Weight loss

I gave up smoking over 6 years ago and since then I’ve put on almost 2 stone. I keep telling myself that its just middle aged spread 'cos I’m over 40 now (only just!) But technically I’m classed as just obese according to a graph my doctor showed me.I’m only 5’8" and I should be about 10st 10lb so I only need to grow another 7 inches and I’ll be at my ideal weight! I tried the gym this time last year and I was bored silly running on the treadmill and using the crosstrainer.So can anyone come up with a foolproof way of losing weight whilst driving a truck or sitting at a computer?