Also, walk fast; really fast, and run up the stairs whenever you can. I work at a big campus so that helps with the fast walking.
Eat vegetarian a few times a week, and as others have said; don't drink sugar, and be wary of the bread and potatoes.
Not bragging here but I'm 59 years old and Friday morning I banged out 140 pushups; a set of 30, a 40, and then I did 70 (my most ever. Typically I do a set of 30 and two 40's, but I will do 50 for the last set at times if they are coming easy enough. And I'll max out once in a while--formerly 60 was my high).
I only got back into working out around 2.4 years ago so its never too late.