A Fad diet from 1927. The add encouraged people to rather smoke a cigarette than to eat food...
Later followed many more e.g. the cabbage soup diet, the lemonade diet, the grapefruit diet, the low carb diet, the HCG diet, the scarsdale diet, etc, etc, etc.........
Nowadays not much changed. At least now we can call it the placebo effect? ;)