The coat is lying to you, in both seasons
A Norwegian Forest Cat in full coat is a spectacular amount of fur arranged over a strong, medium-large frame: dense undercoat, long water-shedding outer hairs, a full ruff, and britches on the hind legs. In winter that wardrobe makes a perfectly lean Wegie look enormous. After the seasonal shed, the same cat can look so much smaller that owners worry in the opposite direction. Neither impression is evidence. Condition is settled by touch at the ribs and waist and by weights compared across the same point in the coat cycle, not by photographs taken six months apart in different fur.
A hands-on routine for a heavily coated cat
Choose a moment when your cat is standing relaxed, ideally after a grooming session when the coat lies as flat as it ever will. Work your fingers through the side coat until you touch skin over the ribs, then assess honestly: ribs traceable with light pressure and a thin cover means condition is likely sound; ribs that require a determined dig means stored fat is in the way. Run a hand over the top line as well. Forest Cats stand higher at the hindquarters, with powerful back legs built for climbing, and you should feel that athletic rear assembly under the britches rather than a uniform softness from shoulder to tail.
Shape checks that survive the fur
From above, do not trust the outline the coat draws. Instead, place a hand on each side behind the ribs and feel whether the body narrows there; that inward step is the waist, and it should exist even when fur fills it visually. From the side, watch the cat walk. A fit Wegie moves with a deliberate, powerful stride and the belly carried up. Extra weight changes the gait before it changes the look: a broader roll through the shoulders, a belly that swings low and heavily, and a cat who studies a jump she once made without thinking, then takes the stepped route instead.
Slow maturing, slow gaining
Like the other northern forest breeds, this cat builds itself gradually, adding frame and muscle over several years, so steady early gains accompanied by real growth in length and height can be normal development. The pattern to question is gain after the frame has clearly finished: same cat, same length, more padding at the ribs, less interest in the tall scratching post and the high shelf circuit. Wegies are capable, enthusiastic climbers, and a shrinking vertical world is useful information. Note it beside the weights rather than treating it as a personality change, because together the notes give your vet a timeline instead of an impression.
When to involve the vet
Arrange a check if the ribs stay hidden under firm pressure, if the felt waist has disappeared, or if weights taken at the same coat stage keep climbing. Ask to be seen sooner if weight gain arrives alongside reduced climbing that looks effortful, panting or open breathing after mild activity, increased thirst, or a coat that has become greasy and clumped despite regular grooming, since those signs deserve a hands-on examination before any food changes. Bring the seasonal record with you so nobody mistakes winter fur for winter fat, or the reverse. Keeping those dated weights and coat-stage notes in KinsLe's Pet Passport makes your Norwegian Forest Cat's true condition clear in any season.