Differences in macronutrient selections in users and nonusers of an oral contraceptive.

One of the problems inherent in using women in clinical research is the effect that oral contraceptive (OC) use might have on physical indexes. Although weight gain is frequently reported as a side effect of OC use, there is little empirical evidence that such weight gain actually occurs. The current study investigated differences in energy balance [ie, dietary intake, resting energy expenditure (REE), and physical activity] between groups of users and nonusers of OCs. Each group completed a protocol that covered one menstrual cycle and consisted of daily recording of dietary intake, measurement of REE once during each phase of the menstrual cycle, and reporting of physical activity over the entire cycle. Comparisons indicate that there was a marginal interaction (P = 0.06) of OC use with total energy intake, indicating a different pattern of intake for the two groups. There were qualitative between-group differences such that the OC group consumed a greater percentage of energy as fat (P = 0.02) and a lesser percentage of energy as carbohydrate (P = 0.008). No group differences were found in the percentage of energy consumed as protein, but both groups consumed significantly less protein during menses (P = 0.008). There were no significant differences in REE. Both groups of women reported marginally more activity (P = 0.09) during menses than during the luteal phase.