Effects of Resistance Exercise Training on Childhood ObesityMinsuk Oh

http://dx.doi.org/10.7570/kjo.2014.23.3.141 pISSN 1226-4407 eISSN 2234-7631

INTRODUCTION

The prevalence of childhood obesity has been steadily increasing during the past few decades worldwide.

According to the current report by World Health Organization (WHO), the worldwide preva- lence of childhood obesity has increased by 2.5% from 1990 to 2010.

Although the specific causes of the rapid increase in childhood obe- sity have not been fully understood, increased sedentary lifestyles (e.g., television viewing, internet use and, playing video games) and decreased physical activity are considered as the major culprits.

Furthermore, increased energy consumption from high-fat or high- calorie foods (e.g., fast foods or sweet beverages) is strongly associat- ed with the rapid increase in childhood obesity.

The obesity epidemic in youth is an important public health con- cern since it is strongly associated with many health risks such as cardiovascular disease (CVD)

, type 2 diabetes mellitus (T2DM)

, low level of quality of life

as well as mental disorders.

In addition, previous studies also reported that childhood obesity tracks well into

adult obesity

, suggesting that effective strategies to combat obesity should be implemented in childhood to prevent increasing risk of chronic disease in adulthood.

Previous literatures

have reported beneficial effects of regular physical activity as a primary treatment strategy for obesity preven- tion or reduction in children and adolescents. Aerobic exercise train- ing has been traditionally employed as an effective intervention tool to combat obesity epidemic in adults

and youth.

Racette et al.

reported that 12 weeks of aerobic exercise (60 to 65% of maximal ox- ygen consumption intensity, 45 minutes, 3 times/week) reduces fat mass in women, and similar positive change in body composition was found in adolescents after 12 weeks of aerobic exercise (2 times/

week, 20 to 30 minutes).

Recently, emerging evidence also suggest that resistance exercise training is an alternative and an effective tool for obesity treatment for both adults

and children.

It is well established that resis- tance exercise training provides positive effects on body composi- tion

, and is also known to improve psychological well-being (en-

Effects of Resistance Exercise Training on Childhood Obesity

Minsuk Oh

, YoonMyung Kim

, Sang-Hoon Suh

, Justin Y. Jeon

*

Department of Sport and Leisure Studies

, Yonsei University, Seoul; University College

, Yonsei University, Seoul; Department of Physical Education

, Yonsei University, Seoul, Korea

The prevalence of childhood obesity has been steadily increasing worldwide. Low level of physical activity, poor cardiorespiratory fitness, sed- entary lifestyle, and increased energy intake are recognized as major culprits in the childhood obesity epidemic. Childhood obesity is closely associated with many chronic comorbidities such as type 2 diabetes mellitus (T2DM), cardiovascular disease (CVD), cancer, and psychological disorders. Studies have suggested that regular exercise is an effective tool for obesity treatment in youth. Aerobic exercise format (either exercise alone or combined with calorie restriction) has been widely and traditionally applied for reducing childhood obesity. A growing body of evi- dence suggests that resistance exercise training is beneficial in improving body composition, thereby is an alternative tool for the treatment of childhood obesity. However, the effects of resistance exercise training alone in childhood obesity are relatively limited in youth. Thus, the pur- pose of this review was to provide an update on current findings associated with resistance exercise training as an effective treatment and pre- vention strategy for childhood obesity reduction.

Key words: Obesity, Childhood, Resistance training

Corresponding author Justin Y. Jeon

Department of Sport and Leisure Studies, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea

Tel +82-2-2123-6197 Fax +82-2-2123-8648 E-mail [email protected] Received May 8, 2014 Reviewed Jul. 18, 2014 Accepted Aug. 14, 2014

Copyright © 2014 Korean Society for the Study of Obesity

This is an Open Access article distributed under the terms of the Creative Commons Attribution

Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits

unrestricted non-commercial use, distribution, and reproduction in any medium, provided the

original work is properly cited.

hance quality of life, decrease level of depression, or anxiety)

, and prevents risks of injury from sports activity.

Although the benefi- cial effects of resistance exercise training have been investigated in adults, its effects on childhood obesity was not fully understood.

Therefore, the purpose of the review was to summarize and provide an update on current findings associated with resistance exercise training, which is gaining recognition as an effective treatment and prevention strategy for childhood obesity. Intervention studies con- cerning the effects of resistance exercise training in obese children are summarized in Table 1. The studies only covered children who were either overweight or obese.

RESISTANCE EXERISE TRAINING AND BODY COMPOSITION IN CHILDHOOD OBESITY

In obese adults, it is well established that resistance exercise train- ing alone, without calorie restriction, positively alters body weight, waist circumference, and body fat mass.

Similar to such observa- tions in adults, several studies with youth reported positive changes in body composition after resistance exercise training.

The summary of findings in youth is shown in Table 2. McGuigan et al.

conducted an 8 week (3 times/week) program of whole body resis- tance exercise training in overweight and obese youth aged 7-12 years. After the intervention, they reported that there was a signifi- cant increase in lean body mass (5.3%, P<0.05), and decrease in per- cent body fat (2.6%, P<0.01), whereas weight and fat mass were not significantly changed. The results were consistent with the findings from adult population studies, and it proved that resistance exercise training is an effective treatment for modifying body composition.

Moreover, Shaibi et al.

also showed a significant reduction in per- cent body fat (2.5%, P<0.05) after 16 weeks (2 times/week,≤60 min/

session) of resistance exercise training intervention in obese adoles- cents. Most studies have reported that resistance exercise training intervention in youth obesity increases lean body mass, and positive- ly modifies percent body fat accordingly. Meanwhile, Sgro et al.

re- ported that fat mass decreased by 8.1% after 24 weeks of resistance exercise training intervention period in overweight or obese children (P<0.05). This was the only study that provided evidence for fat mass reduction after 24 weeks of resistance exercise training.

Since most interventions were set for 8 or 16 weeks of resistance exercise

training while the 24 weeks of intervention was used in the study of Sgro et al.

, the duration of the training intervention may be the fac- tor causing a different outcome in the study of Sgro et al.

compared with the other studies.

It would be safe to conclude that resis- tance exercise training for at least over 16 weeks would be effective in fat mass reduction among youth. Long term resistance exercise is suggested to treat childhood obesity.

Additionally, weight gain was also found after 12 weeks of resistance exercise training in obese adolescents aged 15.5 years.

The weight gain is influenced by the increase of lean body mass after resistance exercise. However, the most noteworthy thing is that normal growth in youth may also cause weight gain during the research intervention period. Resistance exercise training affects lean body mass and per- cent body fat rather than body weight reduction or fat mass reduction in childhood obesity, and this may be attributed to normal growth in children. To conclude, normal growth and resistance exercise train- ing may simultaneously affect body composition. Further study on the effect of minimal time period of resistance exercise training on body composition is needed to exclude the impact of normal growth.

RESISTANCE EXERCISE TRAINING AND ABDOMINAL FAT ON

CHILDHOOD OBESITY

Abdominal obesity, especially visceral abdominal fat is one of the leading cause of T2DM

, and incidence of CVD.

A number of stud- ies in adult population have investigated exercise treatment for ab- dominal obesity.

Intervention studies in adult population showed that 16 weeks of progressive resistance exercise training program (2 times/week) reduced visceral (10.3%, P<0.01) and subcutaneous (11.2%, P<0.01) abdominal fat in seniors of average age of 66.6 years.

Treuth et al.

reported that intra abdominal adipose tissue signifi- cantly decreased (13.9 cm

, P<0.05) even though body weight re- mained the same after 16 weeks of progressive resistance exercise training intervention in older women. According to the collected data of the adult population, it may be suggested that participating in resis- tance exercise training for over 16 weeks reduces visceral abdominal fat in adults. To date, very limited study was found on the effect of re- sistance exercise training alone on abdominal obesity in children.

Meanwhile, a randomized trial study

involving non-obese children

(mean age: 12.2 years) reported that high-intensity progressive resis-

Table 1. Intervention studies of resistance exercise training effects on childhood obesity (overweight or obese youth only) Reference Design Participant (No.), Sex (M, F), Cohort

Age (mean ±SD or range) Duration

Control or comparison condition

Training program & intervention

Training Intervention-frequency (F), intensity (I), time (T)

Outcome Measurement T raining equipment

Van Der Heijden et al. (2010)

21

NRCT N =12 (M =5, F =10)

obese Hispanic, (BMI

≥95th percentile), Tanner 4-5

15.5 (± 12 weeks No W -up/C-down+ST : Hand-held weights Flys, Push- 0.5) yr Ups, Chest Press, Seated Row , Overhead Press, Triceps Extension with hand-held weights, Hand- held weights Curls, Cable Curls, Lateral Raises, Hand-held weights Press, Leg Extension, Static Lunges, Squats with and without weights, Dead Lifts with and without weights, Leg Curl with and without weights, Calf Raises, Bridges on Physio - ball, Curl Ups

F: 2 times/week I: light to moderate week 1-2: 2-3 set, 8-12 reps (~50% of 3RM); week 3-8: increased gradually according to each individual’

s ability; week 9-12: 3 sets,

15-20 reps (~80-85% of 3 RM) T: 60 min (10 min W

-up, 40 min ST , 10 min cool-down)

Body composition (weight, BMI, % body fat, lean body mass, fat mass, ab - dominal fat, hepatic and intramyocellu - lar fat, bone mineral density), peripheral insulin sensitivity , glucose production rate (GPR)

Free weights

McGuigan et al. (2008)

22

NRCT N =48 (M =22, F =26),

overweight (BMI

≥85th percentile)

7-12 yr 8 weeks No

Progressive resistance training (PRT) Day 1: Squat, Bench Press, Lunges, Rows, Shoulder Press, Push- Ups, Sit-Ups, Arm Curl, T riceps Dips, Abdominal Day 2: Squats, Straight leg dead-lifts, Flys, Front raises, Rows, Heal raises, T riceps extensions, Bi -

cep curls, Abdominal Day 3: W

eight squat jumps, CMJs, Explosive hang

pulls, Bench press, Rows, Shoulder presses, Sit- ups, Abdominal F: 3 times/week I: 1st day: 3 sets, 8-10 reps, controlled tempo, 90 sec between sets; 2nd day: 3 sets, 10-12 reps, controlled tempo, 60 sec between sets; 3rd day: 3 sets, 3-5 reps, fast tempo, 3 min between sets

Body composition (% body fat, lean body mass, height, weight, BMI, total fat mss, bone mineral contents)

Machines, free-weight

Lau et al. (2010)

23

NRCT N =18 (M =13, F =5), Obese Chinese

12.45 (± 6 weeks No Circuit-based RT (w-up, C-down, 10 RT stations 1.77) yr (Chest Press, Lat Pull Down, Shoulder Press, Leg Press, Leg Extension, Leg Curl, Heel Raise, Biceps Curl, T riceps Extension, Adjusted Push-Ups) F: 3 times/week I: 70-85% of 1 RM with full motion T: 60 min, 3-5 min rest between sets

Body composition (body fat mass and lean body mass, bone mineral con - tents), muscle strength, leptin, insulin and glucose

Free weights

Treuth et al. (1998)

28

NRCT N =22 Control group (F =11) T reatment group (F =11) obese (BMI ≥95th percentile), Tanner 1-2

7-10 yr 5 months wait-list control Circuit T rai ning: 6 Upper -body exercises (Ben ch Press, Military Press, Biceps Curl, Latissimus Pull Do w n, Tri ce ps Ex te ns ion , a nd S it- Up s) an d 1 Lo w er - body exercise (Leg Press) F: 3 times/week I: upper

→ 2 sets of 12 reps, leg press → 2 sets of 15 reps T: 20 min

Body composition (weight, % body fat, fat free mass), muscle strength, fitness (VO2max),

resting metabolic rate and total energy expenditure

Machines

Lau et al. (2004)

24

RCT N =37 T reatment group (M =14, F =7)

Control group (M =11, F =5), obese

10-17 yr 6 weeks

Diet education and behavior modification program only Exercise: Circuit-based RT (W -up, C-down, 10 RT stations (machines) F: 3 times/week I: 70-85% 1 RM, at least 5 lifts with

full motion T: 60 min 3 set circuit, 3-5 min rest between sets

Body composition (height, weight, BMI, lean mass, fat mass, % body fat, bone mineral contents), lipids, insulin and gl uc os e, b lo od p re ss ur e, c ho le st er ol level

Machines

Shaibi et al. (2006)

25

RCT N =22 T reatment group (M =11) Control group (M =11), Latino,

overweight (BMI

≥85th percentile), Tanner ≥3

Control: 15.6 (

±0.5)

yr Treatment: 15.1 (

±0.5) yr

16 weeks W ait-list control Progressive resistance training (PRT) Day 1: 5 min W -up/C-down: stretches, abdominal exercises Two compound lower -body exercises, three isolat - ed upper -body exercises Da y 2 : 5 m in W -u p/ C- do w n: s tre tc he s, a bd om in al exercises Two compound upper

-body exercises, three isolat - ed lower -body exercises

F: 2 times/week I: moderate intensity

, higher volume

week 1-4: 1 set, 10-15 reps; week 5-10: 2 sets, 13-15 reps; week 11-16: 3 sets, 8-12 reps T: ≤ 60 min 3 set circuit, 1-2 min rest between sets/exercises

Body composition (fat mass and lean body mass), muscle strength, Leptin, in - sulin and glucose

Machines stacked weights

Davis et al. (2009)

26

RCT N =41 Control group (F =7) Nutrition only (N) (F =10),

N+ST (strength training) (F =9) N+CAST (aerobic+ST) (F =15),

Latino girl, overweight (BMI

≥85th percentile)

15.2 ( ±1.1) yr 16 weeks W ait-list control or Diet education program only Progressive resistance training (PRT) Day 1: 5 min W -up/C-down: stretches, abdominal exercises Two compound lower -body exercises, three isolat - ed upper -body exercises Da y 2 : 5 m in W -u p/ C- do w n: s tre tc he s, a bd om in al exercises Two compound upper

-body exercises, three isolat - ed lower -body exercises

F: 2 times/week I: moderate intensity

, higher volume

week 1-4: 1 set, 10-15 reps; week 5-10: 2 sets, 13-15 reps; week 11-16: 3 sets, 8-12 reps T: ≤ 60 min, 3 set circuit, 1-2 min rest between sets/exercises

Body composition (BMI, fat mass, lean body mass), muscle strength, insulin and glucose

Machines, free-weight

Sgro et al. (2009)

27

RCT N =31 G8 : 6 (M =4, F =2) G16 : 9 (M =3, F =6) G24 : 16 (M =4, F =2), overweight (BMI ≥85th

percentile), Tanner 1-2

7-12 yr

8, 16, 24 weeks (three groups) Nutrition check-up, activity records Varying training loads (i.e., undulating variation). M in im al e qu ip m en ts : d um bb el ls, e la st ic b an ds ,

medicine balls, and weight bags Squats, Straight Leg Deadlifts, Flys, Front Raise, Triceps Extension, Biceps Curls and Heel Raise (progressive intensity)

F: 3 times/week I: week 1-8: 3 sets, 6-8 RM; week 9-16: 3 sets, 4-6 RM; week 17-24: 3 sets, 3-5 RM; T: 45-60 min

Body composition (BMI, weight, lean body mass, total fat mass, % body fat and bone mineral contents)

Machines RCT , randomized control trial; NRCT , non-randomized control trial; RM, repetition maximum; BMI, body mass index; LBM, lean body mass; FM, fat mass; BMD, bone mine ral density; BMC, bone mineral content; RMR, resting metabolic rate; ≥95%, obese; ≥85% , overweight; W -up, warm-up; C-down, cool-down; reps, repetitions; G8, training for 8 weeks group; G16, training for 16 weeks group; G24, trai ning for 24 weeks group.

tance exercise training (2 days/week) reduces waist circumference (-0.8 cm), however, the study did not report whether the exercise training reduced either subcutaneous or visceral fat in children. Only one intervention study on effects of resistance exercise training alone on childhood abdominal obesity was found. The study reported that subcutaneous abdominal fat was significantly increased (5±2%) and no variation was shown in visceral abdominal fat after 5 months of resistance exercise training (3 times/week) intervention in obese girls aged 7 to 10 years.

This result is the only report on visceral abdomi- nal fat in obese children, and it suggests that there was no effect of re- sistance exercise training on visceral abdominal fat. The most note- worthy point of the study is that an increase in subcutaneous fat , but

not visceral fat, was found along with weight increase.

In the study, body weight and total fat mass were significantly increased in both resistance exercise training intervention group and control group.

From the results of the study, we may conclude that there is no change in visceral abdominal fat despite the increase in body weight and total fat mass after resistance exercise training.

Either aerobic exercise or resistance exercise combined with aero- bic exercise are effective treatments for reducing abdominal fat in children and adolescents.

In a randomized controlled trial study with obese children aged 7 to 11 years, the exercise intervention group, involving aerobic type of physical training (5 times/week) ,was associated with significant reductions in subcutaneous (-16.2 Table 2. Body composition variables change after resistance exercise training intervention in overweight or obese youth

Reference Height (cm) Weight (kg) BMI (kg/m

) Fat mass (kg) Body fat % Lean Body Mass (kg) Van Der Heijden et al. (2010)

- Pre: 97.0± 3.8

Post: 99.6± 4.2

Pre: 35.3± 0.7 Post: 36.1± 0.9

Pre: 39.7± 1.9 Post: 40.3± 2.3

Pre: 40.8± 1.5 Post: 40.2± 1.7

Pre: 55.7± 2.8 Post: 57.9± 3.0

McGuigan et al. (2008)

Pre: 146.0± 8.0

Post: 147.2± 7.7

Pre: 55.2± 10.0 Post: 56.3± 10.1

Pre: 25.6± 3.1 Post: 25.9± 3.2

Pre: 22.5± 5.7 Post: 21.3± 5.6

Pre: 39.9± 4.6 Post: 37.3± 4.3

Pre: 32.2± 5.5 Post: 33.9± 5.3*

Lau et al. (2010)

Pre: 154.1± 8.9 Pre: 72.7± 15.3 Pre: 30.5± 4.9 Pre: 29.4± 8.9 Pre: 39.3± 5.6 Pre: 43.2± 8.9 Treuth et al. (1998)

Control G

Pre: 130.3± 5.4 Post: 134.3± 5.5*

Treatment G Pre: 136.0± 6.5 Post: 138.3± 6.7*

Control G Pre: 29.1± 2.8 Post: 32.0± 3.0

Treatment G Pre: 46.6± 9.4 Post: 50.6± 10.3

- - Control G Pre: 28.1± 4.8 Post: 28.7± 4.8 Treatment G Pre: 38.9± 6.6 Post: 39.2± 5.9

Control G Pre: 20.2± 2.1 post: 22.1± 2.2

Treatment G Pre: 27.1± 3.2 Post: 29.2± 3.6

Lau et al. (2004)

Control G

Pre: 156.8± 11.7 Post: 157.7± 11.5*

Treatment G Pre: 154.4± 8.7 Post: 155.3± 8.7*

Control G Pre: 72.3± 21.5 Post: 73.0± 22.6 Treatment G Pre: 72.8± 14.9 Post: 73.2± 14.7

Control G Pre: 29.0± 5.1 Post: 28.9± 5.4 Treatment G Pre: 30.4± 4.7 Post: 30.3± 4.7

Control G Pre: 27.4± 11.1 Post: 28.0± 10.9 Treatment G Pre: 29.7± 0.8 Post: 29.8± 8.4

Control G Pre: 35.8± 5.6 Post: 36.4± 5.6 Treatment G Pre: 39.3± 5.3 Post: 39.2± 5.6

Control G Pre: 46.7± 14.4 Post: 46.8± 14.8 Treatment G Pre: 43.7± 8.8 Post: 43.9± 8.4 Shaibi et al. (2006)

Control G

Pre: 168.0± 1.6 Post: 169.0± 1.5 Treatment G Pre: 166.3± 3.1 Post: 167.0± 2.8

Control G Pre: 98.3± 6.9 Post: 100.0± 6.5 Treatment G Pre: 90.0± 5.7 Post: 91.9± 5.6

Control G Pre: 34.6± 2.0 Post: 35.0± 2.0 Treatment G Pre: 32.5± 1.6 Post: 32.8± 1.6

Control G Pre: 30.8± 3.5 Post: 30.7± 3.2 Treatment G Pre: 31.4± 3.4 Post: 30.1± 3.2

Control G Pre: 31.4± 1.6 Post: 30.7± 3.2 Treatment G Pre: 35.3± 2.4 Post: 32.8± 2.1*

Control G Pre: 62.3± 3.2 Post: 64.3± 3.0 Treatment G Pre: 54.4± 3.2 Post: 58.1± 3.1 Davis et al. (2009)

- Control G

Pre: 85.9± 19.6 Change: 0.3± 1.6 Treatment G Pre: 84.5± 21.4 Change: 2.4± 1.8

Control G Pre: 33.8± 5.7 Change: 0.3± 1.2 Treatment G Pre: 32.8± 7.9 Change: 1.1± 0.6

Control G Pre: 34.9± 9.0 Change: - 0.1± 2.1 Treatment G Pre: 34.5± 13.1 Change: 0.6± 2.5

- Control G Pre: 49.7± 8.8 Change: 0.1± 1.5 Treatment G Pre: 47.9± 7.6 Change: 1.4± 1.9 Sgro et al. (2009)

- - - G8, pre: 20.7± 4.5

Change: - 5.9%

G16, pre: 23.1± 8.5 Change: - 6.8%

G8, pre: 21.9± 7.1 Change: - 8.1%

G8, change: - 5.3%

G16, change: - 7.0%

G24, change: - 6.7%:

at week 8

G16, change: 6.4%: at week 8;

6.8%: at week 16

G24, change: 5.3%: at week 8;

8.3%: at week 16;

11.5%: at week 24

Data are mean± SD. The data from Davis et al.

study values are showing change value (mean± SD).

Control G, control group; Treatment G, exercise treatment group; pre, before the treatment; post, after the treatment; G8, training for 8 weeks group; G16, training for 16 weeks group; G24, training for 24 weeks group.

Significant change after intervention,*P < 0.05;

P < 0.01;

P < 0.001.

cm

vs. 48.9 cm

) abdominal fat and less increase of visceral (1.3 cm

vs. 20.9 cm

) abdominal fat.

Although the study of resistance exer- cise training effect on abdominal obesity in obese children is limited and the results are still unclear, we should note that waist circumfer- ence and abdominal subcutaneous fat were changed after resistance exercise training intervention. However, since the visceral abdomi- nal fat is the leading risk factor of chronic diseases, it should be stud- ied with resistance exercise training in obese youth. At the present, the combined aerobic and resistance exercise training was proved as an effective modality, and further research is needed to study the ef- fects of resistance exercise training alone on childhood obesity.

RESISTANCE EXERCISE TRAINING AND RESTING METABOLIC RATE, ENERGY EXPENDITURE ON

CHILDHOOD OBESITY

Prior studies have fully proved muscle hypertrophy with increas- ing lean body mass

, as well as enhancing resting metabolic rate (RMR) in adults. Resistance exercise training increases muscle mass, and enhances daily energy expenditure (EE) accordingly, es- pecially in overweight or obese population.

Numerous studies have fully demonstrated that resistance exercise training increases muscle mass and RMR, and individuals with a higher RMR are less likely to gain body weight compared with those with lower RMR.

The potential advantage of resistance exercise training is muscle mass gain and consequent increase of RMR. Most obese people en- gage only in aerobic type of exercise, however, resistance exercise training should also be emphasized to enhance the efficiency of obe- sity treatment in childhood. The effect of resistance exercise training

can be applied as a resting time effect rather than during exercise time effect. In specific, participating in resistance exercise training can consume calories both during and after the exercise session. Al- though no studies on youth are available regarding the association between resistance exercise training and RMR, the results from adult population studies may support evidence to apply resistance exercise training in youth. Further studies on resistance exercise training in youth concerning RMR and EE is needed to provide gen- eral evidence for its effects in children.

BONE HEALTH WITH RESISTANCE EXERCISE TRAINING FOR

CHILDHOOD OBESITY

The effects of the resistance exercise training on bone mineral con- tents (BMC) or density (BMD) in youth has been investigated in sev- eral studies

, and the summary is shown in Table 3. The Van Der Heijden et al.

demonstrated that BMD were changed (1.07±0.03 g/

cm

to 1.08±0.03 g/cm

, P<0.05) after 12 weeks of resistance exer- cise training (2 times/week) intervention. Similarly, the Lau et al.

investigated that 6 weeks of resistance exercise training (3 times/

week) intervention changed BMC (15.8±2.9 kg to 16.2±3.0 kg, P<

0.01). Additionally, the Lau et al.

reported that both control (1,711 ± 502 g to 1,732 ±493 g, P<0.05) and exercise intervention group (1,609 ±291 g to 1,639±290 g, P<0.05) showed increase in BMCs.

The results may also be explained by normal growth during the 6 weeks of intervention in the control group. The Sgro et al.

reported that after resistance exercise training (3 times/week) in overweight or obese children, the percentage of BMCs were increased signifi- cantly after 16 week (4.9%, P= 0.001), and 24 week (6.2%, P= 0.004).

Table 3. Bone mineral density outcomes after resistance exercise training intervention in overweight or obese youth

Reference Van Der Heijden et al. (2010)

McGuigan et al. (2008)

Lau et al. (2010)

Lau et al. (2004)

Sgro et al. (2009)

Variable change BMD (g/cm

)

pre: 1.07± 0.03 post: 1.08± 0.03*

BMC (g) pre: 1,292± 201 post: 1,310± 226

BMC (kg) pre: 15.8± 2.9 post: 16.2± 3.0

BMC (g) Control G pre: 1,711± 502 post: 1,732± 493*

Treatment G pre: 1,609± 291 post: 1,639± 290*

BMC (%) G16

Change: +4.9% (16 week)

G24

Change: +6.2% (24 week)

Data are mean± SD.

Control G, control group; Treatment G, exercise treatment group; pre, before the treatment; post, after the treatment; BMD, bone mineral density; BMC, bone mineral content; G16, training for 16 weeks group; G24, training for 24 weeks group.

Significant change after intervention, *P < 0.05;

P < 0.01.

On the contrary, the study of McGuigan et al.

reported no signifi- cant change of BMC after 8 weeks of resistance exercise training (3 times/week) in overweight or obese children.

Since BMD is substantially influenced by tensile and compression force

, the resistance exercise training or weight bearing exercise stimulates and enhances the BMD. As proven in studies

involv- ing adolescent weightlifters, weight lifting reinforces BMD. There- fore, resistance exercise training is required in youth to strengthen their bone and prevent bone injury. Consequently, participation of regular resistance exercise training has considerable benefit on bone growth and formation in youth.

PSYCHOLOGICAL HEALTH WITH RESISTANCE TRAINING IN

CHILDHOOD OBESITY

As many literatures

have reported previously, childhood obe- sity is closely associated with various types of psychological prob- lems such as anxiety, depression, low self-esteem, and low level of confidence. Participating in exercise

, especially aerobic exercise, has been applied as a treatment for obesity related psychological problems in childhood obesity. However, only few limited studies are available regarding the effects of resistance exercise training on psy- chological problems in children. On the contrary, resistance exercise training, as an intervention treatment for psychological well-be- ing

, in the adult population proved to be effective in improving mental health and mental well-being. According to limited studies

involving adolescents, the resistance exercise training had an implic- it impact on self-efficacy and confidence, especially in adolescent girls. Strength training increased positive self-awareness of one’s own body image and increased self-confidenc.

Furthermore, Yu et al.

reported that three times per week of resistance exercise train- ing improves patience, physical ability, and confidence of one’s mus- cular strength. Conclusively, since strength training with weight lift- ing increases sense of achievement, and further enhances mental well being

, it would encourages children (8 to 11 years) to partici- pate on resistance training exercise.

Meanwhile, in the randomized trial study of Faigenbaum et al.

, twice a week of supervised resistance exercise training during 8 weeks did not show any significant change in self-efficacy and self- concept in children (7 to 12 years). Further studies which examine

direct effect of resistance exercise training on mental health in chil- dren with reliable measurement are needed; however, prior litera- tures may support the positive association between mental health and resistance exercise training in children. Resistance exercise training may play a role in increasing one’s self-confidence not only during the exercise session, but also after the session since the sense of achievement from lifting weights improves psychological condi- tions when they participate in daily activities or other type of physi- cal activities as in team sports with their classmates.

CONCLUSION

Participation in regular resistance exercise training is an effective obesity treatment tool since it is associated with positive change in body composition, and RMR. Furthermore, the resistance exercise training can improve psychological disorders in childhood obesity effectively without medical treatment (Fig. 1).

We identified the explicit results from the resistance exercise training in childhood obesity in agreement with adult population studies in specific outcomes such as increase of lean body mass, RMR or energy expenditure and percent body fat change after par- ticipation in specific duration of resistance exercise training. As fully determined in the past, the physical activity which includes aerobic type of exercise reduces body fat itself, however, the results were not evident with only resistance exercise training intervention studies.

Lean body mass was increased significantly after resistance exercise training intervention

, and percent body fat was decreased.

Fig. 1. Effects of resistance exercise training on childhood obesity.

Resistance exercise training

Childhood obesity

Body composition change Increase of resting metabolic rate

& energy expenditure Strengthen bone density

Abdominal fat treatment Mental well-being

improvement

Although studies on the effects of combined exercise or physical ac- tivity in obese children have been sufficiently conducted, effects of resistance exercise training alone in obese children have not been fully investigated. Especially regarding abdominal fat or BMD, it is hard to define whether effects from normal growth or resistance ex- ercise training affects the results. There are only limited data on ab- dominal fat change in obese children undergoing resistance exercise training and its results are unclear. Therefore randomized trial to in- vestigate the effects of resistance exercise training on abdominal fat in childhood obesity is needed. Likewise, the BMC or density change after the resistance exercise training intervention is also unclear be- cause of the effect of normal growth on BMC or density in children.

The positive effects of physical activity and exercise on psychological well-being or disorders in children with obesity were fully examined;

however, it is still unclear that resistance exercise training alone can make a positive impact on psychological health in obese children.

More specific randomized interventional trials involving obese chil- dren are needed in the future to further elucidate the effects of resis- tance exercise training.

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