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Research has confirmed what many women trying to lose weight already suspected - diets do not work.

Otago University researchers found that overweight and obese women were more likely to improve their health through treatment approaches that did not rely on just counting calories.

Their study showed that "non-dieting" interventions could be effective in reducing psychological distress. The findings appeared in the latest edition of the American Journal of Health Promotion.

The research tracked the long-term progress of 225 overweight or obese New Zealand women who participated in 10 week-long non-dieting intervention programmes.

Caroline Horwath, of the Department of Human Nutrition, said they only tested women because they were more likely than men to be prone to chronic dieting practices to lose weight.

Non-dieting interventions successfully prevented further weight gain over 12 months, Dr Horwath said.

Research had shown that the traditional dieting approach of restricting both calories and foods types showed poor results in achieving long-term weight loss, she said.

"Within five years, many dieters regain any weight they lose and often end up heavier than when they began.

"They also tend to develop very unhealthy attitudes towards food and to lose their natural ability to recognise when they are hungry or full."

The non-dieting approach focused on improving lifestyle behaviours to enhance health independently of weight loss, she said.

"The three intervention types in the study all encouraged the women to break free from chronic dieting and make sustainable lifestyle changes. "This included listening to their feelings of hunger and fullness, rather than focusing on weight loss."

Dr Horwath said they found the most successful intervention involved providing intensive training in relaxation techniques while equipping the women to recognise and avoid stress-related triggers for eating.

Many overweight women have a fearful and guilt-ridden relationship with food, and their eating was often emotionally triggered.

The intervention, adapted from a programme developed by the Harvard Mind-Body Medical Institute, showed significant improvements in reducing psychological symptoms such as anxiety and depression, and medical symptoms including pain, fatigue and insomnia, Dr Horwath said.

"No one treatment will be ideal for all women, but our findings suggest this may be an effective option for some overweight or obese women seeking to improve their psychological well-being and physical health."