Fast-food restaurants in mainland China have found a magic bullet for both health and company profit: offering consumers meal options that limit sugar and salt and provide balanced nutrition.Lighter meals are rising in popularity in China, with an estimated consumer base of about 33 million across the country, and are becoming a game-changer in the food and drink sector, with big-name restaurant chains like KFC seeking to capitalise on the rising trend.Yum China, the owner of KFC and Pizza Hut...