Collecting title belts, apparently, is a lot like sex. The more you get, the more you want.

Excess can lead to trouble, though.

In both cases.

Erik Morales, a champion in three divisions, wanted a fourth championship. So he invaded the lightweight division Saturday, in hopes of one day challenging the winner of the Oct. 8 rematch between Diego Corrales and Jose Luis Castillo.

He took on Zahir Raheem, a light-punching boxer with good skills. Raheem seemed like a safe choice as Morales’ first lightweight opponent. Then the first round bell rang.

Raheem was bigger, stronger and faster than the suddenly-plodding Morales, who appeared heavy and without the fire that marked his amazing career. In fact, if it wasn’t “El Terrible” in there, you’d have thought that Raheem was using Morales as a tune-up for someone else.

It was that lopsided.

In the biggest upset so far of 2005, Raheem beat Morales by unanimous decision Saturday in a Los Angeles shocker. Morales can forget the winner of Corrales-Castillo. And his proposed winter rematch with Manny Pacquiao likely went out of the window as well.

All because Morales, who won world titles at 122, 126 and 130 pounds, wanted to conquer another weight class.

Fighters biting off more than they can chew is certainly nothing new to boxing. It’s been happening for years.

Here are four examples of respected champions whose careers were altered by an ill-advised jump in weight.

* Renaldo Snipes W 10 Eddie Mustafa Muhammad (1981): Mustafa Muhammad was the reigning WBA light heavyweight champion when he moved up to heavyweight and fought Snipes. Mustafa was a huge puncher as a light heavyweight, and a feared champion. The dream fight of the division was a unification showdown with WBC titlist Matthew Saad Muhammad. That fight, and Mustafa’s career, went kaput when Snipes toyed with him for 10 rounds. The power that marked Mustafa’s 175-pound dominance was nonexistent, and the bigger Snipes walked right through Eddie’s power punches. The fight was dreadful, and the decision was unanimous and predictable. A few months later, Mustafa struggled to get back down to 175 pounds, and lost a wide decision to Michael Spinks. He was never the same after that.

* Terry Norris KO 4 Meldrick Taylor (1992): Taylor had been one of the best fighters on the planet two years prior at junior welterweight, but his classic 1990 loss to Julio Cesar Chavez sent his career into a tailspin. Initially, the 140-pound weight class seemed perfect for Taylor. He was only 5-foot-7, wasn’t much of a puncher, but was strong and bulky enough to stand in there with anyone in the division. And his ungodly speed made him spectacular there. However, he moved up to welterweight in 1991 and picked up a title. He was still effective enough, though quickly losing his edge. Then, in one of the more head-scratching moves in recent boxing history, Taylor moved up in weight yet again and challenged the strong and powerful Norris – the best fighter in the division. Taylor had no chance, and was helpless as Norris marched right through him and bombed away. The massacre was finally stopped in the fourth, and Taylor was never the same. He dropped back down to 154 pounds later in ’92, but, by then, the damage had been done. Underdog Crisanto Espana destroyed him, and Taylor quickly became one of boxing’s sad stories.

* Pernell Whitaker D 12 Julio Cesar Chavez (1993): Officially, this fight was a draw. Unofficially, it was the first loss of Chavez’s incredible career. The reason? Whitaker was naturally bigger and stronger, and the Chavez punches that had so much of an effect on opponents at 130, 135 and 140 pounds didn’t faze “Sweet Pea.” Of course, welterweight was not Whitaker’s original weight class, either. But he had grown into the division naturally. He started at lightweight, whereas Chavez started at junior lightweight – and forced on the extra pounds to compete at 147. The difference was obvious in the ring, as Whitaker not only dominated from the outside as expected, but on the inside – where Chavez was supposedly so much more superior. Whitaker’s awkward, left-handed stance and underrated strength surprised and frustrated Chavez. And though it wasn’t a total runaway, Whitaker deserved the victory. Chavez lost officially four months later, when Frankie Randall dropped him and went on to capture a 12-round decision.

* Erik Morales W 12 Paulie Ayala (2002): Like Taylor, Ayala was an effective fighter in his natural weight class, which was 118 pounds. That’s where he upset Johnny Tapia in 1999, did it again a year later, and made four defenses of his title. Also like Taylor, Ayala was anything but a big puncher, and made up for his lack of power by a feverish work rate. All four of his title defense victories were decisions – most of them controversial. So it was strange to see Ayala move up and try for another world title at junior featherweight. He did it, beating Bones Adams by, yes, controversial decision in 2000. He repeated the victory again in 2001, which convinced him he was ready for another jump in weight. He hopped to 126 pounds in 2002, and faced the taller, bigger, stronger, better Morales. And while Morales won every round and issued a brutal beating, Ayala never wavered. Still, the Fort Worth, Texas, fighter would’ve been better off staying at either 122 or 118 – and likely wouldn’t have suffered the violent beatings at the hands of Morales and Marco Antonio Barrera.

Five years later, it was Morales who discovered what Ayala knew too well: Collecting title belts is great – until you go one weight class too many.

Then, it’s not so great. And, often times, it’s career-threatening. We’ll see if “El Terrible” is ever the same after the upset loss to Raheem.