An implantable device for reducing weight in an individual, the device comprising: - a current generator (42, 43) adapted to produce an electrical signal; - a memory - at least a first set of electrodes comprising two electrodes (10, 12) adapted to be connected to the generator (42, 43) and configured to be fixed to a dorsal vagus nerve of the individual at a predefined distance one from another to apply the electrical signal to a portion of the dorsal vagus nerve located between the electrodes (10, 12); a short-circuiting switch adapted to be turned on for short-circuiting the electrodes (10, 12), wherein - the applied electrical signal is an effective current signal which has an amplitude defined by a method implemented in a computer program stored in the memory, said amplitude increasing gradually during a progressive phase and being maintained constant during a stabilised phase - the device comprises a second set of electrodes comprising two electrodes (24, 26) adapted to be connected to the generator (42, 43) and configured to be fixed to a ventral vagus nerve of the individual body at a predefined distance one from another to feed with current a portion of the ventral vagus nerve located between the electrodes (24, 26); - the device comprises a channel selector switch adapted to connect alternatively the first set of electrodes and the second set of electrodes to said generator (42, 43) according to a predefined frequency to transmit the current generated by said generator (42, 43) alternatively to the dorsal and to the ventral vagus nerves, - each phase comprises an emission period followed by a non emission period, - the generator is adapted to produce pulses during each emission period, and not to produce pulses during the non emission periods, - the short-circuiting switch short-circuits the electrodes of the first and of the second sets during the non emission period, and - during the emission period, the channel selector switch connects alternatively the first set of electrodes and the second set of electrodes to said generator according to the predefined frequency to transmit the current generated by said generator alternatively to the dorsal and to the ventral vagus nerves. - a current generator (42, 43) adapted to produce an electrical signal; - a memory - at least a first set of electrodes comprising two electrodes (10, 12) adapted to be connected to the generator (42, 43) and configured to be fixed to a dorsal vagus nerve of the individual at a predefined distance one from another to apply the electrical signal to a portion of the dorsal vagus nerve located between the electrodes (10, 12); a short-circuiting switch adapted to be turned on for short-circuiting the electrodes (10, 12), wherein - the applied electrical signal is an effective current signal which has an amplitude defined by a method implemented in a computer program stored in the memory, said amplitude increasing gradually during a progressive phase and being maintained constant during a stabilised phase - the device comprises a second set of electrodes comprising two electrodes (24, 26) adapted to be connected to the generator (42, 43) and configured to be fixed to a ventral vagus nerve of the individual body at a predefined distance one from another to feed with current a portion of the ventral vagus nerve located between the electrodes (24, 26); - the device comprises a channel selector switch adapted to connect alternatively the first set of electrodes and the second set of electrodes to said generator (42, 43) according to a predefined frequency to transmit the current generated by said generator (42, 43) alternatively to the dorsal and to the ventral vagus nerves, - each phase comprises an emission period followed by a non emission period, - the generator is adapted to produce pulses during each emission period, and not to produce pulses during the non emission periods, - the short-circuiting switch short-circuits the electrodes of the first and of the second sets during the non emission period, and - during the emission period, the channel selector switch connects alternatively the first set of electrodes and the second set of electrodes to said generator according to the predefined frequency to transmit the current generated by said generator alternatively to the dorsal and to the ventral vagus nerves.