Carole Bayer Sager claims her friend Diane Keaton was "very thin" when she visited the actress "two or three weeks" before her death

However, Carole was "stunned" by "how much weight" Diane "lost" when she saw the star just weeks before the actress' death.

The Grammy and Oscar-winner told People: "I saw her two or three weeks ago, and she was very thin.

"She had lost so much weight.

"She had to go to Palm Springs because her house had been damaged inside, and they had to clean everything.

"She was down there for a while, and when she came back, I was kind of stunned by how much weight she'd lost."

Carole went on to pay tribute to the "happy and upbeat" Diane.

The star said: "She was a magic light for everyone.

"I just loved her. She was so special, she just lit up a room with her energy. She was happy and upbeat, and taking photographs of everything she saw.

"She was completely creative; she never stopped creating."

Carole's comments about Diane's alleged weight loss come a day after it was reported that the Annie Hall star's health "declined very suddenly" in the months before she died.

While no details have been released about the circumstances surrounding Diane's death, a source told People: "She declined very suddenly, which was heartbreaking for everyone who loved her.

"It was so unexpected, especially for someone with such strength and spirit.

"In her final months, she was surrounded only by her closest family, who chose to keep things very private. Even longtime friends weren't fully aware of what was happening."

In March, Diane put her "dream home" in Brentwood, California, up for sale - after the star previously said she would stay there forever - and was not regularly seen in the area walking her dogs.

Another source said: "She lived in Brentwood for many years.

"She loved her neighbourhood. Up until just a few months ago, she'd walk her dog every day. She was usually dressed the same, with a hat and her signature sunglasses, regardless of the weather.

"She was always very nice, funny and chatty. She'd talk to her dog like he was a person. She was eccentric and had this old-school Hollywood aura.

"She was very, very special."

Diane's loved ones have requested privacy as they mourn her loss.

The star - who never married - is survived by her adopted children, daughter Dexter, 29, and 25-year-old son Duke.