As for exercise, not everyone needs to get "ripped", but some exercise is likely to benefit everyone - from better cardiovascular health, to just feeling like you have more energy, as well as getting to a more healthy weight. Admittedly, that's why I've been jogging 3km every day for the last month in addition to strength training, and while I felt horrible the first week, things are better now.

Some of the other advice ends up being a tad too drastic, though.

Stopping doing science/maths probably isn't good idea - maybe just slightly decrease the amount of time you spend on them instead?

The amount of time spent gaming should also be controlled, but quitting "cold turkey" could be harmful. For some people it's a way to cope with bad situations or socialize - take away that escapism and you'll be left dealing with all of the other bad aspects of life with no outlet.

Martial arts and joining social groups all seem like good idea, but for the more introverted folks it might actually make them feel worse. Maybe try going to a few meetups at first instead?

As for Tinder and social media - those might lead to you comparing yourself to others too much, which often isn't entirely healthy. Also, dating apps in general don't work for many guys due to societal factors.