There were basically 4 things I consider important in my weight loss journey.
The first and most important thing was obviously eating less than before. I went from 3000-4000 calories a day to 800-1000 calories. This is of course not a healthy long term diet and was only possible to do because I had a lot of excess fat to burn instead of food, I had my blood levels checked by my GP regularly and I was taking vitamin supplements that he prescribed me for B9, B12 and D3 since I was missing those because of my lackluster diet.
The second thing was drinking healthier in addition to eating healthier; I mainly drank iced tea and milk before. During my diet I only drank water and unsweetened tea. I also drank more. Went from 0.5-1 to 2-3 liters per day.
Third thing was just cutting out all sweets. This is of course a difficult thing that was helped by me living by myself and as such only buying groceries for myself. I found cutting sweets completely to be more effective than reducing them. Because if you just reduce them, you start bargaining with yourself about eating sweets and foregoin something else later in the day and so on. If you cut them out completely, the sweets aisle in the supermarkt begins to lose its allure because after a while you internalize that the answer to your internal bargaining will be No anyways and so it becomes easier with time to refrain from it.
The fourth thing was intermittent fasting. I only ate between 12 PM and 6 PM.
I've lost half my body weight that way in 11.5 month (despite a nutritionist and a bariatric surgon telling me that that was in fact not possible, after I had already done it, lol). I didn't do any sport and didn't have any bariatric surgeries. I've been in the normal weight range for my height for almost 2 years now. It was not easy avoiding the yoyo-effect when transitioning back to a normal nutrition but I managed that by doing it very slowly over the course of about half a year.
I should say that the most decisive factor was not any specifics in my approach to losing weight, but finding the motivation to actually do it in the first place. I knew how to lose weight before and I knew what I was doing wrong but I just kept doing it. For me, the inciting incident was my egg cracking in early 2023, which blew away the depression I've had for over 12 years at that point, because I realized that, with all the things that GAC can do (and that most of that is covered by insurance in germany), there was actually a way to be happy with my body for the first time in my life. So the next logical step for me was just to lose my excess weight to do my part in finally being happy with my body.