Childhood obesity and nonalcoholic fatty liver disease (NAFLD) are increasing problems in most developed countries including Denmark, but they are also rapidly increasing in the developing parts of the world (1). NAFLD usually presents together with features of the metabolic syndrome, including reduced insulin sensitivity, and is reported to have serious negative implications for adolescent and adult health (2). NAFLD is associated with an increased risk of nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma (3–5). In addition, it is associated with an increased risk of type 2 diabetes mellitus and cardiovascular disease (6).
The treatment of childhood NAFLD/NASH is not established, and pharmacological interventions in children lack appropriate clinical trials (7). Present treatment is based on a restriction of dietary energy intake along with increased physical activity, but even the effects of such efforts are only sporadically studied, and long-term follow up data are scarce.
In Denmark, we have the unique opportunity to conduct such studies because of the well-established intensive weight loss camps to which obese schoolchildren are referred for 10-week residencies. The purpose of our study was to examine the assumption that the camp program could immediately reduce the children's prevalence of NAFLD and increased insulin sensitivity through its daily prolonged exercise routines, dietary energy restriction, and the resulting body weight loss. When feasible, we also examined the children 12 months after the camp.
Participants and Study Protocol
We studied 117 obese children from a Danish weight-loss camp (Julemærkehjemmet Hobro, Denmark). The camps are financed with the revenue from the public sale of Christmas seals that are added onto holiday letters; the campers do not pay to participate in the camp. The children were referred by their local school's attending general physician or general practitioner. The reason for attending the camp is obesity issues along with social problems related to school, friends, or family, and where a time out in a new environment with focus on healthy lifestyle, new habits, and increased physical activities is warranted. All of the children and their parents were invited and accepted. We studied the children by collecting their overnight fasting data at baseline and after 10 weeks, at the end of the camp. After 12 months, all of the 117 children were invited for a final follow-up and 71 accepted. The study was approved by the ethics committee of Region Midtjylland (no. 20030185).
While at the camp, the children attended regular school classes and were also taught to adopt a healthy lifestyle and diet. The children were allowed 3 healthy meals per day at fixed time points, with breakfast, lunch, and an evening meal. In between, they have healthy snacks 3 times per day consisting of fruits or vegetables (eg, apple, carrot) or a piece of bread with high fiber content. No soft drinks are allowed and candy in small amounts only once per week. The diet correlates to a daily energy intake of approximately 6475 kJ/day, coming from 230 g carbohydrates (energy percentage 60%), 61 g protein (energy percentage 16%), and 42 g fat (energy percentage 24%). The fiber content was approximately 30 g/day. This basic diet principle is individualized to each child to induce a weight loss during the intervention period.
They also followed a scheduled and moderately strenuous supervised physical activity program for at least 1 hour every day consisting of supervised bicycling, walking, running, gymnastics, swimming, ball games, and so on, performed individually or in groups/teams depending on the exercise. Compliance with diet and exercise is excellent with adult supervision at all times during the camp.
The children's body weight, height, and waist and hip circumferences were recorded. After resting flat in a bed, pulse rate and blood pressure were measured with an automatic noninvasive blood pressure monitor (Critikon Dinamap 8100, Tampa, FL) fitted with a child-size cuff. Their body composition was estimated using multifrequency electrical bioimpedance (Quadscan 4000, Bodystat Ltd, Isle of Man, UK). Their liver morphology was studied with ultrasound. Then, baseline blood samples were drawn for liver enzymes, lipids, glucose, and insulin followed by a 2-hour oral glucose (1.75 g/kg maximal 75 g glucose) tolerance test (OGTT). Twelve months after the camp and without any postcamp contact or other intervention, the same examinations were repeated, except the OGTT. Insulin sensitivity was evaluated using the homeostasis model assessment (HOMA) index and was calculated as the fasting serum insulin (microinternational unit/mL) × fasting plasma glucose (mmol/L)/22.5.
Ultrasonography (3.5 MHz transducer) was performed by 2 radiologists who were experienced in pediatric liver examinations. Fatty liver was determined using 3 measures: ecchogenicity compared with the right kidney, which was graded 0 to 3; change in the liver texture, which was graded 0 to 2; and plump liver sign, which was graded 0 to 2. A score was determined for each measure, and their sum was calculated as a total liver score (8). At the end of the study, data from all of the examinations were blinded and evaluated in random order by both radiologists by a consensus report.
We used standard clinical biochemistry laboratory methods with standardized values for Danish children as reference. Normal values for high-density lipoprotein (HDL) -cholesterol were obtained from the consensus report on metabolic syndrome in children (9). All of the normal values/ranges are provided in tables or text. Serum and plasma samples were frozen and stored at −80 °C. Serum insulin was measured using a 2-site immunospecific insulin enzyme-linked immunosorbent assay (DakoCytomation, Copenhagen, Denmark, interassay coefficient of variation = 7.5% and intraassay coefficient of variation <10%).
Data were analyzed with SPSS version 10.0 (SPSS Inc, Chicago, IL). Nonparametric ANOVA with Friedman test was used initially for all of the children who were studied on the 3 occasions. If significant, then post hoc analysis with the Wilcoxon paired test was performed to compare baseline with 10 weeks (n = 117) and 12 months (n = 71) and 10 weeks versus 12 months (n = 71). Correlations were performed with Spearman ρ and the correlation coefficient (r) provided. P < 0.05 was considered to be statistically significant in a 2-tailed test.
Body Mass Index-Standard Deviation Score (BMI-SDS), Body Composition, Waist Circumference, and Blood Pressure
At baseline, all of the children had elevated BMI-SDS (2.93 ± 0.52), and boys had higher BMI-SDS scores than girls (3.11 ± 0.52 vs 2.77 ± 0.46; P = 0.001). During the camp, all of the children achieved a significant decrease in body weight and BMI (Fig. 1). Boys had significantly higher BMI-SDS change compared with girls (−0.72 ± 0.21 vs −0.56 ± 0.21; P = 0.001). After 12 months, the majority of the children had regained the weight, but 17 of 71 (24%) had maintained or further reduced their BMI-SDS (Table 1) with no sex effect. At baseline, all of the children except 1 had a waist circumference that was >90th percentile for their age (10). The children lost and regained visceral body fat as determined by waist circumference, with no age or sex differences. During the camp, the children's bioimpedance body fat component decreased markedly; however, after 12 months, it increased again in the majority (78%) of the children. As expected, their estimated lean body weight also decreased during the camp but increased again after 12 months.
At baseline, 14 children (12%) had a systolic blood pressure of >130 mmHg and 1 had a diastolic blood pressure of >85 mmHg. These blood pressures were decreased during the camp and increased again after 12 months.
Transaminases and Other Parameters
At baseline, 58 of 117 (50%) of the children had increased ALT (>25 U/L) (Fig. 2), which decreased during the camp in all of the children (P < 0.05) with no further change 12 months later. There were no age or sex differences for ALT levels or changes. Among the 50% of the children with normal ALT at baseline, 12 (12%) developed elevated ALT during the camp, which normalized 12 months later. At baseline, the children's ALT values and their liver ultrasound changes were correlated with echogenicity (r = 0.23, P = 0.01), liver texture (r = 0.26, P < 0.01), plump liver sign (r = 0.36, P < 0.001), and total liver score (r = 0.32, P < 0.001). There were no correlations between their ALT values and the measures of insulin sensitivity, waist circumference, triglycerides, HDL-cholesterol, or blood pressure levels.
Apart from the transaminases, all of the children had normal routine liver tests at baseline (Table 2). After the camp, alkaline phosphatases (P < 0.05), coagulation factors II, VII, X, and γ-glutamyltransferase were decreased (P < 0.05). The coagulation factors increased again after 12 months.
At baseline, 43% of the children had increased liver echogenicity, 21% had plump liver sign, and 18% had changed liver texture. Boys had more frequently increased liver fat echogenicity compared with girls (P = 0.04) at baseline; however, there was no sex effect on liver fat changes during the study period. These frequencies were reduced to 30%, 8%, and 4%, respectively, after the camp and did not change after 12 months. The scores for all 3 measures and their sum decreased during the camp (P < 0.05). At the 12-month follow-up, echogenicity, liver texture, and total liver score significantly improved from baseline (P < 0.05) (Table 3).
At baseline, the children's liver echogenicity score correlated positively with their body fat component (r = 0.19, P = 0.05), waist–hip ratio (r = 0.21, P = 0.03), and their insulin levels after the OGTT (r = 0.19, P = 0.04). There were no correlations between echogenicity and waist circumference, triglycerides, HDL-cholesterol, or blood pressure.
The children's fasting plasma glucose concentrations were unchanged throughout the study, whereas both their insulin and HOMA values decreased markedly during the camp (P < 0.05) (Table 4). Similarly, their OGTT 2-hour glucose and insulin levels decreased (P < 0.05). After 12 months, glucose, insulin, and HOMA were higher than baseline (P < 0.05). No child developed diabetes, but 3 (3%) had an OGTT plasma glucose between 7.8 and 8.5 mol/L, that is, impaired glucose tolerance. There was no effect of age or sex on the above parameters.
The insulin levels at baseline correlated with glucose (r = 0.41, P < 0.001), fat component (r = 0.43, P < 0.001), BMI (r = 0.49, P < 0.001), waist (r = 0.43, P < 0.001), hip (r = 0.30, P < 0.001), systolic (r = 0.29, P = 0.05) and diastolic (r = 0.27, P < 0.005) blood pressure, but not the waist–hip ratio. There were correlations among baseline insulin and triglycerides (r = 0.71, P < 0.001), total cholesterol (r = 0.46, P < 0.001), HDL-cholesterol (r = −0.32, P < 0.001), and low-density lipoprotein (LDL) -cholesterol (r = 0.42, P < 0.001).
During the camp, triglycerides and total and LDL-cholesterol levels decreased significantly (P < 0.05), followed by an increase after 12 months (P < 0.05) (Table 5). There was no change in the HDL-cholesterol fraction (Table 5). There was no effect of age or sex on the above parameters. At baseline, 19 (16%) children had low HDL-cholesterol (boys >1.03 and girls >1.29 mmol/L (9). Nine children (8%) had increased triglycerides at baseline (>1.7 mmol/L) and 4 (3%) had both triglycerides and HDL-cholesterol abnormalities. Two children had an increased total cholesterol (>6.0 mmol/L), and 1 child had an increased LDL-cholesterol (>4.5 mmol/L).
The present study is the first study to investigate the effects of a weight loss camp on NAFLD, body composition, and insulin sensitivity in obese children with a 12-month follow-up. Furthermore, these are the first data on the prevalence of NAFLD and reduced insulin sensitivity in obese Nordic children. Our study shows that this simple and short-term change in lifestyle had profound positive effects on the children's metabolic status.
The main findings were the improvement in the prevalence and severity of NAFLD along with improvements in body composition, insulin, and other aspects of the metabolic syndrome. Twelve months after return to their spontaneous lifestyle, these improvements were maintained in 24% of the children, but 76% had increased their BMI-SDS again. This shows that long-term measures must be implemented in most children so that the positive effects that are readily obtained with the short-term intervention are maintained.
A recommended standard treatment of childhood NAFLD/NASH has not yet been established, and pharmacological interventions in children have not been adequately investigated through appropriate clinical trials (7). Because NAFLD is associated with obesity and reduced insulin sensitivity, specific regimens aimed at reducing body weight and improving insulin sensitivity are recommended. In adults, this has recently proven to be efficient in a randomized clinical trial (11).
In the present study, we observed striking improvements in all of the parameters of liver fat, transaminases, obesity, insulin sensitivity, and parameters of the metabolic syndrome. We previously reported that a moderate increase in exercise and change in diet resulted in marked changes toward normality in sex hormones in the same children during their stay at the weight loss camp (12); however, the rapid weight loss may cause an increase in ALT levels as observed in 12 children with normal ALT levels at baseline. This has been observed in adults during rapid weight loss (13,14).
Unfortunately, in the present study, most changes were lost during follow-up, and it is likely that a steady long-term weight loss program is superior for preserving initial improvements. This trend has been shown with lifestyle changes, such as low-fat and low-glycemic index diet and weight loss reduction, in observational studies of childhood NAFLD/NASH (15,16). A large prospective study of lifestyle intervention in NAFLD children demonstrated significant reductions in ALT levels and NAFLD based on ultrasound for up to 2 years (17). Studies by Reinehr et al (18) and Nobili et al (16) included intervention programs that consisted of physical activity, nutrition education, and behavior therapy, that is, individual psychological care of the child and family.
Twenty-four percent of the children in our intervention program maintained their weight loss induced at the camp; however, we have no data on effect of lifestyle changes after the weight-loss camp stay but speculate that in this subgroup the short-term intervention leads to a sustained change in lifestyle and food habits. The poor long-term effects in the 76% of children in the present study may be multifactorial conditioned. The heritability of NAFLD and obesity must be considered, as recently demonstrated (19). Similarly, we found a high prevalence of obesity and features of the metabolic syndrome among the children's parents (data not shown). When there are obesity issues among the parents, maintaining weight loss or sustaining a stable weight is a difficult task; in childhood, the management of NAFLD and/or obesity may require counseling with the entire family. Our data support the notion that long-term measures must be implemented to maintain the effects of the weight loss camp, and we suggest continuous intervention in the local community using local schools, health authorities, and sports clubs. Long-term effects in the coming years will be interesting to study in this cohort.
The true prevalence of pediatric NAFLD is unknown and depends on the population that is studied, the ALT cutoff values that are used, and the imaging methods that are used (20). In the clinical setting, the NAFLD diagnosis is considered in an obese child with elevated ALT levels and increased liver echogenicity based on ultrasound. Just recently, the ALT cutoff value has been debated in the United States, and it was concluded that an ALT value >25 IU/L (95th percentile) is abnormal in children (21). We observed increased ALT levels in 50% of obese Danish children using this cutoff, which is similar to the 43% prevalence of children with fatty liver based on ultrasound. The discrepancy between ALT levels and liver fat accumulation has been shown by Franzese et al (22) using ultrasound but was also demonstrated with more specific magnetic resonance imaging (23).
The prevalence of transaminasemia and fatty liver based on ultrasound in our study is similar to previous data from obese children in other parts of the world (20,21). In the general population, NAFLD identified by ALT or ultrasound is in the range of 3% in the United States (NHANES III, ALT) (24), Korea (ALT in 3.2%), and Japan (2.6%) using ultrasound (25,26). An autopsy study observed NAFLD in 10% of US children; NAFLD is increasing with age and is associated with obesity (27).
Obesity and reduced insulin sensitivity are critical factors in the pathogenesis of NAFLD/NASH, and previous studies have shown hyperinsulinemia to be strongly associated with transaminasemia in children with biopsy-proven NAFLD (28,29). Thus, a HOMA-insulin resistance index >3 is greatly suggestive of childhood NAFLD/NASH (30,31). In the present study, however, HOMA values were lower, which implied that children in our study showed fewer metabolic derangements than the other studies mentioned above. This may explain the lower prevalence of metabolic abnormalities compared with previous studies, in which most children with biopsy-proven NAFLD/NASH are dyslipidemic; up to 40% were hypertensive, 10% had impaired glucose tolerance, and a few manifest diabetes (28,30,32,33). Because the children in the present study are less metabolically deranged and only showed modestly increased ALT levels, we were unable to demonstrate significant correlations between ALT and the parameters of both insulin sensitivity and the metabolic syndrome; however, ALT levels correlated with ultrasound-based signs of fatty liver. The increase in insulin levels at 12 months may be caused by the return of obesity, but it may also partly be explained by the physiological pubertal decrease in insulin sensitivity (9).
The strength of the present study lies in the validated methods using ultrasound and transaminasemia for NAFLD detection. A weakness of the present study is the dropout rate of 39% at 12 months compared with a previous study by Reinehr et al (17), in which the dropout rate was only 16%. There were no significant differences, however, between children who did or did not complete the 12-month follow-up in terms of baseline characteristics, which indicates no major selection bias.
In conclusion, in obese Danish children with reduced insulin sensitivity, we found the same prevalence of NAFLD determined by ultrasound and ALT levels as in the southern parts of Europe, the United States, and the East, which indicates the universal association between obesity, reduced insulin sensitivity, and NAFLD. We demonstrated that NAFLD and insulin resistance were effectively treated with physical exercise and weight loss during the weight loss camp residency. Twenty-two percent of children maintained weight loss at 12-month follow-up. Long-term actions must be implemented to increase this percentage to counter the long-term complications of obesity, such as NAFLD, reduced insulin sensitivity, and vascular complications.
We thank laboratory technician Jane Hansen, Aarhus University Hospital, Skejby, for helping to collect and process all of the blood samples. We thank the staff at Julemærhjemmet Hobro for collaboration during the study.
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