They have wrong control.

The control they should have is a group that lift weights [1], walks [3], swims or runs [2] for two hours.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3448565/ [2] https://www.ncbi.nlm.nih.gov/pubmed/14628975 [3] https://www.nemours.org/content/dam/nemours/www/filebox/serv...

Also, I think they did not test transience of effect observed - how long will it last?