I have been exercising for 5 weeks now. Generally most days and building intensity from 15 minutes cardio to an hour today (that was exceptional, just had my groove on !!

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I also do 30 minutes of moderately heavy weights as I am trying to tone after losing 140lbs.
My question is how long should I be holding onto the extra 4lbs I seem to have gained whilst exercising? I understand there is a Noobie gain, but thought perhaps it should be shifting by now? Any responses welcome as my intention was to lose the extra lbs and then some more, but seem to be holding.
Also I tend to eat low carb, as this was how I lost the weight. I like the way I eat and am satisfied by it, but was wondering if I need to tweak my w.o.e to suit the exercise? I would not be very happy to add in complex carbs, but do eat masses of veggies and lean protein.
Many thanks