You should avoid hay-based foods, seed mixes, and low protein diets. Unfortunately, this eliminates most foods on the market--including the most popular, Oxbow.
We particularly dislike the Oxbow diet because it is completely inappropriate for hamsters. It is hay-based and extremely low in protein. Hamsters do not digest hay well, so most of the nutrients the food does provide is passed right through the body. While most hamsters are able to survive on this formula, they never thrive. Hamsters on this diet often have poor size, condition, and health overall.
Seed mixes, as discussed above, are great for providing variety. However, they allow the hamster to pick and choose their diet, and in doing so, they often leave the healthiest bits behind. Additionally, this means the diet is very unbalanced from day to day, which is rather undesirable. For these reasons, a seed mix should never be a staple diet.
For more info on foods to avoid, check out the article from the California Hamster Association.
