The theoretically easiest solution is to drink your coffee in a way that doesn’t have calories, or and insulin reaction, as some sweeteners still pump insulin. I fully understand how practically impossible this maybe. I much prefer coffee with at least cream and to really make it perfect 5-10g of sugar.
I don’t know what you mean by losing your will to continue. But if you can go 20 days before losing that will, I’d say that’s a solid win, and definitely not back to square one!
To answer your question tho, yes you will be able to lose weight doing 16:8 IFs even with sugared coffee, hopefully within the “8.”
I don’t know what kind of timeline goals you have to lose 15KG, or what kind of weight that is (feel free to explain and I’ll provide further clarity), but it will be much slower than with prolonged fasting, likely between 6-9 months.
Assuming this is your LAST 15KG to lose, you could cut that most effectively in two months, with rolling 48 hr fasts, where you eat till you’re satisfied once every 48 hours till completion, and then transition to OMAD for maintenance.
Perhaps threading the needle further and providing a more balanced approach would be you start doing omad right away. Have your coffee, and eat soon thereafter (at least 1500 cals per your BMR) preferably after some exercise and fast till the same time the next day. Then just repeat this for about 2-3 months. You’d lose 15KG.
No matter which strategy you apply, there will be bumps in the road. Also, women shouldn’t fast during their period. There’s something to be said for being intuitively connected to your body as well. Maybe you’re feeling strong and you do a 3-day water only fast, then you do omad for a week, then 16:8s for your period, then come back at it hard with 48 hr Rolling fasts.
Why not break your fast in the morning? If this particular coffee is important to you, build your schedule around it instead of fighting it. Stop eating earlier and then break your fast when you would normally have your coffee.
If you have your coffee outside of your fast time, there will be little consequence .
I am no Starbucks fan but I would recommend trying their Caramel Coffee without sugar.It is excellent and MAY bridge the gap for you.
You should buy flavored Stevia Syrup Extract. Brown Sugar Caramel Syrup is bad for you.
I don’t really consider 16:8 with sugar coffee fasting… No you will not lose weight.
this is my flavor but you can see there’s a dozen others. https://www.amazon.com/French-Vanilla-Stevia-Liquid-Foods/dp/B0041UL234