Weight Watchers (WTW) revealed on Friday a stronger-than-expected 65% leap in first-quarter profits, prompting the diet company to boost its full-year guidance above Wall Street’s estimates.

Despite beating the Street and raising its profit outlook, shares of New York-based Weight Watchers slumped nearly 6% out of the gate.

The company said it earned $73.6 million, or $1.00 a share, last quarter, compared with a profit of $44.6 million, or 58 cents a share, a year earlier. Analysts had been calling for EPS of just 89 cents.

Revenue leaped 30% to $503.4 million, surpassing consensus calls for $480 million. Gross margins expanded to 56.2% from 54.6%.

At the same time, Weight Watchers hiked its 2011 EPS view to $3.75 to $4.00, which would easily exceed the $3.71 Wall Street had been expecting.

Weight Watchers shares came under heavy selling pressure, likely because they had been on a tear for the past year, raising the bar on performance.

The company’s stock, which is up 100% on the year and almost 200% from a year ago, declined 5.56% to $70.79 Friday morning.

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