With the rapid development of cloud computing, cloud-based wireless body area networks (WBANs) provide powerful storage services, and process massive medical data efficiently. As the medical data are exploited to perform the clinical diagnosis and other special medical treatments, the integrity of the medical data stored in the cloud server is increasingly important. In this paper, based on the elliptic curve digital signature algorithm (ECDSA), we propose an efficient light-weight cloud storage private auditing scheme for medical data in WBANs. Our scheme enables a data owner to check the medical data integrity effectively personally, and does not need to retrieve the entire medical dataset, thereby dramatically reducing the communication overhead. Moreover, we further extend our private auditing scheme to private batch auditing. Thus, the data owner can perform auditing task for multiple different medical data files simultaneously. The performance comparison demonstrates that our scheme is much more light-weight, and more practical in cloud-based wireless body area networks.