my cat is loosing weght

Question
i have change my cat food and he liked it and now he lost so much weight that his back legs are weak, and very skinny and he won't eat and his voice is getting weaker.

Answer
If your cat has lost this much weight I would recommend taking him to your veterinarian for a full examination.  Without knowing his age and possible health history it is difficult to say what may be happening with your cat in particular, but conditions such as hyperthyroidism, cancer, kidney disease, and heart disease can lead to weight loss and deteriorating health.  Your veterinarian will be able to do bloodwork to be able to help diagnose the problem.

Until you can get him in for an appointment you can try heating canned cat fat or baby food.  Cats are motivated to eat by scent so hopefully you will be able to entice him to eat a bit.

Best of luck to you and your feline friend.