This study was the first randomised trial to evaluate the effects of such training in a lifestyle change programme for overweight women, study co-author Dr Caroline Horwath, a senior lecturer in the university human nutrition department, said.
"The positive results are exciting, given the limited long-term success of traditional dieting approaches," Dr Horwath said.
"Deprivation of food makes people more focused on food."
If the level of psychological distress could be reduced among some overweight and obese women, it was "easier to follow a healthier eating pattern," she said.
The latest findings were from a two-year follow-up of a ground-breaking Otago research project into the effectiveness of non-dieting intervention programmes in improving lifestyle behaviours and reducing psychological distress and medical symptoms.
In the study, 225 women with a body mass index (BMI) of 28 or more were randomly assigned to one of three intervention programmes.
All three 10-week-long programmes helped women in moving their focus away from calorie counting and body weight, towards sustainable lifestyle changes that enhanced their well-being, regardless of weight loss.
Such non-dieting interventions had longer-lasting effects if they included relaxation training, the study, recently published in US journal Preventive Medicine, found.
The training also contributed to reduced insomnia and "very substantial reductions in depression".
Despite giving up dieting, women in all three interventions had successfully prevented any weight gain over the two-year period, which was a promising outcome for a group at high risk of weight gain over time, she said.
After two years, only the women who had received the training had maintained the psychological and medical symptom improvements they had shown after the first year.
Women who were still regularly practising these techniques after two years had also lost an average 2.5kg in weight.
"Stress and negative emotions can trigger women to overeat and consume high-fat and high-sugar foods."
By using relaxation techniques, such as progressive muscle relaxation, and abdominal breathing, women had effective tools to manage stress and emotions without resorting to unhealthy eating, she said.
These techniques were adapted from a Harvard Mind-Body Medical Institute programme.