Taylor Lautner used to be a skinny teenager. Now, he's a symbol of ripped fitness.
Lautner, of course, stars in the Twilight movie series. And when you're playing a werewolf, you can't be wimpy.
Trainer Jordan Yuam guided Lautner from meek to muscular. Here, he shares the keys to Lautner's workout success.
"There are three aspects to changing your body," Yuam says.
Your workout. "You want to be sure you are doing the things that meet your goals," he says.
Why do boys have hair on their face but girls don't?
First of all, that isn't true. Girls do have hair that grows on their face. But it's very faint and usually not noticeable until later in life.
In teenage boys, facial hair grows thick and darkens because of the effect of testosterone. That's the male sex hormone.
When boys enter puberty, their testicles begin producing more testosterone. It's responsible for many of the changes your body goes through. Getting a beard is one of the changes brought about by this hormone.
How come I've got almost no hair on my face when friends my age already have a beard?
Getting hair on your face is one of the last changes of puberty. On average, boys start noticing hair on their face around age 15 or 16.
Exactly when the changes of puberty occur can vary a lot. And how fast the changes occur can also vary.
That means some boys start growing a beard very early in their teenage years. Others don't notice a beard starting until they are much older.
So if the guys you know have whiskers, while you barely have any fuzz on your cheek, there's probably nothing wrong with you. Your beard will start growing soon enough.
Do all guys get the same amount of facial hair?
No. Just like all guys aren't the same height, the amount of facial hair varies from one guy to the next. That's because the amount of hair you have, how dark or light it is, and where it grows on your face, is largely controlled by your genes.
That doesn't mean your beard will necessarily look like your dad's. What it does mean is that somewhere in your family tree, there are men whose beards followed a pattern like yours.
And it may take a while before you know what that pattern is. Usually, though, by the time a guy is in his late teens or early 20s, the pattern of his beard is set.