A mid falling oil prices and Greece’s possible exit from the eurozone, the stock market started the first month of the year with volatility.

The best-performing mutual funds the past three months slowed their buying in January. The outlook on IBD’s market pulse toggled between correction and market-under-pressure in the stock market .

Top mutual funds have been adding to heavy-hitting medical issues such as Celgene (NASDAQ:CELG ) and Biogen Idec (NASDAQ:BIIB ) in their latest reporting periods. Others included Actavis (NYSE:ACT ), Illumina (NASDAQ:ILMN ) and Shire (NASDAQ:SHPG ).

Among IBD’s 197 industries, five medical subgroups ranked in the top 10 as of Tuesday. The biotech/biomed group ranked No. 1.

Top-performing funds continued to give much love to airline stocks, including Southwest Airlines (NYSE:LUV ), United Continental Holdings (NYSE:UAL ) and JetBlue Airways (NASDAQ:JBLU ).

Real estate stocks made their way on the new buys list. Property REITs such as Pebblebrook Hotel (NYSE:PEB ), Extra Space Storage (NYSE:EXR ), Regency Centers (NYSE:REG ), were stellar performers. Lipper’s real estate mutual fund category was the second-best performing group in January, notching a 5.6% gain.

IBD spotted five leading mutual funds adding Nautilus (NYSE:NLS ), investing an estimated $3 million.

The $1.6 billion JPMorgan Small Cap Value Fund added shares in its latest reporting period.

The Vancouver, Wash.-based firm makes and markets fitness products that include home gyms, free weight equipment, treadmills, indoor cycling equipment, ellipticals and fitness accessories. Its portfolio of fitness brands includes Bowflex, Nautilus, Schwinn and Universal, sold through retail and direct sales to consumers.

Nautilus has been pumping 20%-plus sales growth the past five quarters. Analysts see growth opportunities for Nautilus as it continues to deliver innovative products.

The stock is currently forming the handle of a third-stage cup-with-handle base. It’s trading near its buy point of 15.58.

Sell Side

Leading funds have been taking profit from several big REIT stocks, such as Simon Property Group (NYSE:SPG ), Federal Realty Investment Trust (NYSE:FRT ), Aviv (NYSE:AVIV ) and Public Storage (NYSE:PSA ).

Top-performing funds were also selling some biotech stocks, including Gilead Sciences (NASDAQ:GILD ) and Isis Pharmaceuticals (NASDAQ:ISIS ).

A mid falling oil prices and Greece’s possible exit from the eurozone, the stock market started the first month of the year with volatility.

The best-performing mutual funds the past three months slowed their buying in January. The outlook on IBD’s market pulse toggled between correction and market-under-pressure in the stock market .

Top mutual funds have been adding to heavy-hitting medical issues such as Celgene (NASDAQ:CELG ) and Biogen Idec (NASDAQ:BIIB ) in their latest reporting periods. Others included Actavis (NYSE:ACT ), Illumina (NASDAQ:ILMN ) and Shire (NASDAQ:SHPG ).

Among IBD’s 197 industries, five medical subgroups ranked in the top 10 as of Tuesday. The biotech/biomed group ranked No. 1.

Top-performing funds continued to give much love to airline stocks, including Southwest Airlines (NYSE:LUV ), United Continental Holdings (NYSE:UAL ) and JetBlue Airways (NASDAQ:JBLU ).

Real estate stocks made their way on the new buys list. Property REITs such as Pebblebrook Hotel (NYSE:PEB ), Extra Space Storage (NYSE:EXR ), Regency Centers (NYSE:REG ), were stellar performers. Lipper’s real estate mutual fund category was the second-best performing group in January, notching a 5.6% gain.

IBD spotted five leading mutual funds adding Nautilus (NYSE:NLS ), investing an estimated $3 million.

The $1.6 billion JPMorgan Small Cap Value Fund added shares in its latest reporting period.

The Vancouver, Wash.-based firm makes and markets fitness products that include home gyms, free weight equipment, treadmills, indoor cycling equipment, ellipticals and fitness accessories. Its portfolio of fitness brands includes Bowflex, Nautilus, Schwinn and Universal, sold through retail and direct sales to consumers.

Nautilus has been pumping 20%-plus sales growth the past five quarters. Analysts see growth opportunities for Nautilus as it continues to deliver innovative products.

The stock is currently forming the handle of a third-stage cup-with-handle base. It’s trading near its buy point of 15.58.

Sell Side

Leading funds have been taking profit from several big REIT stocks, such as Simon Property Group (NYSE:SPG ), Federal Realty Investment Trust (NYSE:FRT ), Aviv (NYSE:AVIV ) and Public Storage (NYSE:PSA ).

Top-performing funds were also selling some biotech stocks, including Gilead Sciences (NASDAQ:GILD ) and Isis Pharmaceuticals (NASDAQ:ISIS ).