Metabolic Flexibility and Weight Status May Contribute to Inter-Individual Changes in Breastmilk Lipid Content in Response to an Acute Bout of Exercise: Preliminary Findings from a Pilot Study

International Journal of Exercise Science 13(2): 1756-1769, 2020. The purposes of this pilot study were to describe changes in breastmilk lipid content in response to an acute bout of moderate intensity exercise and to explore maternal metabolic health factors, including metabolic flexibility, which may impact this change. A cross-sectional, observational, pilot study design was performed in 14 women between 4 and 6 months postpartum. Whole body fasting lipid oxidation was assessed, a standardized high-fat breakfast was consumed, and lipid oxidation was again measured 120-minutes post-meal. Metabolic flexibility was determined by comparing the change in lipid oxidation before and after the meal. Women completed 30-minutes of moderate intensity treadmill walking 150-minutes post-meal. Breastmilk was expressed and analyzed for lipid content before and after exercise. Overall, there was no significant difference between pre- and post-exercise breastmilk lipid content (pre-exercise 59.4±36.1 g/L vs. post-exercise 52.5±20.7 g/L, p=0.26). However, five (36%) women had an increase in breastmilk lipid content in response to the exercise bout, compared to nine (64%) that had a decrease in breastmilk lipid content suggesting inter-individual variability. The change in breastmilk lipid content from pre- to post-exercise was positively correlated to metabolic flexibility (r=0.595, p=0.03). Additionally, post-exercise lipid content was positively correlated with body mass index (BMI), body composition, and postpartum weight retention. Preliminary findings from this pilot study suggest that metabolic flexibility and maternal weight status may help explain the inter-individual changes in breastmilk lipid content in response to an acute bout of moderate intensity exercise

Metabolism during Pregnancy and Postpartum: How Does it Change and What Factors Influence it?

PURPOSE: Pregnancy is a physically impactful process in a woman’s life. During this time, a woman will gain weight and research has shown that many women will retain some extra weight after delivery. Because of this, recovery in the postpartum period is pivotal to avoiding the implications of weight retention. The postpartum period is vastly understudied in both the research and medical communities and this gap between pregnancy and postpartum research needs to be bridged. Therefore, the purpose of this study was to investigate metabolic changes from pregnancy to postpartum and to study how factors such as sleep and breastfeeding can impact metabolic values in the postpartum period. METHODS: Women participated in a pregnancy study visit at 32-34 weeks of gestation (n = 25) and attended two subsequent visits at 4-6 months (n = 25) and 12-13 months postpartum (n = 16). At these visits, the women had a baseline blood draw and baseline metabolic measurements taken via indirect calorimetry. At the pregnancy visit, participants completed a demographic survey and a dietary questionnaire (DHQ-II). At the postpartum visits, they completed the same surveys, along with validated sleep and breastfeeding surveys. RESULTS: Absolute resting metabolic rate (RMR) was significantly higher during pregnancy than at 4-6 months postpartum and 12-13 months postpartum (p \u3c 0.001 and p = 0.001, respectively). Accounting for body weight, relative RMR was significantly higher during pregnancy than at 4-6 months postpartum. With regard to sleep, women deemed to be “good sleepers” had a significantly higher relative RMR than those who were deemed “poor sleepers” (23.6 ± 2.5 vs 20.8 ± 2.3, p = 0.009). With regard to breastfeeding, women who breastfed had a relative RMR than the women who did not breastfeed (22.8 ± 2.6 vs 20.4 ± 2.3, p = 0.046). CONCLUSIONS: There are hypermetabolic changes that take place during pregnancy. These values seem to decrease into the postpartum period. Women who demonstrate an improved sleep quality and who opt to breastfeed tend to have improved metabolic responses. This could help combat the struggle with postpartum weight retention that some women face