I lost 3.5 stone almost 5 years ago, I've put 1 back on but some of that is muscle mass as I weight train, but I look far better now than I did a stone lighter.
I've never done a diet ever. I changed my bad habits. Things that I saw as "everyday foods" are now "treats".
I cut out having crisps and sandwiches for lunch every day, swapped for lower carb such as cous cous with veg or soup. Crisps are occasional treats.
Cheese was always my go to sandwich filling, now if I do have a sandwich it's chicken salad in a wrap and a cheese board is my occasional treat.
Swapped tea/coffee with full fat milk for green or flavoured tea/black coffee. This also helped my biscuit consumption - I only ever used to reach for them to dunk in my tea, it's not the same when it's green lol
Swapped full fat milk on my breakfast granola/overnight oats for almond or coconut milk (much lower fat).
Reduced my portion sizes - I used to put the same amount of food on my plate as DH who is 6'3"
I exercise at least 3 times a week - combination of running, cycling, swimming and weights sessions in the gym.
I also walk everywhere that's within 1.5/2 miles, school pick up, into town to the shops, dropping DS at parties etc etc
We're an active outdoors family though which makes it A LOT easier, DS has walked everywhere since he was 2 or 3 and now age 10 thinks nothing of doing a 12mile fell walk round the lakes or doing a 30mile bike ride.