It depends on how much you are eating. You can walk twice that many steps and gain weight, if you eat enough food to over compensate for the calories you are burning off.
I recommend going to http://www.fitday.com/
,which on the on-line version is free, and entering what you eat as well as what exercise you do, do see if you are achieving the calorie deficit you need to lose weight.
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My weight loss site, with blog, before and after pics, recipes, tips, charts, and stuff. Annie Takes Off