These should be heady times for weight-loss-management company NutriSystem (NTRI). With a population that is increasingly overweight (but trying again and again), the company should be having no problem attracting customers.

Unfortunately for investors in NutriSystem, it appears that customers are proving difficult to find. As a result, expenses for marketing are on the rise.

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Earlier this month NutriSystem reported earnings for the fourth quarter that beat analyst estimates on both the top and bottom lines. The company generated a profit excluding items of 18 cents per share.

The Wall Street estimate was for a profit of 13 cents per share. On the revenue front, the company posted sales of $106.2 million versus an estimate of $102.2 million.

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Those are fantastic results until you consider the warning for the first quarter of 2010.

The company stated that it was having a difficult first month due to higher marketing expenses.

NutriSystem advertises heavily at the start of each year, seeking customers with resolutions to lose weight. This year’s expenditures came at a time of higher media rates that the company stated will have a $5 million impact.

In the fourth quarter, marketing expenses were already on the rise, having increased by 5% over the year prior.

You may have seen those ads with celebrities touting the benefits of a NutriSystem diet. Unfortunately, those endorsements cost money and leave little room for unexpected surprises, such as media costs going up.

Perhaps the company needs to go on a bit of a diet of its own.

Management did state that it viewed the difficulties of the first quarter as temporary and that the company expected a modest improvement in profitability for the 2010 year as improving sales and margins offset the weak first quarter.

In the conference call, though, NutriSystem acknowledged that intended dieters were still showing a preference to go it alone. Will sales indeed pick up for the remainder of the year on a strengthening economy?

If so, the loss in stock value due to this news may be temporary.

Analysts have not changed expectations for profits in 2010 since the news was released. The average estimate is for the company to make $1.07 per share this year, with that number jumping to $1.30 in the following year.

At current prices, shares trade for just over 16 times expected earnings. That is a reasonable price for a company with significant growth potential.

Assuming the first quarter was a blip, this may be a stock to buy.

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