Dietary Investigations
Dietary investigations suggest that neutered dogs have a lower nutritional requirement than entire (un-neutered) animals, possibly by as much as fifteen per cent.
To avoid a dog putting on weight after it has been neutered, simply reduce its daily food ration.
As with any weight-control regime, it is much easier to prevent the weight going on than to take it off once it's there.
Weigh the dog regularly for a time after the neutering operation, until you have established that its weight is steady.