The only thing this guy hates more than exercising is the late exercise queen Lucille Roberts.

A disgruntled — and apparently doughnut-loving — former employee of the late Roberts’ workout chain is suspected of vandalizing her $90 million Upper East Side mansion by splashing it with white paint early this week.

The portly vandal also allegedly shot BB pellets at the stately 80th Street address and sent a series of nasty letters to Roberts’ family, including one containing white powder and a note reading “Don’t f–k with me.”

The man — whose grudge has apparently been eating at him since he was canned at Christmastime — is so fat that one source who saw a picture of him quipped, “He’s definitely not a member” of Roberts’ health club.

Cops passed a picture of the man around to people in the neighborhood and told residents he’s from New Jersey and his name is David, said a doorman who works near Roberts’ mansion and saw the picture.

“[He’s] in his 20s, fat with a double chin, who looks like he’s smuggling oranges in his cheeks,” the doorman said.

The three hand-scrawled letters arrived Tuesday with no return address.

In addition to the letter filled with powder — which turned out to be harmless — a second note cryptically stated in upper-case letters “1-PAINT, 2-GLASS, 3-BLEACH, 4-BULLET IN THE LEG. JAIL.”

A third letter was stuffed with small screws and pieces of copper wire.

Surveillance cameras were unable to capture an image of the vandal.

According to the doorman, police also discovered pellet casings on the ground fired from a BB gun the previous night around 1 a.m.

The Roberts family’s multimillion-dollar business is also conducted from the mansion.

The Victorian mansion is on the market for $90 million.

Lucille Roberts died in 2003 at 59 from lung cancer. Her business grew into a $50 million health and fitness enterprise for women only and at one point had 50 gyms with 200,000 members.