How about trying honesty?

I remember when Tony had recently become single after many years of marriage, and he was dating women he had met through online dating sites. Tony was chatting with me about one of the women he had met, who loved to run. Tony had told her that he loved to run as well, and they were working out together. She had proposed they run a 10K together, and Tony was genuinely perplexed at what to do, since he hated running, and certainly had no interest in the 10K. He figured he'd have to break up with her before the 10K came around.