Defining "low-carb" in the scientific literature: A scoping review of clinical studies.

There remains a lack of scientific consensus on what level of carbohydrate intake constitutes low-carbohydrate diets. We conducted a scoping review to understand how low-carbohydrate diets were defined in the peer-reviewed literature. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement scoping review extension. Three electronic databases were searched for clinical studies in English. We identified 508 articles (317 randomized controlled, 99 cross-over, 33 before-and-after, 12 non-randomized, and 47 other clinical trials). Most examined effects of low-carbohydrate diets in healthy adults (62.4%), 40 to 59 years old (55.5%), with obesity or overweight (66.1%). The majority reported effects on weight or body composition (29.9%), diabetes (18.7%), or cardiovascular risk factors (12.9%) as primary outcomes. Most articles (56.9%) reported percent of energy from carbohydrates, and of those, 60.3% defined low-carbohydrate diets as being ≤30% of energy from carbohydrates. Some articles (22.9%) reported grams of carbohydrates per day, and of those, most defined low-carbohydrate diets as being under ∼100 grams of carbohydrates per day. Systematic reviews and dose-response meta-regressions utilizing patient-level data on carbohydrate intake, status markers (e.g., RQ/ketones), and health outcomes would be useful in informing consensus around a standardized definition.

Systematic Review and Meta-Analysis to Estimate a Reference Range for Circulating Ionized Magnesium Concentrations in Adult Populations.

BACKGROUND: There is a lack of consensus on a reference range for ionized magnesium (iMg2+) in blood as a measure of the status of circulating iMg2+ for the screening of populations. OBJECTIVES: We estimated the reference range of iMg2+ levels for healthy adult populations and the ranges for populations with cardiovascular disease (CVD), type 2 diabetes, hypertension, and renal disease. We also estimated 95% ranges for circulating magnesium (Mg) in healthy and those with cardiometabolic diseases. METHODS: We searched Ovid MEDLINE, Cochrane Central Register of Controlled Trials, and Embase through 24 July, 2020 to identify articles. We included English, peer-reviewed, randomized controlled trials, prospective and retrospective cohort studies, case-control studies, and cross-sectional studies that measured iMg2+ in blood or circulating Mg at baseline. The protocol was registered on PROSPERO (CRD42020216100). Estimated ranges were calculated by employing a frequentist random-effects model using extracted (or calculated) means and SDs from each included study. We determined the 95% confidence interval of the pooled mean. RESULTS: A total of 95 articles were included with 53 studies having data for healthy participants and 42 studies having data for participants with cardiometabolic diseases. The estimated reference range for iMg2+ for healthy populations was 0.40-0.68 mmol/L, 0.38-0.64 mmol/L for CVD, 0.34-0.66 mmol/L for type 2 diabetes, 0.39-1.04 mmol/L for hypertension, and 0.40-0.76 mmol/L for renal disease. For circulating Mg, the estimated range was 0.72-1.0 mmol/L for healthy adults, 0.56-1.05 mmol/L for CVD, 0.58-1.14 mmol/L for type 2 diabetes, 0.60-1.08 mmol/L for hypertension, and 0.59-1.26 mmol/L for renal disease. CONCLUSIONS: Estimated reference ranges for cardiometabolic disease states for both iMg2+ and circulating Mg were broad and overlapped with the estimated range for healthy populations (0.40-0.68 mmol/L). Further studies should evaluate whether iMg2+ can be used as a biomarker of cardiometabolic disease.

Vitamin D and Calcium in Children 0-36 Months: A Scoping Review of Health Outcomes.

METHODS: Updated literature searches were conducted across 5 electronic databases to identify all randomized controlled trials, cohort studies, nested case-control or case-cohort studies, and systematic reviews published after the 2009 U.S. Agency for Healthcare Research and Quality's (AHRQ) evidence report, Vitamin D and Calcium: a Systematic Review of Health Outcomes. In total, 65 studies were summarized and analyzed in the present review. RESULTS: There was a steady increasing trend in the number of publications reporting outcomes related to skeletal health, growth, and infectious disease from 2008 to 2019, although the number of published vitamin D studies was much larger than calcium studies. CONCLUSIONS: The data presented in this review can facilitate assessment of the variety of outcomes and the amount of potentially useful literature available for each outcome. The results of this scoping review can be used to guide the undertaking of the subsequent systematic reviews.

Short-Term Tea Consumption Is Not Associated with a Reduction in Blood Lipids or Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

BACKGROUND: A recent systematic review of epidemiological evidence suggests that higher amounts of tea intake are associated with lower risks of cardiovascular disease (CVD) incidence and mortality. OBJECTIVES: Our study objective was to assess mechanisms by which tea consumption may influence CVD risks. METHODS: A systematic review and meta-analysis was conducted to investigate the effects of green and/or black tea consumption (≥4 wk) on systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride (TG) in healthy populations and among at-risk adults (analyzed separately) with metabolic syndrome, prediabetes, and hypercholesterolemia. The Grading of Recommendations Assessment, Development and Evaluation approach was used to rate the strength of evidence (SoE). RESULTS: A total of 14 unique RCTs which randomly assigned 798 participants to either green tea, black tea, or placebo controls were included in our analyses. Intervention durations ranged from 4 to 24 wk (mean: 7.4 wk). Individual studies were judged as moderate to high quality based on risk of bias assessments. SoE was low to moderate owing to low sample sizes and insufficient power for most included studies to observe changes in the measured CVD biomarkers. Meta-analyses showed no significant effects of tea consumption on SBP, DBP, total cholesterol, LDL cholesterol, HDL cholesterol, and TG in healthy and at-risk adults (i.e., adults with obesity, prediabetes, borderline hypercholesterolemia, and metabolic syndrome). CONCLUSIONS: Short-term (4-24 wk) tea consumption does not appear to significantly affect blood pressure or lipids in healthy or at-risk adults, although the evidence is limited by insufficient power to detect changes in these CVD biomarkers. High-quality RCTs with longer durations and sufficient sample sizes are needed to fully elucidate the effects of tea. This systematic review was registered at www.crd.york.ac.uk/prospero/ as CRD42020134513.

Associations between Intake of Dietary Sugars and Diet Quality: A Systematic Review of Recent Literature.

Understanding the relationship between the intake of sugars and diet quality can inform public health recommendations. This systematic review synthesized recent literature on associations between sugar intake and diet quality in generally healthy populations aged 2 years or older. We searched databases from 2010 to 2022 for studies of any design examining associations between quantified sugar intake in the daily diet and dietary indexes (DIs) or micronutrient intakes. Different sugar types and diet quality measures were analyzed separately. We converted DI results to Pearson's r correlations and grouped indexes with or without a free or added sugar component to facilitate cross-study comparisons. Meta-analysis was deemed inappropriate. From 13,869 screened records, we included 27 cross-sectional studies. NUQUEST risk of bias ratings were neutral (n = 18 studies) or poor (n = 9), and strength of evidence by the GRADE approach was very low due to study design. Most studies reported negative associations for added and free sugars with diet quality indexes (r ranging from -0.13 to -0.42) and nutrients of public health concern (fiber, vitamin D, calcium, potassium), while associations with total sugars were mixed. Due to cross-sectional study designs, the clinical relevance of these findings is unclear. Prospective studies are needed to minimize confounding and inform causal relationships.

The Relationship of Circulating Choline and Choline-Related Metabolite Levels with Health Outcomes: A Scoping Review of Genome-Wide Association Studies and Mendelian Randomization Studies.

Choline is essential for proper liver, muscle, brain, lipid metabolism, cellular membrane composition, and repair. Understanding genetic determinants of circulating choline metabolites can help identify new determinants of choline metabolism, requirements, and their link to disease endpoints. We conducted a scoping review to identify studies assessing the association of genetic polymorphisms on circulating choline and choline-related metabolite concentrations and subsequent associations with health outcomes. This study follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement scoping review extension. Literature was searched to September 28, 2022, in 4 databases: Embase, MEDLINE, Web of Science, and the Biological Science Index. Studies of any duration in humans were considered. Any genome-wide association study (GWAS) investigating genetic variant associations with circulating choline and/or choline-related metabolites and any Mendelian randomization (MR) study investigating the association of genetically predicted circulating choline and/or choline-related metabolites with any health outcome were considered. Qualitative evidence is presented in summary tables. From 1248 total reviewed articles, 53 were included (GWAS = 27; MR = 26). Forty-two circulating choline-related metabolites were tested in association with genetic variants in GWAS studies, primarily trimethylamine N-oxide, betaine, sphingomyelins, lysophosphatidylcholines, and phosphatidylcholines. MR studies investigated associations between 52 total unique choline metabolites and 66 unique health outcomes. Of these, 47 significant associations were reported between 16 metabolites (primarily choline, lysophosphatidylcholines, phosphatidylcholines, betaine, and sphingomyelins) and 27 health outcomes including cancer, cardiovascular, metabolic, bone, and brain-related outcomes. Some articles reported significant associations between multiple choline types and the same health outcome. Genetically predicted circulating choline and choline-related metabolite concentrations are associated with a wide variety of health outcomes. Further research is needed to assess how genetic variability influences choline metabolism and whether individuals with lower genetically predicted circulating choline and choline-related metabolite concentrations would benefit from a dietary intervention or supplementation.

Piloting a brief assessment to capture consumption of whole plant food and water: version 1.0 of the American College of Lifestyle Medicine Diet Screener (ACLM Diet Screener).

Background: Despite the availability of various dietary assessment tools, there is a need for a tool aligned with the needs of lifestyle medicine (LM) physicians. Such a tool would be brief, aimed at use in a clinical setting, and focused on a "food as medicine" approach consistent with recommendations for a diet based predominately on whole plant foods. The objective of this study is to describe the development and initial pilot testing of a brief, dietary screener to assess the proportion of whole, unrefined plant foods and water relative to total food and beverage intake. Methods: A multidisciplinary study team led the screener development, providing input on the design and food/beverage items included, and existing published dietary assessment tools were reviewed for relevance. Feedback was solicited from LM practitioners in the form of a cross-sectional survey that captured information on medical practice, barriers, and needs in assessing patients' diets, in addition to an opportunity to complete the screener and provide feedback on its utility. The study team assessed feedback and revised the screener accordingly, which included seeking and incorporating feedback on additional food items to be included from subject matter experts in specific cultural and ethnic groups in the United States. The final screener was submitted for professional design, and scoring was developed. Results: Of 539 total participants, the majority reported assessing diet either informally (62%) or formally (26%) during patient encounters, and 73% reported discussing diet with all or most of their patients. Participants also reported facing barriers (80%) to assessing diet. Eighty-eight percent believed the screener was quick enough to use in a clinical setting, and 68% reported they would use it. Conclusion: The ACLM Diet Screener was developed through iterative review and pilot testing. The screener is a brief, 27-item diet assessment tool that can be successfully used in clinical settings to track patient dietary intakes, guide clinical conversations, and support nutrition prescriptions. Pilot testing of the screener found strong alignment with clinician needs for assessing a patient's intake of whole plant food and water relative to the overall diet. Future research will involve pilot testing the screener in clinical interventions and conducting a validation study to establish construct validity.

AI-based digital image dietary assessment methods compared to humans and ground truth: a systematic review.

OBJECTIVE: Human error estimating food intake is a major source of bias in nutrition research. Artificial intelligence (AI) methods may reduce bias, but the overall accuracy of AI estimates is unknown. This study was a systematic review of peer-reviewed journal articles comparing fully automated AI-based (e.g. deep learning) methods of dietary assessment from digital images to human assessors and ground truth (e.g. doubly labelled water). MATERIALS AND METHODS: Literature was searched through May 2023 in four electronic databases plus reference mining. Eligible articles reported AI estimated volume, energy, or nutrients. Independent investigators screened articles and extracted data. Potential sources of bias were documented in absence of an applicable risk of bias assessment tool. RESULTS: Database and hand searches identified 14,059 unique publications; fifty-two papers (studies) published from 2010 to 2023 were retained. For food detection and classification, 79% of papers used a convolutional neural network. Common ground truth sources were calculation using nutrient tables (51%) and weighed food (27%). Included papers varied widely in food image databases and results reported, so meta-analytic synthesis could not be conducted. Relative errors were extracted or calculated from 69% of papers. Average overall relative errors (AI vs. ground truth) ranged from 0.10% to 38.3% for calories and 0.09% to 33% for volume, suggesting similar performance. Ranges of relative error were lower when images had single/simple foods. CONCLUSIONS: Relative errors for volume and calorie estimations suggest that AI methods align with - and have the potential to exceed - accuracy of human estimations. However, variability in food image databases and results reported prevented meta-analytic synthesis. The field can advance by testing AI architectures on a limited number of large-scale food image and nutrition databases that the field determines to be adequate for training and testing and by reporting accuracy of at least absolute and relative error for volume or calorie estimations.

These results suggest that AI methods are in line with ­ and have the potential to exceed ­ accuracy of human estimations of nutrient content based on digital food images.Variability in food image databases used and results reported prevented meta-analytic synthesis.The field can advance by testing AI architectures on a limited number of large-scale food image and nutrition databases that the field determines to be accurate and by reporting accuracy of at least absolute and relative error for volume or calorie estimations.Overall, the tools currently available need more development before deployment as stand-alone dietary assessment methods in nutrition research or clinical practice.

Commonalities among Dietary Recommendations from 2010 to 2021 Clinical Practice Guidelines: A Meta-Epidemiological Study from the American College of Lifestyle Medicine.

Clinical practice guidelines (CPGs) provide recommendations to clinicians based on current medical knowledge to guide and reduce variability in clinical care. With advances in nutrition science research, CPGs increasingly include dietary guidance; however, the degree of consistency in dietary recommendations across CPGs has not been investigated. Using a systematic review approach adapted for meta-epidemiologic research, this study compared dietary guidance from current guidelines developed by governments, major medical professional societies, and large health stakeholder associations owing to their often well-defined and standardized processes for guideline development. CPGs making recommendations for dietary patterns and food groups or components for generally healthy adults or those with prespecified chronic diseases were eligible. Literature from January 2010 to January 2022 was searched in 5 bibliographic databases and augmented by searches in point-of-care resource databases and relevant websites. Reporting followed an adapted PRISMA statement and included narrative synthesis and summary tables. Seventy-eight CPGs for major chronic conditions (autoimmune, 7; cancers, 5; cardiovascular-related, 35; digestive, 11; diabetes, 12; weight-related, 4; or multiple, 3) and general health promotion (n = 1) were included. Nearly, all (91%) made dietary pattern recommendations, and approximately half (49%) endorsed patterns centered on plant foods. Overall, CPGs were most closely aligned in promoting consumption of major plant food groups (vegetables = 74% of CPGs, fruit = 69%, whole grains = 58%), whereas discouraging intake of alcohol (62%) and salt or sodium (56%). CVD and diabetes CPGs were similarly aligned with additional messaging to consume legumes/pulses (60% of CVD CPGs; 75%, diabetes), nuts and seeds (67%, CVD), and low-fat dairy (60%, CVD). Diabetes guidelines discouraged sweets/added sugars (67%) and sweetened beverages (58%). This alignment across CPGs should boost clinician confidence in relaying such dietary guidance to patients in accordance with their relevant CPGs. This trial was registered at the International Prospective Register of Systematic Reviews (https://www.crd.york.ac.uk/prospero; PROSPERO 2021) as CRD42021226281.

Effects of 100% Orange Juice on Markers of Inflammation and Oxidation in Healthy and At-Risk Adult Populations: A Scoping Review, Systematic Review, and Meta-analysis.

One hundred percent orange juice (OJ) has no added sugar, naturally contains flavonoids and ascorbic acid, and can modulate the body's oxidative and inflammatory systems. This scoping review, systematic review, and meta-analysis investigated associations between 100% OJ and markers of inflammation or oxidation in healthy adults and those at risk for chronic diseases. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and scoping review extension. Literature in English was searched to July 2021 in Embase and 4 Ovid platform databases. Clinical and observational studies of any duration were eligible. Cochrane Collaboration tools were used to assess the risk of bias in controlled trials. Strength of evidence was determined using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. The scoping review presents a qualitative synthesis of evidence in summary and results tables. Twenty-one interventional studies (16 controlled trials and 5 before-after studies) conducted in 307 healthy and 327 at-risk participants were included. Six common markers [C-reactive protein (CRP) or high-sensitivity CRP (hs-CRP), IL-6, TNF-α, malondialdehyde (MDA), oxidized LDL (oxLDL), and antioxidant capacity] measured across 16 studies were systematically reviewed, and results were synthesized narratively. Random-effects model meta-analyses were conducted on 10 studies reporting hs-CRP, IL-6, and/or MDA. After consuming 100% OJ, healthy and at-risk participants showed significantly lower IL-6 concentrations (pooled net difference: -1.51 pg/mL; 95% CI: -2.31, -0.70) and lower, but nonsignificant, hs-CRP (pooled net change: -0.58 mg/L; 95% CI: -1.22, 0.05) and MDA (crossover trials pooled net difference: -0.06 µmol/L; 95% CI: -0.19, 0.08). Findings suggest that 100% OJ may reduce inflammation, but results should be interpreted with caution due to moderate risk of bias, very low strength of evidence, and the low number of subjects. This study was registered on PROSPERO (https://www.crd.york.ac.uk/prospero/) as CRD42021235438.

Calcium Intake and Metabolism in Infants and Young Children: A Systematic Review of Balance Studies for Supporting the Development of Calcium Requirements.

Determining calcium requirements for infants and children is vital due to high calcium needs for growth. Balance studies enable comprehensive measurement of calcium metabolism and can support nutrient requirement development. This systematic review summarizes evidence from mass balance and isotopic studies in children aged 0-4 y to address key questions on calcium loss and absorption/retention identified by an expert group developing calcium requirements. Literature searches were implemented in multiple electronic databases to June 2020. Balance studies assessing calcium intake, loss, absorption, or retention in healthy children were eligible. A newly developed risk-of-bias assessment tool was used for balance studies, and a modified Grades of Recommendation, Assessment, Development, and Evaluation approach determined strength of evidence. Altogether, 23 studies (15 mass balance; 8 isotope) with 485 total participants were included. Only 3 studies were of children >6 mo. Mass balance studies suggested infant feed components may influence calcium balance. The random-effects model meta-regression on 42 mass balance study arms showed an average net calcium retention of 40.4% among infants aged 0-6 mo (ß = 0.404 [95% CI: 0.302, 0.506]). Isotope studies suggested calcium intake of 240 to 400 mg/d may promote optimal calcium absorption with minimal loss, and intake from human milk may lead to greater absorption and retention efficacy than formula or solid foods. Most studies had low risk of bias. Strength of evidence was low due to variability in infant feedings, limited endogenous and dermal calcium loss measures, and few studies isolating calcium effects. To improve certainty of the body of evidence, more balance studies isolating effects of calcium intake in this age group are needed. Future work on calcium needs should incorporate both balance measures and biological endpoints of importance (e.g. bone mineral density or content) to determine adequate calcium intake for growth in infants and children.

Vitamin D intakes and health outcomes in infants and preschool children: Summary of an evidence report.

BACKGROUND: A systematic review was commissioned to support an international expert group charged to update the Food and Agriculture Organisation of the United Nations (FAO)/World Health Organisation (WHO)'s vitamin D intake recommendations for children aged 0-4 years. MATERIALS AND METHODS: Multiple electronic databases were searched to capture studies published from database inception to the 2nd week of June 2020 according to key questions formulated by the FAO/WHO. Relevant studies were summarised and synthesised by key questions and by health outcomes using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. RESULTS: The 146 included studies examined the effects of different vitamin D intake levels on a variety of health outcomes (e.g. infectious disease, growth, neurodevelopment, rickets, and bone mineral density), and on outcomes for setting vitamin D upper limits (e.g. hypercalcemia, hypercalciuria, and nephrocalcinosis). For most outcomes, the strength of evidence was low or very low. Evidence was rated moderate for the effect of daily vitamin D supplementation on raising serum 25(OH)D concentrations, and a random-effects meta-regression analysis of 28 randomised controlled trials (mostly in infants 0-12 months) showed that each 100 IU/d increase in vitamin D supplementation was associated with an average of 1.92 (95% CI 0.28, 3.56) nmol/L increase in achieved 25-hydroxy-vitaminn D (25[OH]D) concentration (n = 53 intervention arms; p = .022) with large residual heterogeneity (I2 = 99.39%). Evidence was very low on two of the upper limit outcomes - hypercalcemia and hypercalciuria. CONCLUSIONS: The evidence report provided the expert group with a foundation and core set of data to begin their work to set vitamin D nutrient reference values. To move the field forward, future studies should use standardised 25(OH)D assay measurements and should examine the relationship between long-term vitamin D status and health outcomes.Key MessagesResults of a large complex systematic review suggest the current totality of evidence from trials and prospective observational studies do not reach sufficient certainty level to support a causal relationship between vitamin D intake and asthma, wheeze, eczema, infectious diseases, or rickets (most trials reported no rickets) in generally healthy infants and young children.In this systematic review, the only body of evidence that reached a moderate level of certainty was regarding the effect of daily vitamin D supplementation (vitamin D3 or D2 supplements to infants/children) on increasing serum 25(OH)D concentrations. However, currently there is no consensus on the definitions of vitamin D status, e.g. deficiency, insufficiency, sufficiency and toxicity, based on serum 25(OH)D concentrations.This systematic review provided an international expert group a foundation and core set of data through intake-response modelling to help set vitamin D nutrient reference values for infants and children up to 4 years of age.

Safety of Using Enteral Nutrition Formulations Containing Dietary Fiber in Hospitalized Critical Care Patients: A Systematic Review and Meta-Analysis.

Enteral nutrition (EN) is the preferred route of nutrition support for patients with critical illness undergoing intensive care. Experts in the field caution against using fiber during EN because of perceived adverse patient outcomes; however, a comprehensive assessment of this topic is not evident to date. In this systematic review and meta-analysis, we searched four databases from inception to April 20, 2020, for studies on adverse events or health outcomes associated with using EN formulations containing fiber in hospitalized adults with critical illness. Nineteen articles were included. Random-effects meta-analysis models showed significantly lower diarrhea scores for fiber groups compared with nonfiber groups (pooled mean difference: -2.78; 95% CI, -4.10 to -1.47) but mixed results for risk of diarrhea between groups, depending on measures used for diarrhea (Hart and Dobb scale, pooled risk ratio [RR]: 0.68; 95% CI, 0.45-1.02; other diarrhea scales, pooled RR: 0.42; 95% CI, 0.20-0.89). Models showed 39% lower risk of gastrointestinal (GI) complications overall for fiber compared with nonfiber groups (pooled RR: 0.61; 95% CI, 0.47-0.79) but no group differences for individual GI complications, mortality, and intensive care unit or hospital length of stay. Analyses stratified by soluble- or mixed-fiber interventions reduced heterogeneity in models but showed identical conclusions. EN formulas with fiber may help reduce incidence and severity of diarrhea and GI complications overall in critically ill patients, without increased risk of other adverse events. Bias among specific GI measures indicates more high-quality studies are needed to verify these conclusions.

Lifestyle Medicine Shared Medical Appointments.

Chronic diseases pose many challenges to health care providers and the health care system from a human capital, logistic, and financial perspective. To overcome these challenges, efficient and effective health care delivery models that address multiple chronic conditions need to be leveraged. Shared medical appointments are one potential solution to address these issues. This article offers a brief history of group visits and shared medical appointments and reviews the available data regarding their outcomes. It describes the benefits of using lifestyle medicine as the primary therapeutic modality within a shared medical appointment to treat, reverse, and prevent chronic disease. Key considerations and action steps for the implementation of lifestyle medicine shared medical appointments (LMSMAs) are outlined and the potential delivery of these services via telehealth is explored.

Effectiveness of multimodal nutrition interventions during pregnancy to achieve 2009 Institute of Medicine gestational weight gain guidelines: a systematic review and meta-analysis.

BACKGROUND: In 2009, the Institute of Medicine (IOM) published a revision to its 1990 recommendations on gestational weight gain (GWG). The objective of this review is to update a previous systematic review and meta-analysis to evaluate the effectiveness of nutrition interventions in achieving recommended GWG. METHODS: We conducted updated literature searches in MEDLINE® (2012 through 2019), Web of Science (2012 to 6 February 2017), Embase (2016 through 2019), and Cochrane Central Register of Controlled Trials (2012 through 2019). Literature published before January 2012 was identified from a published systematic review. We included controlled trials conducted in the U.S. or Canada among generally healthy pregnant women that compared nutrition interventions with or without exercise to controls (e.g., usual care) and reported total GWG or rate of GWG based on the 2009 IOM GWG guidelines. Two independent investigators conducted screening, data extraction, and risk-of-bias (ROB) assessment. Random-effects meta-analyses were conducted when data were sufficient. RESULTS: Eighteen unique studies were included, of which 11 were conducted in women with overweight or obesity. Nutrition interventions, compared to controls, had a similar effect on total GWG (mean difference = -1.24 kg; 95% CI [-2.65, 0.18]; I2=67.6%) but significantly decreased second and third trimester rate of GWG (-0.07 kg/week; 95% CI [-0.12, -0.03]; I2=54.7%). Nutrition interventions also reduced the risk of exceeding IOM's rate of GWG targets (pooled RR = 0.71; 95% CI [0.55, 0.92]; I2=86.3%). Meta-analyses showed no significant differences in achieving IOM's total GWG or any secondary outcome (e.g., preterm birth or small/large for gestational age) between groups. Most studies were assessed as having some or high ROB in at least two domains. CONCLUSION: Multimodal nutrition interventions designed to meet the 2009 IOM's GWG targets may decrease the rate of GWG over the second and third trimesters but may not decrease total GWG.Key messagesExcessive gestational weight gain is associated with higher risk of many adverse maternal and fetal outcomes and represents a public health concern in the United States and Canada.Nutrition interventions designed to meet the 2009 IOM GWG guidelines may decrease the rates of GWG over the second and third trimesters but may not be effective at reducing total GWG.