Will putting up the resistance make me thinner?

I have a high metabolism.

It is hard for me to gain weight.

I am 5'6 120 lbs (the weight I did gain was through pregnancy) I used to be a lot thinner.

I pretty much want to bulk my legs up a bit and I do elliptical machine cardio exercise for 30 minutes 3 days a week on resistance 3.

Is this enough to get the effects that I want?

Also,

If I continue to put up the resistance (which causes me to burn more calories) will I get thinner or will I just get stronger looking?

I have a great ass I don't want to lose.
Will putting up the resistance make me thinner?
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