Brits are more likely to buy larger portions, fall for special offers and grab unhealthy food they can eat straight away - if they shop while hungry.
Research of 2,000 adults revealed that shopping for food on an empty stomach means you are more likely to make rash decisions.
More than half of those polled admit they would reach for special offers and food they can eat immediately - with a third buying larger packets than usual - if they are hungry.
And despite spending an average of 19 minutes planning a food shop every week, four in 10 admit they deviate from their list if they hit the shop with a rumbling stomach.
But veering from the shopping list costs an extra £11.03 per shop - an increase of almost 20 per cent on the standard weekly shop of £55.57.
This could rack up to an extra £574-a-year, on top of an already expensive food bill of £2,890.
A spokesman from HelloFresh said: "Shopping when you're hungry and in a rush can be stressful, and our research shows that it can lead to mindlessly buying too much that you have to later throw away.
"Alternatively, this action of dropping all dinner plans can mean many Brits are reaching for unhealthy options they'd never intended to buy.
"Even if we plan on eating healthily, heading to the shops while we're peckish can hamper even the best intended efforts."
Chocolate, crisps and cakes enticed the nation the most, as more than a third are more likely to give in to junk food when they're hungry.
Convenience food that can be prepared as soon as they're home are another pitfall for Brits, drawing in 48 per cent of respondents.
Many of these choices could come from shopping 'mindlessly', rather than making an active decision to treat themselves, which 32 per cent say they're guilty of when they're hungry.
This could also be part of the reason one quarter end up stressed out when they have to head out again later in the week - to pick up things they initially forgot.
One in six adults polled, via OnePoll, also reported feeling stressed out when trying to resist their cravings in the supermarket aisles.
Unfortunately, a lot of this will go to waste as the average household bins food worth more than £25 each month.
An admirable third of those polled claim they don't waste any food during a typical week, but among those that do, a fifth blame shopping while they're hungry.
A further one in five throw away products because they succumbed to a special offer they didn't need.
In an attempt to curb their extra spending, half make sure they make a list before they head to the supermarket.
But only one in 10 will make sure they eat something before they go, to avoid hunger pangs.
A spokesman for HelloFresh added: "From the results, it's clear that food shopping while hungry has a detrimental impact on the nation's choices.
"To avoid spending over your budget on unhealthy options a plan is important.
"Having something to eat before you set off, making a list and being mindful of your choices will help you stick to the plan, saving you money, wasted food and extra empty calories.
"A treat every now and again is good for all of us, but preparing more efficiently can make sure these are a choice rather than a reaction to hunger."
