Should I be concerned about my hamster's weight

[kathryn23]

My female Syrian carlos was originally bought from pets at home but adopted by me after her owners had her for about 1 month. She must have been around 4 month when I got her since I think pet shops normally sell them at around 12 weeks old. When I first got her she weighed 176g and since then she's been continually losing weight. I've had her for about 3 months and she now weighs 154g. However she seems really happy, likes exploring her home, runs round faster than normal sometimes (which I assumed is kind of like a rabbit binkying) and stretches quite often. I feed her 10g a day but found that most of it wasn't being eaten but was just staying stored in a corner. So should I be concerned about her weight loss or do you think he first owners just over fed her and she is now reaching her normal individual weight?