We present a rigorous formalism of information transfer for systems with dynamics fully known. This follows from an accurate classification of the mechanisms for the entropy change of one component into a self-evolution plus a transfer from the other component. The formalism applies to both continuous flows and discrete maps. The resulting transfer measure possesses a property of asymmetry and is qualitatively consistent with the classical measures. It is further validated with the baker transformation and the Hénon map.

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Postpartum weight retention is a significant contributor to obesity in reproductiveaged women, but the key implementation characteristics of postpartum weight management interventions have not been systematically identified to inform policy and practice. This study aimed to evaluate the intervention characteristics associated with weight loss in postpartum women using the Template for Intervention Description and Replication (TIDieR) framework. We searched MEDLINE, CINAHL, EMBASE, PSYCINFO, and EBM databases to identify lifestyle intervention RCTs in postpartum women (within 2 years after birth) published up to January 2018. From 4512 studies, 33 studies were included in the systematic review and meta-analysis (n = 4960 women). Health professional-delivered interventions had significantly greater weight loss than those delivered by nonhealth professionals (mean difference, 95% confidence interval: (−3.22 kg [−4.83, −1.61] vs −0.99 kg [−1.53, −0.45], P = 0.01 for subgroup differences)). Diet and physical activity combined had significantly greater weight loss compared with physical activity-only interventions (−3.15 kg [−4.34, −1.96] vs −0.78 kg [−1.73, 0.16], P = 0.009 for subgroup differences). The extent of weight loss was not influenced by intervention intensity (duration, number of sessions) and setting (individual or group). KEYWORDS implementation, lifestyle, postpartum women, systematic review, weight management 1 | INTRODUCTIONGlobal trends in obesity suggest that women aged 19 to 50 years gain weight more rapidly than men and women of other age groups. [1][2][3] Weight retention or weight gain after birth is a key contributor to obesity in women. Weight gain from early to middle adulthood has been shown to be associated with increased risk of major chronic diseases including type 2 diabetes and cardiovascular disease. 4 A recent systematic review and meta-analysis reported approximately half of all pregnancies had excessive gestational weight gain according to the Institute of Medicine recommendations. 5 There are large variations in weight retained after pregnancy between individuals; on average, women retain 0.5 to 3.5 kg from each pregnancy, 6 and a quarter to half of all women are 4.5 kg or heavier than prepregnancy weight by 1 year postpartum. 7-10 The inability to return to prepregnancy weight or halt weight gain during the postpartum period (birth to 2 years) carries † These authors contributed equally to this manuscript