Everyone is different. I was a few days shy of 50 when I had my DS, and went back to work on day 20. I spent the first week by working 4, 4.5, 5, 6 and 7 hours, then it was a 3 day weekend, and then I was back to work full time, at a desk job. I was tired a lot. But I did a cross-country business trip (SF to DC and NYC, where I gave a talk) at 5 weeks, a trip to Paris (part business, part vacay with a friend who had ovarian cancer and was between chemo rounds, so we were both moving a bit slowly) at 8 weeks, and then at 2.5 months, a 10 day trip back to Paris, London and Edinburgh with my husband (one day giving a talk in London, the rest vacay). I was NOT climbing mountains (though Edinburgh Castle was close!), and resting a lot, but I managed.
I think one of the key things is there is a point - which is different for everyone - where the slowly improving exhaustion from the surgery crosses with the trajectory of improvement that comes from the weight loss and then suddenly - you feel GOOD. Your strength is coming back (remember, your legs were really strong to carry your fat self around) and there's less of you to carry around. For me, at 5 weeks, when I got on the plane to fly to DC, and the goddamned seat belt snapped without an extender and the tray table went all the way down, was a threshold moment. Made a huge difference in the 4 12 hour flights in weeks 8 and 11.
