My ferret is kinda fat

Question
Hi,
I have five ferrets, one girl and four boys. The girl doesn't get along with other girls. They are all rescues. One was picked up off the street by the animal control in a city near mine who gave him to me, another was given to me by my brothers friend and we kept him because no one would take him because he bites, two were adopted from an MSPCA, and the one I am writing to you about was adopted from an MSPCA as well. His name is Yogi Bear. All of my ferrets weigh between 1lb 13oz and 3lb 3oz. Yogi weighs about 2lb 8 oz. He is pear shaped(skinny at his chest and slightly bulging belly). I can still feel his ribs though. He loves eating; he eats some of my other ferret Frankie's duk soup. Frankie eats duk soup because he is underweight and he has insulinoma. The duk soup is made from chicken or turkey baby food, yogurt, kitten formula, and sometimes pieces of raw meat if we have it. I don't think that's why he's fat though because he's always been around the same weight as he is now ever since we got him a little over a year ago. I let them out of their cage almost for the whole day and sometimes all night. The cage they live in is a two story ferret nation. He plays a lot. The food I feed them is 8-in-1 ultimate. The only treats I give them are N-bones and sometimes leantreats for dogs that I get from the vet, but I usually do not give them treats very much. I give them ferretone sometimes while I clip their nails, but not ferretvite or any of those sugary ferret lax supplements. I don't know any of his history from before we got him because the shelter that we got him at did not know much about him either. Does he seem fat or overweight to you? What should I do about it?
Thanks in advance.

Answer
Dear Cherry,

Wow!! Your question is complex and I hope I can answer it in one swoop.  First of all, you seem to be doing everything RIGHT!!

I wish everyone were as attentive to their furry little friends.

Lets talk about weight.  It is very important to keep a ferrets weight on track.  Because their metabolism is high, they tend to burn a lot of calories.  So, it is important to make sure they maintain a healthy body weight.  However, don't worry if you feel little hip bones or ribs.  You'll not feel any fat or weight there.  The problem occurs around the lymph nodes.  Unfortunately, ferrets are prone to lymphoma.  This can be determined by an enlargement of the nodes behind the front and back legs and the neck area.

Your vet can show you how to feel the nodes and determine any changes that may need to be addressed.  I just took one of my little guys for a checkup yesterday.  

I suggest you take your little fat guy in for a wellness checkup and ask the vet to show you how to feel the lymph nodes.  Believe me, you'll sleep much better knowing your little guys are okay.

Fondest Regards,
Janet