By shopping less often, you are less likely to be exposed to the temptations of unhealthy checkout sales. However, shopping once a week also has a downside.
Full pantry
Research shows that if you do your shopping once a week, you will eat extra food in the following three days, because there are so many tasty things in the house. 30 percent of those surveyed immediately start eating as soon as they get home.
Temptations in the supermarket
It would be better to do the groceries you really need a few times a week. The tricky part is that you have to be able to resist the temptation to buy tasty things.