Southern Cross boss Anthony McPhail said while puppy dog eyes could be hard to resist, it was important the 52 per cent of New Zealanders who own pets realised the dangers of being over generous around mealtime.
"This is a worry as there are a lot of human foods that cats and dogs aren't able to eat - things like onions and chocolate for example - are actually poisonous.
"Not only that but a bit of your lunch here and there is the equivalent of an extra meal for an animal and can add up to significant weight gain. This puts a lot of stress on the animal's joints, and can lead to diabetes, heart conditions and generally a shorter life span."
However, most pet owners were proactive when they realised their pet was getting a bit chubby, McPhail said.
Nearly three quarters (72 per cent) of overweight dogs and nearly half (47 per cent) of overweight cats are on a diet.
"The health risks of obesity for a pet are significant and can be costly - if you think your animal is overweight you need to discuss it with your vet and put a plan in place to fix it.
"There's no public health system for pets which means that as an owner it's up to you to pay for any treatment."
The Southern Cross survey was conducted by TNS online amongst 2006 randomly selected New Zealanders and was carried out in June 2016.