I am overweight myself. I tend to tolerate my pets being overweight more than most people would.
However, there's a limit. If it starts to seriously impact their ability to move around, then that's an obvious problem.
My cat Pelé has always been sedentary, even when she had opportunities to get outside and play. Lately, she has gotten very fat and weak, and it's become difficult for her to climb up on the couch and bed, even though she's only middle-aged. I don't mind being a little overweight, but being both fat and weak is not good.
The goal is modest reduction in her intake, and modest increases in activity. Drastic changes may be unnecessary, and are more likely to trigger problems such as food competition between the two cats.
What's the best approach, calorie-reduction or increased exercise? Likely some of both. However, getting cats to exercise a lot goes against their very nature, so the emphasis may have to be on calorie reduction. (while still acknowledging that trying to increase activity to whatever extent is possible will also help)
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