Green’s Dictionary of Slang

chameleon diet n.

a poor diet.

c.1698		B.E. Dict. Canting Crew n.p.: Cameleon-Diet, Air, or a very thin slender Diet.
1869		E.M. Whitley Political Portraits 226: He offers to his contingent members ‘chameleon’s diet-eating-the-air promises crammed’.
1900		London Standard 22 Oct. 4/3: Luckily he [i.e. a poet] was not doomed to live upon the chameleon diet of song.