Obesity affects ovulation, response to fertility treatment, pregnancy rates and outcome. In this prospective study, a weight loss programme was assessed to determine whether it could help obese infertile women, irrespective of their infertility diagnosis, to achieve a viable pregnancy, ideally without further medical intervention. The subjects underwent a weekly programme aimed at lifestyle changes in relation to exercise and diet for 6 months; those that did not complete the 6 months were treated as a comparison group. Women in the study lost an average of 10.2 kg/m2, with 60 of the 67 anovulatory subjects resuming spontaneous ovulation, 52 achieving a pregnancy (18 spontaneously) and 45 a live birth. The miscarriage rate was 18%, compared to 75% for the same women prior to the programme. Psychometric measurements also improved. None of these changes occurred in the comparison group. The cost savings of the programme were considerable. Prior to the programme, the 67 women had had treatment costing a total of A$550,000 for two live births, a cost of A$275,000 per baby. After the programme, the same women had treatment costing a total of A$210,000 for 45 babies, a cost of A$4600 per baby. Thus weight loss should be considered as a first option for women who are infertile and overweight.