Under pressure to provide healthier meals, McDonald’s announced on Thursday that it would no longer market some of its less nutritional options to children and said it also planned to include offerings of fruits and vegetables in many of its adult menu combinations.

It plans to make the changes to its menu in 20 of the company’s largest markets, which account for more than 85 percent of its overall sales, including overseas. But it will take three years or more to put them into place in about half the restaurants in those markets, and the remainder may not have the changes until 2020.

The offerings, which were announced in conjunction with the Clinton Foundation’s campaigns to reduce childhood obesity, are part of McDonald’s efforts to compete for health-conscious customers by featuring food choices that are lower in fat, salt or sugar content than its more traditional burger-and-fries options.