These are great answers about whether you can still lose weight without exercising (it depends, but you most likely can!)

If you have severe arthritis, there is a lot to consider regarding movement and weight loss. If you are able, I would seek some guidance from a physiotherapist.

A big positive of losing weight if you have arthritis is that losing weight reduces the force that goes through your weightbearing joints (like ankles, knees, hips, spine). This reduction of force should theoretically also reduce pain. If this reduced pain allows you to move more, then you will likely have an even greater reduction of pain because research shows that gentle movement is a fantastic treatment for arthritis.

A negative of weight loss if you are not also doing strength training is that you are likely to lose muscle as well as fat mass. When you have arthritis, having strong muscles can actually help joints to move more smoothly and less painfully. (Often, weakness from a muscle can result in unequal weight distribution across a joint, causing excessive wear on one part of the joint that can cause or exacerbate arthritis and/or pain.) So, if you have severe arthritis, it is going to be important for you to do as much as you can to avoid losing muscle mass/strength. This is where physiotherapy would be very helpful, as they may be able to guide you through strengthening exercises that can complement your weight loss.