Just had bariatric revision from sleeve to bypass and i am stuck
I'm a Certified Fitness Trainer :) ( Really), Nicole ( I've tried just about every job when I couldn't keep my weight down adequately to perform--which was basically most of my life )
and we were taught that if a client has over 40 lbs to lose, walking is definitely the safest and most efficient exercise they can do.
Trying to run not only won't make you lose any more ( don't forget walking is HARD WORK 
cuz you're toting all that heavy FAT! ( temporarily 
)
Building muscle through circuit training or lifting weights also works GREAT for us post WLS patients - its scientifically proven that we usually can build muscle far faster than "normies " (who usually really have to struggle and incorporate muscle building protein shakes).
More muscle tissue is they long term key to keeping the weight off while eating deliciously.
Muscle tissue burns 10 or more x the calories fat tissue of the same volume does , 24 hours around the clock even when you are resting and sleeping.
Muscle also WEIGHS 3x more than fat of the same volume - so don't expect to see much scale loss when you first start regular exercise ( but you Can expect to be fitting into smaller clothes sizes almost immediately 
... and lots of compliments on your tighter, more shapely figure !).
( and lets not forget daily exercise makes you feel SO amazing emotionally and mood wise .. and a lot less likely to crave the wrong foods )
Please make sure you get your surgeon's OK before you start at a gym... It takes a WHILE ( like 4 months ) for the internal stitches to heal completely.
Walking for now is by far the BEST and most efficient exercise you can do now ( it will also help you heal faster and drop far more weight than you would if you stayed stationary ) and the fall weather is so amazing - enjoy it !
hugs 
