I've watched some science docs on this issue. When you double your size, you quadruple your mass. A person would be around 800 pounds in weight.
Things that would happen if a person woke up one morning and discovered a second growth spurt.
First, no clothing would fit. Birthday suit attire only.
Second, doorways would be a struggle to pass through. Flexibility would be needed to squeeze through the door frame.
Next, walking outside in public will cause a stir. Internet sensation immediately. Federal agents and military will be called once the viral news broke. Law enforcement not sure what to do.
After that, hunger will require a trip to the local fast food drive-thru or walk-thru.
Finally, the world beats a path to your front door.
The free stuff starts to roll in.
1) The fashion industry will compete for the endorsement of their clothing line to fit you.
Italian threads, Nike, etc...
2) Food and drink companies vying for endorsements.
3) Car manufacturers designing a vehicle to fit the new height and weight standards.
4) Home builders designing a house to fit the new height standards.
Just to name a few.