Table 1. Studies examining the association between breast milk leptin concentrations and maternal BMI.
| Author, Year | Maternal n number | Sample Type, Preparation and Analysis, Protease inhibitor used | Time of day, fasted/fed | Timing of Collection (day/week/month) | Maternal BMI (kg/m2) | Breast milk Leptin (ng/mL) | Statistical Analysis | ||
| Houseknecht, 1997 | 14 | Complete breast expression. Skimmed and sonicated whole milk samples prepared. RIA. No protease inhibitor. | 08:00am post-prandial | N/A | Not disclosed | Whole milk 10.1 ± 2.6* | Skimmed Milk 1.5 ± 0.9 | Positive correlation seen with: Whole milk: r = 0.5, p<0.06 Skimmed Milk: r = 0.66, p<0.001 | |
| Ucar, 2000 | 18 | Foremilk and hindmilk. Skimmed. RIA. No protease inhibitor. | Not disclosed | 40 days post-partum | 25.9±0.74, time not reported | 3.36 ± 11.0 | No correlation between breast milk leptin and maternal adiposity. Pearson’s correlation using log transformed values | ||
| Uysal, 2002 | 50 | Foremilk. Analysis of Skimmed milk by RIA, No protease inhibitor. | 08:00-11:00amNot disclosed | 3 months post-partum | BMI at sample collection 25.9±4.4 | Mothers of obese infants 0.27±0.2 | Mothers of lean infants 0.37±0.4 | Leptin concentrations were correlated with maternal BMI; r = 0.62, p<0.001 using Spearman correlation | |
| Bielicki, 2004 | 33 | Foremilk. Sonicated. RIA. No protease inhibitor. | Not disclosed.Fed | 2-3 days post-partum 4-5 days post-partum 6 weeks post-partum | BMI taken at sample collection, 25.1±0.8, not reported, 23.6±0.85 | 2-3D = 1.15±0.12, 4-5D = 0.79±0.10, 6W not reported | Linear regression of log values. Correlation with maternal BMI: 2-3 days: r2 = 0.15, p = 0.02. No correlation found at 6 weeks | ||
| Dundar, 2005 | AGA = 22 LGA = 14 SGA = 11 | Foremilk. Sonicated, RIA, No protease inhibitor. | 10:00-11:00am, not disclosed. | 15 days post-partum 1 month post-partum 2 months post-partum 3 months post-partum | 23.8 ± 0.77, time not reported | AGA 13.4±2.2 17.0±3.4 11.4±2.3 9.1±1.8 | SGA 28.5±4.4 15.5±4.9 15.1±2.7 17.4±3.4 | LGA 18.2±2.0 19.4±1.7 18.3±2.4 11.8±1.8 | No relation between breast milk leptin and BMI. Pearson’s correlation |
| Bronsky, 2006 | 59 | Hindmilk, skimmed. ELISA, EDTA tubes and protease inhibitor | 7:00 am Not disclosed | 48 hours post lactation | Pre-pregnancy 21.4±(0.4), time of delivery 26.8 ± (0.4) | 0.5 ± 0.05 | Correlation with: Pre-pregnancy BMI: r = 0.397, p = 0.003 BMI at delivery: r = 0.498, p<0.0001 | ||
| Miralles, 2006 | 28 | Hindmilk. Whole milk. ELISA No protease inhibitor. | Morning, Not disclosed | 1±3 days post-partum 3 months post-partum 6 months post-partum 9 months ± 1 week | Pre-pregnancy, 21.6±0.5, range 16.3-27.3 | 1 month: 0.156 ± 0.039 | Maternal BMI positively correlated with milk leptin concentration at each time point; r = 0.387, p<0.01. Stronger association found when concentrations were log transformed (r = 0.607). Pearson’s correlation | ||
| Weyermann, 2007 | 651 | Foremilk. Analysis of skimmed milk samples by ELISA No protease inhibitor. | Not disclosed | 33-71 days post-partum | Pre-pregnancy 23.6 ± 4.0 (16.7–45.7) | Median (Range): 0.175 (0-4.12), BMI <20: 0.122±0.129, BMI 20-24.9: 0.234±0.264, BMI 25-29.9: 0.388±0.335, BMI> 30: 0.807±0.885 | Leptin concentrations were strongly associated with pre-pregnancy BMI | ||
| Bronsky, 2011 | 72 | Hindmilk, skimmed. ELISA. EDTA tubes and protease inhibitor. | Not disclosed | 0 day post lactation, 1 month, 3 months, 6 months, 12 months | Pre- pregnancy 21.9±0.4 | 0D = 0.3 ± 0.04, 1M = 0.2 ± 0.03, 3M = 0.1 ± 0.01, 6M = 0.1 ± 0.02, 12M = 0.2 ± 0.04 | No correlation throughout the lactation period between pre-pregnancy BMI and leptin using Spearman’s correlation | ||
| Eilers, 2011 | Term = 40 Preterm = 37 | Type of milk not specified. Skimmed milk. RIA. No protease inhibitor. | 16:00- 20:00 ‘No big meals’ | Day 3 lactation, Day 28 lactation | Pre-pregnancy 23±3.5 | Preterm, 3D = 0.7±0.79, 28D = 0.5±0.4 | Term, 3D = 0.65±0.67, 28D = 0.5±0.4 | Spearman’s correlation with pre-pregnancy BMI: Term: Day 3: r = 0.28, p<0.01; Day 28: 0.45, p<0.0001. Preterm: Day 3: r = 0.40, p = 0.016; Day 28: r = 0.56, p<0.01. Mothers with BMI>25 had higher leptin concentrations compared to those with a BMI <25, p<0.01 | |
| Schuster 2011 | 23 | Sample sonicated and then skimmed. RIA. No protease inhibitor. | Not disclosed | 1 week post-partum, 6 months post-partum | Pre-pregnancy 21.4±2.6, Median (IQR) 20.9 (19.3-22.6) | 1W = 0.21±0.19, 6M = 0.18±0.15 | Leptin concentration correlated with maternal BMI; r = 0.298, p<0.001. Pre-pregnancy BMI did not correlate with leptin concentration, Spearman’s correlation | ||
| Fields, 2012 | 19 | Complete breast expression. Skimmed. Immunoassay. No protease inhibitor. | 8:00-10:00am. Fasted 2h | 40±4 days post-partum | Pre-pregnancy 26.6±6.6 | 0.092 ± 0.05 | Positive Spearman’s correlation between pre-pregnancy BMI and leptin concentration; r = 0.78, p<0.0001 | ||
| Savino, 2012 | 23 | Sample sonicated and then skimmed. RIA. No protease inhibitor. | Not disclosed | 87±40 days post-partum | Median (IQR) 27.4 (4.9), time not reported | Median (IQR): 2.34 (5.73) | No correlation between maternal anthropometric parameters and leptin using Spearman’s correlation | ||
| Schueler, 2013 | 13 | Foremilk and hindmilk. Skimmed. RIA. No protease inhibitor used. | 07:00-10:00am, fasted 10h | 4-5 weeks post-partum | BMI at sample collection 25.9±4.23 Range 20.35-32.9 | 1.0 ± 0.7 Range 0.2-2.6 | Leptin concentrations were positively correlated with maternal BMI, r = 0.82, p = 0.001. Pearson correlation | ||
| Brunner, 2014 | 6 weeks 152, 4 months 120 | Complete breast expression. Sonicated then skimmed. RIA. No protease inhibitor used. | After overnight fast | 6 weeks post-partum 4 months post-partum | Pre- and during pregnancy BMI. Values not reported | Median (IQR) 6W = 0.11 (0.19), 4M = 0.09 (0.18) | A strong positive correlation was observed between milk leptin and maternal pre-pregnancy BMI, 15wk and 32nd wk gestation BMI, r = 0.49, 052 and 0.57 respectively, p = <0.001 for all, at both time points, (6 week correlations shown). Spearman correlation | ||
AGA: Appropriate for gestational age; EDTA: Ethylenediaminetetraacetic acid; ELISA: Enzyme-linked immunosorbent assay; IQR: Interquartile range; LGA: Large for gestational age; N/A: Not available; RIA: Radioimmunoassay; SGA: Small for gestational age.
*Data are given as means and standard deviations unless stated otherwise.