A bariatric balloon having a gas-filled antral chamber of a flexible sheet material, the antral chamber having an elastic superior wall joined peripherally with a less-elastic annular wall, the annular wall further joined peripherally with a non-elastic inferior wall, the inferior wall of a more rigid character than the superior wall and the annular wall. The superior wall has a convex shape, the annular wall has a cylindrical shape, and the inferior wall has a planar shape. Secured below the antral chamber, a gas filled pyloric chamber joined to, and contiguous with, the antral chamber, a pyloric wall encompasses the cyloric chamber. The gas-filled antral and pyloric chambers define a volume less than the volume of a human stomach. Safety arms are mounted on a gas inlet/outlet valve and extend radially from the valve in order to prevent the deflated balloon from passing through the pyloric sphincter.
