Sports scientists and nutritionists warn there are no short-cuts and the quest to match Williams could consume your life.
Dr Nigel Harris, a senior lecturer in physical conditioning at Auckland University of Technology, said while Williams was genetically blessed, good genes weren't the be-all and end-all.
"You need to be genetically blessed to both look and perform like that. But body builders can look astonishing."
Dr Harris said to develop Williams' muscle mass a person would need to adopt a body-building style gym programme, heavy on weight-lifting.
But there isn't any need to live in the gym - slabs of muscle mass can be developed with three or four intense sessions a week targeting different body areas.
"The idea is within one workout you're exhausting a particular area, rather than trying to get through the entire body in one go."
Healthy Food Guide nutritionist Claire Turnbull, who has worked with the North Harbour Rugby Union, said unless a rigid diet was followed gym work would go to waste.
"The biggest thing I found with the guys who got the best bodies were the ones who were consistent."
That meant meals that were high in fibre, fruit and vegetables, and lean protein - alcohol and fatty foods are all but ruled out.
The All Blacks eat up to 2 grams of protein for every kilogram they weigh a day, which is the maximum and shouldn't be exceeded.
"People often think it's better to have more, but if you have more protein than your body can use it will end up turning to fat."
Both Ms Turnbull and Mr Harris said the usefulness of supplements like protein powders was debatable, and even steroids were no "magic potions".
"The higher you get up in rugby, ironically the fewer supplements people use."
Getting as in-shape as Williams would require a rigid discipline out of step with ordinary daily life, Ms Turnbull said.
"It's a huge amount of work - and that's his job. People can be unrealistic in their expectations of themselves.
"Looking like that on top of a full-time job is likely to place a lot of pressure on other areas of you life. You have to give up a lot of things to look like that."
Ms Turnbull said genetics and a person's age meant regardless of effort or money spent such a transformation would be beyond some "skinny white men".
But Mr Harris said he had seen plenty of "average mums" and "corporate overweight guys" achieve dramatic change.
Still, Williams' 110kg of bulk would look very different attached to a frame shorter than his 1.91 metres.
"Obviously you're genetically disposed to look a certain way, even if you do build muscle tissue."