It's a bit nuanced because addiction in this context is a lay word running a spectrum from essentially "bad habit" to "mental illness causing life ruining dysfunction of executive faculties" and it's hard to speak broadly about both at the same time. But behaviors can easily straddle both, with for example buying a lottery ticket every time you get gas being "bad habit" gambling and what happened to your friend being on the other end.
Addiction almost always has its origins in a useful adaptive behavior. For example cigarettes, esp when not dependent on nicotine, are calming, and taking a little break to think your thoughts at points in the day can be effective at managing stress during intense work. Or social media on your phone can be a way to avoid moments of boredom, which often our minds find distressing. On the other end serious drug addicts are very often unknowingly self-medicating severe mental illness like anxiety, ptsd, depression, BPD.
Without addressing the underlying reason for the original use, a relapse or displacement addiction is much more likely. In the case of "lighter" ones like smoking or social media often no intentional change is necessary. In the intervening years you got better at your job and it's not experienced as so stressful anymore, or you're older now and just able to tolerate the boredom of the toilet better, etc. But yeah you're still gonna be bored waiting in line at the store or whatever, and you either figure out another way to handle that, or your mind will insist you handle it the way it is used to, with scrolling an app.
In your friend's case it seems likely he was using food to cope with something else, and when he removed food he didn't have the support and skills to address the underlying problem.
Addiction almost always has its origins in a useful adaptive behavior. For example cigarettes, esp when not dependent on nicotine, are calming, and taking a little break to think your thoughts at points in the day can be effective at managing stress during intense work. Or social media on your phone can be a way to avoid moments of boredom, which often our minds find distressing. On the other end serious drug addicts are very often unknowingly self-medicating severe mental illness like anxiety, ptsd, depression, BPD.
Without addressing the underlying reason for the original use, a relapse or displacement addiction is much more likely. In the case of "lighter" ones like smoking or social media often no intentional change is necessary. In the intervening years you got better at your job and it's not experienced as so stressful anymore, or you're older now and just able to tolerate the boredom of the toilet better, etc. But yeah you're still gonna be bored waiting in line at the store or whatever, and you either figure out another way to handle that, or your mind will insist you handle it the way it is used to, with scrolling an app.
In your friend's case it seems likely he was using food to cope with something else, and when he removed food he didn't have the support and skills to address the underlying problem.