Reaching the Tipping Point: Identification of Thresholds at which Visceral Adipose Tissue May Steeply Increase in Youth

The Association between Sarcopenic Obesity and DXA-Derived Visceral Adipose Tissue (VAT) in Adults

Many people with overweight and obesity are affected by sarcopenia, which is represented by a phenotype known as sarcopenic obesity (SO), characterized by excessive body fat (BF), combined with reduced muscle mass and strength. In this population, it is vital to identify the factors associated with SO. With this aim in mind, we investigated the association between visceral adipose tissue (VAT) mass and SO in patients with overweight or obesity in a nutritional setting. A total of 256 participants (23.8% female) with overweight or obesity were involved and completed a body composition assessment, including VAT mass, using dual-energy X-ray absorptiometry (DXA). The sample was initially categorized according to whether the individual had the SO phenotype; they were then classified according to their VAT mass into three tertiles (lowest, medium, and highest). Among the 256 participants, who had a median body mass index (BMI) of 29.3 (interquartile range (IQR): 27.0-32.4) kg/m2 and a median age of 51.0 (IQR: 47.0-54.0) years, 32.4% were identified as having SO, and they displayed a higher median VAT mass (517.0 (IQR: 384.5-677.0) vs. 790.0 (IQR: 654.0-1007.0) g; p < 0.05). The logistic regression model that accounted for age, sex and BMI revealed that a higher VAT mass increases the risk of SO (odds ratio (OR) = 1.003; 95% confidence interval (CI): 1.001-1.004; p < 0.05). In conclusion, VAT mass appears to be an independent factor associated with SO in people with overweight or obesity. However, due to the cross-sectional design, no information regarding any causality between higher VAT mass and SO can be provided. Additional longitudinal research in this direction should therefore be conducted.

Changes in adipose tissue distribution and relation to cardiometabolic risk factors after Roux-en-Y gastric bypass in adolescents

BACKGROUND

Roux-en-Y gastric bypass (RYGB) among adolescents with obesity results in significant weight loss; however, depot-specific changes have been understudied.

OBJECTIVE

We hypothesized that visceral adipose tissue (VAT) reduction in adolescents undergoing RYGB would be greater than other depots and associated with improvement in cardiometabolic risk factors.

SETTING

Three specialized treatment centers in Sweden.

METHODS

Fifty-nine adolescents underwent dual x-ray absorptiometry before surgery and at 1, 2, and 5 years after RYGB. Changes in body composition in multiple depots (total fat, lean body, gynoid fat, android fat, subcutaneous adipose tissue, and VAT) and cardiometabolic risk factors were assessed using multiple linear regression analysis and generalized estimating equations adjusting for age, sex, and baseline risk factor levels. Data are presented as percent change (95% CI) with regression models showing slopes and estimated P values.

RESULTS

At 1 year post-RYGB, a significant reduction was observed across all body composition measures (P < .001) with the greatest reduction observed in VAT (-65.1% [-68.7, -61.8]). From year 1 to 5 years post-RYGB, a regain was observed in all depots except lean body mass (1.2% [.3, 2.7], P = .105). A sex-specific difference in overall trajectories was only observed in lean body mass with males consistently having higher mean levels. Change in VAT at 1 year correlated with change in triglycerides (slope: .21 mg/dL/kg, P = .034) and fasting plasma insulin (slope: 44 pmol/L/kg, P = .027).

CONCLUSIONS

Adiposity measures all decreased after RYGB but poorly predicted change in cardiometabolic risk. Despite significant reductions at 1 year, a steady regain was observed out to 5 years, with values still well below baseline. Further research should consider control group comparison and extended follow-up.

Sex steroids and adiposity in a prospective observational cohort of youth

OBJECTIVE

Adiposity, particularly visceral adipose tissue (VAT), predicts adverse cardiovascular risk factor profiles in children as well as adults. Although endogenous sex steroids likely influence VAT in adults, such an association has not been established in youth. The association between childhood and adolescent sex steroids with adiposity, specifically VAT, was examined before and after adjustment for other hormone changes.

METHODS

These analyses examined longitudinal associations between sex steroids (testosterone, estradiol, dehydroepiandrosterone [DHEA]) and magnetic resonance imaging assessments of VAT in 418 children, 49% of whom were non-White, at approximately 10 years old at Visit 1 (V1) and 17 years old at Visit 2 (V2). Linear mixed effects models adjusted for maternal education, household income, child caloric intake, physical activity, fasting insulin and leptin, and hepatic fat fraction. Differences in associations by race and pubertal stage were also assessed.

RESULTS

At V1, mean body mass index (BMI) for boys was 19.1 (4.7) kg/m2 and for girls was 18.5 (4.1) kg/m2. At V2, mean BMI for boys was 23.7 (5.5) kg/m2 and for girls was 23.6 (5.7) kg/m2. For each ng/dl (0.035 nmol/L) increase in testosterone at V1, there was a 0.25 cm2 increase in concurrent and future VAT in non-White (p = 0.04) but not White girls (p = 0.78). Higher levels of testosterone and DHEA at V1 were associated with greater concurrent and future VAT at V2. These associations were consistent regardless of pubertal stage. In boys, higher testosterone predicted higher future VAT but lower concurrent VAT. Estradiol and DHEA did not predict future VAT in boys. In girls, DHEA predicted future subcutaneous adipose tissue (SAT), and no sex steroids predicted future SAT in boys.

CONCLUSIONS

Testosterone levels predict VAT in boys and girls, and DHEA predicts VAT in girls, even after adjustment for other hormone changes.

Adiposity in Survivors of Cancer in Childhood: How is it Measured and Why Does it Matter?

Survival of cancer in childhood is increasingly common with modern therapeutic protocols but leads frequently to adverse long-term impacts on health, including metabolic and cardiovascular disease. Changes in body composition, especially an increase in fat mass and a decrease in muscle mass, are found early in patients with pediatric cancer, persist long after treatment has been completed and seem to contribute to the development of chronic disease. This review details the effects of such changes in body composition and reviews the underlying pathophysiology of the development of sarcopenic obesity and its adverse metabolic impact. The authors discuss the particular challenges in identifying obesity accurately in survivors of pediatric cancer using available measurement techniques, given that common measures, such as body mass index, do not distinguish between muscle and adipose tissue or assess their distribution. The authors highlight the importance of a harmonized approach to the assessment of body composition in pediatric cancer survivors and early identification of risk using "gold-standard" measurements. This will improve our understanding of the significance of adiposity and sarcopenia in this population, help identify thresholds predictive of metabolic risk, and ultimately prevent or ameliorate the long-term metabolic and cardiovascular impacts on health experienced by survivors of cancer in childhood.