The higher the work/life stress the less likely it is for families to eat together.
Highly stressed parents are preparing only four meals a week at home, compared with 5 and half meals for those who are not stressed.
Mothers who work full time spend 8.8 hours a week cooking and preparing meals, as opposed to 11 and a half hours put by those who are not employed.
Similarly, fathers who work full time also spend less time preparing meals.
Those who do not work at all or work part time spend 7.4 hours a week preparing food, compared with 4.7 hours for those who work full time.
Lead researcher Dr Katherine Bauer of Temple University said reducing parents' work/life stress could benefit family food.
"Engaging all (the) family ... in meal preparation can also alleviate the burden on working women," News.co.au quoted Dr Bauer as saying.
Dietitian Kate di Prima sees full time working parents as those who are "time-strapped and not as organised as they would like to be to cook every night".
"Many people see cooking as very labour-intensive and tiring at night and so it goes to the bottom of the priority pile and they end up ringing up for pizza," she added.