Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of VIVUS (NASDAQ: VVUS), a biopharmaceutical company focused on a gambit of unmet conditions including obesity, sleep apnea, and sexual dysfunction, dipped as much as 15% after the company reported its fourth quarter earnings results after the bell last night.

So what: For the quarter, VIVUS saw its net loss shrink by 70% to just $17.2 million or $0.17 per share, compared to the mammoth $56.7 million loss reported in the year-ago quarter. Comparatively speaking, this loss was $0.21 narrower than Wall Street had expected. During the quarter, VIVUS also recognized $34.8 million in licensing revenue tied to deals with Auxilium Pharmaceuticals and Sanofi, which helped defray its losses.

Ultimately, the weakness in antiobesity drug Qsymia proved too much, with sales totaling just $7.7 million during the quarter in spite of a 12% rise in prescription written from the sequential third quarter. Following its report, VIVUS was hit by a downgrade from JPMorgan Chase to neutral from overweight, with its price target being chopped nearly in half to $8 from $15.

Now what: I believe the antiobesity craze may be beginning to wane for investors after VIVUS has been given more than a year to prove its worth with Qsymia. The concern for shareholders here has to be that physicians favor Arena Pharmaceuticals' (NASDAQ: ARNA) Belviq for its safety profile; that Qsymia (known as Qsiva in Europe) was sent packing in the EU; and that rival Orexigen Therapeutics (NASDAQ: OREX) has already completed a 9,800 patient cardiovascular outcomes study known as the Light Study, which could, if its antiobesity drug Contrave is approved, put it in the driver's seat in this space since it has the most conclusive safety data of the bunch. With heavy losses still to come for VIVUS, I'm suggesting investors keep their distance.

Although there could be billions of dollars to be made in the anti-obesity space, I suspect even VIVUS will have a hard time keeping up with this top stock
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Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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