A double-blind evaluation of evening primrose oil as an antiobesity agent.

Evening Primrose Oil (EPO) is a naturally occurring rich source of essential fatty acids, especially linoleic and gamma-linolenic acid. It has been suggested that it has antiobesity properties. This double-blind 12-week study was undertaken in 100 women with substantial obesity: 40 with refractory obesity, and 60 at time of initial referral to a hospital clinic. Seventy-four subjects completed the study. Those treated with EPO were comparable in age and degree of obesity with the placebo-treated group. There was no significant difference in the weight loss achieved by those taking EPO compared with placebo, either in the subjects with refractory obesity or in those treated at time of initial referral. It would appear that any antiobesity property possessed by EPO is clinically insignificant.