NutriSystems (NTRI: sentiment, chart, options) is charging higher today after the stock was selected to replace the newly bankrupt Frontier Airlines as a member of the S&P SmallCap 600 Index (SML). Oppenheimer analyst Vivian Ma is also giving NTRI a boost; earlier, she noted that the meal-delivery segment of the weight-loss industry is growing.

Today's news sparked some heavy volume in NTRI's options pits. The April 2.50 call (NSI DZ) was among the most heavily traded options on the Philadelphia exchange at midday, with 5,410 contracts changing hands. Since open interest on this deep in-the-money call stood at just 13 contracts heading into today's trading, it's a safe bet to assume that the bulk of today's activity will translate to new open interest tomorrow.

Option traders are already quite optimistic toward NTRI. The stock's Schaeffer's put/call open interest ratio (SOIR) stands at 0.70, which ranks lower than 89% of comparable readings taken during the past year.

Analysts are more bearishly aligned, with Zacks reporting that 6 out of NTRI's 8 ratings are of the "hold" variety. Considering the stock's 71% decline during the past 52 weeks, though, this skeptical sentiment seems well-deserved. With resistance looming overhead from the equity's 10-week and 20-week moving averages, it may be a while before these bears have a change of opinion on the weight-loss firm.