Diet and Health With Key to the Calories

First published in 1918, 'Diet and Health With Key to the Calories' was written by Dr. Lulu Hunt Peters, who lost 70 pounds using the calorie-counting method she described in the book.

The book was a significant bestseller, selling between 800,000 and 2 million copies, and it was the first weight-loss book to achieve such widespread success.

Peters' work popularized the idea of reducing calorie intake for weight loss, a concept that was revolutionary at the time.

The book also included calorie planning and different types of diet foods to help with long-term weight loss, particularly targeting American women during the context of World War I food shortages.