With Ruby her weight has never been a problem. Reno however is a different story - he's developed a small weight problem and is 1/2 pound overweight. I didn't want this to become a bigger problem for him so decided to get the weight under control now.
In talking with his breeder I realized I had been feeding too much at 1/2 cup per day. She says only 1/4 cup per day
that seemed a bit extreme to me, so I compromised and am currently feeding about 1/3 cup per day. FYI, Reno is a little over 5 lbs and should be in the 4 to 4-1/2 pound range.
We have also started to be more active now that the weather is nice enough to be outside everyday. By becoming more active and reducing the calorie intake, I think he will lose the extra in no time.
My inlaws fox terrier had a significant weight problem. Their vet suggested letting her eat green beans to satisfy her need to eat more. So, they give her 1/2 cup along with her normal food in the morning and the same in the evenings.
Reno has been on his diet only for a few days. I can let you know his progress here in a couple of weeks, if you're interested.