I do not believe no buy month is helpful because most people who live frugally have already optimized their spending and keep on improving themselves.
For example... I buy my clothing about once in a year in a considerate quantities, and I use them for maybe 2-3 years or longer. I am still wearing a hoodie I bought in 2015. So taking no buy month actually disrupts my flow or rhythm, I never know when I will take the apparel purchase again because I do not know when the bargain or clearance sale will take place.
so your healthy food and no buy month... I do not know, for fun or challenge yourself that should be good, but again... I do not believe it is the optimum way to save up. However I believe everyone has their own preference and compatibility