The Lakers played as if they nursed the New Year’s hangover a few extra hours. Their 103-99 loss Tuesday to the Philadelphia 76ers may have made the 18,997 at Staples Center have a stronger headache than if they just drank aging champagne. All the New Year’s resolutions the Lakers may have adopted regarding improved health and improved hustle immediately evaporated in 2013.

Kobe Bryant has a simple reason why that’s the case.

“Because we’re old as [expletive],” he said after scoring 36 points on 14 of 29 shooting. “What do you want? We just have to figure out how to play when we don’t have that energy. We have to change things up a bit defensively and figure out what we want to do offensively and what we want to do on nights we don’t have those legs and nights we don’t have that energy.”

The Lakers hardly exhibited such qualities against the Sixers.

They shot 39.4 percent from the field, went 3 of 22 from 3-point range and allowed the Sixers to feature six players cracking double figures. That included former UCLA product Jrue Holiday (26 points), Evan Turner (22), Spencer Hawes (13), Thaddeus Young (12) Dorell Wright (10) and Lavoy Allen (10). Even with the Lakers scoring 52 points in the paint, limiting Philadelphia to seven second-chance points and scoring 25 fast-break points, the team still lost.

It all left Lakers coach Mike D’Antoni shaking his head.

“We had two or three days off so this should not be a game where we’re tired at all,” D’Antoni said. “Everybody should have their legs.”

But the Lakers didn’t.

Dwight Howard hustled on defense, but his lack of explosion and fatigue contributed to a seven-point effort on 1 of 7 shooting. Howard denied that his eight month back surgery has still limited him, but D’Antoni believed Howard looked “tired.” Pau Gasol scored only 11 points on 2 of 12 shooting, and acknowledged the plantar fasciitis in his right foot partly contributed to his lack of lift and aggressiveness.

Metta World Peace wouldn’t buy any such excuse about age after hearing the Eastern Conference-leading Knicks have an older roster than the Lakers.

“That’s no excuse, the Knicks are playing great, so that’s no excuse,” said World Peace, after scoring 13 points on only 6 of 17 shooting. “You can’t use it as an excuse for us. Thank you. Thanks for trying.”

Instead, Gasol believes such issues has contributed to the Lakers feeling frustrated and disconnected in other areas.

“We’re not the most athletic team in the league. We know that. But we are experience,” Gasol said. “We should create energy for ourselves out there. It starts by talking to each other, communicating and letting our teammates know we’re there. That will create more energy that we need on the floor.”

The Lakers main energy spark plugs included reserves Jordan Hill (10 points, eight rebounds) and Jodie Meeks (7 points on 3 of 7 shooting). But D’Antoni said he was reluctant to play them more minutes because he believed the Lakers’ starting lineup, mainly Howard and Gasol, would soon find a rhythm.

That didn’t happen.

“We didn’t play together especially on the defensive end,” Howard said. “Nobody rotated fast enough. That’s where we lost the game.”

The Lakers have actually fared better in that area, winning six of their last seven games heading into the New Year’s Day contest against the Philadelphia. But the Lakers’ lone loss last week in Denver featured the team conceding a season-high 126 points and Howard-Gasol frontline playing with passivity. Howard argued the Lakers need to practice more, but then backtracked moments later and said the team also needs rest. So how do the Lakers overcome such sluggishness?

“Individually we have to figure out how we get ready each and every game to have high level of energy,” Bryant said. “It’s figuring it out. That’s a big thing as you’re starting to age how you get yourself ready game in and game out. It’s tough. It takes a lot of commitment.”

Follow L.A. Daily News Lakers beat writer Mark Medina on Twitter. E-mail him at mark.medina@dailynews.com