I honestly just noticed this thread for the first time. I am passionate about this subject. I let myself go in my 30s. At 38 I knew I needed a change as I was almost 100lbs overweight. Just carrying my infant son in his carrier from the car to upstairs in my had me winded. I lost eh 100lbs over the course of 18 months and have generally kept it off for over a decade. (I always put on 15 lbs. during the Holidays which I take off in the Spring though now that I am in my 50s that gets harder each year and I am going to have to be more mindful in the winter.)
Outside of certain general principles I believe it is not a one-size fits all (pun intended) approach to weight loss because everyone is so different. My general principles:
1. 90% of weight loss happens the kitchen because it always comes down to calories in/calories out. My diet can be healthier or crap but as long as I take in less calories than I burn, I will be skinnier. I may be "skinny-fat" or "skinny-unhealthy" but I will weigh less.
2. Finding a workout that I love. I loath a traditional gym. Bores me to tears. In my 30s, I would start at the Planet Fitness-type place and by month three started finding excuses not to go and then drop. At age 38, a friend took me to my first live and local MMA Show on a Saturday Night. I fell in love in my heart I added a goal to fight MMA at least once. I accompanied my friend to his MMA Gym that Monday and never left.
I still train grappling and striking 4-5 times a week, earned my BJJ black belt, fought in striking smokers , and had my MMA debut in my mid 40s winning by submission. I LOVE fighting and training to fight. It is a brutal workout but doesn't feel like one. I can burn 600-800 calories in Jiu Jitsu sparring and have blast doing. I branched into trail running as a side hobby to help manage weight and cardio when injured before a major national BJJ tournament. I came to love the masochism involved in that and now have an eye to a 100 miler ultra as a long-term goal - if I can get my knees to cooperate. I even lift and do traditional gym stuff again -but just enough to prevent injury in the physical hobbies I love. Had I never discovered MMA I would have never been regular in exercise and wouldn't have been as effective on willpower with diet. Having to cut/maintain weight for a fight/competition makes it much easier to say no to the chips or cookies. Plus the lighter you are, the easier the trail race becomes.
3. Intermittent fasting. Doesn't work for everyone, but it does for me. I can do a lot of things fasted and hold out quite awhile before I have to eat, but once I do eat I have willpower issues with grazing/snacking. Intermittent fasting keeps on track for my calories goals for the day. I take all my calories in a 5 hour window each day absent special circumstances - vacation, holiday season, etc.
4. MyFitnessPal app. I log everything. Great app and its free though unfortunately some of the functionality has moved behind the paywall but still in my opinion the best out there.
I can drone on about this stuff forever, but will stop there. I am happy to chat about MMA for old dudes or trail running especially those with Ultra experience who may let me pick their brains.