A food processing system includes a food slicing machine having a control arrangement for regulating a thickness of slices cut by the machine so that they are cut according to a current value of a slice size parameter. An under-weight signal is generated which is responsive to generation of any under-weight groups of slices by the slicing machine, and an end-of-line weighing device monitors the weight of groups of slices outputted by the system and generates an end-of-line weight signal responsive thereto. The system identifies any under-weight groups of slices so that their weight can be increased by addition of a further slice before being outputted by the system. The control arrangement receives the two signals and determines the value of the slice size parameter having regard to them. The slice size parameter may be adjusted to minimize give-away by the system.