At the surgery, your pet will be weighed and an estimate made of what your pet should weigh! An accurate measure can then be made for the amount of food to be fed.
The pet can be weighed again in a month and the degree of weight loss assessed and then the amount fed changed accordingly.
Once your pet has lost the desired amount of weight, it can be changed on to a diet to maintain that weight.
Close monitoring is advisable to ensure those pounds don’t sneak back on.