Obesogenic Programming Effects during Lactation: A Narrative Review and Conceptual Model Focusing on Underlying Mechanisms and Promising Future Research Avenues

The Effect of Maternal Overweight/Obesity on Serum and Breastmilk Leptin, and Its Associations with Body Composition, Cardiometabolic Health Indices, and Maternal Diet: The BLOOM Study

In overweight and obese patients, elevated serum and breastmilk leptin concentrations are observed, with serum leptin also being likely affected by the diet. We analyzed serum and breastmilk leptin in normal weight (NW) and overweight/obese (OW/OB) mothers, and evaluated its associations with (1) maternal anthropometric parameters; (2) markers of cardiometabolic health; and (3) the maternal diet. The BLOOM (Breastmilk and the Link to Overweight/Obesity and Maternal diet) study was conducted among 40 women (n = 20 OW/OB; n = 20, NW) who were exclusively or predominantly breastfeeding for 15.5 ± 1.2 (OW/OB group (0.99)) weeks. We collected 24 h breastmilk and fasting blood samples for leptin analysis by ELISA. Maternal dietary habits were evaluated using a 3-day dietary record and food frequency questionnaire, which were used to calculate the Polish-adapted Mediterranean Diet score. Maternal anthropometric measurements and DEXA scans were performed, and anthropometric and cardiometabolic indices were calculated. The OW mothers had 1.4 times higher serum levels, while OB mothers had 4.5 and 6.2 higher serum and breastmilk leptin levels, respectively, in comparison to the NW mothers. The FM% was correlated with serum and breastmilk leptin levels (r = 0.878, r = 0.638). Serum leptin was associated with markers of cardiometabolic health such as AIP, CMI, and VAI in the NW mothers, and with LAP in the OW/OB mothers. Higher energy, fructose intake and adherence to the Mediterranean diet were associated with serum leptin in the NW mothers (β = 0.323, 0.039-0.608; β = 0.318, 0.065-0.572; β = 0.279, 0.031-0.528); meanwhile, higher adherence to the Mediterranean diet could protect against elevated breastmilk leptin concentrations in OW/OB mothers (β = -0.444, -0.839--0.050), even after adjustment for FM%. Our results suggest a potential association between maternal serum leptin concentrations and cardiometabolic health. In addition, we confirm the importance of healthy dietary patterns in the improvement of breastmilk composition.

Understanding risk and causal mechanisms for developing obesity in infants and young children: A National Institutes of Health workshop

Obesity in children remains a major public health problem, with the current prevalence in youth ages 2-19 years estimated to be 19.7%. Despite progress in identifying risk factors, current models do not accurately predict development of obesity in early childhood. There is also substantial individual variability in response to a given intervention that is not well understood. On April 29-30, 2021, the National Institutes of Health convened a virtual workshop on "Understanding Risk and Causal Mechanisms for Developing Obesity in Infants and Young Children." The workshop brought together scientists from diverse disciplines to discuss (1) what is known regarding epidemiology and underlying biological and behavioral mechanisms for rapid weight gain and development of obesity and (2) what new approaches can improve risk prediction and gain novel insights into causes of obesity in early life. Participants identified gaps and opportunities for future research to advance understanding of risk and underlying mechanisms for development of obesity in early life. It was emphasized that future studies will require multi-disciplinary efforts across basic, behavioral, and clinical sciences. An exposome framework is needed to elucidate how behavioral, biological, and environmental risk factors interact. Use of novel statistical methods may provide greater insights into causal mechanisms.

The mediation effect of breastfeeding duration on the relationship between maternal preconception BMI and childhood nutritional risk

BACKGROUND

Higher maternal preconception body mass index (BMI) is associated with lower breastfeeding duration, which may contribute to the development of poor child eating behaviours and dietary intake patterns (components of nutritional risk). A higher maternal preconception BMI has been found to be associated with higher child nutritional risk. This study aimed to determine whether breastfeeding duration mediated the association between maternal preconception BMI and child nutritional risk.

METHODS

In this longitudinal cohort study, children ages 18 months to 5 years were recruited from The Applied Research Group for Kids (TARGet Kids!) in Canada. The primary outcome was child nutritional risk, using The NutriSTEP®, a validated, parent-reported questionnaire. Statistical mediation analysis was performed to assess whether total duration of any breastfeeding mediated the association between maternal preconception BMI and child nutritional risk.

RESULTS

This study included 4733 children with 8611 NutriSTEP® observations. The mean (SD) maternal preconception BMI was 23.6 (4.4) and the mean (SD) breastfeeding duration was 12.4 (8.0) months. Each 1-unit higher maternal preconception BMI was associated with a 0.081 unit higher nutritional risk (95% CI (0.051, 0.112); p < 0.001) (total effect), where 0.011(95% CI (0.006, 0.016); p < 0.001) of that total effect or 13.18% (95% CI: 7.13, 21.25) was mediated through breastfeeding duration.

CONCLUSION

Total breastfeeding duration showed to mediate part of the association between maternal preconception BMI and child nutritional risk. Interventions to support breastfeeding in those with higher maternal preconception BMI should be evaluated for their potential effect in reducing nutritional risk in young children.

Pre-gestational overweight and polyunsaturated fatty acids in human milk: theoretical causality model

A number of studies have focused on the evaluation of the relationship between pre-pregnancy overweight and polyunsaturated fatty acids content in human milk. However, given the complexity of potentially confounding risk factors, the use of graphical tools is recommended to identify possible biases. This article aims to propose a theoretical model of causality using the directed acyclic graph between pre-pregnancy overweight and polyunsaturated fatty acids content in human milk. Methods: An extensive literature review was performed to identify variables with causal relationships with exposure and/or outcome. The choice of variables for adjustment followed the graphic algorithm that comprises six criteria for selecting a minimum set of potentially confounding variables. Socioeconomic conditions, interpartum interval, maternal age and food consumption pattern were the variables that would have to be adjusted in order to estimate the total effect of pre-pregnancy overweight on polyunsaturated fatty acids content in human milk. The minimum set of variables found in the present study can be used in the analysis of other studies that evaluate this association.

Obesity-derived alterations in the lactating mammary gland: Focus on prolactin

Obesity is a modern pandemic with negative consequences in women's reproductive health. Women with overweight and obesity can develop mammary gland alterations that unable exclusive breastfeeding. Obesity associates with a disturbed lactating mammary gland endocrine environment including a decreased action of the hormone prolactin (PRL), the master regulator of lactation. The PRL receptor and the action of PRL are reduced in the mammary gland of lactating rodents fed an obesogenic diet and are contributing factors to impaired lactation in obesity. Also, treatment with PRL improves milk yield in women with lactation insufficiency. This review focuses on the impact of diet-induced obesity in the lactating mammary gland and how obesity impairs the lactogenic action of PRL. Although obesity alters lactation performance in humans and rodents, the responsible mechanisms have been mainly addressed in rodents.

The impact of maternal high-fat diet on offspring neurodevelopment

A maternal high-fat diet affects offspring neurodevelopment with long-term consequences on their brain health and behavior. During the past three decades, obesity has rapidly increased in the whole human population worldwide, including women of reproductive age. It is known that maternal obesity caused by a high-fat diet may lead to neurodevelopmental disorders in their offspring, such as autism spectrum disorder, attention deficit hyperactivity disorder, anxiety, depression, and schizophrenia. A maternal high-fat diet can affect offspring neurodevelopment due to inflammatory activation of the maternal gut, adipose tissue, and placenta, mirrored by increased levels of pro-inflammatory cytokines in both maternal and fetal circulation. Furthermore, a maternal high fat diet causes gut microbial dysbiosis further contributing to increased inflammatory milieu during pregnancy and lactation, thus disturbing both prenatal and postnatal neurodevelopment of the offspring. In addition, global molecular and cellular changes in the offspring's brain may occur due to epigenetic modifications including the downregulation of brain-derived neurotrophic factor (BDNF) expression and the activation of the endocannabinoid system. These neurodevelopmental aberrations are reflected in behavioral deficits observed in animals, corresponding to behavioral phenotypes of certain neurodevelopmental disorders in humans. Here we reviewed recent findings from rodent models and from human studies to reveal potential mechanisms by which a maternal high-fat diet interferes with the neurodevelopment of the offspring.

Maternal Diet During Pregnancy and Lactation and Child Food Preferences, Dietary Patterns, and Weight Outcomes: a Review of Recent Research

PURPOSE OF REVIEW

Efforts to promote children's preferences for healthy foods hold much potential for improving diet quality and preventing obesity. The purpose of this review was to summarize recent evidence for associations between maternal diet during pregnancy and lactation and child food preferences, dietary patterns, and weight outcomes.

RECENT FINDINGS

Recent research illustrates greater maternal vegetable intakes during pregnancy and lactation predict greater child preferences for and intakes of vegetables. Recent randomized clinical trials to improve maternal weight outcomes during the perinatal period via behavioral lifestyle interventions that included dietary components have yielded mixed findings for effects on child weight outcomes. There is strong evidence that maternal diet during pregnancy and lactation shapes flavor preferences during infancy; more research is needed to understand factors that facilitate versus hinder the translation of these preferences to later dietary patterns and weight outcomes.