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Recent 3D optical (3DO) imaging advancements have provided more accessible, affordable, and self–operating opportunities for assessing body composition. 3DO is accurate and precise with respect to clinical measures made by dual–energy X–ray absorptiometry (DXA). However, the sensitivity for monitoring body composition change over time with 3DO body shape is unknown. Therefore, this study aimed to evaluate 3DO ability to monitor body composition changes across multiple intervention studies. A retrospective analysis was performed using intervention studies on healthy adults that were complimentary to the cross–sectional study, Shape Up! Adults. Each participant received a DXA (Hologic Discovery/A system) and 3DO (Fit3D ProScanner) scan at baseline and follow–up. 3DO meshes were digitally registered and reposed using Meshcapade to standardize the vertices and pose. Each 3DO mesh was transformed into principal components (PCs) using an established statistical shape model. The PCs were used to predict whole–body and regional body composition values using published equations. Body composition changes (follow–up minus baseline) were compared to DXA with linear regression. The analysis included 128 participants (43 females) in six studies. The mean (SD) length of follow-up was 13 (5) weeks, range of 3-23 weeks; change in percent fat was 2.8% (2.1%), with a range of 2.4 – 8.3%. Agreement between 3DO and DXA (R2) for changes in total fat mass (FM), total fat–free mass (FFM), and appendicular lean mass, respectively, were 0.89, 0.77, and 0.69 with RMSEs of 1.78 kg, 1.42 kg, and 0.37 kg in females, and 0.77, 0.76, and 0.46 with RMSEs of 2.28 kg, 1.67 kg, and 0.51 kg in males. Statistical significance of individual changes agreed for both DXA and 3DO in the majority of the sample for total FM (70%) and FFM (81%). Further adjustment with demographic descriptors improved the 3DO change agreement to changes observed with DXA. Compared to DXA, 3DO was highly sensitive in detecting body shape changes over time. The 3DO method was sensitive enough to detect even small changes in body composition during intervention studies. The safety and accessibility of 3DO allow users to self–monitor frequently throughout interventions.

Heart rate variability (HRV) provides a simple method to evaluate autonomic function in health and disease. A reduction in HRV may indicate autonomic dysfunction and is strongly associated with aspects of cardiometabolic disease, including hyperglycemia. Reduced nitric oxide (NO) bioavailability is also implicated in the development of cardiometabolic disease and autonomic dysfunction. Watermelons are natural sources of L-arginine and L-citrulline, substrates used for NO synthesis. Watermelon consumption can improve NO bioavailability. We conducted a randomized, double-blind, placebo-controlled crossover trial to test the effects of 2 weeks of daily watermelon juice (WMJ) supplementation on HRV in response to an oral glucose challenge (OGC) in healthy young adults. We also performed indirect calorimetry to assess if our intervention altered the metabolic response to the OGC. WMJ supplementation preserved high-frequency power (HF) (treatment effect, p = 0.03) and the percentage of successive differences that differ by more than 50 ms (pNN50) (treatment effect, p = 0.009) when compared to the placebo treatment. There was no difference in resting energy expenditure or substate oxidation according to treatment. We report that WMJ supplementation attenuates OGC-induced reductions in HRV. Future work should emphasize the importance of NO bioavailability in autonomic dysfunction in cardiometabolic disease.

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