A semi-stationary balloon in the gastric antrum provided with an anchoring rod for inducing weight reduction in human beings is disclosed, a device for inducing a lesser appetite and early prandial satiety, said balloon being made of inflatable per-os medical grade silicone having a volume of up to 240 ml, with an average space of 120 ml to be filled with non-elastic fluid provided with radio-opaque contrast and dye, preferably methylene blue, so that the maximum diameter of 8 cm is reached after it is filled up with a volume of up to 240 ml and the average diameter of 6 cm with a volume of 120 ml, to be endoscopically placed inside the stomach (E); said intra-gastric balloon (1) being positioned in a semi-stationary way in the gastric antrum (GAC) and provided with an anchoring or duodenal rod (2) having a distal counter-weight (5) installed in the duodenum (D); particularly, the inner face of the pear-shaped medium portion of lesser diameter is coated with a malleable ribbon (f) that provides said balloon (1) with resistance and flexibility.