The findings will be presented by BBC Panorama and the British Medical Journal and on BBC One at 8pm tonight.
The Oxford team examined 431 claims in 104 sport product advertisements and discovered a “worrying” lack of quality research.
As a result, it called for more intensive studies to better inform consumers.
The team’s report is highly critical of the benefits of carbohydrate sports drinks, protein supplements, amino acid supplements and expensive sports shoes supposed to cushion an athete’s foot as they run.
GlaxoSmithKline, which produces Lucozade sports drinks, and GSK, producers of the Maxinutrion range of supplements, both argue their cases in the Panorama programme. However, Puma declined to be part of the investigation.