The 34-year-old Mad Men star gave birth to her baby boy Xander in September 2011 and has already been showing off her new svelte figure.
It seems like the excess weight has dropped off without any extra effort on Jones' part.
She revealed: "I haven't been dieting or working out much.
"I've just been running around, nursing and keeping busy. That's exercise enough."
Another celebrity who seemed to find it easy to regain her shape after giving birth is Miranda Kerr.
The Victoria's Secret model focused on healthy eating after the birth of baby Flynn in 2011 and turned to organic food, plenty of greens and a good breakfast to help her keep on top of her busy schedule.
She has also previously revealed her preference for the Blood Type Diet, which requires people to follow distinct diet plans depending on their individual blood group.