrP1)
Before the training, the concentrations of metabolites and hormones in
the plasma were not different between groups. After the intervention,
the concentrations of plasma NEFA decreased significantly only for
GFatmax (time 3 group interaction effect: P 5 0.01; Figure 2A) due to
decreased resting concentrations of NEFA (225%; Table 1;
P 5 0.002); however, this parameter remained similar for GHIIT. The
co-variate, the pre-training resting plasma NEFA values, was not significantly related to the post-training resting values (P 5 0.25), and
the difference between groups remained significant (P 5 0.05). The
concentrations of plasma glycerol and glucose showed no significant
differences in either group (Figures 2B and C). The concentrations of
plasma lactate (time effect: P 5 0.001; Figure 2D) and plasma E and
NE (time effect: P 0.02; Figures 3A and B) decreased significantly
in both groups. For these variables, there was no significant time 3
group 3 exercise intensity interaction effect. Plasma fasting insulin
levels decreased significantly (224%) at rest only in GFatmax (time 3
group 3 exercise intensity interaction effect: P 5 0.04; Figure 3C,
Table 1). The co-variate, the pre-training resting plasma insulin values, was significantly related to the post-training values (P 0.001);
however, the difference between groups tended to be significant
(P 5 0.09). HOMA2-IR showed a significant time 3 group interaction
effect and decreased significantly only in GFatmax (P 0.001; Table
1). The co-variate, the pre-training HOMA2-IR values, was significantly related to the post-training values (P 0.001); however, the difference between groups tended to be significant (P 5 0.099).
Discussion
This study showed that both 2 weeks of adapted HIIT and Fatmax
training are effective in improving aerobic fitness and FORs during
exercise in men with class II and III obesity. The aerobic fitness and
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Original Article
Obesity
CLINICAL TRIALS AND INVESTIGATIONS
Figure 1 The mean (A) respiratory exchange ratio (RER), whole-body fat oxidation kinetics in absolute [(B) g.min21 and (C) mg.kg21.min21] and (D) relative
[% of maximal fat oxidation (MFO)] values, and carbohydrate (CHO) oxidation rates in absolute [(E) g.min21 and (F) mg.kg21.min21] values in pre- and
post-training conditions expressed as a function of the pre-training peak power output reached during the maximal incremental test (PPOIncrPre) in the Fatmax training (GFatmax) and adapted high-intensity interval training (HIIT: GHIIT) groups. Values are the means 6 SE. *P 0.05 for the significant time effect.
FORs were not improved to a greater extent after adapted HIIT,
which was, however, feasible and beneficial for this population. In
addition, the decreased levels of resting plasma NEFA observed
only after Fatmax training may be a potential mechanism involved in
decreased insulin resistance only in this group.
_ 2peak increased in both groups after 2 weeks of intervention.
VO
Although there was no significant difference between groups, most
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likely related to small sample size (statistical power: 34%), the magni_ 2peak was 8% in GHIIT and 4% in GFatmax.
tude of the increase in VO
Moreover, ES analyses revealed a large ES for GHIIT and a small ES
for GFatmax. Thus, our results suggest that the adapted HIIT had a tendency toward promoting a more marked increase in aerobic fitness
compared to Fatmax training. This improvement may be related to the
_ 2peak is in agreement
exercise intensity (26). This rapid increase in VO
with previous findings that suggested that high-intensity training may
Obesity | VOLUME 23 | NUMBER 10 | OCTOBER 2015
1991
Obesity
Exercise Training in Severe Obesity Lanzi et al.
Figure 2 The mean concentrations of (A) non-esterified fatty acids (NEFA), (B) glycerol, (C) glucose, and (D) lactate at rest and at the end of the first phase
of the pre-training maximal incremental test (IncrP1Pre) in pre- and post-training conditions in the Fatmax training (GFatmax) and adapted high-intensity interval training (HIIT: GHIIT) groups. Values are the means 6 SE. The values at IncrP1Pre correspond to 75% of the peak power output reached during the
pre-training Incr. ‡P 0.05 for the significant time 3 group interaction effect for GFatmax; *P 0.05 for the significant time effect.
_ 2peak compared
be preferable for the induction of early changes in VO
with moderate exercise training (13).
After the intervention, FORs during exercise were higher and
whole-body fat oxidation kinetics were characterized by a greater
dilatation and right-shift translation in both groups. We recently
showed that men with obesity and severe obesity presented a lower
Fatmax and reliance on fat oxidation compared to their lean counterparts (20). These findings demonstrated that only 2 weeks of training may increase Fatmax and FORs, which suggests that fat oxidation may rapidly improve in this population. The increased FORs
may be attributable to a similar increase in mitochondrial enzyme
activities and/or content in response to both training modalities (27).
_ 2peak , we observed a large ES in
However, consistent with the VO
GHIIT and a small ES in GFatmax for the MFO (statistical power:
28%), highlighting the primacy of exercise intensity in the improvement of fat oxidation during exercise in men with class II and III
obesity. This finding is in agreement with recent results that suggested a greater mitochondrial biogenesis following higher compared with a work-matched bout of lower exercise intensity (28).
The training adaptations of fat metabolism may also be related to
extra-muscular factors (29). However, although the catecholamine
response after training presented a significant reduction [probably
because it was assessed at the same absolute exercise intensity
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Obesity | VOLUME 23 | NUMBER 10 | OCTOBER 2015
(14)], the concentration of plasma glycerol (lipolytic index)
remained similar at rest and during exercise after both types of
training. The lack of changes in lipolysis concomitant with
increased FORs during exercise may improve the mismatching
between the availability and oxidation of NEFA in individuals with
obesity, suggesting that the regulation of fat metabolism in the early
phase of exercise training may be principally related to muscular,
rather than extra-muscular, factors (30).
Our results are in agreement with previous studies that reported
decreased insulin resistance after Fatmax training (4), highlighting
the clinical relevance of Fatmax training in the treatment of obesity
(31). In fact, HOMA2-IR decreased significantly only in GFatmax
(statistical power: 60%) and this difference tended to be significant
after the inclusion of baseline values as co-variate, demonstrating
the importance of this change in GFatmax even in our small sample
size. These results suggest that insulin resistance shows a significant
decrease in GFatmax compared to GHIIT. This may be related, in part,
to decreased levels of resting plasma NEFA after training (225%)
observed only in GFatmax, which remain significant even after covariance analysis. This result is consistent with previous studies
showing an increase in insulin sensitivity after a pharmacological
decrease in plasma NEFA levels (32). We can speculate that, with
respect to adapted HIIT, Fatmax training may lead to an increased
www.obesityjournal.org
Original Article
Obesity
CLINICAL TRIALS AND INVESTIGATIONS
degrading enzyme (36). Taken together our findings may suggest
the pivotal role of fat oxidation during the exercise session in the
improvement of insulin resistance in men with class II and III obesity. On the other hand, HIIT did not improve insulin resistance in
this population. This in agreement with previous results using
reduced-volume HIIT (8,11) and adapted HIIT (37) in men with
overweight/obesity but in contrast to others using adapted HIIT in
sedentary adults with overweight (12) and in patients with type 2
diabetes (22). The lack of a consistent response after HIIT may be
related to the different classes of obesity tested in these studies or to
a lower training stimulus (11). It has been suggested that the exercise duration is the most important determinant when the training is
designed to induce improvement in insulin sensitivity in sedentary
adults with overweight/obesity (38).
Some methodological limitations need to be addressed. Firstly,
although it has been demonstrated a strong agreement between the
estimates of substrate oxidation rates measured with indirect calo_ 2max in
rimetry and by an isotope method during exercise at 85% VO
cyclists (39), this, to our knowledge, has never been validated in
individuals with obesity and need, therefore, further investigations.
However, the indirect calorimetry has been widely used in this population to assess FORs during exercise (2-4,20). Secondly, this study
lacks of a control group (enrolled in the lifestyle intervention but
not in exercise training) to directly assess the potential health adaptations of these two training modalities and to avoid the confounding
influence of the lifestyle intervention. Indeed, our subjects followed
a lifestyle education program, which included balanced diet control
and weight loss, and this might have influenced our results [especially decrease insulin resistance (40)]. Thirdly, because of the small
sample size (and low statistical power), it was not possible to detect
a significant different adaptation between the two groups for the
_ 2peak and MFO). However, our results
main variables (i.e., VO
(attested by ES) seem to suggest a greater increase of these variables
after adapted HIIT compared to Fatmax training, highlighting the
potential pivotal role of the high-intensity training in this
population.
Figure 3 The mean concentrations of (A) epinephrine, (B) norepinephrine, and (C)
insulin at rest and at the end of the first phase of the pre-training maximal incremental test (IncrP1Pre) in pre- and post-training conditions in the Fatmax training
(GFatmax) and adapted high-intensity interval training (HIIT: GHIIT) groups. Values are
the means 6 SE. The values at IncrP1Pre correspond to 75% of the peak power
output reached during the pre-training Incr. *P 0.05 for significant time effect;
†P 0.05 for the significant time 3 group 3 exercise intensity interaction effect;
§P 0.05 for the significant difference between the pre- and post-training conditions for GFatmax.
In summary, 2 weeks of adapted HIIT and Fatmax training are both
effective for the improvement of aerobic fitness and FORs during
exercise in men with class II and III obesity. In addition, decreased
plasma NEFA at rest only in GFatmax may provide, in part, a mechanism involved in decreased fasting insulin and insulin resistance in
this group. Further research is needed to investigate the long-term
effects of these two training modalities in this population.
Acknowledgments
capacity to oxidize intra-muscular triglycerides (IMTG) in our subjects, as previously reported (33). This might induce IMTG turnover,
which may be involved in the reduction of plasma NEFA levels
[most likely used to restore the IMTG pool (33)] and accumulation
of lipotoxic intermediates, which may contribute to the increase in
insulin sensitivity (34). The post-training decline in plasma NEFA in
GFatmax may be also involved in the decreased fasting plasma insulin
[a marker of insulin sensitivity (35)] found only in this group. After
weight loss programs, the lower plasma insulin concentration may
be associated to an increase in insulin clearance from plasma
through a decreased inhibition of plasma NEFA on insulin-
www.obesityjournal.org
The authors thank Cinzia Parisio for the planning of the training sessions, Lele Baldo for his helpful assistance during the training sessions, Andre Berchtold for statistical assistance, and all the
volunteers for their participation.
C 2015 The Obesity Society
V
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