Hey there... the thing is that once you slip into Starvation mode, you basically need to take things easier... Bumping from 50% Maintenance, say 1400 ~ 1500 cals to Maintenance (about 3000 cals) in ONE day... will most likely make things worse...
since the body is already holding on to everything, upping the cals right away will make your body hold on to it: this most likely comes as an evolutionary advantage: We were hunters before... so, you have a hunt, eat, then go on a fast for a number of days until the next hunt... then you eat again... in between hunts, you would go into starvation mode, and then inmediately after a hunt you would be storing all that fat "Just in case". (you never knew when the next meal would be)
In our lazy days, I would say the best way to get out of starvation mode is by adding some 200 cals per day (or start adding meals, this works superbly fine for people used to eating three mini squares per day) until you get to maintenance. All the while increase energy expenditure (cardio, weight lifting). This would depend on how low you were, but I believe it would go between 1 week to 4 weeks.
Also, a trick to avoid slipping into starvation is keeping your fats relatively high. Our body recognizes fat intake as a pattern of food availability.
I guess our bodys haven't really catched up with the fact we are no longer hunters but farmers....