The term 'Diet Doctor' can be summarized by the crossword solution 'Atkins, ' which is a six-letter word. Atkins is a popular diet plan created by Dr. Robert Atkins in the 1970s. It is a low-carbohydrate diet that emphasizes eating protein and fat-rich foods while avoiding carbohydrates. The diet has been controversial due to its potential health risks, but it remains popular among those looking to lose weight.