We consider a Wireless Body Area Network (WBAN) where wearable sensor devices are distributed on a body and have to send the measured data to a coordinator. The network uses the Carrier Sense Multiple Access with Collision Avoidance algorithm defined by the IEEE 802.15.4 standard as Medium Access Control protocol, whereas different modulation schemes are assumed to be available at the physical layer. We propose to use the Link Adaptation (LA) in this WBAN scenario, with the aim of reducing packet losses. Nodes select the modulation scheme according to the experienced channel quality: when the Signal-to-Noise Ratio is large, regardless of the actual interference, nodes increase the bit rate, in order to decrease the time the channel is occupied and, therefore, the collision probability. Performance is evaluated in terms of packet error rate and results achieved with and without LA are compared. Results show that the proposed strategy improves performance.