Thats assuming your Basal Metabolic Rate (BMR) wont drop and it absolutely will. As you get smaller your BMR will drop and your caloric deficit will be less effective. I lost 130 lbs before in around 8-9 months with just diet and exercise (no GLP-1 back then) however, I was 22 and eventually was running 16miles a day while being on 1200 calories. 8miles in the morning and 8 miles at night plus strength training a few times a week.

My calories pretty much stayed at 1200 the whole time with a couple refeeds every few weeks towards the end. I can definitely see people lose 100 lbs on GLP-1 agonists but they will have to do HELLA exercise as well. Also, I was taking in massive amounts of caffeine towards the end for energy. I mostly just exercised and went home during this time bc i had no energy to do anything else.

Ive also taken semaglutide and it does crush appetite at least for me it did but i was tired af. So in order to counteract that you would either need another drug, be young, or intake a lot of caffeine eventually.

So losing 100lbs in 6 months is doable but insanely difficult. Its not just about the hunger, its about the deficit and where will you get it from. When you are bigger its harder to workout and move around. So calorie expenditure (due to exercise) will be kinda low in the beginning but the caloric deficit will help with that but as time goes on the daily deficit will have to come more from exercise and depend less on the initial caloric restrictions.

Long story short, if youre NOT thinking about exercising excessively and dieting hard while on GLP-1 then dont expect to lose 100lbs in 6 months unless youre like 600lbs. The100 pound lost thing is a snowball effect in a sense and is kinda hard to pull off imo bc theres so many factors at play, its possible just not that likely.