Not just that study - there was a UK Panorama program on "health supplements" ranging from energy drinks like lukazade (sp?) to protein shakes and similar stuff.
At best they're just a replacement for what you should be eating anyway and at worse they're either useless or detrimental - and they';re not covered by labelling laws... YET. However this year the EU is bringing in regulation for them and the companies all say they're going to have to "modify" their claims that they help burn fat or increase energy levels or metabolism or whatever.
Basically it's a big con.