We used to notice that with our last cat Gracie, who was an athletic hunter outdoors, but not so much in the winter live in VT and 2 feet of snow and minus 20F temps will curb any cats desire for the great outdoors. She'd put on a few ounces (6lb-7lb cat) in the winter being a not-so-active couch potato, and trim up in the spring when she was out roaming more.
Don't notice it as much with Midori who is a 99% indoor all the time lazy sofa sphinx.
My experience has been similar to Lyrajean's; when I was growing up and had outdoor cats, I noticed a weight gain in winter. I haven't noticed it in cats kept strictly indoors, but I suppose it's possible.
My two indoor cats haven't changed at all from last fall to now. Juniper, an Abyssinian, weighs the same as always now that he's fully grown -- about 10.2 lbs. Bixby, a balinese, is also the same, although he changes color in the wintertime ;D
I have noticed our cats eat more when it's cold outside and eat less when warmer. Here in North West, we have been having unusually cold spring. But we had spots of 70 degrees + record breaking days. Whenever it's warm outside, their apatite decrease. Whenever cold rainy days come