Around 20 stores have so far been helped by the locally funded scheme which, like the government-funded Change 4 Life programme, involves re-merchandising, boosting fresh fruit and vegetable ranges and educating retailers and consumers about the benefits of fresh produce and how to store it correctly.
"Before the scheme was launched many of the stores would have only one sorry box of fruit right at the back of the store," Buywell project co-ordinator Hannah Williams told Convenience Store.
"One of the biggest problems was that retailers didn't know how to store fresh produce properly; there were lots of cases of bananas stored in fridges."
She added: "Now retailers have big, bright displays at the entrance. The displays look fantastic and the vast increase in sales proves it is well received."
Each of the stores has also appointed a member of staff to champion the use of fresh fruit and vegetables.
Costcutter retailer Salam Sheikh said the scheme had boosted footfall and sales. "Since making the changes I've sold more fruit and veg in a day than I usually do in a week," he said.
London Food Board chairwoman Rosie Boycott said schemes such as Buywell were vital to help improve the health of the nation.
"The patchy provision of good-quality, affordable fresh fruit and veg can be a major problem for some Londoners," she said. "Buywell is excellent as it puts fresh fruit and vegetables directly into stores where people want to do their day-to-day shopping. It also enthuses staff so they can be more knowledgeable about stocking healthier food."