Since launching in 2005, calorie-counting and exercise-tracking app MyFitnessPal has boostrapped its way to a profitable business reaching more than 40 million users worldwide. But, after years of going it alone, the company said on Sunday that it had raised $18 million from some of Silicon Valley’s biggest investors. The Series A round was led by Kleiner Perkins Caufield & Byers and included Accel Partners.