What is the question?

• The question is: What is the relationship between dietary patterns consumed during lactation and postpartum weight loss?

What is the answer to the question?

• Insufficient evidence is available to determine the relationship between dietary patterns during lactation and postpartum weight loss.

Why was this question asked?

• This important public health question was identified by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to be examined by the 2020 Dietary Guidelines Advisory Committee.

How was this question answered?

• The 2020 Dietary Guidelines Advisory Committee, Pregnancy and Lactation Subcommittee conducted a systematic review to answer this question with support from the Nutrition Evidence Systematic Review (NESR) team.
• Dietary patterns were defined as the quantities, proportions, variety, or combination of different foods, drinks, and nutrients (when available) in diets, and the frequency with which they are habitually consumed. 
• Diets based on macronutrient distribution were examined when at least one macronutrient proportion was outside of the acceptable macronutrient distribution range (AMDR) for carbohydrate, fat, and/or protein, whether or not the foods/food groups consumed were provided.

What is the population of interest? 

• The population of interest is generally healthy, lactating women.

What evidence was found? 

• This systematic review includes one randomized controlled trial (RCT) conducted in the U.S., which compared postpartum weight loss between lactating women who were randomized to a Mediterranean-style diet vs. the USDA MyPyramid diet. 
• There were no significant differences in postpartum weight loss between the two groups. 
• There were notable limitations in this study, including a large number of participants dropping out of the study, issues with how the study was conducted, and participants and researchers being aware of the diet received.

How up-to-date is this systematic review?

• This review searched for studies from January 2000 to November 2019.

Background

• This important public health question was identified by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to be examined by the 2020 Dietary Guidelines Advisory Committee.
• The 2020 Dietary Guidelines Advisory Committee, Pregnancy and Lactation Subcommittee conducted a systematic review to answer this question with support from the Nutrition Evidence Systematic Review (NESR) team.
• The goal of this systematic review was to examine the following question: What is the relationship between dietary patterns consumed during lactation and postpartum weight loss?

Conclusion statement and grade

• Insufficient evidence is available to determine the relationship between dietary patterns during lactation and postpartum weight loss. (Grade: Grade not assignable)

Methods

• A literature search was conducted using four databases (PubMed, Cochrane, Embase, and CINAHL) to identify articles that evaluated the intervention or exposure of dietary patterns during lactation and the outcome of postpartum weight loss, defined as change in weight from baseline (postpartum) to a later time point during the postpartum period. Postpartum weight retention was also considered as an outcome when gestational weight gain was accounted for. A manual search was conducted to identify articles that may not have been included in the electronic databases searched. Articles were screened by two NESR analysts independently for inclusion based on pre-determined criteria. 
• Data extraction and risk of bias assessment were conducted for each included study, and both were checked for accuracy. The Committee qualitatively synthesized the body of evidence to inform development of a conclusion statement(s), and graded the strength of evidence using pre-established criteria for risk of bias, consistency, directness, precision, and generalizability.

Summary of the evidence

• This systematic review includes one randomized controlled trial (RCT) conducted in the U.S., which compared postpartum weight loss (PPWL) between lactating women who were randomized to a Mediterranean-style diet vs. the USDA MyPyramid diet. 
• The two groups showed no significant differences in PPWL.
• This study had notable limitations, including high attrition (approximately 21 percent), issues with implementation of the intervention, and lack of blinding of participants and investigators.