"People blame food choices on lack of willpower, I don't buy that," the nutritionist and author said.
There were chemical messages in the body driving bodyweight such as sleep, stress, sex and thyroid hormones which played more of a role than independent thinking, she said.
Dr Weaver, known as Dr Libby, was in Dunedin yesterday with husband Chris Weaver, former chief executive of Auckland Racing Club, on the first step of a nationwide tour of the country presenting her health and inspiration seminars.
Mr Weaver has just taken on the "Dr Libby brand" full-time, joining her on her travels, promoting her books and seminars.
Dr Weaver will present her message to 9000 people at an upcoming United States health conference also featuring American television doctor Dr Oz and talk-show host Larry King.
An Australian who moved to New Zealand five years ago "for love", Dr Weaver has combined her degree in dietetics with the knowledge gained from her Phd in biochemical and nutritional factors in children with autism, to develop her approach to health and weight-loss.
When her Auckland practice developed a six-month waiting list, she looked at other ways of reaching people and penned her book Accidentally Overweight, which became a bestseller and followed it this year with Rushing Woman's Syndrome.
She hoped to help people make sense of the conflicting nutritional information available, work out how to understand their body and what was right for them, she said.
"I get real joy from seeing the lights go on. It's not all or nothing; it's encouraging change that is sustainable."
People often wondered why their clothes were getting tighter but their diet or exercise regime had not changed or "starving themselves or exercising maniacally" had not worked, Dr Weaver said.
In some cases, it was hormones such as the two stress hormones which had a "powerful effect" on appetite. In others, it was a person's emotional response to food which could be to blame.
The seminars helped people understand their body systems and enabled them to focus on improvements that could make a difference.
Dr Weaver also spoke in Balclutha yesterday and will hold a seminar in Queenstown today.
Dr Libby's five winter tips
1. Slow-cooked stews and casseroles, packed full of vegetables, are the best and ready to eat when you get home; they make great leftovers.
2. Take a packed lunch - have leftovers, try mountain bread (wraps) instead of bread.
3. You have permission to eat afternoon tea but if you like baking, try using healthier recipes.
4. Get outside when the sun shines, even if just for 10 minutes and try diaphragmatic breathing - schedule 20 breaths a day.
5. Focus on what you are grateful for, for 5 minutes a day - you can't be stressed when you're gratified.
