This happens to me sometimes. I used to be someone who would finish all the food on my plate. Now I eat half of my meal, especially at dinner. My window is 12pm-8pm, so I usually have a good appetite during my first meal of the day, but not as consistent with my second meal. And if I don’t LOVE the food in front of me, I definitely won’t eat much of it. If you are worried about eating too little you can try tracking your calories each day to make sure you are not in too much of a calorie deficit. I have only been doing IF for a few weeks, so I’m curious to hear from others who are more experienced.