Changes in body composition among female athletes using a levonorgestrel-releasing intrauterine system in preparation for the Paris 2024 Paralympic Games: an exploratory study

Both baseline cardiorespiratory fitness and adiposity predict the risk of cancer mortality. However, the effects of changes in these two factors over time have not been evaluated thoroughly. The aim of this study was to examine the independent and joint associations of changes in cardiorespiratory fitness and body composition on cancer mortality. The cohort consisted of 13,930 men (initially cancer-free) with two or more medical examinations from 1974 to 2002. Cardiorespiratory fitness was assessed by a maximal treadmill exercise test, and body composition was expressed by body mass index (BMI) and percent body fat. Changes in cardiorespiratory fitness and body composition between the baseline and the last examination were classified into loss, stable, and gain groups. There were 386 deaths from cancer during an average of 12.5 yr of follow-up. After adjusting for possible confounders and BMI, change hazard ratios (95% confidence intervals) of cancer mortality were 0.74 (0.57-0.96) for stable fitness and 0.74 (0.56-0.98) for fitness gain. Inverse dose-response relationships were observed between changes in maximal METs and cancer mortality (P for linear trend = 0.05). Neither BMI change nor percent body fat change was associated with cancer mortality after adjusting for possible confounders and maximal METs change. In the joint analyses, men who became less fit had a higher risk of cancer mortality (P for linear trend = 0.03) compared with those who became more fit, regardless of BMI change levels. Being unfit or losing cardiorespiratory fitness over time was found to predict cancer mortality in men. Improving or maintaining adequate levels of cardiorespiratory fitness appears to be important for decreasing cancer mortality in men.

Physical activity interventions alone often do not elicit favorable changes in body composition. However, most studies have reported only mean changes in body composition across treatment groups. PURPOSE: To examine the extent to which individual-level energy expended (EE) during an exercise program is associated with changes in body mass and composition. METHODS: The sample included 666 adult participants (43% men, 32% black) from the HERITAGE Family Study. The training involved a progressive (55-75% VO2max) 20-week cycling program. The power output and duration of each training session was recorded, and the EE (kcal) was calculated for each individual. Body weight, BMI, waist and hip circumference, fat mass (FM), fat free mass (FFM), percent body fat (%BF), CT-derived visceral adipose tissue (VAT) and subcutaneous tissue (SAT) were measured pre- and post-training. Stepwise regression models were used to determine associations between absolute changes (post-pre) in body composition from EE, age, race and baseline values. RESULTS: For the total sample, EE (mean ± SD) was 18,509 ± 6,966 kcal with -0.3 ± 2.5 kg weight loss. On average, men expended more than women (23,664 ± 6,652 vs. 14,607 ± 4,056 kcal; p<0.001) and whites expended more than blacks (20,200 ± 7,126 vs. 14,938 ± 5,008 kcal; p<0.001). For the total sample, changes in FM (p<0.01) and %BF (p<0.01) were negatively associated with EE. In women, EE was positively associated with changes in FFM (p<0.02). For men, EE was negatively associated with changes in weight (p<0.01), BMI (p<0.01), FM (p<0.03), and FFM (p<0.01). Overall, the variance in changes in body composition explained by EE was low (partial r2 = 0.5-2.3%). CONCLUSIONS: The average weight loss in this study was nominal and individual level energy expended was weakly associated with changes in body composition, particularly in men.

Changes in body composition in women using long-acting reversible contraception

Progestin-only contraceptives (POCs) are appropriate for many women who cannot or should not take estrogen. Many POCs are long-acting, cost-effective methods of preventing pregnancy. However, concern about weight gain can deter the initiation of contraceptives and cause early discontinuation among users. The primary objective was to evaluate the association between progestin-only contraceptive use and changes in body weight. Through May 2013, we searched MEDLINE, CENTRAL, POPLINE, LILACS, ClinicalTrials.gov, and ICTRP. The 2010 search also included EMBASE. For the initial review, we contacted investigators to identify other trials. All comparative studies were eligible that examined a POC versus another contraceptive method or no contraceptive. The primary outcome was mean change in body weight or mean change in body composition. We also considered the dichotomous outcome of loss or gain of a specified amount of weight. Two authors extracted the data. We computed the mean difference (MD) with 95% confidence interval (CI) for continuous variables. For dichotomous outcomes, the Mantel-Haenszel odds ratio (OR) with 95% CI was calculated. We found 16 studies; one examined progestin-only pills, one studied the levonorgestrel-releasing intrauterine system (LNG-IUS), four examined an implant, and 10 focused on depot medroxyprogesterone acetate (DMPA). Outcomes examined were changes in body weight only (14 studies), changes in both body weight and body composition (1 study), and changes in body composition only (1 study). We did not conduct meta-analysis due to the various contraceptive methods and weight change measures.Comparison groups did not differ significantly for weight change in 12 studies. However, three studies showed weight change differences for POC users compared to women not using a hormonal method. In one study, weight gain (kg) was greater for the DMPA group than the group using a non-hormonal IUD in years one through three [(MD 2.28; 95% CI 1.79 to 2.77), (MD 2.71, 95% CI 2.12 to 3.30), and (MD 3.17; 95% CI 2.51 to 3.83), respectively]. The differences were notable within the normal weight and overweight subgroups. Two implant studies also showed differences in weight change. The implant group (six-capsule) had greater weight gain (kg) compared to the group using a non-hormonal IUD in both studies [(MD 0.47 (95% CI 0.29 to 0.65); (MD 1.10; 95% CI 0.36 to 1.84)]. In one of those studies, the implant group also had greater weight gain than a group using a barrier method or no contraceptive (MD 0.74; 95% CI 0.52 to 0.96).The two studies that assessed body composition change showed differences between POC users and women not using a hormonal method. Adolescents using DMPA had a greater increase in body fat (%) compared to a group not using a hormonal method (MD 11.00; 95% CI 2.64 to 19.36). The DMPA group also had a greater decrease in lean body mass (%) (MD -4.00; 95% CI -6.93 to -1.07). The other study reported differences between an LNG-IUS group and a non-hormonal IUD group in percent change in body fat mass (2.5% versus -1.3%, respectively; reported P value = 0.029) and percent change in lean body mass (-1.4% versus 1.0%, respectively; reported P value = 0.027). The overall quality of evidence was moderate to low, given that the studies were evenly divided across the evidence quality groups (high, moderate, low, or very low quality). We found limited evidence of weight gain when using POCs. Mean gain was less than 2 kg for most studies up to 12 months. Weight change for the POC group generally did not differ significantly from that of the comparison group using another contraceptive. Two studies that assessed body composition showed that POC users had greater increases in body fat and decreases in lean body mass compared to users of non-hormonal methods. Appropriate counseling about typical weight gain may help reduce discontinuation of contraceptives due to perceptions of weight gain.

Most of the mothers are very attentitve to changes in body composition, especially postpartum weight loss. One of the factors believed to facilitate the weight loss and body fat loss in postpartum mothers is breastfeeding. Factor that affect the relationship between breastfeeding with maternal postpartum body composition are food intake and physical activity. The aim of this study is to analyze the change in body composition between the mother who give exclusive breastfeeding for 6 months and the mother who don’t and also attempts to analyze the effect of breastfeeding duration to the change in body composition and the factor affecting it.This study used the panel study with longitudinal approach. 32 respondents observed for 6 months. Fat mass measurement data are collected using skinfold caliper and breastfeeding status, food intake and physical actiuvity data are collected using interview. The relationship between breastfeeding with the change in body composition is analyzed using t-test analysis. T-test analysis are also used to test the effect of food intake and physical activity to breastfeeding. Regression analysis are used to analyze the effect of food intake and physical activity to body composition.According to the result of statistical analysis, there is no significance effect of breastfeeding for 6 months to the change in maternal postpartum body composition (fat mass and free fat mass) (p = 0.743; p = 0.771) and also no significance effect of food intake and physical activity to the relation between breastfeeding with the change in body composition. There is a significance effect of breastfeeding for 4 months to the change in the body composition (p = 0.046). The average fat mass change in mother who give exclusive breastfeed is higher than the one who don’t.From 32 respondents in this study, only 4 mothers can successfully give exclusive breastfeed for 6 months. The average fat mass change in mother who give exclusive breastfeed is higher than the one who don’t. There is no significance effect of breastfeeding for 6 months to the change in maternal postpartum body composition (fat mass and free fat mass). There is a significance effect of breastfeeding for 4 months to the change in maternal postpartum body composition.Keywords: Breastfeeding, body composition, maternal postpartum

Because of the improved survival rate, both short term and long term adverse effects of breast cancer treatment have become increasingly important. Body weight and body composition before, during, and after chemotherapy may influence side effects during treatment and survival. The aims of this thesis were to assess among stage I-IIIB breast cancer patients: 1) the association between pre-treatment body composition and dose-limiting toxicities during chemotherapy, 2) potential changes in body weight and body composition during and after chemotherapy compared to changes in age-matched women without cancer in the same time period, and 3) dietary intake during chemotherapy compared to age-matched women without cancer in the same time period. Chapter 2 describes the association between pre-treatment body composition and dose-limiting toxicities during chemotherapy. Data from 172 breast cancer patients who participated in the COBRA-study were analysed. Body composition was measured using a total body Dual Energy X-ray Absorption (DEXA) scan. Information regarding dose-limiting toxicities was abstracted from medical records. A higher BMI (kg/m2) and a higher fat mass (kg and percentage) were associated with an increased risk of dose-limiting toxicity, while lean body mass (kg) was not associated with risk of toxicities. Chapter 3 presents the findings of a meta-analysis on changes in body weight during chemotherapy in breast cancer patients. The meta-analysis showed an overall gain in body weight of 2.7 kg (95% CI: 2.0-3.3) during chemotherapy, with a high degree of heterogeneity (I2= 94.2%). Weight gain in breast cancer patients was more pronounced in papers published before 2000 and studies including cyclophosphamide, methotrexate and 5-fluorouracil as chemotherapy regime. Chapter 4 describes changes in body weight and body composition during and after chemotherapy. Data from 145 patients and 121 women of an age-matched comparison group, participating in the COBRA-study were analysed. Body composition was measured using DEXA-scan at three time points during the study period. For the patient group, these tie points were: before start of chemotherapy, shortly after chemotherapy, and 6 months after chemotherapy. For the comparison group these measurements were conducted over a similar time frame: baseline, 6 months after baseline, and 12 months after baseline. In addition, we identified determinants of changes in body weight and body composition. Shortly after chemotherapy, patients had a significantly higher body weight, BMI, and lean body mass than women in the comparison group, while fat mass was similar. Six months after chemotherapy no differences in body weight or body composition were observed between the patient and comparison group. A younger age, better appetite during chemotherapy, and an ER-receptor negative tumour were associated with greater changes in body weight over time. A younger age and better appetite during chemotherapy were associated with greater changes in fat mass over time, while the only determinant associated with greater changes in lean body mass over time was a better appetite during chemotherapy. Chapter 5 describes the dietary intake and food groups before and during chemotherapy of breast cancer patients compared with women without cancer. In addition we assessed the association between symptoms and energy intake. Data from 117 breast cancer patients and 88 women without breast cancer who participated in the COBRA-study were used. Habitual dietary intake before chemotherapy was assessed using a food frequency questionnaire. Two 24-hr dietary recalls were used to assess actual dietary intake during chemotherapy for patients and within 6 months for the comparison group. Shortly after the 24-hr dietary recall, participants filled out questionnaires about symptoms. Before chemotherapy, dietary intake was similar for both groups. During chemotherapy, breast cancer patients reported significantly lower total energy, total fat, total protein, and alcohol intake than women without cancer, which could be explained by a lower intake of specific food groups. Overall results from this thesis suggest that pre-treatment fat mass is associated with dose-limiting toxicities during chemotherapy. Weight gain during chemotherapy appeared to be more modest than we expected based on literature and changes in body composition during chemotherapy consist mainly of an increase in lean body mass, which is only temporary and returned to baseline within 6 months after chemotherapy. A higher appetite during chemotherapy was associated with changes in body weight and body composition. A younger age at diagnosis was associated with greater changes in body weight and fat mass, but not with changes in lean body mass. In addition, an ER-receptor negative tumour was associated with greater changes in body weight, but not with changes in fat mass or lean body mass. During chemotherapy women with breast cancer have a lower intake of energy, fat, protein and alcohol compared to age-matched women without cancer, which was expressed in a lower intake of specific food groups. The results of this thesis do not suggest that dietary intake is associated with weight gain during chemotherapy.

Air pollution exacerbates mild obstructive sleep apnea by disrupting nocturnal changes in lower-limb body composition: a cross-sectional study conducted in urban northern Taiwan

Introduction: A previous epigenome-wide association study has causally linked DNA methylation (DNAm) at the SREBF1 gene (cg11024682) with obesity and lipids. However, little is known about whether DNAm at SREBF1 is associated with long-term changes in body adiposity and composition. Hypothesis: We hypothesized that participants with different DNAm at SRBF1 might respond differently to dietary weight-loss interventions on changes in body adiposity and composition. Methods: The current study included 314 individuals with overweight or obese, who participated in POUNDS Lost: a 2-year randomized dietary weight-loss trial. The blood DNAm level was profiled by methylC-capture sequencing at baseline. Regional DNAm at SREBF1 was calculated as the average methylation level over CpGs within ±250 bp of cg11024682. Body composition, including total fat mass (FM), percentage of FM (FM%), total fat-free mass (FFM), percentage of FFM (FFM%), and percentage of trunk fat (TF%) were measured by dual-energy X-ray absorptiometry (DEXA) at baseline, 6 months, and 2 years. Results: Lower regional DNAm at SREBF1 was significantly associated with changes in body composition across 2 years ( Table ). At 6 months, per SD lower regional DNAm at SREBF1 was significantly associated with greater reductions in FM (β [SE] -0.23 [0.07], p=0.002), FM% (-0.30 [0.09], p&lt;0.001), and TF% (-0.44 [0.13], p&lt;0.001), and greater increases in FFM (0.18 [0.08], p=0.028) and FFM% (0.30 [0.09], p&lt;0.001), regardless of dietary intervention groups and independent of concurrent weight loss. Such association remained at 2 years: FM (β [SE] -0.21 [0.10], p=0.045), FM% (-0.32 [0.11], p=0.004), TF% (-0.36 [0.16], p=0.026), FFM (0.22 [0.12], p=0.07) and FFM% (0.32 [0.11], p=0.004). Conclusions: Overweight and obese individuals with a lower regional DNAm at SREBF1 achieved greater improvement in body composition across the 2-year intervention, independent of concurrent weight loss, suggesting DNAm at SREBF1 is predictive of individuals’ response to treatment.

Ghrelin, a gut-brain peptide involved in energy homeostasis, circulates predominantly (>90%) in unacylated form. Previous studies, however, have focused on total and acylated ghrelin, and the role of unacylated ghrelin (UAG) is not well understood. Particularly, the association of UAG with weight loss and changes in body composition in adults remains unclear. We hypothesized that exercise-associated increase in UAG level is associated with weight loss, favorable changes in body composition, and body fat distribution. A prospective study of 552 young men (mean age 19.3 and range 19-28 years) undergoing military service with structured 6-month exercise training program. Exercise performance, body composition, and biochemical measurements were obtained at baseline and follow-up. Association between changes in UAG levels and body composition and body fat distribution were evaluated. An increase in UAG level during the exercise intervention was associated with reduced weight, fat mass (FM), fat percentage (fat %), and waist circumference, but not with fat-free mass. Inverse associations of changes in UAG level with changes in waist circumference and fat % were independent of weight at baseline, and changes in weight and exercise performance. Associations of changes in UAG level with waist circumference were significantly stronger than with fat % after the adjustment for confounding variables. UAG is associated with changes in body weight and body composition during an intensive long-term exercise intervention in young men. The association of UAG levels with changes in central obesity was stronger than with total FM.

During recovery, stroke patients are at risk of developing long-term complications that impact quality of life, including changes in body weight and composition, depression and anxiety, as well as an increased risk of subsequent vascular events. The aetiologies and time-course of these post-stroke complications have not been extensively studied and are poorly understood. Therefore, we assessed long-term changes in body composition, metabolic markers and behaviour after middle cerebral artery occlusion in mice. These outcomes were also studied in the context of obesity, a common stroke co-morbidity proposed to protect against post-stroke weight loss in patients. We found that stroke induced long-term changes in body composition, characterised by a sustained loss of fat mass with a recovery of lean weight loss. These global changes in response to stroke were accompanied by an altered lipid profile (increased plasma free fatty acids and triglycerides) and increased adipokine release at 60 days. After stroke, the liver also showed histological changes indicative of liver damage and a decrease in plasma alanine aminotransferase (ALT) was observed. Stroke induced depression and anxiety-like behaviours in mice, illustrated by deficits in exploration, nest building and burrowing behaviours. When initial infarct volumes were matched between mice with and without comorbid obesity, these outcomes were not drastically altered. Overall, we found that stroke induced long-term changes in depressive/anxiety-like behaviours, and changes in plasma lipids, adipokines and the liver that may impact negatively on future vascular health.

Selecting study endpoints in prospective cancer cachexia trials remains poorly defined. The aim of this study was to further evaluate associations in changes in weight, body composition, functional outcomes, and patient-reported outcomes (PROs) in patients with metastatic cancer. We completed a 2-year (2016-2018) observational study in patients with metastatic solid cancer and ECOG performance status 0 to 2 while receiving chemotherapy and/or immunotherapy. We completed assessments at study enrollment and 3months from enrollment. We analyzed longitudinal changes in weight and body composition using validated methods. Functional assessments included the 6-Min Walk Test, Timed Up and Go Test, and Short Physical Performance Battery. PROs included the Functional Assessment of Anorexia/Cachexia Therapy and Functional Assessment of Cancer Therapy Fatigue. We analyzed changes in body composition and functional assessment using paired t tests. Additionally, we utilized linear regression models to assess relationships between changes in body composition and function outcomes and PROs, adjusting for age and sex. A total of 57 patients completed baseline assessments, but 19 patients did not complete 3-month assessments (5 died, 1 hospice, 13 withdrew). Of the 38 patients with complete data, the mean age was 61.8years and 47% were female. Metastatic cancer types included 71% gastrointestinal, 13% lung, and 8% gynecologic. Half received chemotherapy, 16% immunotherapy, and 34% a combination. From enrollment to 3months, we did not observe a change in weight or skeletal muscle but did find an increase in total adipose tissue (16.9 ± 52.4cm2, 95% CI -33.79-0.63; p= 0.059; ~ 1.5 pounds). We did not observe any association with changes in weight with any functional outcomes or PROs. However, greater losses in skeletal muscle were associated with greater declines in physical function (6-Min Walk Test [B= 0.04, p= 0.01], Short Physical Performance Battery [B= 2.44, p< 0.01]). Patients with metastatic cancer receiving cancer-directed therapy may not experience a change in body weight. However, we found an association between losses in skeletal muscle and greater declines in physical function. Therefore, when selecting study endpoints, prospective cancer cachexia studies may consider selecting changes in body composition over weight.

Sarcopenia and changes in body composition following neoadjuvant chemotherapy (NAC) may affect clinical outcome. We assessed the associations between CT body composition changes following NAC and outcomes in oesophageal cancer. A total of 35 patients who received NAC followed by oesophagectomy, and underwent CT assessment pre- and post-NAC were included. Fat mass (FM), fat-free mass (FFM), subcutaneous fat to muscle ratio (FMR) and visceral to subcutaneous adipose tissue ratio (VA/SA) were derived from CT. Changes in FM, FFM, FMR, VA/SA and sarcopenia were correlated to chemotherapy dose reductions, postoperative complications, length of hospital stay (LOS), circumferential resection margin (CRM), pathological chemotherapy response, disease-free survival (DFS) and overall survival (OS). Nine (26 %) patients were sarcopenic before NAC and this increased to 15 (43 %) after NAC. Average weight loss was 3.7 % ± 6.4 (SD) in comparison to FM index (-1.2 ± 4.2), FFM index (-4.6 ± 6.8), FMR (-1.2 ± 24.3) and VA/SA (-62.3 ± 12.7). Changes in FM index (p = 0.022), FMR (p = 0.028), VA/SA (p = 0.024) and weight (p = 0.007) were significant univariable factors for CRM status. There was no significant association between changes in body composition and survival. Loss of FM, differential loss of VA/SA and skeletal muscle were associated with risk of CRM positivity. • Changes in CT body composition occur after neoadjuvant chemotherapy in oesophageal cancer. • Sarcopenia was more prevalent after neoadjuvant chemotherapy. • Fat mass, fat-free mass and weight decreased after neoadjuvant chemotherapy. • Changes in body composition were associated with CRM positivity. • Changes in body composition did not affect perioperative complications and survival.

Excess adiposity has been shown to be associated with increased risk for breast cancer recurrence, and a plant-based eating pattern has been hypothesized to be protective. Whether a plant-based diet without specific energy goals will result in weight loss or changes in body composition in women who have been diagnosed with breast cancer has not been fully explored. This study was conducted to identify changes in body weight, anthropometric measures, and body composition over a four year period in a sub-sample of breast cancer survivors participating in a dietary intervention targeting increased intake of vegetables, fruit and fiber and decreased dietary fat intake. This randomized, controlled dietary intervention study compared longitudinal changes in intakes, body weight, waist:hip ratio (WHR), body mass index (BMI) and body composition by treatment group among fifty-two women previously treated for Stage I, II, or IIIA breast cancer from the Arizona site of the Women's Healthy Eating and Living Study. The dietary intervention aimed for eight servings of fruit and vegetables, 30 g fiber, < or = 20% total energy from fat per day, as well as daily intake of vegetable juice. The comparison group was advised to follow general dietary guidelines for cancer prevention. The dietary intervention resulted in a significant and sustained increase in fiber, fruit, vegetable, and vegetable juice consumption (p < 0.05) among intervention group subjects as compared to comparison group subjects. The first 6 months resulted in a reduction in body weight and body fat among the intervention group subjects while the comparison group subjects remained stable. Subsequent measurements, at 12, 24 or 36, and 48 months, showed no significant differences in mean body weight, BMI, WHR, or body composition by study group. Also, no significant changes in these measures were demonstrated for either study group between baseline and 48 months. The dietary intervention efforts resulted in significant changes in diet toward an increase in plant foods and a decrease in dietary fat. Changes in weight, WHR, BMI, and body composition were not different over time or by study group assignment. Interventions that promote a plant-based diet without specific energy restriction do not appear to promote changes in body weight or body composition in women who have been diagnosed with breast cancer. To adequately examine the role of energy restriction in reducing obesity-associated breast cancer recurrence, future interventions should include prescribed energy imbalance either through reduced intake and/or increased expenditure.

We aimed to compare the level of agreement between leg-to-leg bioelectrical impedance analysis (LBIA) and dual-energy X-ray absorptiometry (DXA) for assessing changes in body composition following exercise intervention among individuals with Type 2 diabetes mellitus (T2DM). Forty-four adults with T2DM, age 53.2 ± 9.1 years; BMI 30.8 ± 5.9 kg/m2 participated in a 6-month exercise program with pre and post intervention assessments of body composition. Fat free mass (FFM), % body fat (%FM) and fat mass (FM) were measured by LBIA (TBF-300A) and DXA. LBIA assessments of changes in %FM and FM post intervention showed good relative agreements with DXA variables (P < 0.001). However, Bland-Altman plot(s) indicated that there were systematic errors in the assessment of the changes in body composition using LBIA compared to DXA such that, the greater the changes in participant body composition, the greater the disparity in body composition data obtained via LBIA versus DXA data (FFM, P = 0.013; %FM, P < 0.001; FM, P < 0.001). In conclusion, assessment of pre and post intervention body composition implies that LBIA is a good tool for assessment qualitative change in body composition (gain or loss) among people with T2DM but is not sufficiently sensitive to track quantitative changes in an individual's body composition.

The relationship between in-season changes in aerobic fitness and body composition in collegiate athletes is poorly defined. PURPOSE: To evaluate in-season changes in aerobic fitness among collegiate athletes, and how these are influenced by gender, sport and body composition. METHODS: 50 NCAA Division 1 athletes [23 female (11 hockey, 12 soccer), 27 male (11 hockey, 16 soccer)] completed testing immediately before and after their competitive seasons for determination of lean body mass (LBM) and percentage body fat (BF%) by dual-energy x-ray absorptiometry (DXA) and maximal treadmill testing for maximal aerobic capacity (VO2max), time to exhaustion (Tmax), and ventilatory threshold (VT). Pre- and post-season fitness and body composition values were compared using paired t-tests. Multivariable regression analysis was used to identify independent predictors of in-season change in body composition using gender and sport as covariates, as well as in-season changes in fitness measures using sport, gender and body composition as covariates. RESULTS: Compared to pre-season, post-season values for the entire group were lower for VO2max (4.30±0.88 v 4.08±0.86 L/min, p=0.002), and unchanged for Tmax (16.5±2.2 v 16.1±2.3 min, p=0.13), VT (3.05±0.77 v 3.15±0.66 L/min, p=0.18), BF% (19.1±6.8 v 19.4±6.5 %, p=0.39) and LBM (56.7±10.5 v 56.3±9.8 kg, p=0.48). (p>0.05 for all). LBM was a significant, independent predictor of in-season changes in VO2max (r2=0.33, p<0.001), Tmax (r2=0.19, p=0.003) and VT (r2=0.21, p=0.003). In-season change in BF% was not related to VO2max (r2=0.04, p=0.29) or VT (r2=0.03, p=0.51), but was a strong predictor of changes in Tmax (r2=0.32, p<0.001). Gender and sport were not related to in-season changes in body composition or fitness variables (p>0.05 for all). CONCLUSION: In collegiate intermittent sport athletes, in-season change in LBM explains a significant portion of changes in VO2max and VT, whereas in-season changes in Tmax are independently predicted by changes in both LBM and BF%. In-season changes in aerobic fitness and body composition do not differ across sport or gender. This suggests that efforts to influence body composition during the competitive season can significantly impact aerobic fitness in intermittent sport athletes.