Now since I have semi-retired and only working Friday, Saturday and Sunday, I notice that my weight tends to go down. Since I drive a shuttle bus, a sedentary job, I can mainly attribute this to the diet part. I have a big meal in the morning followed by a McDonalds apple pie and a coffee on my way to work.
Since my breaktime is limited, I usually just head across the street to Del Taco and mostly get the same thing the 3 days: mini bacon quesadilla, bean cheese cup and a grilled chicken taco. Lately I also get a medium size Coke Zero. This may not be everybody's cup of tea but it definitely works for me.
I usually ride my exercycle each of the three work days as well. Oh, and at night when I get home I eat about a tablespoon of peanut butter and wash it down with a cup of milk. That last has eliminated all my nighttime stomach acid issues which I had off and on for decades.
Of course though, sometimes on one of my four days off I might head out to a buffet ;-)