The Changes of Body Composition, Glucolipid Metabolism and Bone Metabolism in Obese Children After Weight Loss
The Changes of Body Composition, Glucolipid Metabolism and Bone Metabolism in Obese Children After Weight Loss
Vitamin D plays a significant role in calcium and phosphorus homeostasis for maintaining
 structural integrity and function of musculoskeletal system. Furthermore, recent studies have
 revealed that vitamin D can decrease the risk of many conditions other than skeletal disease,
 including autoimmune diseases, cancers, obesity and obesity-related diseases, such as type 2
 diabetes and cardiovascular disease. Vitamin D may influence calcium absorption to affect
 obesity indirectly, regulate adipocyte differentiation and relieve the development of
 metabolic syndrome by mediating levels of inflammatory factors.

 Another indicator of bone metabolism-osteocalcin may also be involved in energy metabolism
 and glucose metabolism, and undercarboxylated osteocalcin (ucOC) is the form which has
 physiological activity. ucOC may recombine with the receptors on the surface of pancreas β
 cells, adipocytes, hepatocytes and intestinal endocrine cell to regulate insulin secretion
 and insulin sensitivity.

 Currently, the prevalence of vitamin D deficiency is a global problem in all age groups
 currently, even in countries with sun exposure all year around. The obesity group tend to
 have a higher incidence of vitamin D deficiency.Moreover, the obesity group tend to have a
 higher incidence of vitamin D deficiency and a lower level of serum osteocalcin.

 This study observed the changes of body composition and glucolipid metabolism and bone
 metabolism during weight loss, and investigated the correlations among them.
Obese children have a higher incidence of vitamin D deficiency (VDD), which resulted from
 unhealthy life style such as less time outdoors, more sedentary time, imbalance of dietary
 intake. Adipose tissue is the storage position of vitamin D, and the storage formation
 include 25-OHD2 and 25-OHD3. Theoretically, the reserves of vitamin D in adipose tissue of
 obese children might release to the circulation after weight loss. For further, it is
 necessary to clarify the relationship between the improvement of metabolic risk with vitamin
 D status after weight loss.

 Osteocalcin is produced and secreted by osteoblast specifically. Recent studies have shown
 that it regulated glucose metabolism and energy metabolism. Obese group may have a lower
 level of serum osteocalcin. Both 25-OHD and osteocalcin have association with energy
 metabolism. This study will provide evidence to realize the relationship between bone
 metabolism and obesity.

 In our study, all subjects were recruited from the obese children and adolescents aged 9~17
 years who participated in six-week weight loss camp in July ~ August, 2014. Body mass index
 (BMI) was calculated as weight (kg) divided by height squared (m2). Obesity was defined as
 having a BMI greater than or equal to the 95th percentile for age and sex according to WHO
 standard. Exclusion criteria included: 1) obesity caused by endocrine or heredity diseases
 (eg, hypothyroidism, Prader-Willi syndrome, single-gene defects); 2) any disease influencing
 vitamin D metabolism (eg, such as metabolic bone diseases, rickets, nephritic syndrome and
 hepatic failure); 3) any supplementation use or any medication affecting vitamin D metabolism
 use.

 All subjects underwent a closed-off weight loss program for six weeks. The intervention
 methods included aerobic exercise and appropriate caloric control. The dietary was designed
 on the basis of ensuring the daily energy physiological requirement, and basal metabolic rate
 (BMR) was calculated to formulate diet project according to Harris-Benedict formula. The diet
 was composed of 20% protein, 30% fat and 50% carbohydrates. During the camp, all subjects had
 never taken any kinds of nutritional supplements.

 Before intervention, all subjects received exercise load test to ensure safe and effective
 physical exercise. In the exercise, heart rate was monitored to ensure the small-medial load
 aerobic exercise. The exercise programs included ball games, such as badminton, table tennis,
 and basketball, and also included jogging, brisk walking, swimming and cycle ergometer. All
 kinds of sports were conducted indoor, twice per day, 6 days per week, and lasted for 2 hours
 every time. The weight loss camp was staffed by professional sports coaches and medical
 workers. Exercise intensity was estimated by a formula: exercise intensity (target heart
 rate) =resting heart rate + heart rate reserve (maximum heart rate-resting heart rate) ×
 (20%~40%).

 Before and after intervention, fasting blood samples were collected and sent to Shanghai
 Adicon Central Lab Test Menu immediately stored in 4°C ice packs. The indicators of
 glucolipid metabolism and bone metabolism were tested. Total cholesterol (TC) with
 cholesterol oxidase, triglyceride (TG) with enzyme method (GPO-POD), high density lipoprotein
 (HDL) and low density lipoprotein (LDL) with homogeneous methods, fasting blood glucose (FBG)
 with hexokinase (HK) method, fasting insulin (FINS) with chemiluminescence method. Among the
 indicators of bone metabolism, osteocalcin, parathyroid hormone (PTH) and 25-OHD were assayed
 by electrochemiluminescence immunoassay, while bone specific alkaline phosphatase (BALP),
 total propeptide of type I procollagen (T-PINP) and β-isomerized form carboxy-terminal
 telopeptide of type I collagen (β-CTX) were determined by immunoenzymatic methods.

 After blood samples were collected, anthropometric parameters were measured, including height
 (Seca 264, Germany), weight (Biospace 370, South Korea), triceps skinfold thickness (TST) and
 subscapular skinfold thickness (SST) (skinfold caliper 689900). For error reduction, every
 anthropometric measurement was conducted by the same trained personnels before and after
 weight-loss.
Inclusion Criteria:

 -  Obesity was defined as having a body mass index (BMI) greater than or equal to the
 95th percentile for age and sex according to WHO standard. BMI was calculated as
 weight (kg) divided by height squared (m2).

 Exclusion Criteria:

 -  1) obesity caused by endocrine or heredity diseases (eg, hypothyroidism, Prader-Willi
 syndrome, single-gene defects);

 -  2) any disease influencing vitamin D metabolism (eg, such as metabolic bone diseases,
 rickets, nephritic syndrome and hepatic failure);

 -  3) any supplementation use or any medication affecting vitamin D metabolism use.