Male Rat Loosing Weight?

Question
Hi,
I am a proud owner of two male rats, around the age of 2 or 3 years old. Both rats were from the local pet shop, both looking very healthy and active.
But lately, one of my male rats, Dale, has seem to fall sick maybe. He looks 2x smaller now then his brother, skinner and more fragile, while his brother looks full and healthy. I started to worry that maybe it was because his brother kept him from eating their food, almost an dominant behavior? But i soon saw that he wouldn't completely eat the food he was given. I tired extra foods such as fruits and veggies, but he would only take a few bites then walk away.
Is my rat sick? or is this just a behavior that happens between two male rats?
Thank you,
Katy.

Answer
Are you keeping food down at all times for them to eat at their own leisure?

At this age, yes, it could be from an illness that is causing weight loss.  Please check my website, sandyscrittercity.com and refer to the page on heart disease and also on kidney disease. Check over the symptoms and see if anything sounds like your rat. Sometimes we miss things and once we start reading, it all makes sense!   What type of food do you use?