Shares in Yum Brands, which owns KFC and Pizza Hut, fell more than 17% in after-hours trading in the US after the firm reported poorer than expected results for the three months to 5 September.
Yum also lowered its full-year earnings growth forecast in its key market of China.
The firm blamed a stronger US currency against the yuan for its poor results.
But it also still recovering from a food scandal last year.
The group's KFC restaurants in China suffered in July last year after a television news story linked the brand to supplier Shanghai Husi Food, which was accused of selling meat that was out of date.
"The pace of recovery in our China Division is below our expectations," said Chief executive Greg Creed in a statement.
"While it remains difficult to forecast China sales, we are now estimating full-year same-store sales to be low single-digit negative," the firm said.
"Given a slower-than-expected recovery in China sales, particularly at Pizza Hut Casual Dining, as well as stronger foreign exchange headwinds, we now expect full-year EPS (earnings per share) growth to be low-single-digit positive."

Globally, Yum Brands reported third-quarter earnings per share growth of 14%, with adjusted third-quarter earnings of $1 (£0.65) a share and revenue of $3.43bn (£2.25bn).
Expectations were for earnings per share growth of $1.06 per share and revenue of $3.67bn.
"Outside of China, our Taco Bell and KFC Divisions continued to sustain their positive sales momentum," said Mr Creed, "while Pizza Hut was relatively flat."
"Given our lower full-year expectations in China, combined with additional foreign exchange impact, we now expect 2015 EPS growth to be well below our target of at least 10%."


Fifa president Sepp Blatter is facing a 90-day provisional suspension.
Members of Fifa's ethics committee have recommended the sanction after the Swiss attorney general opened criminal proceedings against the 79-year-old.
He is accused of signing a contract "unfavourable" to football's governing body and making a "disloyal payment" to Uefa president Michel Platini.
Blatter denies any wrongdoing and his lawyers said he had "not been notified of any action".
European football chief Platini - who wants to succeed Blatter - has said the payment was "valid compensation" from his time working under the Swiss more than nine years ago.
The investigatory chamber of Fifa's ethics committee has requested the ban and a final decision is likely to be made on Thursday by Hans Joachim Eckert, the head of Fifa's ethics adjudicatory chamber.
Blatter's adviser Klaus Stohlker said the Fifa president was "calm" after being told the news, but a statement from his legal representatives denied he had been made aware of any decision.
It said: "We would expect that the ethics committee would want to hear from the president and his counsel, and conduct a thorough review of the evidence, before making any recommendation to take disciplinary action."
On Wednesday, Blatter told a German magazine  he was being "condemned without there being any evidence for wrongdoing".
The investigation is centred on allegations believed to be around a 2005 TV rights deal between Fifa and Jack Warner, the former president of Concacaf, the governing body of football in North and Central America and the Caribbean.
The ethics committee had been meeting in Zurich since Monday and have yet to make a decision on Platini, 60.
It is also examining a payment of two million Swiss francs (£1.35m) that Platini received in 2011 for working for Blatter.
The Frenchman has provided information to the criminal investigation but said he has done so as a witness.
Swiss prosecutors said he is being treated as "in between a witness and an accused person" as they investigate corruption at world football's governing body.
The latest development came hours after former Fifa vice-president Chung Mong-joon, who is also under investigation by Fifa's ethics committee, told BBC Sport his campaign to succeed Blatter was being "smeared".
Blatter won a fifth consecutive Fifa presidential election on 29 May but, following claims of corruption, announced his decision to step down on 2 June. He is due to finish his term at a Fifa extraordinary congress on 26 February.


South Korean tech giant Samsung Electronics expects its third-quarter operating profit to beat market forecasts on the back of strong semiconductor sales.
It forecasts that operating profit jumped nearly 80% from a year ago to 7.3 trillion won ($6.29bn; £4.13bn).
The guidance figures for the three months to September exceeded analysts' expectations of about 6.8tn won.
The amount would mark the firm's first quarterly profit growth in two years.
The world's biggest smartphone maker has been facing stiff competition for its premium smartphones from rival Apple, while cheaper Chinese competitors such as Xiaomi continue to eat into its market share on the bottom end.
Analysts said stronger sales in its chip business and favourable currency exchange rates had offset the weakness in its mobile business.
Samsung is also the world's biggest maker of memory chips and its semiconductor unit is expected to be its top earner for the fifth consecutive quarter.
A weaker won has made the firm's products cheaper to buy overseas and helps boost its bottom line when it repatriates its earnings.
Samsung expects its sales to have risen by 7.5% to 51tn won in the same time period.
Seoul-listed shares of Samsung jumped nearly 9% after the positive earnings guidance.
The guidance release does not include a breakdown of results in its various divisions or a net income figure. Its final audited results are due out later this month.


Bryan Habana equalled Jonah Lomu's World Cup try-scoring record with a hat-trick as South Africa reached the quarter-finals by thrashing USA.
The winger scored three times in 21 second-half minutes to draw level with Lomu's mark of 15 World Cup tries.
The Springboks ran in eight second-half tries in all to earn a bonus-point win at the Olympic Stadium.
South Africa top Pool B and will now play the loser of Saturday's Pool A decider between Australia and Wales.

A tale of two halves

A mixture of South Africa's ill-discipline and poor finishing kept the score down in the first half, while USA only made it into the Boks' 22 in the last minute of the half, despite enjoying plenty of possession.
Centre Damien de Allende scored his first international try before South Africa were awarded a penalty try as USA struggled at the scrum.
A different South Africa came out after the break as Habana scored almost from the restart, collecting a Fourie du Preez kick to go over in the corner.
Bismarck du Plessis and Francois Louw both crossed the line, before Habana scored two tries in two minutes to complete his hat-trick.
Louw scored his second with Jesse Kriel also getting on the scoresheet, before Lwazi Mvovo rounded off a dominant Springboks performance.

Brilliant Habana

Habana had a subdued first half, with his only contribution of note seeing him clatter into Blaine Scully as the pair competed for a high ball.
But he came out firing in the second half and his hat-trick not only saw him equal New Zealand legend Lomu as the tournament's all-time leading try scorer, but also draw level with Australia's David Campese for joint second in the list of Test try scorers with 64.
The 32-year-old, a 2007 World Cup-winner with the Boks, scored 62 seconds into the second half for his 13th World Cup try.
He then went over unopposed in the 59th minute after a break by De Allende and swooped on a loose ball to dive over in the corner just two minutes later.
Habana could have broken All Black winger Lomu's record but a knock-on as he tried to collect another chip through denied him a fourth try on the night.


Wales are so close to qualifying for the Euro 2016 finals in France they can almost smell the croissants.
Manager Chris Coleman's men go into the final Group B qualifiers - away to Bosnia-Herzegovina in Zenica on 10 October and against Andorra, on 13 October - knowing just a point will guarantee them a place at a major finals for the first time since 1958.
Last month's 0-0 draw with Israel ruined the qualification party plans for that day in Cardiff but, after 57 years of waiting, another few weeks won't hurt...will it?

The wait goes on

Victory against Israel would have secured qualification and a sense of expectation engulfed the Cardiff City Stadium on a fair-weather day made for partying.
In the hours that followed the draw with Israel, there was another scenario so typical of Wales' footballing history, littered with near-misses.
Welsh fans had expectations lifted again as, with growing excitement, they watched Belgium toil to break down Cyprus in Nicosia.
If Cyprus had drawn or beaten Belgium, Wales would have qualified that day.
Again Wales' hopes were thwarted. Chelsea midfielder Eden Hazard scored with just four minutes to go to give Belgium a 1-0 win over Cyprus.
Some fans would have felt that this would have been an anticlimactic way to make it in any case. Captain Ashley Williams and his players probably would not have complained.


In the last week, there have been media reports questioning the future of the British Grand Prix and the announcement of a 21-race calendar for the 2016 season.
In combination with this weekend's stop on the schedule - the Russian Grand Prix - it is a reminder of the direction in which Formula 1 appears to be headed.
More of the historic European events that reflect the essence of racing are disappearing off the F1 schedule to be replaced by big state-funded projects that fail to deliver the same kind of racing and atmosphere.
That the F1 schedule is in a state of major flux is without doubt; whether that is necessarily a good thing is a different matter.

Does F1 need European races?

Europe is where F1's heart is - in terms of the teams, the drivers and its core audience. And yet the future of a number of countries as race holders is in doubt.
Silverstone has a contract to stage the British Grand Prix that lasts until 2026, with the first break clause after 2019, but that has not stoppedquestions about its future. 
Monza in Italy, the oldest race of them all, has one more year on its deal and there has so far been no agreement on the financial conditions for a new one.
Germany dropped off the calendar this year because of financial problems at the Nurburgring and there are doubts about its long-term future after a poor crowd at the other venue, Hockenheim, in 2014.
These are all circuits with a long and rich history. Nurburgring has held 40 grands prix; Hockenheim 34; Silverstone 49. Monza has been on the grand prix calendar almost uninterrupted since 1922.


More than 10% of elite athletes could be cheating, says Wada director general David Howman but the number of children doping to reach the elite is the World Anti-Doping Agency's "biggest concern".
Howman said sport's increasing profitability had led to young athletes becoming more "vulnerable".
Drug testing is limited in non-elite events, and Howman admits teenagers are "under the radar" of doping agencies.
He also said doping could become a criminal offence in five years.
"We have some guestimates based on some research undertaken over the last years," Howman told BBC's Hardtalk.
"It's far more than we would wish it to be - over 10%. That is of concern because those being caught by the system is far lower than that. Not in all sports, in some sports," he said.
"The area of most concern for us is the level of young athletes who have not broken through into the elite who are trying to get that breakthrough and are susceptible to taking drugs because that's a shortcut," he added.
"Not only are they susceptible to taking drugs, they are being encouraged to do so by any one of a number of people that surround them - coaches, trainers, even parents - because it's way to make a lot of money."
Nigerian weightlifter Chika Amalaha, 16, was stripped of her gold medal after failing a drugs test at last year's Commonwealth Games.


Doubts about cycling

Former Wada president Dick Pound has previously said that four out of five cheats are not being caught.
And Howman said he wondered if there were still riders doping on this year's Tour de France after former winner Lance Armstrong was stripped of seven titles following his admission he took performance-enhancing drugs.
Leader Chris Froome has been questioned about his performance during this year's race but the Team Sky rider has denied doping.
Howman said that the numbers of riders doping had fallen "majorly" since Armstrong won Tours from 1999 to 2005, adding: "I have great respect for the way in which the UCI [world cycling's governing body] are now running their anti-doping programme."