However, the contract stipulates that Simpson must lose a hefty amount of weight to be paid in full by the company, according to Us Weekly.
A source claimed: ''As soon as Jessica heals from the C-section, she is extremely determined to get back in the gym and work out. She wants to show the world and is excited to do it.
''She'll have to meet the weight loss goals for the deal to go through. She hasn't chosen a trainer yet."
An insider added: "In fact, she hasn't even thought about working out for a year. But if she wants this, she'll need to work out a good five times a week.''
The 31-year-old, who revealed that she grew to 170 pounds during pregnancy, had to deny rumours that she was having twins.
Watch Jessica Simpson on The Ellen DeGeneres Show before going into labour below: