Like a “Cathy” cartoon strip in cinematic form, “Bridget Jones: The Edge of Reason” takes unmarried feminine angst and whips it into a harmless, light-hearted comic meringue. Our long-suffering heroine (Renée Zellweger) frets about her weight, obsesses on her boyfriend, says inappropriate things at the most inopportune moments and generally plays the goat wherever she goes.

In other words, nothing much has changed since “Bridget Jones's Diary” (2001), the first movie adapted from Helen Fielding's best-selling literary franchise. Set one month after the original, “Edge of Reason” finds the irrepressible Londoner head-over- jumper in love with stoic human rights attorney Mark Darcy (Colin Firth), insane with jealousy over Darcy's coltish female colleague (Jacinda Barrett from “Ladder 49”) and bumbling her way through a fluffy TV news job.

When paranoia and insecurity leave her relationship with Darcy in tatters, in pops Daniel Cleaver (Hugh Grant), Bridget's rakish former boss and lover and now — somewhat too conveniently — Britain's hottest cable television star. A sojourn of temptation follows, involving exotic foreign beaches, a hallucinogenic mushroom trip and a brief stay in a Thai jail. Undeterred by the horrors of a Third World prison term, Bridget teaches her cellmates how to properly mangle Madonna's “Like a Virgin.”

Do you see the larger picture yet? “The Edge of Reason” is even more of a Mentos commercial than the first “Jones.” The jokes are broader (although Bridget's inventive use of the word “shag” is always worth a laugh), the plotting screwier (Grant and Firth once again engage in a girly slap-fight) and the leading lady fleshier (my tabloid of choice claims that Zellweger gained 60 pounds for the role). Director Beeban Kidron (“To Wong Foo, Thanks for Everything! Julie Newmar”) invests it all with an emotional sophistication to rival a good Harry Potter movie.

Maybe that's too glib. Bridget, while temperamental and melodramatic, does have a stubborn streak of dignity that neatly jibes with Zellweger's feisty, sardonic performance. To wit: when somebody disrespects her or takes her for granted, Bridget doesn't hold her tongue, and reserves the right to walk away from any foundering relationship. There's something to be said for that kind of emotional transparency — like her ideological predecessor “Cathy,” this is one cartoon heroine who always wears her heart on her shirt.