Half of UK children "drink" almost five litres of cooking oil every year as a result of their pack-a-day crisp habit, experts warn.
The ad carries the caption "What goes into crisps goes into you"
Nearly a fifth of children eat two packets of crisps per day, says the British Heart Foundation.
Its Food4Thought campaign aims to expose hidden salt, fat and sugar in common foods.
Pictures of a girl drinking cooking oil with the caption "What goes into crisps goes into you" will appear nationwide.
But the campaign has been criticised as "scare tactics", by the food industry body.
And the Snacks, Nuts and Crisps Manufacturers Association claims the BHF "over-estimated" the oil content by basing its calculations on large crisp packets.
A typical 35g bag of crisps contains about two-and-a-half teaspoons of oil.
A larger 50g pack contains three-and-a-half.
Figures from Mintel reveal that we eat a tonne of crisps every three minutes in the UK.
This would be enough to fill a telephone box every 43 seconds and an Olympic size swimming pool every 14 hours.
Another recent survey found nearly three quarters of mothers said they fed their children ready meals or takeaways more than three times a week.
By 2020, it is thought that a quarter of UK children will be overweight.
Over 9 billion packs of crisps, snacks & nuts are eaten every year, equating to 150 bags per person per year
The UK Crisps & Snacks market is worth £2 billion per year
Crisps are found in 69% of the 5.5 billion lunchboxes packed for children in the UK
Sources: Food Standards Agency and Information Resources Inc
BHF is calling for a ban on the marketing of junk food products to children, particularly on the TV and the internet.
It also says cooking skills should be a compulsory part of schooling.
BHF medical director Professor Peter Weissberg said: "Daily unhealthy snacking is a worrying habit.
"Rising rates of childhood obesity and type 2 diabetes paint a particularly grim picture for the future.
"The campaign is about challenging our children about what's lurking in their snacks, takeaways and ready meals."
Teaching resources in the shape of over-sized burger boxes will be sent to 2,500 UK schools. Student packs will be delivered to 400,000 children later this year.
More than 200 schoolchildren have volunteered to become BHF Young Ambassadors, who will be lobbying their schools, MPs and local media.
A Department of Health spokesperson said: "Government is committed to halting the rise of childhood obesity but we cannot do it on our own.
"Ofcom recently consulted on restricting food advertising to children and we await the outcome of that consultation.
"We are working with the food manufacturers and retailers to reduce fat, salt and sugar in their foods and to provide clear labelling."
Neil Campbell, general manager for Walkers, said: "We wholeheartedly agree that people should avoid products that are high in saturated fat, which is why we invested millions of pounds in developing Sunseed oil, one of the healthiest oils there is.
"We introduced Sunseed oil in February this year, resulting in a 70% reduction in the saturated fat content of Walkers Crisps."
Julian Hunt of the Food and Drink Federation said: "One of the great things about our industry is that we strive to give consumers genuine choice, whether it is a better for you version or a completely reformulated standard product."