The actor Mary Tyler Moore, who has died aged 80, spent decades as “America’s sweetheart”, her time in that role reflecting changes in American society and the turmoil of her own private life. Her outwardly bubbly personality and trademark broad, toothy smile disguised an inner fragility that appealed to an audience facing the new trials of modern-day existence. She grew into the role on television; her parts tracked changing opportunities for women, but were always channelled through her own character. “I am not an actress who can create a character,” she said. “I play me.”

Moore came to notice in 1959 in the TV series Richard Diamond, Private Detective, as the private eye’s message service operator Sam. Seen only as a disembodied, deep-voiced pair of legs at a switchboard, she was literally objectified. She became a star in The Dick Van Dyke Show, playing Laura Petrie, the wife of the comedy writer, Rob, played by Van Dyke. In tight capri pants (between shorts and trousers), with a Jackie Kennedy flip in her hair, Laura was pitched somewhere between the elegance of 50s sitcom housewives such as Donna Reed and the frantic ditz-under-pressure of Lucille Ball. The show ran from 1961 to 1966, and Moore won two Emmy awards for best actress, prompting her move to more serious work.

She was cast alongside Richard Chamberlain in a Broadway musical version of Breakfast at Tiffany’s, called Holly Golightly. The producer, David Merrick, closed the show after four previews, a week before it was due to open in December 1966, “out of consideration for the audience”.

In 1967 she starred alongside Julie Andrews in the musical Thoroughly Modern Millie, which was one of the most successful films of the year. However, some forgettable movies followed, including Change of Habit (1969), in which she played a nun who is the love interest to Elvis Presley’s doctor, Moore returned to the small screen in another sitcom, The Mary Tyler Moore Show. There she was Mary Richards, a 30-year-old small-town woman recently jilted by her boyfriend. She moves to big-city Minneapolis looking for a secretarial job, but is hired as an associate producer for a local news show. The Laura Petrie of The Dick Van Dyke Show was taking very tentative steps into becoming a career woman.

Moore seemed to be doing the same thing off-screen. The show was hugely successful, winning a then-record 29 Emmys, spawning three spin-off programmes from its supporting cast, all produced, as was The Mary Tyler Moore Show, by the star’s own MTM Enterprises, nominally hers but actually the brainchild of her second husband, the TV executive Grant Tinker. As ever, life and art were not reflected perfectly.

Moore was born in Brooklyn, New York, where her father, George Tyler Moore, was a clerk. Her mother, Marjorie (nee Hackett) was an alcoholic, and this, combined with a strict upbringing, made Mary’s childhood difficult. The family moved to California when Mary was eight, and she was educated at Catholic schools. At 17 she made her show-business debut dancing as Happy Hotpoint, wearing an elf costume that showed off her legs, in appliance commercials shown live during the TV series The Adventures of Ozzie & Harriet.

Soon after graduation from Immaculate Heart high school, Los Angeles, in 1955 she married Richard Meeker and became pregnant with a son, Richie. (In The Dick Van Dyke Show she would be given a son, named Richie.) When her condition became visible, she had to give up the Hotpoint job, and she now decided to pursue acting rather than dancing. She later said she had calculated that this would be a better route to stardom.

She and Meeker divorced in 1961; the following year she married Tinker, a former ad man who had just become a west coast programming executive for NBC. With Moore’s film career having stalled, Tinker pitched The Mary Tyler Moore Show to CBS and it debuted in 1970. For six seasons it stayed in the ratings top 20. Mary’s best friend Rhoda (Valerie Harper) got her own sitcom in 1974; her landlady Phyllis (Cloris Leachman) followed with another in 1975. The drain of characters may have hurt the original show and when, in its seventh season, it fell to 39 in the ratings, CBS cancelled it, prompting a third spin-off, a drama moving the crusty editor Lou Grant (Ed Asner) to Los Angeles to become the city editor of a newspaper.

An episode of The Mary Tyler Moore Show from 1974

MTM would go on to produce comedies including The Bob Newhart Show (1972-78) and WKRP in Cincinnati (1978-82), and the successful dramas Hill Street Blues (1981-87) and St Elsewhere (1982-88), as well as a Tony-winning revival of Peter Nichols’ play Joe Egg on Broadway in 1985. Three years later it was sold to Television South, then part of ITV.

CBS tried to keep Moore in the spotlight with a number of musical variety specials, and two separate series which failed quickly in the 1978-79 season, prompting Moore’s return to theatre. In 1980 she took over the lead in Whose Life Is It Anyway on Broadway, and although replacement cast members are not eligible for Tony awards, was given a special Tony for her performance. Her role in Ordinary People (also 1980), as the grief-stricken suburban mother turning on the son who survived an accident that killed his brother, won her an Oscar nomination. “I was thinking of my own family history,” she explained, “and how we missed the mark of being everything that I’m sure people thought I was.”

Moore’s sister Elizabeth had died of a drug overdose in 1978. Shortly after the film’s release, her son, Richie, shot himself and died, in what appeared to be an accident. By this time she and Tinker had separated; they divorced in 1981. In 1983 Moore married Robert Levine, a doctor who had treated her mother.

She twice tried to return to television with sitcoms that failed quickly, Mary (1985-86) and Annie McGuire (1988-89). But she received an Emmy nomination for playing Mary Todd Lincoln, wife of the president and another grieving mother, in the TV movie Lincoln (1988), which began more casting against type. She won another Emmy playing a baby smuggler in Stolen Babies (1993). She continued to make frequent guest appearances on television, including a show that reunited the cast of The Dick Van Dyke Show.

In 1995 she published a memoir, After All, in which she described her experiences as a recovering alcoholic. A second memoir, Growing Up Again (2009), detailed her life with type 1 diabetes, with which she had been diagnosed in 1969. The inspirational subtext of her books made her a popular guest on talk programmes. She became an active campaigner on diabetic issues, serving as chair of the Juvenile Diabetes Foundation International, as well as for animal charities.

Her health eventually deteriorated: she had a brain tumour removed in 2011, and suffered from vision, kidney and heart problems related to her diabetes.

She is survived by Robert.

• Mary Tyler Moore, actor, born 29 December 1936; died 25 January 2017