Significant effect of information placebo on exercise test results in children with normal weight, overweight and obesity

AIM: The aim of the study was to examine the effect of information placebo on fitness test results in normal weight, overweight and obese children. METHODS: Twenty-four pre-pubertal children with overweight or obesity and 24 age and maturity-matched normal weight children performed a progressive treadmill exercise test twice. Different types of information were randomly provided regarding a water drink consumed prior to testing; standard (water) vs deliberate positive (presumed energy drink, placebo) information. RESULTS: Following the placebo drink, both groups demonstrated significantly higher peak heart rate (overweight 165.8 +/- 16.7 vs 174.2 +/- 14.8 bpm and normal weight 177.9 +/- 13.6 vs 189.8 +/- 12.2 bpm) and longer time to exhaustion (overweight 396.9 +/- 161.9 vs 521.5 +/- 182.5 seconds; normal weight: 700.1 +/- 155.2 vs 893.3 +/- 150.1 seconds). Despite longer exercise duration and higher peak heart rate, average and peak rate of perceived exertion were significantly lower after the placebo drink (overweight 14.1 +/- 2.5 vs 12.5 +/- 2.5; normal weight 12.1 +/- 1.4 vs 10.7 +/- 1.5), with significantly shorter recovery time (overweight 132.2 +/- 28.5 vs 118.4 +/- 31.6; normal weight: 106.7 +/- 18.6 vs 96.7 +/- 17.8 seconds). CONCLUSION: Our results demonstrate a significant effect of information placebo on fitness test results that is unrelated to body weight. Children with obesity may enhance their physical activity levels and energy expenditure if properly encouraged.