Hong Kong singer-actress Charlene Choi has clarified that her fellow Twins singer Gillian Chung is battling hormonal imbalance, after the latter's latest appearance sparked concerns.

Chung, 40, recently appeared in a trailer for new Chinese reality show Twinkle Love, in which 10 graduates, who are all 20 years old, take part in a graduation trip.

Chung, who will be one of the regular guests on the show, disclosed in the trailer that her first love was a Japanese and that she would tell her 20-year-old self to be a good person.

However, viewers were more interested in her appearance, with several commenting online that she has gained a lot of weight, judging by her rounder face and fatter neck. Some, however, said she still looked pretty despite the weight gain.

Chung has not reacted to these claims.

However, Choi, who was attending the premiere of her latest movie 77 Heartwarmings, a romance also starring Pakho Chau and Mario Maurer, said that Chung's weight gain was due to hormonal imbalance.

She added: "What matters is health and happiness."

The 38-year-old also said she did not express too much concern as she did not want to add pressure on Chung.

It is not the first time Chung's weight gain has made the news. Netizens said she looked rounder last July when she appeared on a live-streaming show.

The episode took place after news broke last May that she had parted ways with her Taiwanese husband, aesthetics doctor Michael Lai, after less than two years of marriage.

Chung also suffered a head injury last September, after an accident in her hotel room while filming a movie in Xiamen, China.