Thanks to an influx of fast casual restaurant chains going public over the last five years, there are more stocks to watch in what we're eating than ever before. The restaurant industry is big business, and a wealth of smaller chains have sought more robust funding with the hopes of delivering big time growth. The National Restaurant Association estimates American spending on dining out in 2014 totaled roughly $709 billion, and spending at restaurants is booming.

With new eateries entering the fray and vying for expansion and positive momentum in the broader industry, it's an exciting time for the restaurant biz and potentially a good time to invest in some of these relatively new fast casual chains. Here's why Chipotle Mexican Grill (NYSE:CMG), Shake Shack (NYSE:SHAK), and Habit Restaurants (NASDAQ:HABT) should be on your watch list.

Chipotle Mexican Grill is one of the companies at the forefront of the fast casual revolution that is currently transforming the restaurant landscape. Most known for its customizable burritos, the restaurant chain has cultivated a strong public image by using higher quality ingredients than many fast food competitors and has delivered huge sales growth over the last decade. Annual revenue has grown nearly 400% since going public in 2006, and shares have gained over 3,000% from the initial offering price, and roughly 370% over the last 5 years.

Chipotle has a market cap of roughly $20 billion and a forward P/E value of approximately 38. The company's valuation implies healthy growth, and revenues look to continue expanding as the company explores international markets and increases its store count. Annual sales have grown roughly 124% over the last five years, and last quarter saw the company record 17% growth in same store sales and total quarterly sales grew roughly 20% to $1.09 billion. As of its last reporting period, Chipotle had just 1,831 locations worldwide, and the company anticipates adding roughly 200 new locations per year going forward. Strong branding and demand for the company's food looks like it will enable the burrito-maker to carve out a bigger share of the restaurant market going forward.

Shake Shack
Burger and shake company Shake Shack went public in January 2015, and shares quickly doubled as investors looked to hitch their dollars to the next big fast casual sensation. Company stock has increased roughly 143% since initial pricing of $21 a share, however its share price has fallen more than 31% in the last month, owing partially to a more-cautious revised outlook from Morgan Stanley. Even after the significant stock decline, Shake Shack has a forward P/S value of roughly 11Company stock is priced for big growth and its lofty valuation is worth considering before investing in the restaurant chain, but with just 68 locations as of its last quarterly report, there is lots of room for expansion.

Like Chipotle, Shake Shack emphasizes its use of high quality ingredients and comparatively high-end dining areas relative to other fast food chains and is aiming to ride momentum in fast casual dining experiences to continued growth. Shake Shack also sells beer and wine, which provide high margin revenue and could provide a buffer from rising food prices.

The company anticipates that it will grow to 450 locations in the U.S. alone, though it hasn't given a timetable for hitting that target. To its credit, Shake Shack has a solid balance sheet and relatively little debt, which should help grow its location count, but the company will also need to continue growing brand strength if it's to deliver Chipotle-like wins for investors.

Habit Restaurants
Habit Restaurants has a few characteristics that help it stand out from the increasingly crowded fast casual competition. Chief among Habit's competitive advantages: People seem to really enjoy the company's hamburgers. Habit's burgers topped Consumer Reports' 2014 Best Burger poll, an achievement that created a nice splash of publicity for the company and cemented a notable laurel for the company to market around.

Habit's pricing model may also help the company achieve continued growth. Its menu is priced relatively low compared to competitors like Five Guys and Shake Shack, and the combination of affordable prices and tasty burgers could help the company deliver growth even if macro conditions worsen. The company's last quarterly report delivered 12.6% comparable sales growth and 44% revenue growth, establishing the company's 45th consecutive quarter with year-over-year sales growth.

Habit has a market cap of roughly $800 million and a forward price-to-sales ratio of roughly 3.6. The company operates just 125 stores across six American states, so it has lots of room for expansion. Shares are up roughly 75% from the company's $18 IPO price, however the stock is down roughly 20% from its closing price after its first day of trading in November 2014. Even with the dips, Habit's highly regarded food and expansion potential make it a stock to watch in what we eat.