I was 50 pounds overweight when I got into H&F. I did not understand nutrition, exercise, or my body at the time. I was fat because I ate whatever I wanted & never exercised.
I had kidney surgery as a kid & never felt very good after that. I didn't know it at the time, but I had a stomach condition called SIBO (most likely caused by invasive surgery), which mimics food allergies. I also had undiagnosed
exercise intolerance (from SIBO) &
reactive hypoglycemia. As far as exercise intolerance goes, basically whenever I exercised, it felt like a drain was pulled on my energy & I'd feel like crap...joint pain, super nauseous, etc. Always just figured I was a wuss...pale skin, inhaler, glasses, the works. Turns out I wasn't digesting food very well. The reactive hypoglycemia was hard to track down because it didn't show up on my A1C or anything. I got treatment for SIBO a couple years ago & can now eat normally (hallelujah). Still have reactive hypoglycemia, however, which I mange by simply splitting my meals in half (i.e. 6 smaller meals instead of 3 bigger one) & making sure I get enough protein throughout the day.
I started out by doing clean eating & exercise. It worked, but it was not very fun. I went through a bunch of systems over the years for exercise & dieting and have finally settled on IIFYM & calisthenics. I like IIFYM because it's simple to follow & not restrictive (eat whatever you want, as long as you meet your daily macro numbers & calories), and also gives me the best results of any eating program I've ever tried. I combine this with eating smaller meals (re: reactive hypoglycemia) and feel pretty good all the time. Probably the biggest thing I learned is that food controls fat, not exercise. The exception is if you really like to exercise (if you're a runner or Michael Phelps), you can pretty much eat whatever you want & still be lean, but I don't really like to workout.
I like calisthenics because I don't have to go to a gym to workout...roll out of bed & bang out some pushups & stuff. Although not technically necessary, I do cardio because I have terrible digestion (from SIBO...basically slow motility causes the food to move slowly through my body & crap digestion means I do better by, ah, manually doing exercise to help things...compress). Cardio more or less forces my stomach work properly. For cardio, I typically do 30 minutes of VR biking in the morning. I do not like exercise & am not a natural athlete, but riding my VirZoom bike around in VR makes it pretty fun. And my calisthenics routine is fairly simple & goes by pretty quickly, and gives awesome visible results. Combining IIFYM & calisthenics is a great combination for me.
I also learned that there are some hidden aspects of getting in shape, namely motivation & energy. I found that the best source of those came from managing my sleep, basically going to bed early & getting enough sleep for your body. I get sleepy around 8:30pm & need about 7 hours of sleep to feel good. I fail on this on a regular basis haha, partly due to my work schedule & family & mostly due to bad habits. But I can always get back on track by hitting the hay early for a few days; it's like a fountain of natural energy & motivation appears...exercise becomes fun instead of work, meal prep gets easy because I'm not tired & don't mentally fight myself, etc.
Overall, going from fat to fit was a lifestyle change, but not a really big one once I figured out what I liked & what worked for me. The basics for me are going to bed early, eating multiple smaller macro-based meals, and banging out my calisthenics & cardio workout in the morning so I get it done for the day. I should I also note that one of the reasons I like IIFYM is that I actually look forward to my meals now, instead of yet another Tupperware dish of plain chicken, broccoli, and brown rice. Same with exercise...the calisthenics routine is quick & VR makes indoor cycling fun. So it's not really all that hard to keep up with because I get to play video games in the morning & eat delicious food all day.