In response to national calls for improved physical sciences education for students pursuing careers in the life sciences and medicine, reformed introductory physics for life sciences (IPLS) courses are being developed. This exploratory study is among the first to assess the effect of an IPLS course on students' attitudes, interest, and performance. The IPLS course studied was the second semester of introductory physics, following a standard first semester course, allowing the outcomes of the same students in a standard course and in an IPLS course to be compared. In the IPLS course, each physics topic was introduced and elaborated in the context of a life science example, and developing students' skills in applying physics to life science situations was an explicitly stated course goal. Items from the Colorado Learning about Science Survey were used to assess change in students' attitudes toward and their interest in physics. Whereas the same students' attitudes declined during the standard first semester course, we found that students' attitudes toward physics hold steady or improve in the IPLS course. In particular, students with low initial interest in physics displayed greater increases in both attitudes and interest during the IPLS course than in the preceding standard course. We also find that in the IPLS course, students' interest in the life science examples is a better predictor of their performance than their pre-IPLS interest in physics. Our work suggests that the life science examples in the IPLS course can support the development of student interest in physics and positively influence their performance.