By Richa Naidu and Uday Sampath Kumar

(Reuters) - Beyond Meat Inc reported its first ever net profit and raised its full-year sales forecast, but shares tumbled 6.5% in extended trading as the vegan burger maker said it would need to offer more store discounts or promotions as competition heats up.

Plant-based burgers, sausages and other meat-lookalikes have become the hottest food trend in recent years, gaining popularity among mainstream consumers looking to cut back on meat consumption. Retailers from Kroger Co to Walmart Inc are making space in their meat aisles as more food makers enter the faux-meat market.

Spending on store discounts more than tripled during the quarter as Beyond Meat fended off competition from rivals including Impossible Foods. Last month, the company began selling its Impossible Burgers in grocery stores.

"We do anticipate we'll be doing more promotion through trade and discounts going into the future," Chief Executive Ethan Brown said on a post-earnings call. To be sure, Brown said the additional competition in stores had so far not hit stores sales.

"The stock is moving on the pace of the competitive landscape around Beyond Meat," D.A. Davidson Co analyst Brian Holland said. "Whether that's restaurants using rivals' products or retailers stocking them up."

The surge in discount spending overshadowed a beat on quarterly revenue and a raised forecast for full-year sales. The California-based company's shares, which closed up 4.5% on Monday, have gained over four-fold in value since their May initial public offering price. The IPO share lockup period expires on Tuesday. Holland said the company's stock was sensitive to the end of the lockup period, with investors trying to get ahead of a potential sell-off on Tuesday.

Beyond Meat's stock is trading at an exceptionally high 23 times revenues expected by analysts for this year and 14 times revenue expected for 2020, according to Refinitiv data.

Restaurants like Carl's Jr and Yum Brands Inc's KFC have rushed to get Beyond Meat's products on their menus. Last month, the world's No.1 burger chain, McDonald's Corp said it would test a "plant, lettuce and tomato" sandwich in Canada using Beyond Meat patties.

Beyond Meat raised its full-year net revenue forecast for the second time to $265 million to $275 million. It had previously forecast net revenue to exceed $240 million. Third-quarter discounts rose about 254%.

Operating expenses surged 124% to $29 million in the three months ended Sept. 28. Net revenue rose 250% in the third quarter to $91.96 million, above Wall Street's estimate of $82.2 million, according to Refinitiv IBES data.

Beyond Meat reported a quarterly net income of $4.1 million, or 6 cents per share, compared with a loss $9.3 million, or $1.45 per share, a year earlier. Analysts had expected a profit of 3 cents per share.

(Reporting by Richa Naidu in Chicago and Uday Sampath in Bengaluru; Additional reporting by Noel Randewich in San Francisco; Editing by Sriraj Kalluvila and Lisa Shumaker)