Usually, failing to respond to the ASA is a surefire way of having a complaint upheld. Indeed, failing to respond to the ASA is a breach of the CAP Code in itself. 

However, in the Fenton Fitness decision, the ASA decided against upholding a complaint even though the advertiser failed to respond to the ASA's investigation.

Despite the lack of response, the ASA took an intelligent approach and considered the ad on its merits. The complainant had complained that the ad (which involved a model pulling down her leggings to reveal her hip) was degrading to women. However, the ASA rejected the complaint on the basis that there was no explicit nudity, and the exposing of the woman's hip was related to the advertising message of fitness.

It is good to see the ASA critically evaluating complaints, even when the advertiser has failed to engage in the process.