Effects of Exercise and Yogurt on Bone Mineral Density and Immunological Factors in Human Milk: The MEEMA Study

Obesity in America has risen to epidemic levels over the past 20 years. For women, childbearing itself could be a contributing factor to this high prevalence of excess weight. In addition, for women who breastfeed, lactation is a time of rapid bone loss due to hyperprolactinemia, amenorrhea, and increased bone turnover, especially in the lumbar spine and hip. The American Academy of Pediatrics recommends exclusive breastfeeding for the first 6 months, continue to at least 12 months with the introduction of complementary foods and up to 2 years. Breastfeeding helps reduce long term maternal weight retention from pregnancy, the risk of childhood obesity and provides a number of immunological factors to promote the immune system and gastrointestinal system of the neonate.

Bone loss due to lactation is usually reversed with weaning; however, not all women recover from this bone loss which increases the risk of osteoporosis later in life. Weight bearing exercise and dairy intake (milk, yogurt, cheese) plus vitamin D supplementation may provide some protection from bone loss. Thus, the objective of this study is to promote long-term lifestyle changes that support healthy lifelong weight management through a community based exercise intervention and daily yogurt consumption program aimed at overweight- to- obese lactating postpartum women.

The specific aims of this project are to evaluate in overweight lactating women at 6 and 20 weeks postpartum (PP) whether an exercise and yogurt supplementation intervention, compared to a minimal care group, will:

1. Improve body composition. The working hypothesis for this aim, based on previous studies (Lovelady et al 2009; Colleran et al 2012), is thatthe intervention group will have less loss of lean body mass and bone mineral density but more fat loss compared to the minimal care group at 20 weeks PP.
2. Promote an increase in cardiovascular fitness. The working hypothesis for this aim, based on previous studies (Lovelady et al 2009; Colleran et al 2012), is that the intervention group will exhibit an increase in predicted maximal oxygen consumption and maximal strength compared to the minimal care group at 20 weeks PP.
3. Increase immunological factors within breastmilk. The working hypothesis for this aim, based on a previous study (Lovelady et al 2003), is that the intervention group will exhibit an increase in IgA, lactoferrin, lysozyme and Bidfidus factor concentrations in breast milk which will improve immunological benefits to the nursing infant.

Eligibility Criteria:
Inclusion Criteria:

* women must be at least 2 weeks postpartum
* be between the ages of 25 to 40
* have a self-reported body mass index (BMI) between 25 and 35 kg/m2
* be fully breastfeeding (\< 4 oz of formula given to the infant only on occasion)
* be sedentary for the past 3 months (\< 3 weekly sessions of moderate aerobic activity)
* be non-smokers
* had a singleton birth.

Exclusion Criteria:

* delivery by cesarean section
* have medical complications where exercise was contraindicated
* have an inability to consume yogurt (i.e. maternal or infant allergies/intolerance to the dairy protein or sugar) or
* a have diagnosis with a disease that affects hormone levels.