Fortunately, we are dining outdoors at Rosetta - the latest addition to Neil Perry's Southbank empire at Crown - and ultimate gustatory enjoyment has prevailed over ultimate wellness. The waiter recommends the lamb but warns of a ''little strip of fat that keeps it nice and moist''. With a rueful glance at Phelps, I say: ''I'd better ask my doctor.''

We order funghi marinati (charcoal-grilled marinated mushrooms with pecorino) to share, followed by two specials: John Dory San Pietro for Phelps, grilled yellowfin tuna for me. Sides are organic baby carrots with ricotta salata, broccolini with lemon and olive oil, and potatoes with garlic and rosemary salt.

We nod more firmly to wellness by ordering sparkling water (at $9.50 a bottle, we could have had a glass of sauvignon blanc). Phelps does not drink at lunchtime but enjoys wine in limited quantities. ''But it has to be worth it,'' she says.

Phelps' journey to wellness, and the reason she wrote her book, began in 2003. She was completing her three-year term as president of the Australian Medical Association - a job that required 18-hour days, constant travel and meetings - when she was struck down by a pulmonary embolism, an adverse effect from recent hormone treatment. It nearly killed her.

Physician, heal thyself - but her recovery was slow. The illness forced Phelps to examine her own quality of life and how she dealt with its fundamentals: exercise, diet, sleep and stress management. ''I found my own new normal,'' she writes.

Phelps wants others to find their new normals, which is why she wrote the book. ''I like to think it's the only self-help book you'll need to read,'' she says. What, exactly, is wellness, apart from the opposite of sickness? ''It's a nuanced concept - not just about absence of disease or being healthy, but also a physical, emotional and spiritual sense of being well,'' she says. ''Ultimate wellness doesn't mean running a marathon next year but feeling as well as you can by being as fit as you can be, based on your capability.''

The mushrooms arrive. ''No danger here,'' the good doctor says. ''Lots of protein and no fat in the olive oil.''

The vital ingredient (we're back to wellness) is happiness? ''An absence of happiness is going to affect your emotional health,'' Phelps says. ''You can't achieve ultimate wellness unless you tackle the issues in your life that make you unhappy.''

Is she happy? ''I love my work, feel challenged and I have a wonderful home life - a wife, three kids.'' Phelps' two elder children, Jaime and Carl, are from her first marriage; her third, Gabi, she adopted with Jackie Stricker, which required a change in NSW law whereupon same-sex couples could both adopt children, instead of only one partner. Phelps and Stricker lobbied long and hard, and the law was finally amended in 2010.

The couple were married twice, each time in New York. The first, in 1998, was a religious ceremony (Phelps has converted to Judaism); the second, in 2011, was a legal ceremony. The couple, long-time advocates for gay marriage, have seen a positive shift in public attitude. ''Being gay is no longer a secret minority,'' Phelps says.

She draws inspiration from President Barack Obama's second inauguration address: ''Our journey is not complete until our gay brothers and sisters are treated like anyone else under the law - for if we are truly created equal, then surely the love we commit to one another must be equal as well.''

This, she says, is still not the case in Australia. ''There are now so many people who think equality is inevitable and it should happen. The only people who seem to be standing in its way are Julia Gillard and Tony Abbott.''

John D and yellowfin arrive with accompanying vegetables. Phelps helps herself to the broccolini and carrots, politely declining the potatoes. Because she has just signed her book for me, we're talking about writing left- or right-handed. Phelps may be a southpaw with a pen but she has fine, legible writing. ''I spent my life being metaphorically left-handed, didn't I?''

Many Australians still associate Phelps with her AMA presidency and the exhaustive - and, as it turned out, exhausting - agenda she set herself. ''I wanted to fix law reform, which I was told was impossible. I don't mind being given impossible tasks. I wanted to try to sort out the medical workforce shortage and introduce some pretty edgy policy issues - look at environment, climate change and indigenous health.''

The Phelps agenda was finally achieved, but not without political struggle. The battles between Phelps and the Howard government's health minister at the time, Michael Wooldridge, were particularly fierce. Getting his attention, she says, was not easy. ''I ended up having to work through the office of the PM quite directly.''

After the AMA, Phelps returned to medical work, especially teaching. She is now conjoint professor in the faculty of medicine at the University of NSW. Along the way, she has also written a medical textbook on integrating different cultural healthcare practices: ''All that solid, grounded, Western medical general practice, fused with the concept of complementary therapies and non-medical, non-pharmaceutical treatments.''

No sweets, alas; just coffee. Double espresso for me, decaf cappuccino for Phelps.

Did she always want to be a doctor? ''All the way through school I thought I was going to be a lawyer. I would have enjoyed a legal career. But, pen poised above the page when I was writing down my matriculation requests, I went with medicine first. I really like science, the sciences and the arts. I have more of a penchant for that, and working with people more than with paper.

''I knew I wanted to be in a profession that made a difference. To be honest, if you love what you do and you do it well, you're making a difference. I was lucky enough I had the choice to be able to do what I wanted, really. Medicine was the right choice.''

■ Ultimate Wellness: The 3-Step Plan, by Kerryn Phelps, is published by Macmillan.