The scientists from the University of Wollongong say that for overweight or obese people, higher protein meals may have a subtle fat-burning effect and the glycaemic index (GI) of a meal has no additional effect on fat breakdown.
Dietitian Dr. Marijka Batterman says research has already shown that overweight or obese people are not as good at burning fat and this new research shows that fat oxidation, or the body's ability to 'burn' fat, improves in obese people when they eat a higher protein diet.
For the study participants were put on two protein-enriched meals and one standard meal, which all contained the same number of kilojoules - the two protein-enriched meals differed in the type of carbohydrate they contained - either high- or low-GI and included a cheese and tomato omelette for breakfast, and a beef, chutney and salad sandwich, with a tub of low-fat yoghurt, for lunch.
When the amount of kilojoules the subjects burnt was measured it was found that the high-protein meals led to the greatest level of fat oxidation.
Dr. Batterman from the Smart Foods Centre at the University of Wollongong says they found a clear relationship between body composition and the effect of dietary protein on fat oxidation.
Dr. Batterman says our bodies burn energy and use fat differently, and this needs to be taken into account when planning a diet.
Claire Hewat, Executive Director of the Dietitians Association of Australia (DAA) says all foods could fit into a healthy diet if eaten in the right amounts, and are combined with regular physical activity.
Ms Hewat advises people to forget fashionable 'fad' diets and instead, include lean protein from healthy foods such as lean red meat, chicken and fish, legumes, eggs, nuts and reduced-fat dairy foods and if necessary seek individual advice on how much protein they need from an Accredited Practising Dietitian.
The study is published in Nutrition & Dietetics.
The questionnaires explored a range of aspects of the women's health and lifestyle, including the mother's occupation and possible exposure to different chemical substances, family history of disease, maternal occupation, vegetarianism, smoking and use of folate supplements.
Professor Elliott, who led the study, says while the finding did not prove that hairspray - or any phthalates it contained - was the culprit - it does provide a little more evidence about these chemicals, but more research will be needed to demonstrate that the link exists and pregnant women will need to make their own choices about whether or not to avoid these kind of exposures.
Experts say this new study is "important research" and women need to be given the evidence linking phthalates to health problems; they suggest that women who are planning a pregnancy should avoid (or at least minimise) use of cosmetics, body creams/lotions etc, especially in the first three months of pregnancy to avoid unnecessary chemical exposures.
Another finding of the study provides further backing of the government's recommendation that pregnant women should take extra folate to prevent similar defects to hypospadias, which arise early in pregnancy.
Researchers from University College Cork and the Centre for Research in Environmental Epidemiology in Barcelona also contributed to the study which is published in the journal Environmental Health Perspectives.
The study was funded by a grant from the UK Health and Safety Executive, the Department of Health, the Department of the Environment, Transport and The Regions and the European Chemical Industry Council.