New acquired weight gain (vs) life long weight

I haven't seen any studies, but I would say in a perfect controlled experiment they should be the same. Fat is designed to be stores of energy in times of need. Your body doesn't "rotate stock", it just grabs whatever it grabs. It doesn't make sense to have say, 50% fat really hard to lose and 50% fat easy to lose. (But it can be hard to lose fat in the areas you want to lose) However, being human beings, it is the "human factor" that makes certain circumstances harder.

Someone who has had the extra 40lbs for many years via bad diet/lack of exercise may find it really hard to change habits that are decades old.

Someone who has gained 40lbs over 12 months due to X reason may find it hard due to not realising why (or even not really caring). They may think it's the medicine magically adding fat, but really it's just lowering the calorie intake limbo bar and they can no longer consume the same amount and stay under. Or in the instance of pregnancy, they may still be heavily involved in taking care of a newborn baby or just view it as part of being a mummy.

You can't get fat by your hereditary alone. You might get genes from your ancestors that result in you burning less calories being alive than someone else, but your genes don't make you fat. I find more often than not it's the bad habits they are inheriting that makes them heavy, not their genepool. This comes back to changing life-long habits.