Lifting once a week does little for your muscles if you're in your twenties. It does pretty much nothing once you've reached your forties. (It's still better than doing nothing, but it won't show much in terms of visible change)

And no, exercising once a week won't make your waist shrink. Losing one pound requires a caloric deficit of ~3,500 calories. If you're the average desk-bound adult male, that means eating no more than 1,500-1,700 calories a day to lose a pound/week. (Your deadlifting burns around 500 calories/hour, so if you do an hour a week, that barely influences what you can eat)

Intermittent fasting is a way to get there, but... it's a fad. It can easily lead to eating disorders. I'd look at what you eat, and how healthy it is, first.