Effectiveness of Workplace Exercise Interventions on Body Composition: A Systematic Review and Meta-Analysis

Abstract

Objective:

The aim of this review was to analyze the effectiveness of workplace exercise interventions on body composition (BC).

Data Source:

Studies published in PubMed, Scopus, SPORTDiscus, Web of Science, CINAHL and PsycINFO, from the earliest time point until 8 July 2020.

Study Inclusion and Exclusion Criteria:

Inclusion criteria were worksite interventions, in adults, Randomized Controlled Trials (RCTs), real exercise practice, and measuring BC outcomes. Exclusion criteria were full-text non-available, abstract not in English, and exercise protocol missing.

Data Extraction:

157 studies were retrieved and assessed for inclusion by 2 independent reviewers, who also used the Cochrane’s Collaboration Tool to assess study quality and risk of bias.

Data Synthesis:

We performed a meta-analysis to determine the effect size of the interventions on BC outcomes reported in at least 5 studies.

Results:

Twelve RCTs were included (n = 1270, 66% women), quality of studies being low to high (25% moderate, 67% high). Interventions achieved a statistically significant decrease in waist circumference (SMD = 0.24; 95% confidence interval (CI): 0.06 to 0.41; p = 0.008), total mass fat (SMD = 0.21; 95%CI: 0.00 to 0.41; p = 0.047), and body adiposity index (SMD = 0.20; 95%CI: 0.00 to 0.41; p = 0.049). No changes were observed in body weight (SMD = 0.08 95%CI: −0.02 to 0.18; p = 0.128). Additionally, muscle mass increased in interventions that included strength training. There were no adverse events reported.

Conclusion:

The most effective workplace exercise interventions to improve BC combined supervised, moderate-intensity aerobic and strength training, for at least 4 months.

Keywords

worksite workplace exercise interventions body composition

Introduction

About a half of total sedentary time spent by the working-age population takes place in the workplace, representing an average of 375 minutes of sitting time on workdays. In addition, individuals who spend more time sitting at work are also those who report less leisure-time physical activity, and the proportion of obesity among these workers is higher.¹

Physical inactivity is responsible of 6% of deaths worldwide, being the fourth leading risk factor for mortality from all-causes. It is associated with overweight and obesity-related comorbidities, which represent 27% worldwide of type 2 diabetes mellitus and 30% of coronary heart disease.²

In terms of mortality, compared with adults who sit for 6 hours/day, those who sit for 8 hours/day have a 14% greater risk, and those who sit for 10 hours/day have a 29% greater risk.³ It has been reported that one additional hour of sedentary behavior has an impact on body composition (BC), as it increases the risk of being overweight (13%) and the risk of developing high abdominal fat (26%).⁴

In the BC analysis, visceral adipose tissue (VAT) is the most clinically relevant variable. Located around vital organs, VAT releases pro-inflammatory biomarkers into the bloodstream, which participate in chronic inflammation related to insulin resistance, a precursor to type 2 diabetes mellitus. These pro-inflammatory biomarkers also lead to the inflammation of the vascular endothelium, contributing to the pathogenesis of atherosclerosis.^5,6

VAT values are highly correlated with body adiposity index (BAI) values, and with waist circumference (WC). This is the reason why WC is a very useful anthropometric variable.⁷

Body mass index (BMI) is an easy and fast tool for screening the population, although it does not have a strong association with VAT,^7,8 so WC and BAI are more clinically relevant. Individuals who are overweight/obese have greater health risks compared to normal-weight individuals, and therefore they are a priority in interventions targeting a BC improvement.⁹

Friedenreich et al¹⁰ consider clinically beneficial to reduce BAI by 1% or total mass fat (TMF) by 1 kg. Regarding body weight (BW) and WC, respectively, a reduction of 5%¹¹ or 3 cm⁵ is considered clinically significant.

Interventions that only reduce sedentary time are able to reduce the risk of cardiometabolic diseases, but do not achieve significant changes in BMI or WC.¹² In order to achieve a healthier BC, with an adequate ratio of muscle and fat, and a lower risk of developing cardiometabolic diseases, interventions should consist in a physical activity program.¹³

In fact, cardiometabolic diseases are 60% related to lifestyle, and the most influential factor is physical activity.¹⁴ The effect of physical activity on BC has been shown to depend on the dose and type of exercise.¹⁵

The position stand of the American College of Sports Medicine points out that the optimal dose to achieve clinically significant weight loss is 250 minutes/week of moderate-intensity aerobic exercise (65-75% HR max), for 3-6 months, being 150 minutes per week the minimum dose required.¹⁶ These doses of exercise are different according to sex and BMI, being obese women those who obtain a greater improvement in BC with lower doses of exercise. In this type of population, 135-150 minutes/week of moderate-intensity aerobic exercise are sufficient to achieve clinically beneficial decreases in BW, BAI and WC.¹⁰

According to Keating et al,¹⁷ a physical exercise intervention should last at least for 4 weeks in order to see some changes in BC, while other authors point out that the minimum duration so as to see a clinically relevant impact on BC should be 10-16 weeks.^18,19

Regarding the type of exercise, aerobic exercise is more effective than resistance exercise in reducing adipose tissue, but resistance training provides other advantages, such as the maintenance of fat-free mass (FFM). So in order to achieve a healthier BC, interventions should combine both types of exercises.²⁰

Within the aerobic exercise, high intensity interval training (HIIT) is more effective in reducing adipose tissue than moderate-intensity aerobic exercise, but not significantly, so both options are effective. HIIT is more profitable in terms of time invested.^21,22

Physical activity should be promoted in all age groups, according to the 2020 WHO physical activity recommendations,²³ since health risk factors develop from childhood. The work environment covers an age group with risk factors, but generally without declared diseases, on which it is easy to act from the occupational health teams of the companies, due to the high number of hours spent in the workplace. Therefore, we believe that these occupational health teams should carry out lifestyle interventions within the workplace.

Objective

The objective of this review was to analyze the effectiveness on BC of physical exercise programs carried out in the workplace.

Methods

This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement.²⁴

Data Source

Studies were identified in 6 databases: PubMed, Scopus, SPORTDiscus, Web of Science, CINAHL and PsycINFO, published from the earliest time point until 8th July 2020. The search terms were: “(Worksite OR workplace) AND exercise interventions AND body composition.” Grey literature (eg, abstracts, conference proceedings and editorials) and reviews were excluded. After the duplicates were removed, 2 authors (GGPS and FCVA) independently screened the titles and abstracts and then evaluated the full text of potentially relevant studies. Disagreements were resolved through consultation with a third review author (MPR). Studies were eligible for inclusion if they met the eligibility criteria. All studies removed were recorded, with the reasons of exclusion.

Inclusion and Exclusion Criteria

The criteria for inclusion were (1) population: men or women aged between 18 and 70 years old; (2) type of study: RCT; (3) type of intervention: physical exercise program with real exercise practice; (4) any workplace; and (5) the outcomes included short term or long-term measurement of BC.

Finally, the exclusion criteria were (1) abstract not in English; (2) exercise protocol not included in the paper; and (3) control group subjects receiving an exercise program.

Data Extraction

Full text articles were retrieved for all studies matching the inclusion criteria. They were stored electronically and systematically reviewed.

Pre and post-exercise mean and standard deviation of descriptive (age, gender) and BC outcomes [BW, BMI, WC, BAI, Fat Mass Index (FMI), TMF, Regional Fat Mass (RFM), VAT, FFM, Appendicular Skeletal Muscle Mass (ASM), Skeletal Muscle Mass Index (SMI)] were extracted and recorded using a spreadsheet, by 2 authors (GGPS and OBG).

The characteristics of the physical exercise programs and the BC-measuring instrument were also extracted and recorded.

A total of 3 primary study authors were contacted by e-mail to request missing data. They all responded by providing the necessary data.

Data Synthesis

Characteristics of studies, interventions, and participants were summarized in tables. Revised Cochrane risk-of-bias tool for randomized trials (RoB 2)²⁵ was used to assess the following characteristics: 1) bias arising from the randomization process; 2) bias due to deviations from intended interventions; 3) bias due to missing outcome data; 4) bias in measurement of the outcome; 5) bias in selection of the reported result. Two investigators (GGPS and FCVA) performed separate assessments of risk-of-bias. In cases of disagreement, a third investigator (MPR) assessed the study and the disagreement was resolved by consensus.

Statistical Analysis

This review limits the meta-analysis to the outcomes of BC that were analyzed in at least 5 studies, using the same measuring instrument, which were BW, WC, TMF, and BAI; assessed with DXA.

Meta-analyses were conducted using the statistical software package Stata 16.1 (StataCorp, College Station, TX, USA) to assess the magnitude of effect on BC outcomes (BW, WC, TMF, BAI).

Pre-and Post-intervention data were used to calculate the mean of differences and pooled standard deviation (SD). Effect sizes (ESs) and adjusted Hedges’ g (95% confidence intervals (CIs)) were calculated for each study by means of t-scores, number of subjects, and standard deviation (SD).

At the same time, the Q and I² statistics were calculated, which indicate the percentage of the observed variability that is due to heterogeneity and not random. Usually I2 values of <25%, 25% to 50%, and >50% are considered to represent small, medium, and large amounts of inconsistency.²⁶

An analysis of heterogeneity was carried out by interpreting the L´Abbé and Galbraith graphs.²⁷

Additionally, the identification of publication biases was identified using the Begg or funnel plot test and the Egger test, which allow us to detect asymmetries in the funnel graph because of the existence of publication bias.²⁸ Significance level was used at 5% (0.05).

Finally, there were not any analysis of subgroups, as we performed an analysis of all subjects included in the manuscripts.

Results

Flow of Studies Through the Review

Search outcome

The search strategy identified 157 articles from electronic databases. Following removal of duplicates, 70 articles were initially screened via title and abstract, and 24 were identified as potentially relevant. Full-text examination further excluded 12 studies, leaving 12 studies for inclusion in this analysis, all randomized controlled trials (Figure 1).

Figure 1.

Preferred reporting items for systematic reviews and meta-analyses flow diagram for study selection.

Characteristics of the Included Studies

Subjects

Participant demographics, intervention characteristics and BC outcomes are outlined in Table 1. Twelve studies examined BC outcomes in 1270 adults (range 18-70 years) (66% female), most of them overweight.

Table 1.

Participants Demographics, Program Characteristics and Body Composition Outcomes for Included Studies.

Author	Participants	BC variables	Instrument assessing BC	Intervention characteristics						Intervention effects
Author	Participants	BC variables	Instrument assessing BC	Type	Duration	Frequency	Intensity	Supervised	Groups	Intervention effects
Pritchard et al²⁹(2002)	N = 38 ♀ 43,4 ± 5,7 years old, IG = 20 CG = 18	BW, TMF, ABF, PF, FFM	DXA	AE	12 months	3 s/w 30′	65-75% HRmax	No	Individual	BW↓; TMF↓; ABF↓; PF↓; FFM ↔
Barene et al³⁰(2013)	N = 89 ♂ 45,8 ± 9,3 years old, IG1 = 30 IG2 = 28 CG = 31	BW, BAI, TMF, LLFM, TRF	DXA	AE IG1: zumba IG2: soccer	3 months	2-3 s/w 60′	IG1 = 75,3 ± 7,1% HRmax IG2 = 78,3 ± 4,4% HRmax	Yes	Group	IG1: BW↔; BAI↔; TMF↓; LLFM↔; TRF↔ IG2: BW↓; BAI↓; TMF↓; LLFM↓; TRF↔
Gepner et al³¹(2017)	N = 184 47,8 ± 9,3 years old, 89% ♀ IG1 = 60 IG2 = 66 CG = 58	BW, WC, VAT	MRI, Anthropometric measuring tape	IG1: LFD + AE + SE IG2: MLCD + AE + SE	12 months	3 s/w 60′ (45′ AE + 1-2sets 7 SE MMG	AE = 80% HRmax SE = 60-80% 1RM	Yes	Group	IG1: BW↔; WC↓; VAT ↔ IG2: BW↔; WC↓;VAT↓
Iturriaga et al³²(2019)	N = 56 ♂ 43,7 ± 5,3 years old, IG = 27 CG = 29	BW, BMI, BAI, FMI, SMI, ASM, LLLFM, LRLFM	DXA	AE: aqua fitness or zumba	3 months	3s/w 45′	6 RPE (BORG 0 to 10)	Yes	Group	BW↔; BMI↓; BAI↓; FMI↓; SMI ↔; ASM↔; LLLFM↓; LRLFM↓
Hunter et al³³(2019)	N = 23 ♀ N = 55 ♂ 43,2 ± 9,8 years old, IG1 = 28 IG2 = 24 CG = 26	BW, TMF, BAI, FFM	DXA	IG1: AE + SE IG2: AE + SE	4 months	2 s/w (30′ EA+ 2 sets 8-12reps 6 SE MMG)	AE = 55-80% HRmax SE = 15-18 RPE (BORG 6 to 20)	IG1: yes IG2: no	IG1 individual IG2 group	IG1: BW↔; TMF↓; BAI↓; FFM↑ IG2: BW↔; TMF↔; BAI↔; FFM↔
Karatrantou et al³⁴(2020)	N = 15 ♀ N = 21 ♂ 43,4 ± 5,9 years old, IG = 18 CG = 18	BAI, TMF, FFM	BIA	AE + SE MMG + FX + BL	6 months	5 s/w 40′ (AE 3-4 s/w 20′)	AE = 65-80% HRmax	Yes	Group 4-5 persons	BAI↓; TMF↓; FFM↑
Dalager et al³⁵(2016)	N = 387 44 ± 10 years old, 74% ♂ IG = 193 CG = 194	BAI, BW, BMI	BIA	AE + SE	12 months	1 s/w 60′ (AE 20′ + 3sets 8 reps 5 SE MMG)	AE = 77-95% HRmax SE = 60-80% 1RM	Yes	Individual	BAI↔; BW↔; BMI↓
Ribeiro et al ³⁶(2014)	N = 151 ♂ 40-50 years old, IG1 = 26 IG2 = 47 IG3 = 33 CG = 45	BW, WC	Digital scale Steel tape	IG1: AE IG2: pedometer IG3: pedometer	3 months	2 s/w 30-40′	11-13 RPE (BORG 6 to 20)	IG1: yes IG2: no IG3: yes	IG1 group IG2 individual IG3 group	IG1: BW↓; WC↓ IG2: BW↔; WC↔ IG3: BW↔; WC↔
Barene et al ³⁷(2014)	N = 70 ♂ 45,8 ± 9,3 years old, IG1 = 25 IG2 = 22 CG = 23	BW, BMI, BAI, TMF, LLFM, TRF	DXA	AE IG1: zumba IG2: soccer	10 months	2-3 s/w 60′	Zumba = 74,9 ± 7,2% HRmax Soccer = 78,6 ± 3,2% HRmax	Yes	Group	IG1: BW↓; BMI↓; BAI↓; TMF↓; LLFM↔; TRF↓ IG2: BW↔; BMI↔; BAI↓; TMF↓; LLFM↓; TRF↓
Murphy et al³⁸(2006)	N = 11 ♀ n = 22 ♂ 41,5 ± 9,3 years old, IG = 21 CG = 12	BW, BAI, WC	Scale Body meter BIA	AE	2 months	2s/w 45′	62% HRmax or 12 RPE (BORG 6 to 20)	No	Individual	BW↔; BAI↓; WC↔
Vilela et al ³⁹(2015)	N = 60 ♀ 25-35 years old, IG = 30 CG = 30	BW, BAI, FFM, TMF	Lange skindfold calliper	SE (muscular endurance training)	4 months	5 s/w 15′ (3 sets × 30″ × 5 SE MMG)	No data	Yes	Group	BW↔; BAI↓; FFM↑; TMF↓
Kong et al⁴⁰(2017)	N = 88 34,3 ± 8,9 years old, 72% ♂ IG = 43 CG = 45	BW, WC	BIA Body meter	Diet + AE (zumba)	3 months	3 s/w 45-60′	High intensity	Yes	Group	BW↓; WC↓

Abbreviations of participants: IG, intervention group; CG, control group.

Abbreviations of body composition (BC) variables: BW, body weight; TMF, total mass fat; ABF, abdominal fat; PF, peripheral fat; FFM, fat free mass; BAI, body adiposity index; LLFM, lower limb fat mass; TRF, trunk fat; WC, waist circumference; VAT, visceral adipose tissue; BMI, body mass index; FMI, fat mass index; SMI, skeletal muscle mass index, ASM, appendicular skeletal muscle mass; LLLFM, Lower Left Limbs Fat Mass; LRLFM, Lower Right Limbs Fat Mass.

Abbreviations of instrument assessing BC: DXA, dual-energy x-ray absorptiometry; MRI, magnetic resonance imaging; BIA, bioelectrical impedance analysis.

Abbreviations of intervention: s/w, sessions per week; HR max, heart rate max; reps, repetitions; nSE, number of strength exercises; SE, strength exercise; AE, aerobic exercise; FX, flexibility; BL, balance; LFD, low fat diet; MLCD, Mediterranean low carbohydrate diet; MMG, major muscles groups.

Interventions

Interventions were conducted for 6.16 ± 3.91 months (range 2-12 months), and the modes of exercise were aerobic exercise (7 studies), resistance training (1 study) and combined aerobic-resistance training (4 studies).

The participants trained 1-5 days per week, for 60-200 minutes per week, mostly at a moderate intensity.

Outcome measures

BC was assessed by DXA (5 studies), BIO (4 studies), Skinfold (1 study), MRI (1 study) and a scale and a meter (1 study).

Results

BC variables were grouped into 3 different categories, according to the objective of the study:

-BW, BMI, WC.

-Fat mass: BAI, TMF, VAT, FMI and RFM (which regrouped the following outcomes: abdominal fat (ABF), peripheral fat (PF), lower limb fat mass (LLFM); lower right limbs fat mass (LRLFM); lower left limbs fat mass (LLLFM); trunk fat (TRK)).

-Muscle mass: SMI, ASM, FFM.

Quality Assessment of Study Methodology

The risk of bias analysis revealed that 8 (67%) studies presented low risk, 3 (25%) studies were classified as presenting some concerns, and 1 (8%) study presented high risk of bias. The most common biases were “bias arising from the randomization process,” where 6 studies (50%) were classified as “some concerns” and 1 study (8%) as “high risk,” mainly because it was not sufficiently described; and “bias due to missing outcome data,” where 3 studies (25%) presented “some concerns” and 1 (8%) “high risk.”

Effect of the Intervention

BW, BMI and WC

Five studies^{29,30,36,37,40} observed statistically significant decreases in BW, while in 6 of them there were no changes (Table 1),^{31-33,35,38,39} being the ES SMD = 0.08 (95%CI: −0.02 to 0.18; p = 0.128), with no heterogeneity (Q = 2.14, p = 1.000; I2 = 0.00%) (Figure 2). In the case of BMI, a significant improvement was found in all studies (Table 1).^37,32,35 Regarding WC, most of the studies obtained a statistically significant decrease,^31,36,40 with only 1 study in which no changes were observed.³⁸ The ES in the WC is low (SMD = 0.24; 95%CI: 0.06 to 0.41; p = 0.008), with low heterogeneity (Q = 6.97; p = 0.324; I2 = 14%) (Figure 3).

Figure 2.

Meta-analysis and forest plot of body weight (BW).

Figure 3.

Meta-analysis and forest plot of waist circumference (WC).

Fat mass

Statistically significant decreases in TMF were observed in all studies,^{29,30,33,34,37,39} with a low ES (SMD = 0.21; 95%CI: 0.00 to 0.41; p = 0.047), and no heterogeneity (Q = 1.87; p = 0.931; I2 = 0.00%) (Figure 4). In the case of BAI, a statistically significant decrease was found in all^{30,32-34,37-39} but 1 study,³⁵ with a low ES (SMD = 0.20; 95%CI: 0.00 to 0.41; p = 0.049), and no heterogeneity (Q = 2.52; p = 0.866; I2 = 0.00%) (Figure 5). Regarding RFM, there was a lot of diversity in the variables analyzed for each article (ABF, PF, LLFM, TRF, LLLFM, LRLFM), but all of them obtained a statistically significant decrease (Table 1).^29,30,32,37 Regarding the FMI³² and VAT,³¹ the authors obtained a statistically significant decrease (Table 1).

Figure 4.

Meta-analysis and forest plot of total mass fat (TMF).

Figure 5.

Meta-analysis and forest plot of body adiposity index (BAI).

Muscle mass

Five studies analyzed muscle mass,^29,32-34,39 3 of which found a significant increase,^33,34,39 while the other 2 observed maintenance in this tissue. Regarding FFM, 3 studies^33,34,39 obtained a statistically significant increase, but Pritchard et al²⁹ obtained a maintenance of this variable. Regarding the SMI and ASM, no changes were observed in the study of Iturriaga et al³² (Table 1).

Discussion

Overall, findings from this meta-analytic review indicate that physical exercise interventions in the workplace achieved statistically significant improvements on BC, reducing fat mass and increasing muscle mass. 10 studies of the 12 included in this review reported significant results in BC, and 2 studies reported less favorable results.^35,38 Of these 2 studies, one lasted for 2 months, and the other for 12 months, and they both used a protocol with a low dose of exercise. The quality of these 2 studies was high³⁵ and low.³⁸

In this review, the type of exercise, intensity, weekly volume, or supervision, were more determining parameters than the duration of the interventions.

The population studied in this review were overweight adult subjects, 66% women, who participated in programs to promote physical activity carried out by the occupational health teams of the companies. These lifestyle interventions aimed to improve BC, and contributed to preventing the development of cardiometabolic diseases.¹³

In 2016, more than 1.9 billion adults in the world were overweight. Of these, more than 650 million were obese. In addition, in 2019, 38 million children under the age of 5 were overweight or obese.⁴¹ These data are especially alarming because overweight individuals have greater health risks, especially regarding cardiometabolic diseases, and therefore they are a priority in interventions targeting BC.⁹ It is important to note that BC assessment is also relevant in non-overweight/obese populations, because of the clinical importance of the muscle mass.

Considering this type of population, a dose of 135-150 minutes/week of moderate-intensity aerobic exercise for at least 3-4 months may be sufficient to obtain clinically significant decreases in BW, BAI and WC.^10,16

The interventions that reached the threshold of 135-150 weekly minutes of moderate-intensity aerobic exercise were: Barene et al^30,37 (150 minutes/week); Iturriaga et al³² (135 minutes/week); and Gepner et al³¹ (135 minutes/week). On the other hand, Kong et al⁴⁰ used a HIIT protocol of 135 minutes/week. All these interventions were carried out in overweight adults, 61% women, which should justify clinically significant results in BW, BAI and WC.¹⁰

Moderate intensity aerobic exercise has proven to be an effective strategy for reducing fat mass, if the exercise volume is sufficient.^10,15,18 HIIT has not been shown to be significantly more effective for this purpose.^21,22 All the aerobic exercise protocols in this review were of moderate-intensity,^29,30-37,39 except for 2.^38,40 Murphy et al³⁸ used a low-intensity protocol, in addition to being of short duration (2 months), which could explain why they did not obtain clinically significant improvements in BC. The exercise protocol used by Kong et al⁴⁰ was HIIT, at a high volume (135 minutes/week), which could explain why they obtained clinically significant improvements in BW,¹¹ and in WC,⁵ with a large ES.

Gepner et al³¹ also achieved a clinically significant result in WC.⁵ However, both Kong et al and Gepner et al added a diet intervention to the exercise protocol, so these improvements cannot be attributed to the exercise intervention alone. The rest of the studies that analyzed BW, WC or BMI did not achieve clinically significant improvements, despite the fact that Barene et al,^30,37 and Iturriaga et al³² used recommended doses of exercise for it.

However, a clinically relevant improvement in BC does not consist in an isolated loss of body weight, but in a decrease in fat tissue and an increase in muscle mass.

Friedenreich et al¹⁰ consider a loss of −1% BAI or −1Kg TMF clinically beneficial. Of the studies that achieved these results in the TMF,^{29,30,33,34,37,39} or in the BAI,^{30,32,33,34,37,39} 3^30,32,37 used a protocol of at least 135 minutes per week of moderate-intensity aerobic exercise; Pritchard et al²⁹ used a lower volume (90 minutes/week) but with a very long duration (12 months); Karatrantou et al³⁴ combined 80 minutes/week of moderate-intensity aerobic exercise with 3 weekly strength training sessions; Hunter et al³³ combined 60 weekly minutes of moderate-intensity aerobic exercise with 2 weekly strength training sessions; and Vilela et al³⁹ carried out a low-volume strength training protocol, with a frequency of 5 days a week. Except for the study carried out by Vilela et al,³⁹ all the others had a sample of overweight subjects, which favors a greater loss of fat mass even with lower volumes of exercise.

A loss of VAT is the most relevant clinical manifestation within a decrease in adipose tissue.^5,6 VAT is closely related to the BAI and the WC,⁷ but not to the RFM or the FMI. It is also associated with a decrease in triglycerides and fasting glycemia,^15,42 factors strongly related to the development of diseases such as type 2 diabetes mellitus, hypertension and atherosclerosis.⁴³

However, of all the studies analyzed in this review, only the study conducted by Gepner et al³¹ assessed VAT, obtaining a statistically significant reduction through a combined intervention of diet, aerobic exercise, and strength training.

In order to prevent cardiometabolic diseases,⁴³ in addition to reducing excessive fat mass, muscle mass must be maintained or even increased, since muscle is a powerful endocrine organ capable of reducing low-grade chronic inflammation,⁴⁴ contributing to reduce the risk of developing metabolic syndrome.⁴⁵

Strength training has been shown to be less effective than aerobic exercise in achieving a loss of fat mass,⁴⁶ but it has other advantages, such as maintaining or increasing muscle mass, when there is a loss of BW.²⁰ The dose necessary to achieve this is to perform at least 2 times a week 1-3 sets of 6-8 exercises for major muscle groups, at a moderate intensity.^20,47 In this review, 5 studies used resistance exercise in their intervention,^{31,33,34,35,39} and all met these criteria, except for the study carried out by Dalager et al.³⁵ However, both this study and the one carried out by Gepner et al³¹ did not report data on muscle mass. The other 3 studies,^33,34,39 used a mixed program of aerobic exercise and strength training that lasted 4 to 6 months, obtaining a statistically significant increase in muscle mass, in addition to a clinically significant reduction in fat mass, and therefore achieved the greatest improvements in terms of BC.

On the other hand, the studies that achieved a clinically significant decrease in fat mass while maintaining muscle mass^29,32 used a moderate-intensity aerobic exercise protocol alone.

Therefore, the most effective physical exercise interventions to improve BC in the workplace combine aerobic exercise and strength,²⁰ with supervision,³³ and have a duration of 4-6 months.

It is important to note that interventions lasting 3 months^30,32,36,40 achieved a clinically improvement in BC. However, this follow-up time is not enough to achieve long-term adherence to healthy exercise and/or nutrition habits.

In addition to BC outcomes, most of the studies^{29-31,33-35,37,38,40} measured the impact of the interventions on risk factors for cardiometabolic diseases, like blood pressure, HDL, LDL, TG, HbA1c, or fasting glucose. Some studies found statistically significant improvements regarding blood pressure,^31,34,38,40 TG,^29,40 insulin,²⁹ and LDL,⁴⁰ HDL,⁴⁰ fasting glucose,⁴⁰ and Hb1Ac.⁴⁰ Concerning clinically significant improvements on cardiometabolic diseases risk factors, only the study carried out by Karatrantou et al³⁴ achieved a significant reduction in systolic pressure.⁴⁸

The limitations of this review were that the studies analyzed did not detail the strength exercise protocols sufficiently; and that we did not find enough studies that analyzed VAT, or the same muscle mass variable, to be able to provide statistical data on the change produced by the intervention. In addition, BC outcomes were measured by various methods (DXA, BIO, skinfold, MRI, scale, and a meter), which was a limitation when comparing results between studies.

Conclusion

Physical exercise interventions in the workplace, especially those who last for at least 4 months and combine supervised, moderate-intensity aerobic exercise and strength exercise, are effective in improving BC, achieving a reduction in BMI, WC, TMF, BAI, FMI and VAT; and an increase in FFM, in an overweight adult population.

SO WHAT? Implications for Health Promotion Practitioners and Researchers

What is already known on this topic?

In order to achieve a healthier BC, with an adequate ratio of muscle and fat, and therefore reduce the risk of developing cardiometabolic diseases, it is necessary to promote physical activity, and an appropriate way is through the occupational health teams of the companies, within the workplace.

What does this article add?

Findings from this meta-analysis offers information about the characteristics of physical exercise interventions in the workplace that achieve to improve BC, and highlights the importance of exercise supervision.

What are the implications for health promotion practitioners or research?

Physical exercise interventions in the workplace are a useful disease prevention tool, and should be carried out whenever possible. More research is needed to better assess the effectiveness of these interventions on VAT, because of its importance on the prevention of chronic non-communicable diseases.

Footnotes

Authors’ Note

This meta-analytic review has been registered in PROSPERO (International prospective register of systematic reviews) on 8th July 2020, with the registration number CRD42020185057.

Acknowledgments

We would like to thank the authors of included studies who provided us with extra data for this review.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Guillermo García Pérez de Sevilla, MSc

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