The restrictions prohibit adverts for these products on television between 5:30 am and 9 pm, and online at all times.
The ban targets items high in fat, salt, and sugar across 13 categories, including certain breakfast cereals, porridge, pizza, sweets, and soft drinks.
The government estimates this measure will prevent approximately 20,000 cases of childhood obesity, a move experts describe as "long overdue".
Companies can still advertise healthier versions of products and brand names, aiming to encourage recipe reformulation within the food industry.