Optifast and sweating

I'm sorry if this is a little gross, but has anyone any input on what I'm experiencing?  

I'm 4 days into 7 on these shakes, with my surgery on Monday.  I walk to and from work, 7 miles round trip.  On these walks, this week in particular I've been sweating profusely!  I get home and it looks like I've wandered through a car wash.  The sweat seems saltier than usual too.  I know it's been warmer out but this seems more to do with my body regulating from the inside if that makes sense.  Is this part of ketosis? I'm not scared about it or anything, and it's certainly working.  I'm down 7 lbs in 4 days, consuming these shakes and 3l of water daily.  By my calculations I'm consuming 900 calories from the Opti, and burning 1500 exercising.  I guess it makes sense, just seems weird to be sweating like this. 

Makes perfect sense.  Your metabolism is working overtime.  Months down the road when you have lost all of your weight, you will have the opposite problem of being cold most of the time, ;).

LOL I'm already kinda there.  I've dropped 71 pounds now, compared to a couple of winters ago, and now I'm feeling the cold more.  My wife adds (jokingly) that I'm getting old too.  Haha