Yeah my dad is 280 lbs so you can see I have some “fat genes”. It definitely has been harder leaning out as I aged, I think the main reason why it is so hard is because I only do calisthenics now and no gym like in my 20s, in the gym I would hit every muscle group and calisthenics only hits some. I probably lost 15 lbs of muscle from the first pic lmao.
I can tell you from personnal experience that calisthenics can do wonder if you can add in a few weighted exercices.
A few years ago I got quite sick (genetically induced hepatitis) and lost 13kg/28.6lbs in only 2 weeks and I was around 70kg/154lbs for 1.75m/5'9''ft lean before that. I basically lost around 20% of my body weight while prolly being around 15% body fat so I fatally lost a lot of muscle, further amplified by the fact that I couldn't really do any physical activity for a while and even now I can't do as much as I'd like because of the tireness I have to deal with every day.
I started dong some calisthenics around 5-6 months ago and was at 67kg/139-143kg for 1.78m/5'10''ft and prolly a bit over 20% body fat. I now stand at 73kg/161lbs at I would say pretty damn close to 15% body fat. I didn't do any bulk for this as well. I also had to train less hard during summer as heat is a big problem for me since I got sick and I still had to get my job done as a priority (I'm a future farmer so physical work as well).
From reading scientific litterature, looking at some youtube channels (Hybrid Calisthenics ftw, that guy is incredible) I managed to get a pretty decent grasp on exercice/bodybuilding which I'd say transalted into fairly decent results (I still carry those cursed love handles though, these are a pain).
I crafted myself a bench of sorts with planks and use stones in place of dumbells to target the chest/shoulders/back/arms if I feel like it (push-up variations are already more than enough for a lot of muscles but I like to try out things), made myself a pull-up bar with a chestnut tree branch placed between two other trees, toyed around exercices variations (like incline push-ups for the higher part of the pecs, varying grips on chin/pull-ups, incline raises for delts, ...) and all that stuff makes for solid exercices overall. I also am lucky enough to have relatively heavy weights that we use for our tractors that I can use (mostly for squats as of now, sets of 30 using 20kg/45lbs but I may either go for the 45kg/100lbs of start working towards 1 legged squats) so there's that. Admitedly none of my solutions are perfect and a gym would be better but the closest one is like over 30km away (19 miles) and even if one was close I like to be alone.
I don't have a picture of before, I suppose I could take one now but to be fair I have a lot of hair that really hide the mucle definition (especially on legs) so it wouldn't be too useful I guess.
But yeah genetics do play a big role (quite possibly the biggest factor). I know a lot of people that gain fat a lot faster but I personnaly have to admit I have top-tier genetics when it comes to fat-regulation so I do have it easier on that side (though it sure as hell doesn't help when you try to regain weight ^^).
Diet/cardio is gonna be key. Once again for me I love to walk and have done it all my life (living in the mountains help for that too) and living on a small farm I always had an excellent diet (admitedly lacking in fish) so those aren't an issue but depending on where you live/how accessible great food is it can quickly become one.
If you have some space to grow some vegetables I can only tell you to go for it, the quality of your food/price ratio is unbeatable and it's a goddamned pleasure to do especially if you enjoy cooking (I can give you a recipe for a killer ratatouille).
And do as much cardio as you can do (while enjoying it ofc). For people with "fat genes" it really is the best option. 1 to 2 hours of walking a day (30 minutes if your job takes too much time is fine too) will do wonders. No need for jogging, walking is arguably much more efficient.
So yeah, I never cared for any of that stuff before as I already had more than enough physical activity but as I was doing this to speed my recovery up I ended up loving it and I really have a blast haha. Doing something fun that is healthy is an absolute win for me. You can challenge both brawns and brains while bettering yourself, simplifying your life (especially long-term) and getting a better physique as well.
I apologize for the lenghty post but when I enjoy things I tend to ramble on ^^.