Losing 50 pounds or gaining 50 pounds? Which is more difficult?

Depends on the person. Someone with a low appetite will find it more difficult to gain, someone with a big appetite will find it more difficult to lose. As a person with a big appetite who used to be obese, I know that I could easily gain 50lbs in a couple of months, but losing 50lbs would take the best part of a year.

It depends on your body type and your hormones.

Some people can eat and eat and still stay skinny, others (most people) gain weight easily and find it hard to lose.

Losing

gaining

Depend on how long of a period of time.

None is really difficult if you don't put constraints on what this weight should be. Maybe if you go extreme you can lose faster than you can gain, because eating is tiring (while not eating is just passive), but anyway if you don't put precise constraints it's easy in both cases.

But losing 50 pounds of fat without losing a single pound of muscle is very difficult (or impossible, because I just don't have 50 pounds of fat, far from that), and gaining 50 pounds of muscle without gaining a single pound of fat is very difficult.

Unfortunately it's much easier to put weight on.

Losing it, of course. There is food everywhere, you're home, stores, billboards, on every block. You are being tortured by thoughts of the one thing you can't have. So losing is much, much harder.

neither some people can eat like a horse and put no weight on and some eat a cookie and blow up sadly that's life

easier to gain than to lose