Regarding depression, I believe that working towards a goal, such as retiring early, would actually help combat depression because it gives purpose to work otherwise meaningless or monotonous. Also, I don't think early retirement planning is correlated to depression, i.e. they are orthogonal.
Regarding fat, the same argument, planning to retire early is not going to cause you to become fat. It is more of a lifestyle choice unrelated to when you want to retire.
Curious on why you would think they are linked to early retirement.
Regarding hobby, I have specifically talked about this in the website. If you already have a hobby, you shouldn't give it up just to retire early. However, if your current work is interfering your capacity on practicing your hobby, then maybe early retirement offers a "faster track" to be able to go back to your hobby than the traditional retirement route.
I've had a very volatile career, but I'm actually quite thankful that I've been forced to work at least 2 or 3 years less then your average person, even though I have no money to show for it. In retrospect, while it would be nice to have that money, I have memories of aimlessly travelling, hanging out with friends for hours a day in summer, and if I were to have waited till my late 30s, I'd have worked those memories away. I'm also im great shape and have a good relationship with staying in great shape, such that work will always be secondary. I also have some good friends that I've spent a lot of time with already. I know that won't always be possible, but I've established them and am decent at establishing new ones. These are things that careerist people end up losing out on entirely, a lot of the time.
By contrast, if I were to not only have worked regular hours for those missing years, but probably worked extra by even oke more hour every day, a bit on weekends, and saved a higher proportion than I already was, all I'd have to show for it is money, and that's pretty hollow. Thinking about retirement doesn't make you fat, lack of spending $ and time on physical hobbies does. Spending most of your time in a chair and eating cheap/quick food does too, none of this is a stretch to reach depression.
Early retirement requires doing things a little differently than the average. Luck is always a factor, but you want to stack the cards in your favor.
I didn't take the FIRE route, but I don't recognize this picture in friends I know who did. Some have kids, most have multiple hobbies, plenty of friends, and take regular vacations.
They mainly did two things early and consistently:
1. Were incredibly intentional about their careers. They always maximized for both pay and potential career growth and were absolutely ruthless about leaving a job if they began to stagnate on either metric.
2. Identified expenses that didn't make them happy enough per dollar and cut them. No fancy car, decent but not incredible living space, adequate furniture, vacations that aren't $1000+ a day (camping is great for this if you're into it).
Remember that if you're a knowledge worker putting in 60 hour weeks into your career is almost certainly an anti-pattern. The best data available says you're probably going to be do way better somewhere in the 30-50 hour a week range. That leaves an awful lot of time for the rest of life.
Once you hit financial independence it's not like you stop working, you just no longer have to ask the question "will my work let me pay the bills?" You can find the exact balance you find most fulfilling.
In contrast to what you describe, I find that with the intention to do this sort of thing, you end up predicating your interests based on the price of them entirely, rather than being frugal within them. Camping requires a tent, but if you're not willing to buy one and maybe a backpack and some shoes, you're just dull. I did do this for a period of time, and I look back on it largely with thanks that I didn't continue.
Sometimes this is sensible, sometimes it's not. Getting into car racing or mountaineering is just inherently very very costly, so I'd not blame someone for avoiding them even if they did have the cash. There is just a certain amount of unpleasentness involved in not excessively not spending coupled with excessively working.
I'm on track to be able to retire early. To be able to do that, it requires a deep personal understanding of what I want. Sure, there are SV engineers who could retire early and do it only to flounder because they haven't answered those questions, but I'm also sure there are many many people who learn very quickly that the question of what do I want is the only one that needs to be answered.
personal curiosity: are you <35 or >35? I've been curious as I drafted this.
That said, of course you don't need to spend your whole paycheck, but for the vast majority of people, I think you would have to spend so little that you'd really be sacrificing too much.
It's people who make the least money and can't retire who work the most hours.
at 33 i bought a farm. and this year at 35 i started a framing business. using skills i acquired in the interim. i couldve never made the transition if i hadnt the interim period. i still code for fun, and leverage my engineering skills to write software and build hardware to automate my farm.