Prediction of Visceral Adipose Tissue Using Air Displacement Plethysmography in Children

Intra-abdominal and subcutaneous abdominal fat as predictors of cardiometabolic risk in a sample of Mexican children

BACKGROUND/OBJECTIVE

Few studies in Latin American paediatric populations have differentiated fat deposits in specific areas, such as intra-abdominal fat (IAF) and subcutaneous abdominal fat (SAF). Research in diverse populations is needed, as patterns of fat accumulation vary by ethnicity. The aim of this study was to determine whether IAF and/or SAF are related to cardiometabolic risk factors, independent of total body fat (TBF), in a group of Mexican schoolchildren.

SUBJECTS/METHODS

A cross-sectional study was conducted in Mexico City with 94 children aged between 5 and 11 years. IAF and SAF were assessed by magnetic resonance using two different estimation methods: (a) at the midpoint of lumbar vertebras 4 and 5 (L4-L5) and (b) the sum of the areas of four slices (L1-L2, L2-L3, L3-L4 and L4-L5, which will be referred to as 'total' IAF and SAF). TBF was measured by dual-energy X-ray absorptiometry. The following cardiometabolic risk factors were assessed: total cholesterol, low-density lipoprotein-cholesterol, triglycerides, glucose, insulin, high-density lipoprotein-cholesterol, blood pressure, insulin resistance, number of risk factors and metabolic syndrome score.

RESULTS

After adjusting for sex, age and TBF, total SAF was related to the number of cardiometabolic risk factors and metabolic syndrome score. Although IAF at L4-L5 was also related to the number of cardiometabolic risk factors, there was evidence of collinearity with TBF.

CONCLUSIONS

In this sample of Mexican schoolchildren, TBF and SAF, but not IAF, were associated with higher cardiometabolic risk.

Effect of a program of short bouts of exercise on bone health in adolescents involved in different sports: the PRO-BONE study protocol

BACKGROUND

Osteoporosis is a skeletal disease associated with high morbidity, mortality and increased economic costs. Early prevention during adolescence appears to be one of the most beneficial practices. Exercise is an effective approach for developing bone mass during puberty, but some sports may have a positive or negative impact on bone mass accrual. Plyometric jump training has been suggested as a type of exercise that can augment bone, but its effects on adolescent bone mass have not been rigorously assessed. The aims of the PRO-BONE study are to: 1) longitudinally assess bone health and its metabolism in adolescents engaged in osteogenic (football), non-osteogenic (cycling and swimming) sports and in a control group, and 2) examine the effect of a 9 month plyometric jump training programme on bone related outcomes in the sport groups.

METHODS/DESIGN

This study will recruit 105 males aged 12-14 years who have participated in sport specific training for at least 3 hours per week during the last 3 years in the following sports groups: football (n = 30), cycling (n = 30) and swimming (n = 30). An age-matched control group (n = 15) that does not engage in these sports more than 3 hours per week will also be recruited. Participants will be measured on 5 occasions: 1) at baseline; 2) after 12 months of sport specific training where each sport group will be randomly allocated into two sub-groups: intervention group (sport + plyometric jump training) and sport group (sport only); 3) exactly after the 9 months of intervention; 4) 6 months following the intervention; 5) 12 months following the intervention. Body composition (dual energy X-ray absorptiometry, air displacement plethysmography and bioelectrical impedance), bone stiffness index (ultrasounds), physical activity (accelerometers), diet (24 h recall questionnaire), pubertal maturation (Tanner stage), physical fitness (cardiorespiratory and muscular), bone turnover markers and vitamin D will be measured at each visit.

DISCUSSION

The PRO-BONE study is designed to investigate the impact of osteogenic and non-osteogenic sports on bone development in adolescent males during puberty, and how a plyometric jump training programme is associated with body composition parameters.

Whole-body MRI-based fat quantification: a comparison to air displacement plethysmography

PURPOSE

To demonstrate the feasibility of an algorithm for MRI whole-body quantification of internal and subcutaneous fat and quantitative comparison of total adipose tissue to air displacement plethysmography (ADP).

MATERIALS AND METHODS

For comparison with ADP, whole-body MR data of 11 volunteers were obtained using a continuously moving table Dixon sequence. Resulting fat images were corrected for B1 related intensity inhomogeneities before fat segmentation.

RESULTS

The performed MR measurements of the whole body provided a direct comparison to ADP measurements. The segmentation of subcutaneous and internal fat in the abdomen worked reliably with an accuracy of 98%. Depending on the underlying model for fat quantification, the resultant MR fat masses represent an upper and a lower limit for the true fat masses. In comparison to ADP, the results were in good agreement with ρ ≥ 0.97, P < 0.0001.

CONCLUSION

Whole-body fat quantities derived noninvasively by using a continuously moving table Dixon acquisition were directly compared with ADP. The accuracy of the method and the high reproducibility of results indicate its potential for clinical applications.

Whole body fat: content and distribution

Obesity and its co-morbidities, including type II diabetes, insulin resistance and cardiovascular diseases, have become one of the biggest health issues of present times. The impact of obesity goes well beyond the individual and is so far-reaching that, if it continues unabated, it will cause havoc with the economies of most countries. In order to be able to fully understand the relationship between increased adiposity (obesity) and its co-morbidity, it has been necessary to develop proper methodology to accurately and reproducibly determine both body fat content and distribution, including ectopic fat depots. Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) have recently emerged as the gold-standard for accomplishing this task. Here, we will review the use of different MRI techniques currently being used to determine body fat content and distribution. We also discuss the pros and cons of MRS to determine ectopic fat depots in liver, muscle, pancreas and heart and compare these to emerging MRI techniques currently being put forward to create ectopic fat maps. Finally, we will discuss how MRI/MRS techniques are helping in changing the perception of what is healthy and what is normal and desirable body-fat content and distribution.

The clinical importance of visceral adiposity: a critical review of methods for visceral adipose tissue analysis

As a result of the rising epidemic of obesity, understanding body fat distribution and its clinical implications is critical to timely treatment. Visceral adipose tissue is a hormonally active component of total body fat, which possesses unique biochemical characteristics that influence several normal and pathological processes in the human body. Abnormally high deposition of visceral adipose tissue is known as visceral obesity. This body composition phenotype is associated with medical disorders such as metabolic syndrome, cardiovascular disease and several malignancies including prostate, breast and colorectal cancers. Quantitative assessment of visceral obesity is important for evaluating the potential risk of development of these pathologies, as well as providing an accurate prognosis. This review aims to compare different methods of measuring visceral adiposity with emphasis on their advantages and drawbacks in clinical practice.

Methods for assessing body composition, cardiovascular and metabolic function in children and adolescents: implications for exercise studies

PURPOSE OF REVIEW

To critically evaluate the most recent literature on the methods used to assess body composition, cardiovascular and metabolic function in children and adolescents.

RECENT FINDINGS

Although regional body composition can be fairly accurately calculated by dual-energy X-ray absorptiometry, the accuracy of noninvasive estimations of visceral adipose tissue is questionable. Regarding the cardiovascular and metabolic adaptations, there is no doubt that direct and invasive methods provide high accuracy and reproducibility. For instance, exercise until exhaustion, direct Fick equation, nuclear magnetic resonance and magnetic resonance imaging are valid methods to determine maximum oxygen uptake, cardiac output and tissue substrate metabolism, respectively. Except for the direct Fick equation, all have been successfully used in pediatric studies. Relatively new techniques for the assessment of exercise training-induced adaptations in youths include the thoracic bioimpedance and the Modelflow method for cardiac output determination, and magnetic resonance spectroscopy for intramuscular and intrahepatic lipid content. Additional validation and reliability studies in pediatric populations are needed for some of these techniques (e.g. the Modelflow method).

SUMMARY

Most of the techniques used in adults appear not directly applicable to youths. A combination of techniques and/or the application of new, promising and easy to use ones, such as near-infrared spectroscopy and Laser Doppler flowmetry, may advance our knowledge in pediatric exercise science.