Urinary markers of hydration during 3-day water restriction and graded rehydration.

PURPOSE: This investigation had three purposes: (a) to evaluate changes in hydration biomarkers in response to a graded rehydration intervention (GRHI) following 3 days of water restriction (WR), (b) assess within-day variation in urine concentrations, and (c) quantify the volume of fluid needed to return to euhydration as demonstrated by change in Ucol. METHODS: 115 adult males and females were observed during 1 week of habitual fluid intake, 3 days of fluid restriction (1000 mL day-1), and a fourth day in which the sample was randomized into five different GRHI groups: no additional water, CON; additional 500 mL, G+0.50; additional 1000 mL, G+1.00; additional 1500 mL, G+1.50; additional 2250 mL, G+2.25. All urine was collected on 1 day of the baseline week, during the final 2 days of the WR, and during the day of GRHI, and evaluated for urine osmolality, color, and specific gravity. RESULTS: Following the GRHI, only G+1.50 and G+2.25 resulted in all urinary values being significantly different from CON. The mean volume of water increase was significantly greater for those whose Ucol changed from > 4 to < 4 (+ 1435 ± 812 mL) than those whose Ucol remained ≥ 4 (+ 667 ± 722 mL, p < 0.001). CONCLUSIONS: An additional 500 mL of water is not sufficient, while approximately 1500 mL of additional water (for a total intake between 2990 and 3515 mL day-1) is required to return to a urine color associated with adequate water intake, following 3 days of WR.

Thyroid Function and Nutrient Status in the Athlete.

Thyroid disease is common in the general population, especially in women, and also may be prevalent among athletes. Autoimmune disorders are the most common cause of thyroid disorders in countries with iodine-fortification programs; however, thyroid dysfunction can be brought on by nutritional factors, including insufficient energy intake and iodine, selenium, iron, and vitamin D deficiency. Additionally, strenuous exercise may be associated with transient alterations in thyroid hormones. While the development of thyroid related disorders has the potential to impact health and peak performance, typical clinical manifestations are highly variable, lack specificity, and are frequently confused with other health problems. The assessment process should focus on anthropometric changes, biochemical tests (thyroid panel), personal and family history, examination for appropriate signs and symptoms, and diet and environmental assessment that includes adequacy of energy, iodine, iron, selenium, and vitamin D intake/status along with excess stress and exposure to environmental contaminants and dietary goitrogens.

Dietary Practices Adopted by Track-and-Field Athletes: Gluten-Free, Low FODMAP, Vegetarian, and Fasting.

Some track-and-field athletes implement special diets aiming to improve health and/or performance. An evidence-based approach to any diet is recommended to minimize the risks associated with unnecessary dietary restriction, which may potentially do more harm than good. Four prevalent diets are reviewed in this study: (a) gluten-free; (b) low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP); (c) vegetarian; and (d) fasting diets. Recently, gluten-free diets and low FODMAP diets have emerged as novel regimes thought to improve gastrointestinal health and reduce the risk of exercise-associated gastrointestinal symptoms. No direct beneficial outcomes have been associated with avoiding gluten for clinically healthy athletes. Indirectly, a gluten-free diet is associated with other dietary changes, particularly FODMAP reduction, which may improve adverse gastrointestinal symptoms. Vegetarian diets can optimally support athletic demands. However, attention is required to ensure adequate energy and intake of specific nutrients that are less abundant or less well absorbed from plant sources. Finally, fasting is a long-standing concept that is undertaken on a voluntary and obligatory basis. Despite limited supporting research, voluntary fasting is a popular alternative to conventional diets perceptually offering health and body composition benefits. Strict obligatory fasting guidelines likely require the implementation of tailored nutrition strategies to help athletes cope with athletic demands. Overall, a multitude of factors influence adherence to special diets. Even when adherence to a special diet is a necessity, education and advice from an accredited dietitian/nutritionist are recommended for track-and-field athletes to optimize nutrition for health and performance.

IOC consensus statement: dietary supplements and the high-performance athlete.

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete's health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.

Dietary Supplements for Health, Adaptation, and Recovery in Athletes.

Some dietary supplements are recommended to athletes based on data that supports improved exercise performance. Other dietary supplements are not ergogenic per se, but may improve health, adaptation to exercise, or recovery from injury, and so could help athletes to train and/or compete more effectively. In this review, we describe several dietary supplements that may improve health, exercise adaptation, or recovery. Creatine monohydrate may improve recovery from and adaptation to intense training, recovery from periods of injury with extreme inactivity, cognitive processing, and reduce severity of or enhance recovery from mild traumatic brain injury (mTBI). Omega 3-fatty acid supplementation may also reduce severity of or enhance recovery from mTBI. Replenishment of vitamin D insufficiency or deficiency will likely improve some aspects of immune, bone, and muscle health. Probiotic supplementation can reduce the incidence, duration, and severity of upper respiratory tract infection, which may indirectly improve training or competitive performance. Preliminary data show that gelatin and/or collagen may improve connective tissue health. Some anti-inflammatory supplements, such as curcumin or tart cherry juice, may reduce inflammation and possibly delayed onset muscle soreness (DOMS). Beta-hydroxy beta-methylbutyrate (HMB) does not consistently increase strength and/or lean mass or reduce markers of muscle damage, but more research on recovery from injury that includes periods of extreme inactivity is needed. Several dietary supplements, including creatine monohydrate, omega 3-fatty acids, vitamin D, probiotics, gelatin, and curcumin/tart cherry juice could help athletes train and/or compete more effectively.

Assessment of Nutrient Status in Athletes and the Need for Supplementation.

Nutrition assessment is a necessary first step in advising athletes on dietary strategies that include dietary supplementation, and in evaluating the effectiveness of supplementation regimens. Although dietary assessment is the cornerstone component of the nutrition assessment process, it should be performed within the context of a complete assessment that includes collection/evaluation of anthropometric, biochemical, clinical, and environmental data. Collection of dietary intake data can be challenging, with the potential for significant error of validity and reliability, which include inherent errors of the collection methodology, coding of data by dietitians, estimation of nutrient composition using nutrient food tables and/or dietary software programs, and expression of data relative to reference standards including eating guidance systems, macronutrient guidelines for athletes, and recommended dietary allowances. Limitations in methodologies used to complete anthropometric assessment and biochemical analysis also exist, as reference norms for the athlete are not well established and practical and reliable biomarkers are not available for all nutrients. A clinical assessment collected from history information and the nutrition-focused physical exam may help identify overt nutrient deficiencies but may be unremarkable in the well-trained athlete. Assessment of potential food-drug interactions and environmental components further helps make appropriate dietary and supplement recommendations. Overall, the assessment process can help the athlete understand that supplement intake cannot make up for poor food choices and an inadequate diet, while a healthy diet helps ensure maximal benefit from supplementation. Establishment of reference norms specifically for well-trained athletes for the nutrition assessment process is a future research priority.

IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete.

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete's health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.

Consensus Statement Immunonutrition and Exercise.

In this consensus statement on immunonutrition and exercise, a panel of knowledgeable contributors from across the globe provides a consensus of updated science, including the background, the aspects for which a consensus actually exists, the controversies and, when possible, suggested directions for future research.

Relation between vitamin D status and body composition in collegiate athletes.

Excess body fat or obesity is known to increase risk of poor vitamin D status in nonathletes but it is not known if this is the case in athletes. Furthermore, the reason for this association is not understood, but is thought to be due to either sequestration of the fat-soluble vitamin within adipose tissue or the effect of volume dilution related to obese individuals' larger body size. Forty two US college athletes (24 men 18 women, 20.7 ± 1.6 years, 85.0 ± 28.7 kg, BMI = 25.7 ± 6.1 kg/m2) provided blood samples during the fall and underwent measurement of body composition via dual energy X-ray absorptiometry. Serum samples were evaluated for 25-hydroxyvitamin D (25(OH)D) concentration to assess vitamin D status using Diasorin 25(OH)D radioiodine assay. Serum 25(OH)D concentration was negatively associated with height (r = -0.45), total body mass (r = -0.57), BMI (r = -0.57), body fat percentage (r = -0.45), fat mass (r = -0.60) and fat-free mass (r = -0.51) (p < .05). These associations did not change after controlling for sex. In a linear regression mixed model, fat mass (coefficient -0.47, p = .01), but not fat-free mass (coefficient -0.18, p = .32) significantly predicted vitamin D status and explained approximately 36% of the variation in serum 25(OH)D concentration. These results suggest that athletes with a large body size and/or excess adiposity may be at higher risk for vitamin D insufficiency and deficiency. In addition, the significant association between serum 25(OH)D concentration and fat mass in the mixed model, which remained after controlling for sex, is in support of vitamin D sequestration rather than volume dilution as an explanation for such association.

A Randomized Trial of Healthy Weight Gain in Athletic Individuals.

PURPOSE: The purpose of this study is to evaluate the outcomes of a 10-wk diet and exercise regimen designed to promote healthy weight gain with excess energy from peanut-containing or high-carbohydrate foods. METHODS: Nineteen male and 13 female athletes were randomly assigned to receive an additional 500 kcal·d -1 above typical intake through provision of either peanut-based whole foods/snacks (PNT group) or a similar, high-carbohydrate, peanut-free snack (CHO group) along with supervised, whole-body RT (3 d·wk -1 for 60-120 min). Body composition was assessed by dual-energyx-ray absorptiometry at baseline and postintervention. RESULTS: Total body mass (TBM) increased 2.2 ± 1.3 kg with 1.5 ± 1.1 kg as LBM after week 10. The PNT group ( n = 16; 27 ± 7 yr; 10 men, 6 women) gained less TBM than the CHO group ( n = 16; 23 ± 3 yr; 9 men, 7 women) (1.6 ± 1.1 kg vs 2.7 ± 1.2 kg, respectively, P = 0.007) with no differences in LBM (1.2 ± 1.1 kg vs 1.9 ± 1.0 kg, P = 0.136). CONCLUSIONS: These results suggest that the addition of 500 kcal·d -1 from whole foods/snacks in combination with a rigorous RT program promotes a similar weight gain of ~0.22 kg·wk -1 , primarily as LBM, over 10 wk in both male and female athletes. However, snack macronutrient content may impact the effectiveness of this regimen.

Vitamin D Knowledge, Awareness, and Attitudes of Adolescents and Adults: A Systematic Review.

INTRODUCTION: The aims of this systematic review were 2-fold: (1) evaluate the effect of vitamin D educational interventions on serum 25-hydroxyvitamin D (25-OHD) concentration in adolescents (aged 10-19 years) and adults, and (2) assess the association between serum 25-OHD concentration and vitamin D knowledge, awareness of vitamin D deficiency risk, and attitudes toward behaviors associated with acquiring vitamin D. METHODS: Medline, CINAHL, Embase, and SPORTDiscus were systematically searched for studies reporting associations between serum 25-OHD concentration and vitamin D knowledge, awareness, and attitudes. Results were summarized narratively. Effect sizes were calculated when data were available. RESULTS: Eight studies reported experimental effects (2 randomized controlled trials, 1 cluster randomized trial, 4 quasi-experiments, 1 clinical audit), and 14 reported cross-sectional associations. Seven of 8 interventions reported no effect of educational interventions on serum 25-OHD concentration. A slight majority (53%; κ = 19) of studies reported statistically significant associations between serum 25-OHD concentration and vitamin D knowledge and attitudes. IMPLICATIONS FOR RESEARCH AND PRACTICE: The few educational interventions employed to increase serum 25-OHD concentration lack effectiveness. Future studies may use randomized controlled trial designs, enroll those at risk for vitamin D insufficiency and underrepresented in the literature, increase the salience of the information to the target population, and include safe sun exposure recommendations.

RMR Ratio as a Surrogate Marker for Low Energy Availability.

PURPOSE OF REVIEW: Low energy availability (EA) poses severe consequences to athlete performance and overall health. Suppressed resting metabolic rate (RMR) has been observed during periods of low EA. Thus, it has been suggested that the ratio of RMR measured via indirect calorimetry to predictive RMR using a standard predictive equation (RMR ratio) may be a useful assessment of EA in athletes. This review evaluated the use of RMR ratio as a surrogate marker for low EA in athletes and compared methodologies for measuring RMR ratio. RECENT FINDINGS: Decreased RMR ratio in recent studies often correlates with signs of low EA; however, athletes with less severe cases of energy deficiency may not present with a low RMR ratio. Additionally, the methodology for RMR ratio measurements lacks standardization and varies in recent studies. Use of RMR ratio has promise as a complementary EA measurement when used in combination with other assessment tools.

Weight Gain Recommendations for Athletes and Military Personnel: a Critical Review of the Evidence.

PURPOSE OF REVIEW: Sports nutrition guidelines typically state that athletes desiring weight gain follow a regimen that includes increasing energy intake by ~ 300-500 kcal/day with an emphasis on adequate protein and carbohydrate and judicious inclusion of energy-dense foods, in combination with rigorous resistance training. This regimen is thought to promote weekly gains of ~ 0.45 kg (1 lb), mostly as lean body mass (LBM). This review summarizes the evidence supporting these intentional weight gain regimens in athletes. RECENT FINDINGS: Although some research has been conducted in the past 5 years, research on intentional weight gain is lacking. Currently, available data suggests that weekly weight gain of 0.45 kg (1 lb), primarily as LBM, may be difficult for some athletes to achieve. Available evidence, however, suggests that commonly recommended strategies to promote calorie surplus, including consuming larger portions, incorporating energy-dense foods, and prioritizing liquid over solid foods, may prove helpful.

Changes in Bone Mineral Density and Serum Lipids across the First Postpartum Year: Effect of Aerobic Fitness and Physical Activity.

This study evaluated the changes in bone mineral density (BMD) and serum lipids across the first postpartum year in lactating women compared to never-pregnant controls, and the influence of physical activity (PA). The study also explored whether N-telopeptides, pyridinoline, and deoxypyridinoline in urine serve as biomarkers of bone resorption. A cohort of 18 initially lactating postpartum women and 16 never pregnant controls were studied. BMD (dual energy X-ray absorptiometry), serum lipid profiles, and PA (Baecke PA Questionnaire) were assessed at baseline (4-6 weeks postpartum), 6 months, and 12 months. Postpartum women lost 5.2 ± 1.4 kg body weight and BMD decreased by 1.4% and 3.1% in the total body and dual-femur, respectively. Furthermore, BMDdid not show signs of rebound. Lipid profiles improved, with increases in high-density lipoprotein-cholesterol (HDL-C) and decreases in low-density lipoprotein cholesterol (LDL-C) and the cholesterol/HDL-C ratio at 12 months (vs. baseline). These changes were not influenced by lactation, but the fall the Cholesterol/HDL-C ratio was influenced by leisure-time (p = 0.051, time X group) and sport (p = 0.028, time effect) PA. The decrease in BMD from baseline to 12 months in total body and dual femur, however, was greater in those who continued to breastfeed for a full year compared to those who stopped at close to 6 months. Urinary markers of bone resorption, measured in a subset of participants, reflect BMD loss, particularly in the dual-femur, and may reflect changes bone resorption before observed changes in BMD. Results provide support that habitual postpartum PA may favorably influence changes in serum lipids but not necessarily BMD. The benefit of exercise and use of urinary biomarkers of bone deserves further exploration.

An Association between Bioavailable 25-Hydroxyvitamin D and Bone Mineral Density in a Diverse Cohort of Collegiate Athletes.

INTRODUCTION: Although vitamin D is intimately involved in bone metabolism, the relationship between vitamin D status, as measured by serum total 25-hydroxyvitamin D [25(OH)D] concentration, and bone mineral density (BMD) is weak, particularly in non-White populations. Measurement of bioavailable 25(OH)D has been suggested as a better indicator of vitamin D status than total 25(OH)D concentration. To date, the bioavailable 25(OH)D biomarker has been explored minimally in athletic populations. The purpose of this study was to investigate the relationship between total and bioavailable 25(OH)D concentrations and BMD in collegiate athletes. METHODS: NCAA Division I basketball and swimming athletes served as study participants (n = 53; 28 females, 25 males; 28 basketball players, 25 swimmers). All participants completed dual-energy x-ray absorptiometry scans for analysis of BMD, blood draws for vitamin D measures, and diet/lifestyle questionnaires. RESULTS: Overall, total 25(OH)D was 80.0 + 13.9 nmol·L-1 and bioavailable 25(OH)D was 6.0 ± 1.9 nmol·L-1. There was strong disagreement between total 25(OH)D and bioavailable 25(OH)D concentrations (κ = -0.299, r = -0.129) (P = 0.100); 53% of total participants and 77% of Black participants were classified differently (low vs normal vitamin D status) based on total and bioavailable 25(OH)D criteria. Black participants had significantly lower total 25(OH)D and higher bioavailable 25(OH)D concentrations than White participants (59.5 vs 102.5 nmol·L-1 and 7.9 vs 5.4 nmol·L-1, respectively) (P < 0.001). Total 25(OH)D and total BMD were not correlated, but bioavailable 25(OH)D and total BMD demonstrated a positive correlation (r = 0.618, P < 0.01). CONCLUSIONS: These results suggest that bioavailable 25(OH)D concentration may be a better clinical measure of vitamin D status than total 25(OH)D as related to BMD in collegiate athletes, particularly in Black athletes. Further research on the utility of the bioavailable 25(OH)D biomarker in athletes is needed.

Exercise economy in African American and European American women.

We have previously shown that Achilles tendon length is related to walking economy on the flat, presumably because of increased stretch-shortening cycle elastic energy savings. In addition, greater walking economy in African American (AA) women compared to European American (EA) women is explained by longer Achilles tendons in AA women. The purposes of this study were to determine whether economy while walking up a grade and during isometric plantar flexion, two tasks expected to produce proportionately less energy savings from elastic savings are different between AA and EA women. We evaluated walking economy at 4.8 km/h at 0 and 2.5% grade in 48 AA and 48 EA premenopausal women. Plantar flexor muscle metabolic economy (force/ATP) was also evaluated using (31) phosphate magnetic resonance spectroscopy ((31)P-MRS). AA women walked on the flat more economically (net VO(2), AA 8.3 and EA 8.9 ml kg(-1) min(-1), P = 0.04). No significant ethnic differences were observed while walking up a 2.5% grade or in (31)P-MRS determined plantar flexor muscle metabolic economy. These data support our previous study's suggestion that AA women are more economical while walking on the flat. On the other hand, in activities in which stretch-shortening cycle elastic energy savings would be expected to be reduced (grade walking and isometric force production), no differences in economy during grade walking or isometric force production were observed suggesting that biomechanical, i.e. stretch-shortening cycle elastic energy savings differences rather biochemical differences contribute to the better flat walking economy observed in AA women.

Age, muscle fatigue, and walking endurance in pre-menopausal women.

Aging is associated with loss of endurance; however, aging is also associated with decreased fatigue during maximal isometric contractions. The aims of this study were to examine the relationship between age and walking endurance (WE) and maximal isometric fatigue (MIF) and to determine which metabolic/fitness components explain the expected age effects on WE and MIF. Subjects were 96 pre-menopausal women. Oxygen uptake (walking economy) was assessed during a 3-mph walk; aerobic capacity and WE by progressive treadmill test; knee extension strength by isometric contractions, MIF during a 90-s isometric plantar flexion (muscle metabolism measured by (31)P MRS). Age was related to increased walking economy (low VO(2), r = -0.19, P < 0.03) and muscle metabolic economy (force/ATP, 0.34, P = 0.01), and reduced MIF (-0.26, P < 0.03). However, age was associated with reduced WE (-0.28, P < 0.01). Multiple regression showed that muscle metabolic economy explained the age-related decrease in MIF (partial r for MIF and age -0.13, P = 0.35) whereas walking economy did not explain the age-related decrease in WE (partial r for WE and age -0.25, P < 0.02). Inclusion of VO(2max) and knee endurance strength accounted for the age-related decreased WE (partial r for WE and age = 0.03, P > 0.80). In premenopausal women, age is related to WE and MIF. In addition, these results support the hypothesis that age-related increases in metabolic economy may decrease MIF. However, decreased muscle strength and oxidative capacity are related to WE.

Reflection of Dietary Iodine in the 24 h Urinary Iodine Concentration, Serum Iodine and Thyroglobulin as Biomarkers of Iodine Status: A Pilot Study.

BACKGROUND: The iodine status of the US population is considered adequate, but subpopulations remain at risk for iodine deficiency and a biomarker of individual iodine status has yet to be determined. The purpose of this study was to determine whether a 3 day titration diet, providing known quantities of iodized salt, is reflected in 24 h urinary iodine concentration (UIC), serum iodine, and thyroglobulin (Tg). METHODS: A total of 10 participants (31.3 ± 4.0 years, 76.1 ± 6.3 kg) completed three, 3 day iodine titration diets (minimal iodine, US RDA, (United States Recommended Daily Allowance), and 3× RDA). The 24 h UIC, serum iodine, and Tg were measured following each diet. The 24 h UIC and an iodine-specific food frequency questionnaire (FFQ) were completed at baseline. RESULTS: UIC increased an average of 19.3 µg/L for every gram of iodized salt consumed and was different from minimal to RDA (p = 0.001) and RDA to 3× RDA diets (p = 0.04). Serum iodine was different from RDA to 3× RDA (p = 0.006) whereas Tg was not responsive to diet. Baseline UIC was associated with iodine intake from milk (r = 0.688, p = 0.028) and fish/seafood (r = 0.646, p = 0.043). CONCLUSION: These results suggest that 24 h UIC and serum iodine may be reflective of individual iodine status and may serve as biomarkers of iodine status.

Appetite-Regulating Hormones in Human Milk: A Plausible Biological Factor for Obesity Risk Reduction?

BACKGROUND: Human milk contains appetite-regulating hormones that may influence infant growth and obesity risk. RESEARCH AIMS: We evaluated whether leptin, peptide tyrosine-tyrosine (PYY), glucagon-like peptide-1 (GLP-1), and ghrelin concentrations in human milk (1) changed during feeding (from foremilk to hindmilk) and during the first 6 months of infancy; (2) were explained by maternal factors; and (3) were associated with infant anthropometrics and growth. METHODS: Mother-infant dyads (N = 22) participated. Samples of foremilk and hindmilk at 1 month postpartum were collected and analyzed for leptin, PYY, GLP-1, and ghrelin via radioimmunoassay and milkfat percentage estimated via creamatocrit. Samples were also collected in mothers (n = 15) who breastfed through 6 months. Anthropometrics were obtained on all mother-infant dyads at 1 month and all infants at 6 months and 12 months. RESULTS: At 1 month, milk GLP-1 and milkfat concentration increased from foremilk to hindmilk (p ≤ .05) while leptin and PYY concentrations remained stable during feeding. Milk hormone concentrations and milkfat tended to decline overtime, with lower leptin, PYY, and ghrelin at 6 months versus 1 month (p < .05). At 1 month, milk leptin and milkfat content were associated with maternal markers of adiposity (r = 0.49-0.78, p < .001); whereas, milk PYY was correlated with maternal serum PYY concentration (r = 0.672, p = .001). Average 1-month milk concentrations of GLP-1 and leptin were negatively associated with weight-for-age z-scores at 6 months (r = -0.46, p < .05) and 12 months (r = -0.49, p < .05), respectively. CONCLUSION: The content of certain appetite-regulating hormones in human milk may be influenced by maternal factors and play a role in infant growth; much needs to be learned about their role in the obesity protection of breastfed infants.