Do I overfeed my dog?

Weather is really changeable here, from very cold days it has changed to almost summer temperature. Pippi likes it a lot; nonetheless she seemed to be tired a bit. Usually she can run very quickly and fast and now she seemed to be fatigued and to need more rest than usual. I hope it is not connected to the fact that she is being overfed. I want her to be fit and in case I give her too much food, I will reduce it. It is easy to not see that our dog is overweight when it is a Yorkie, sometimes I am not sure if her "bigger" appearance is caused by her growing coat or does she have too much fat tissue? Hmmmmm..... http://www.drlianamawer.ca/obesity_overfeeding.html: In pets, as in humans, obesity is a common problem. In the US it is estimated that 25 – 40% of the pet population is obese. (...)at least 70% of pets are overweight or obese. The health issues that are caused by, related to, or worsened by obesity include:

• diabetes,
• arthritis,
• skin problems,
• respiratory problems,
• liver disease (cats),
• worsened fatigue,
• higher anesthetic risk,
• unwillingness to eat special diets when they are sick,
• shortened life span.

That is why I have decied to give my dog smaller portions of food and of course we need to have plenty of movement. I must admit that because days got shorter and colder (in general, today it is warm though) we have started to walk less. My neighbour's dog got obese unnoticeably (also a Yorkie) and I want Pippi to avoid his fate.