Most people who come to me think they need to train five or six days a week to see results. They have usually tried it, kept it up for three weeks and then stopped completely.
Recovery is part of the plan
Strength is built between sessions, not during them. With three sessions a week you get a full day of rest after each one, which is exactly what a body that sits all day needs.
What a week looks like
Monday, Wednesday and Friday, or any three days with a gap between them. Each session has two main lifts and two or three smaller exercises. Sixty minutes, then you go home.
After twelve weeks of this, the clients on my results page added between fourteen and thirty eight kilos to their main lifts. None of them trained more than three times a week.