Fitbit's stock lost as much as 18 percent of its value after the company lowered its guidance for the full financial year on disappointing sales for the second quarter of the company's new smartwatch model, the Versa Lite. Announced in March, the device is a spin-off of the Versa.

Revenues from fitness trackers jumped by 51 percent in the quarter, but sales of smartwatches declined by 27 percent, weighed down by sluggish sales of the Versa Lite Edition. This led the company to cut its full-year revenue guidance to a range of $1.43 to $1.48 billion, compared to a previous forecast of $1.52 billion to $1.58 billion.

However, the management expressed confidence in its long-term transformation strategy, indicating that the company has demonstrated good results across key areas of the business. Indeed, Fitbit had quite a few bright spots in the quarter, as it saw growth in both the number of devices sold and the number active users.

In addition, Fitbit's net loss narrowed to $68.5 million in the second quarter from a loss of $118.2 million for the year-ago period. Its total revenues gained 5 percent to $313.5 million, but its gross margin contracted by 5.2 percentage points to 34.5 percent on lower selling prices and the impact of lower warranty benefits in the corresponding period in 2018.

The shift in the product mix toward lower-priced fitness bands and away from smartwatches sent average selling prices down by 19 percent to $89, but the number of units shipped soared by 31 percent to 3.5 million.

In the U.S., sales inched down by 1 percent to $181 million, accounting for 58 percent of total revenues, while international sales improved by 14 percent to $133 million, with EMEA going up by 33 percent to $88 million and the Americas excluding the U.S. rising by 21 percent to $19 million. However, revenues in the Asia-Pacific region dropped by 26 percent to $26 million. Fitbit Health Solutions performed well, growing by 16 percent.