Table 2 Basic characteristics of the included studies.

Type of the study

Study described as randomised, controlled, double-blind with parallel-groups

Study described as randomised, controlled, double-blind with parallel-groups

Study described as randomised (block randomisation), controlled, double-blind

Study described as randomised, controlled.

Number of individuals

N = 20

N = 48

N = 287 (n = 200 in total in placebo and control/ no-intervention group)

N = 81 (n = 53 in total in placebo and control group)

Age, mean ± SD [years]

10.43 ± 2.09^

Excess body weight (overweight + obesity): 10.35 ± 2.12

Normal body weight: 9.78 ± 1.65

Placebo: 8.18 ± 1.01

Control: 8.29 ± 1.04

13.1 (no data on SD)

Sex

n = 7 girls

n = 13 boys

Excess body weight (overweight + obesity): n = 10 girls;

n = 14 boys;

Normal body weight: n = 12 girls;

n = 12 boys

Placebo: n = 50 girls, n = 50 boys

Control: n = 50 girls, n = 50 boys

No data

BMI status

Children with obesity (BMI ≥ 95 percentile)

Children with normal weight (BMI percentile ≥ 5 and < 85), overweight (BMI percentile ≥ 85 and < 95) and obesity (BMI percentile ≥ 95)

Z-score of 0 to −3 SD for height-for-age and weight-for-age

Adolescents with a BMI that exceeded the 98th percentile for age and sex

Inclusion criteria

-pre-pubertal (Tanner stage 1) children;

-children with obesity;

-consent of parents/legal guardians

-pre-pubertal (Tanner stage 1) children;

-consent of parents/ legal guardians

-written informed consent from the parents/legal guardians and participants

-written, informed consent;

-BMI that exceeded the 98th percentile for age and sex according to 1990 United Kingdom reference data

Exclusion criteria

-organic disease;

-medications that might interfere with growth, weight control, or exercise tolerance (e.g., corticosteroids, thyroid hormone substitution, and recombinant growth hormone).

-organic disease;

-medications that might interfere with growth, weight control, or exercise tolerance (e.g., corticosteroids, thyroid hormone substitution, and recombinant growth hormone).

-severe anemia (Hb 0.80 g × L21), cardiovascular or respiratory disease, physical disability, recent history of serious infections, or surgery or injuries that would impair their ability to perform the study tests;

-individuals who were already taking nutritional supplements, if they had participated in a nutrition intervention study in the preceding year, or if they were family members of staff employed at the study site or with the sponsor

-medical conditions that would restrict the ability to be active 3 times per week for 8 weeks;

-unwillingness to attend supervised exercise sessions 3 times per week for 8 weeks;

-major cognitive or psychiatric impairments;

-diagnosis of insulin-dependent diabetes mellitus or oral steroid treatment

Placebo and control intervention

Before each testing session, the participants drank a glass of a drink:

-placebo: the drink was described by the examiner as a drink that increases energy levels, strengthens muscles, and is therefore likely to improve exercise performance; the bottles were opaque, blue-coloured, and included a label proclaiming the content to be an energy drink that strengthens muscles and improves athletic performance;

-control: the participants were informed that they are drinking water; the bottles were standard, transparent water bottles.

Before each testing session, the participants drank a glass of a drink:

-placebo: the drink was described by the examiner as a drink that increases energy levels, strengthens muscles, and is therefore likely to improve exercise performance; the bottles were opaque, blue-coloured and included a label proclaiming the content to be an energy drink that strengthens muscles and improves athletic performance;

-control: the participants were informed that they are drinking water; the bottles were standard, transparent water bottles.

Placebo group was administered an unfortified choco-malt beverage powder (energy equivalent of fortified choco-malt powder in experimental group) as single servings of 40 g in 100 mL water. Administration once a day for 4 months under supervision of study personnel on all school days (6 days per week) and for self-consumption at weekends and/ or on holidays.

Control group received no intervention.

Placebo: instead of aerobic exercise, participants performed light body-conditioning/stretching exercises, during which HR was maintained at 40% of HR reserve, and no exercise counselling or behavioural change advice was given.

Control (usual care): participants were asked to continue with their lives as normal.

Duration of the study

The participants were tested twice – once with water and once with placebo drink, in random order.

The participants were tested twice – once with water and once with placebo drink, in random order.

120 days

After participants completed their 8-week interventions, they were given an individualised home exercise or body conditioning program (in line with their group assignments) to follow on their own for an additional 6 weeks (14-week follow-up period)

End points of interest

-heart rate (initial and maximal), measured using Polar H10 heart rate monitor;

- recovery time, measured as the time from the end of exercise until heart rate reached 100 bpm;

-rate of perceived exertion (RPE), evaluated using the Borg scale

-duration of ergometry phase

-heart rate (initial and maximal), measured using Polar H10 heart rate monitor;

-recovery time, measured as the time from the end of exercise until heart rate reached 100 bpm;

-rate of perceived exertion (RPE), evaluated using the Borg scale

-duration of ergometry phase

-maximal aerobic capacity (VO₂max) - defined as the maximum rate of oxygen consumption, measured during incremental exercise (externally placed 12-inch step test);

-aerobic capacity(VO₂peak) - defined as maximum rate of oxygen consumption attained on a particular exercise test (20 m shuttle run test);

-40 m sprint was used to assess speed with time taken to complete the sprint being recorded manually using a digital stopwatch;

-maximal handgrip strength for dominant and non-dominant hand, measured using Jamar hand dynamometer;

-time to fatigue, defined as the time in seconds taken for the handgrip to fall from maximal value to 50% of the maximal value;

-rate of decline of muscle strength was assessed to measure the muscle endurance of forearm; sustained isometric contraction of forearm flexors to 50% of maximal handgrip was measured using the Jamar hand dynamometer and was performed on the non-dominant arm.

-the poorly fit category of the modified Balke protocol was used to assess fitness (distance walked was recorded as a result);

-resting heart rate

Participants lost to follow-up/ who discontinued the study

All of the participants completed the study.

All of the participants completed the study.

13 participants did not complete the study, of whom 2 were lost to follow-up and 11 withdrew consent (including in n = 4 placebo and n = 2 in control)

7 participants lost to follow-up (1/23 in placebo and 5/30 in control group).

Baseline values for the endpoints of interest

N.D.

N.D.

Placebo (N = 95), mean ± SD:

-VO₂max: 37.9 ± 5.6;

-VO₂peak: 32.8 ± 4.1;

-40-meter sprint [s]: 8.9 ± 1.0;

-maximal handgrip strength (dominant hand) [kg]: 9.4 ± 3.7;

- maximal handgrip strength (non-dominant hand) [kg]: 8.6 ± 3.5;

-time to fatigue in handgrip strength test [s]: 12.36 ± 7.66;

-decline of muscle strength [kg/s]: 0.38 ± 0.24.

Control (N = 97), mean ± SD:

-VO₂max: 37.0 ± 5.3;

-VO₂peak: 32.4 ± 4.2;

-40 meter sprint [s]: 8.9 ± 1.0;

-maximal handgrip strength (dominant hand) [kg]: 9.8 ± 3.4;

-maximal handgrip strength (non-dominant hand) [kg]: 8.5 ± 3.2;

-time to fatigue in handgrip strength test [s]: 11.13 ± 9.85;

-decline of muscle strength [kg/s]: 0.42 ± 0.26.

Placebo (N = 95), mean ± SD:

-resting heart rate [bpm]: 82.26 ± 8.30;

-aerobic function [miles]: 0.36 ± 0.10;

Control (N = 95), mean ± SD:

-resting heart rate [bpm]: 84.62 ± 10.57;

-aerobic function [miles]: 0.38 ± 0.12;

Final follow-up values for the end points of interest

Placebo (N = 20), mean ± SD:

-initial heart rate (bpm): 104.6 ± 12.8;

-ergometry phase: 5.1 ± 1.2*;

-running time [s]: 559.9 ± 151.0;

-maximal heart rate (bpm): 176.1 ± 13.7*;

-peak RPE: 18.0 ± 1.1;

-average RPE: 12.1 ± 2.3*;

-recovery time (s) 119.2 ± 25.3*

Control (N = 20), mean ± SD:

-initial heart rate (bpm): 104.2 ± 11.6;

-ergometry phase: 3.9 ± 1.2;

-running time (s): 434.4 ± 140.3;

-maximal heart rate (bpm): 167.5 ± 16.8;

-peak RPE: 19.1 ± 1.5;

-average RPE: 13.6 ± 2.1;

-recovery time (s)133.2 ± 23.7

Placebo (N = 20), mean ± SD:

-excess body weight (obesity+overweight):

-initial heart rate (bpm): 103.8 ± 11.8;

-ergometry phase: 4.8 ± 1.4*;

-running time (s): 521.5 ± 182.5*;

-maximal heart rate (bpm): 174.2 ± 14.8*;

-peak RPE: 17.9 ± 1.7*;

-average RPE: 12.5 ± 2.5*;

- ecovery time (s)118.4 ± 31.6*;

-normal body weight:

-initial heart rate (bpm): 95.0 ± 7.6*;

-ergometry phase: 7.6 ± 1.3*;

-running time (s): 893.3 ± 150.1*;

-maximal heart rate (bpm): 189.8 ± 12.2*;

-peak RPE: 16.2 ± 1.5*;

-average RPE: 10.7 ± 1.5*;

-recovery time (s)96.7 ± 17.8*;

Control (N = 20), mean ± SD:

- excess body weight (obesity+overweight):

-initial heart rate (bpm): 103.8 ± 11.8;

-ergometry phase: 3.6 ± 1.4;

-running time (s): 396.9 ± 161.9;

-maximal heart rate (bpm): 165.8 ± 16.7;

-peak RPE: 19.2 ± 1.0;

-average RPE:14.1 ± 2.5;

-recovery time (s)132.2 ± 28.5;

-normal body weight:

-initial heart rate (bpm): 94.8 ± 7.4;

-ergometry phase: 6.0 ± 1.3;

-running time (s): 700.1 ± 155.2;

-maximal heart rate (bpm): 177.9 ± 13.6;

-peak RPE: 18.3 ± 1.4;

-average RPE: 12.1 ± 1.4;

-recovery time (s)106.7 ± 18.6.

Placebo (N = 95), mean ± SD:

-VO₂max: 37.6 ± 5.3;

-VO₂peak: 38.6 ± 3.7;

-40 meter sprint [s]: 8.9 ± 1.0;

-maximal handgrip strength (dominant hand) [kg]: 10.6 ± 3.0;

-maximal handgrip strength (non-dominant hand) [kg]: 9.5 ± 3.0;

-time to fatigue in handgrip strength test [s]: 14.62 ± 6.35;

-decline of muscle strength [kg/s]: 0.33 ± 0.16.

Control (N = 97), mean ± SD:

-VO₂max: 37.8 ± 5.3;

-VO₂peak: 38.2 ± 4.2;

-40 meter sprint [s]: 8.7 ± 1.0;

-maximal handgrip strength (dominant hand) [kg]: 10.9 ± 3.2;

- maximal handgrip strength (non-dominant hand) [kg]: 9.6 ± 2.6;

-time to fatigue in handgrip strength test [s]: 14.03 ± 7.25;

-decline of muscle strength [kg/s]: 0.35 ± 0.16.

Placebo (N = 95), mean ± SD:

-resting heart rate [bpm]: 80.24 ± 1.01;

-aerobic function [miles]: 0.37 ± 0.01;

Control (N = 95), mean ± SD:

-resting heart rate [bpm]: 81.12 ± 1.10;

-aerobic function [miles]: 0.36 ± 0.01;