I have been "skaarfing" my snakes since I started keeping them 8 odd years ago and have had no signs of any health issues at all in relation to overfeeding. My macs are up for their 5th season this year and have produced clutches every year.
The one thing I do see a lot of in this industry is a vast amount of underfed animals around. I mate recently bought an adult diamond from a person he had been dealing with since the guy bought it as a hatchie. When I saw the animal it was skin and bones, a 6 ft diamond that weighed in just over 1kg is way undernourished. Why, because the breeder had told him that diamonds need to grow really slowly and to feed it once a month. Totally incorrect IMO. The animal is here at home being fed up at the moment so it can get back some condition.
I have also seen 3 yr old macs that look like 12 month old animals that are still being fed rat pups, why, because they were told not too feed their animals too much.
I could go on for ages with these stories that I have seen and honestly believe way too many people are being given the wrong information about how much too feed their animals. I also believe some breeders mislead purchasers about how much to feed their animals so they don't "pump" their animals and produce offspring to compete with their own market too soon.
When it is all said and done an animal should look healthy, that is, their should be nice muscle tone down either side of the spine which gives the impression of an "M" shape. If you don't see this in your animal it is either too skinny/underweight and the spine would show easily through the back or it is too fat and looks round with no muscle tone. Although lack of excercise may also be an influencing factor in this side of the coin.
Oce again these are just my opinions.
Cheers
Daz