Thank you for getting back to me. We've now ruled out some conditions, but unfortunately, there are still a number of others that may be responsible. It may turn out that Molly needs to be seen by a vet. However, before taking that step, I recommend that you get rid of the pine bedding, and replace it with a paper-based bedding, such as CareFresh. I realize that pet stores recommend pine and cedar because they keep odors down, but these litters have been solidly linked to a number of health problems, some of which would cause weight loss. Most of these health conditions don't show up right away, but take months to develop. The occur in all small a mammals, including guinea pigs, rabbits, gerbils, hamsters, and rats and mice. Kidney failure, liver disease, and tumors are some of the possibilities. Animals kept on pine and cedar will seem fine for a length of time, but often by the time these problems develop, it is usually too late to treat them. However, getting rid of those beddings cna keep the condition from progressing. The following links will give you more details on the cedar and pine problems in small animals:http://www.rabbit.org/care/shavings.html
I would also discontinue the small animal dust. If no external pests are present, these dusts are simply exposing our pets to a toxin they don't need. That can suppress the immune system and lead to illness.
One of the most common causes of weight loss in young hamsters is a dental problem. Not all of these are detectable by looking at the teeth. Problems with molars are only found by x-ray. Intestinal parasites can also cause weight loss. A vet would have to examine a sample of Molly's droppings to diagnose these.
I would get a kitchen scale and weigh Molly. Switch the litter and add some quality sources of protein, such as a bit of boiled egg to her diet. In nature, hamsters don't live on seeds and grains alone. They eat insects, bird eggs, and bits of plants. Then weigh her every few days. If she doesn't quickly begin gaining, you'll need to schedule a vet appointment to get to the source of the problem. The following links will take you to directories of vets who treat small rodents. At the first site, you'll come to a log-in page. Sign in as 'member' and use 'member' as your password XXXXX well.
If you want to be sure you know how to give a hamster the best care you can, the hamsterific web site is a reliable resource. On the left side of the page is a menu where you can choose topics. There is a huge amount of information on hamsters on this site. You could start with the basic care and go on from there.http://www.hamsterific.com
If you have more questions, let me know by clicking on REPLY. I hope Molly will soon be chubby again.