The former BBC One baking series will air on Channel 4 for the first time next Tuesday, August 29, and will feature a total of 17 minutes of adverts during its 75-minute slot.
During a Q&A to launch the show, Leith quipped: "I want to comfort some people who might think, 'Oh, I don't want to go to Channel 4 because I don't want to have the ads'."
"You don't have to watch it in real time, do you?"
The first sponsors of the show are Lyle's Golden Syrup and Dr Oetker, who have signed up as part of a multi million-pound deal.
The seven-figure deal marks the first time the popular baking programme has received sponsorship following its move from the commercial-free BBC to Channel 4.
The deal includes sponsorship bumpers either side of ad breaks.
It also includes Jo Brand-fronted spin-off Bake Off: An Extra Slice, as well as festive episodes.
Jay Hunt, Channel 4's outgoing chief creative officer had earlier said that she "made no apology" for there being adverts on Bake Off, due to the commercial nature of the broadcaster.
She said: "We need to be really, really careful that audiences go with the programme and they're comfortable watching it and they (adverts) are not a distraction."
"But we are a commercial broadcaster and we do need to pay for shows like Bake Off, so I make no apology for there being ads in it."
Hunt added: "We've been very, very careful about thinking where the ad breaks sit ...So I think it's quite seamless."
Channel 4 said: "As the programme format remains unchanged, Bake Off episodes are 75 mins long to ensure that viewers can enjoy all of the competition action they love.
"Channel 4 is a commercially funded, public service broadcaster which puts its profits into programmes. Advertising allows us to invest in high-quality British productions like the Great British Bake Off and keep them free to air for viewers."
"A 75-minute slot is not usual in the Channel 4 schedule so there isn't a standard programme run-time, however, the Bake Off run-time (58 mins) across the 75-minute slot is consistent with the run-time of programmes on other free-to-air commercial public service broadcaster's channels in similar peak time slots."
:: The Great British Bake Off airs on Channel 4 on Tuesday 29 August at 8pm