Carmelo Anthony took a $5 million pay cut on his new contract, but it appears he took a bigger cut in weight. According to an Anthony confidant, Anthony has done so in order to resemble his physique as a rookie with the Nuggets and to be more viable in Phil Jackson’s triangle offense.

A photo of Anthony this week on his Instagram showed what appeared to be a dramatic weight loss since the season ended. Anthony, who turned 30 on May 29, looks younger with the weight loss.

“He wants to be as athletic as he was when he was a rookie,’’ the confidant told The Post. “Plus he wants to be a facilitator in the triangle and speed will help that.’’

Anthony was listed at 230 pounds as a Denver rookie in 2003 and appears to be close to that goal. Last season, the 6-foot-8 Anthony was listed in the Knicks preseason media guide at 240, but likely played at least 5 to 10 pounds heavier as the season wore on.

Orlando Magic forward Tobias Harris, a Long Island product, worked out three times with Anthony in June at the Terminal 23 gym Anthony owns in midtown. Harris noticed a major difference in his appearance. “He looked real good,’’ Harris told The Post recently.

According to a source, the Harris camp was told Anthony was working out three times a day, doing basketball drills, agility drills, weights and yoga.

With regard to his diet, Anthony has followed LeBron James’ lead in a mostly no-carb diet. But Anthony has a history of crash diets and “fasting.’’

During the 2012-13 season, Anthony claimed he was on a “15-day fast’’ and blamed a slump on it.

“I haven’t had a good meal in about 2 ¹/₂ weeks,’’ Anthony said after a poor performance in January 2013. “No meats, no carbs, anything like that. … But I surrender, I’m done. I’m going to get some food right now. I’m going to get me the biggest steak I can possibly get.’’

When he was with Denver, he told reporters he was observing a three-week “Daniel Fast,’’ which bans meat and wine and promotes eating vegetables and fruits.

Because former coach Mike Woodson played Anthony a lot at power forward the past two seasons, it would have been unwise to drop too much weight. However, team president Phil Jackson sees Anthony more as the starting small forward this season.

The toothpick-thin Reggie Miller said James and Anthony are being wise.

“It will prolong their career,’’ Miller told TMZ. “You carry on too much weight, it shortens longevity of a basketball player especially later on. You get up in years, it’s less wear and tear on your body. It’s actually pretty smart.’’

Anthony also was not nearly as effective in the fourth quarters last season, especially in the final minute. His clutch-shooting stats were awful and that may have been due to fatigue.