Fat fighters sweat on with a vengeance. Purchased mostly by women, four fitness tapes muscled their way to the top 10 of the sales charts for the past two weeks. This week, seven exercise tapes weigh in. Cher and Richard Simmons, No.'s 2 and 3 respectively, lead the workout pack; their rivals have spread themselves thinner by releasing more titles: The top 25 list sports five different Callanetics tapes, four Kathy Smiths, and three Jane Fondas. Women show strength on the rental chart as well, with Geena Davis and Susan Sarandon outperforming Arnold's formidable Terminator their second week on the list. LAST RENTALS WEEKS ON WEEK CHART

1 5 Thelma & Louise 2 Geena Davis (MGM/UA) 2 2 City Slickers 7 Billy Crystal, Daniel Stern (New Line) 3 1 Terminator 2: Judgment Day 6 Arnold Schwarzenegger (LIVE) 4 15 Dying Young 2 Julia Roberts (FoxVideo) 5 3 Naked Gun 21/2 : The Smell Of Fear 5 Leslie Nielsen (Paramount) 6 6 Backdraft 11 Kurt Russell (MCA/Universal) 7 14 Bill & Ted's Bogus Journey 2 Keanu Reeves (Orion) 8 4 Doc Hollywood 5 Michael J. Fox (Warner) 9 9 Soapdish 8 Sally Field, Kevin Kline (Paramount) 10 11 What About Bob? 11 Bill Murray (Touchstone)

SALES

1 1 Fantasia 12 Animated (Disney, $24.99) 2 2 Cherfitness 9 Cher (CBS/Fox, $19.95) 3 3 Richard Simmons: Sweatin' To The Oldies 53 Richard Simmons (Warner, $19.98) 4 5 The Little Mermaid 64 Animated (Disney, $26.99) 5 12 Quick Callanetics: Stomach 14 C. Pinckney (MCA/Universal, $14.95) 6 8 The Terminator 27 A. Schwarzenegger (Hemdale, $14.95) 7 4 Jane Fonda's Lower Body Solution 11 Jane Fonda (Warner, $19.97) 8 17 Quick Callanetics: Hips & Behind 14 C. Pinckney (MCA/Universal, $14.95) 9 11 Callanetics 47 C. Pinckney (MCA/Universal, $24.95) 10 16 Kathy Smith's Ultimate Stomach And Thighs 38 Kathy Smith (Media, $19.95) For the week ending January 19