Kellogg quarterly sales dropped 6.6 percent, missing analysts' estimates, as demand slid further for its breakfast foods and snacks, which include Corn Flakes and Froot Loops.
Kellogg also said a strong dollar was expected to hurt sales this year more than it had anticipated, mainly due to a sharp fall in the pound after Britain voted to exit the European Union and a collapse of the Venezuelan bolivar.
The Cheez-It crackers and Pringles chips maker said it now expected 2016 adjusted sales, excluding the impact of its Venezuela operations, to stay flat or rise slightly. It had earlier forecast a growth of up to 2 percent.
Kellogg's sales have fallen for six straight quarters as the company, like other processed foods makers, struggles to adapt to the shift in consumer preference to fresh foods and items perceived as healthier.
Sales in Kellogg's U.S. morning foods business, which sells cereals and other breakfast items, fell 2 percent in the second quarter. In its U.S. snacks business, its biggest, sales fell 3.8 percent.
However, net income attributable to the company rose more than a quarter to $280 million, or 79 cents per share, in the three months ended July 2.
Excluding items, Kellogg earned 91 cents per share, in line with the average analyst estimate, according to Thomson Reuters I/B/E/S.
Net sales slumped to $3.27 billion, missing the average estimate of $3.36 billion.