two ways where i pretty quickly lost weight.
first way: cause the amount of my migraine headaches increased drastically at some point and at that time my diet was not the best (which didn't have not much impact cause i don't gain weight easily) i started to make fresh juice mainly from carrots, apples, cucumbers, beetroot, spinach, celery. did drink this exclusively besides water for two or three weeks. helped me to balance my acid/base balance and after that my stomach reacted much better to painkillers and also to coffee. i maintained drinking fresh juice for some time but also started eating normally. weight loss was significant but i can't tell in numbers cause i never had a scale but for sure 2 holes on my belt.
one key is also not to use some cheap juicer but a better one which slowly presses the juice out of the fruits and vegetables. it really makes a significant difference in the quality of the juice.
second way: at my suicidal time 3 years ago i was completely broke (did think i need to corner myself to make it easier to ctb). cause of that at some point i had nothing to eat or drink. so i started to drink water. the first two or three days were hard but after that it got easier. i did that for straight 11 days. i always wanted to do that but never had the discipline for it. i wanted to do it cause i did see a documentary about this way of fasting. one psychiatrist noticed at some point that the mood of his clients, who refused to eat for some time, got better.
i also felt this and my mood increased and maybe saved my life back then.
if you have health problems it might be good to make this under surveillance of a doctor. when i did it i was in the mid forties without any surveillance and had no problems. it is important not to go to heavy with the eating when you start again.
it also learned me to sometimes to replace the feeling of hunger with drinking water instead of eating.
my general observation about weight: when i eat healthy i can eat the same amount but don't gain weight (even loose weight when i have a bit too much). healthy means for me. mainly vegetables and fruits, mainly water and tea, nearly no bread, nearly never pasta (but thats cause i get easily headaches of it), no sweeties, rarely meat.
when i was reading about healthy eating i did read a book about tcm cooking and one thing was interesting. the author told that if you eat healthy the body has enough energy to remove the unneeded stuff out of your body - short - you shit it out. but if you eat not healthy the body has not enough energy to do that and stores unused stuff it in the body.
i observed this more than once on myself by having sometimes more or less food discipline.
i don't do any sports for over 25 years and sit a lot in front of my computer. but i walk maybe a bit more than average cause i have no drivers license and do my food shopping in the city by walking.
edit: i also never was on any medication which might have and impact on weight. so i don't know anything about this.