you could do alternate day fasting. on the day that you eat, dont eat so much that you make up for the day skipped. as long as you eat sensibly, its practically effortless.
caution, with details:
hours fasted isnt what results in fat loss; calories are the only factor. lets say you skipped monday (100% calorie deficit) and ate tuesday. if you eat tuesday and mondays calories (200% calorie intake), you have refilled the fat cells spent while fasting on monday, erasing the fat loss effect of the fast.
put another way, lets say you fasted for 23 hours. yes, you really did burn fat for a good portion of it; but if you then ate weight maintenance calories on the 24th hour (OMAD), you have just re-filled those fat cells that were emptied during those 23 hours.
thats why fasted hours really arent what you should aim for, but instead should aim for a calorie deficit while breaking each fast.
Sounds like you’ve got a great start! I’d move from what you’re doing now, a 12:12, to a 14:10, or cutting two hours off of your eating window, and see how it feels. If/when that feels comfortable cut out either breakfast or dinner and eat in a 16:8 or 18:6 pattern.
Best of luck!
If you’re only eating breakfast, lunch, and dinner. Then you’re off to a good start. The biggest issue is snacking between meals.
As for increasing fasting times, there’s lots of options.
You can drop one of your meals. Most ideal would be dinner so that your stomach is less full when you go to bed. But breakfast is the most practical and easiest meal to skip, at least for me. This would push you into a 16:8 or 18:6 schedule.