Insulin dynamics predict body mass index and z-score response to insulin suppression or sensitization pharmacotherapy in obese children

Adipose Tissue Insulin Resistance Is Not Associated With Changes in the Degree of Obesity in Children and Adolescents

CONTEXT

The "carbohydrate-insulin model" claims that adipose tissue insulin sensitivity explains development of obesity via adipocyte energy storage and/or low postprandial metabolic fuel levels.

OBJECTIVE

We tested whether adipose tissue insulin sensitivity predicts changes in the degree of obesity over time.

METHODS

This secondary analysis of an observational study of youth with obesity included 213 youths at a pediatric weight management clinic. Adipose tissue insulin sensitivity/resistance and whole-body insulin sensitivity were evaluated using oral glucose tolerance test (OGTT)-derived surrogates in the face of changes in the degree of obesity over time. The main outcome measure was change in body mass index (BMI) z score.

RESULTS

Mean BMI z change was 0.05 ± 0.28 (range, -1.15 to 1.19), representing a broad distribution of changes in the degree of obesity over a follow-up period of 1.88 ± 1.27 years. Adipose tissue insulin resistance was not associated with changes in the degree of obesity in univariate or multivariate analyses (adjusted for baseline age, BMI z score, sex, ethnicity, and time of follow-up). Low postprandial free fatty acid concentrations or their suppression during the OGTT were not associated with changes in the degree of obesity in univariate or multivariate analyses. Whole-body insulin sensitivity was not associated with changes in the degree of obesity in univariate or multivariate analyses.

CONCLUSION

In this secondary analysis, in youth with obesity, adipose tissue insulin resistance is not protective from increases of the degree of obesity and skeletal muscle insulin resistance is not associated with increases of the degree of obesity.The analysis was performed using data derived from NCT00000112 and NCT00536250.

[Clinical guidelines «Obesity in children»]

Childhood obesity is an urgent problem of pediatric endocrinology due to the widespread occurrence, the development of metabolic complications and their steady tracking into adulthood. The developed clinical guidelines are the main working tool of the practitioner. They briefly and structurally present the main information about the epidemiology and modern classification of obesity, methods of its diagnosis and treatment based on the principles of evidence-based medicine.

Methylphenidate improves weight control in childhood brain tumor survivors with hypothalamic obesity

BACKGROUND

Hypothalamic obesity causes unrelenting weight gain for childhood brain tumor survivors. No single therapy has proven effective for treatment. We aimed to evaluate effectiveness of long-term methylphenidate therapy on body mass index (BMI) change in children with hypothalamic obesity.

METHODS

A retrospective analysis included children with a history of brain tumor and hypothalamic obesity receiving methylphenidate (10-60 mg/day) for hypothalamic obesity. Subjects were evaluated for BMI trajectory before and after methylphenidate start. Given that z-scores can be skewed in severely obese children, we calculated BMI as a percent of the BMI at the 95th percentile for the child's age and gender (BMI% 95th).

RESULTS

Twelve patients with hypothalamic obesity completed methylphenidate therapy for at least 6 months (median 3.1 years, range 1.0-5.8 years). All subjects had a suprasellar tumor (nine [75%] with craniopharyngioma) and pituitary dysfunction. Pretreatment median BMI percent of the 95th percentile was 125.6% (interquartile range [IQR] 25-75: 115.3-138.3%) with BMI z-score of 2.4 (IQR 25-75: 2.1-2.6). Following methylphenidate treatment, there was a 69.9% reduction in the median slope of BMI change. Eleven of 12 patients (92%) had a reduction in the slope of their BMI change on methylphenidate treatment. Postmethylphenidate median BMI percent of the 95th percentile decrease to 115.2% (IQR 25-75: 103.6-121.2%) with median BMI z-score of 2.1 (IQR 25-75: 1.8-2.2). Mild side effects were noted in six patients.

CONCLUSIONS

Methylphenidate use reduced and sustained BMI change in children with hypothalamic obesity. Stimulant therapy is an effective first-line agent for treatment of hypothalamic obesity.

Hypothalamic Obesity: 4 Years of the International Registry of Hypothalamic Obesity Disorders

OBJECTIVE

Hypothalamic obesity (HyOb) is a rare cause of rapid weight gain and early metabolic comorbidities. Effective treatment strategies are limited. The registry collected participant data and compared treatment approaches.

METHODS

The International Registry of Hypothalamic Obesity Disorders (IRHOD) was created as a registry portal to provide education. Data collected from the initial 4 years were evaluated.

RESULTS

Eighty-seven participants were included for analysis (median age: 27 years, range: 3-71 years). A total of 96.5% had obesity, and 3.5% had overweight at maximal weight. Seventy-five had brain tumors (86%)-the majority were craniopharyngiomas (72% of those with tumors). Nontumor etiologies included congenital brain malformation (4.6%), traumatic brain injury (3.4%), and genetic anomaly (2.3%). Ninety percent received obesity treatments including nutritional counseling (82%), pharmacotherapy (59%), bariatric surgery (8%), and vagal nerve stimulation (1%). Forty-six percent reported follow-up BMI results after obesity treatment. Surgery was most effective (median BMI decrease: -8.2 kg/m2 , median interval: 2.6 years), with lifestyle intervention (BMI: -3.4 kg/m2 , interval: 1.2 years) and pharmacological therapy (BMI: -2.3 kg/m2 , interval: 0.8 years) being less effective. Eighty percent of participants reporting follow-up weight remained in the obesity range.

CONCLUSIONS

IRHOD identified a large cohort with self-reported HyOb. Surgical therapy was most effective at weight reduction. Nutritional counseling and pharmacotherapy modestly improved BMI. Stepwise treatment strategy for HyOb (including nutritional, pharmacological, and surgical therapies in an experienced center) may be most valuable.

A longitudinal study of serum insulin and insulin resistance as predictors of weight and body fat gain in African American and Caucasian children

BACKGROUND

The influence of insulin and insulin resistance (IR) on children's weight and fat gain is unclear.

OBJECTIVE

To evaluate insulin and IR as predictors of weight and body fat gain in children at high risk for adult obesity. We hypothesized that baseline IR would be positively associated with follow-up body mass index (BMI) and fat mass.

SUBJECTS/METHODS

Two hundred and forty-nine healthy African American and Caucasian children aged 6-12 years at high risk for adult obesity because of early-onset childhood overweight and/or parental overweight were followed for up to 15 years with repeated BMI and fat mass measurements. We examined baseline serum insulin and homeostasis model of assessment-IR (HOMA-IR) as predictors of follow-up BMI Z-score and fat mass by dual-energy X-ray absorptiometry in mixed model longitudinal analyses accounting for baseline body composition, pubertal stage, sociodemographic factors and follow-up interval.

RESULTS

At baseline, 39% were obese (BMI⩾95th percentile for age/sex). Data from 1335 annual visits were examined. Children were followed for an average of 7.2±4.3 years, with a maximum follow-up of 15 years. After accounting for covariates, neither baseline insulin nor HOMA-IR was significantly associated with follow-up BMI (Ps>0.26), BMIz score (Ps>0.22), fat mass (Ps>0.78) or fat mass percentage (Ps>0.71). In all models, baseline BMI (P<0.0001), body fat mass (P<0.0001) and percentage of fat (P<0.001) were strong positive predictors for change in BMI and fat mass. In models restricted to children without obesity at baseline, some but not all models had significant interaction terms between body adiposity and insulinemia/HOMA-IR that suggested less gain in mass among those with greater insulin or IR. The opposite was found in some models restricted to children with obesity at baseline.

CONCLUSIONS

In middle childhood, BMI and fat mass, but not insulin or IR, are strong predictors of children's gains in BMI and fat mass during adolescence.

Late endocrine effects of childhood cancer

The cure rate for paediatric malignancies is increasing, and most patients who have cancer during childhood survive and enter adulthood. Surveillance for late endocrine effects after childhood cancer is required to ensure early diagnosis and treatment and to optimize physical, cognitive and psychosocial health. The degree of risk of endocrine deficiency is related to the child's sex and their age at the time the tumour is diagnosed, as well as to tumour location and characteristics and the therapies used (surgery, chemotherapy or radiation therapy). Potential endocrine problems can include growth hormone deficiency, hypothyroidism (primary or central), adrenocorticotropin deficiency, hyperprolactinaemia, precocious puberty, hypogonadism (primary or central), altered fertility and/or sexual function, low BMD, the metabolic syndrome and hypothalamic obesity. Optimal endocrine care for survivors of childhood cancer should be delivered in a multidisciplinary setting, providing continuity from acute cancer treatment to long-term follow-up of late endocrine effects throughout the lifespan. Endocrine therapies are important to improve long-term quality of life for survivors of childhood cancer.

Race, childhood insulin, childhood caloric intake, and class 3 obesity at age 24: 14-year prospective study of schoolgirls

The prevalence of Class 3 obesity (BMI ≥40 kg/m(2)) has more than doubled in the past 25 years. In a 14-year prospective study from age 10 to 24 of a biracial schoolgirl cohort (293 black, 256 white), we assessed childhood correlates of Class 3 BMI at age 24. Of 42 girls with Class 3 BMI at age 24, 36 (86%) were black. By logistic regression, significant explanatory variables of Class 3 BMI at age 24 included top decile waist circumference at age 11 (odds ratio (OR) 5.7, 95% confidence interval (CI) 2.3-13.9, P = 0.0002), age 10 BMI ≥ the Center for Disease Control (CDC) 2000 top 15% (OR 7.0, 95% CI 2.5-19.3, P = 0.0002), and a three-way interaction between race, childhood insulin, and average caloric intake from age 10 to age 19 (for each unit increase, OR 1.7 95% CI 1.3-2.2, P = 0.0003). Age 10 BMI, age 11 waist circumference, and interaction of race, childhood insulin, and childhood caloric intake predict Class 3 obesity in young adulthood, facilitating childhood identification of girls at high risk for developing Class 3 obesity.

Treatment of obesity in children and adolescents

The prevalence of childhood and adolescent obesity continues to rise in the United States (US). Immediate health consequences are being observed, and long-term risks are mounting within the pediatric population, secondary to obesity. The hallmark of prevention and treatment of obesity in children and adolescents includes lifestyle modification (i.e., dietary modification, increased physical activity, and behavioral modifications). However, when intensive lifestyle modification is insufficient to reach weight loss goals, adjunctive pharmacotherapy is recommended. Among the group of weight-loss medications, orlistat is the only US Food and Drug Administration (FDA)-approved prescription drug for the treatment of overweight and obese adolescents. Other medications, including metformin, need larger studies to establish their role in treatment. No single approach to management of pediatric obesity is the answer, given the complexity of the disorder and the many reasons for failure. Evidence of weight loss medications in addition to lifestyle modification supports short-term efficacy for treatment of obese children and adolescents, although long-term results remain unclear.

Effects of metformin on body weight and body composition in obese insulin-resistant children: a randomized clinical trial

OBJECTIVE

Metformin can decrease adiposity and ameliorate obesity-related comorbid conditions, including abnormalities in glucose homeostasis in adolescents, but there are few data evaluating the efficacy of metformin among younger children. Our objective was to determine whether metformin treatment causes weight loss and improves obesity-related comorbidities in obese children, who are insulin-resistant.

RESEARCH DESIGN AND METHODS

This study was a randomized double-blind placebo-controlled trial consisting of 100 severely obese (mean BMI 34.6 ± 6.6 kg/m(2)) insulin-resistant children aged 6-12 years, randomized to 1,000 mg metformin (n = 53) or placebo (n = 47) twice daily for 6 months, followed by open-label metformin treatment for 6 months. All children and their parents participated in a monthly dietitian-administered weight-reduction program.

RESULTS

Eighty-five percent completed the 6-month randomized phase. Children prescribed metformin had significantly greater decreases in BMI (difference -1.09 kg/m(2), CI -1.87 to -0.31, P = 0.006), body weight (difference -3.38 kg, CI -5.2 to -1.57, P < 0.001), BMI Z score (difference between metformin and placebo groups -0.07, CI -0.12 to -0.01, P = 0.02), and fat mass (difference -1.40 kg, CI -2.74 to -0.06, P = 0.04). Fasting plasma glucose (P = 0.007) and homeostasis model assessment (HOMA) insulin resistance index (P = 0.006) also improved more in metformin-treated children than in placebo-treated children. Gastrointestinal symptoms were significantly more prevalent in metformin-treated children, which limited maximal tolerated dosage in 17%. During the 6-month open-label phase, children treated previously with placebo decreased their BMI Z score; those treated continuously with metformin did not significantly change BMI Z score further.

CONCLUSIONS

Metformin had modest but favorable effects on body weight, body composition, and glucose homeostasis in obese insulin-resistant children participating in a low-intensity weight-reduction program.

Long-term effects of metformin and lifestyle modification on nonalcoholic Fatty liver disease obese adolescents

Objective. To assess the long-term effects of metformin in combination with lifestyle intervention and its association between insulin levels and the degree of steatosis at ultrasonography (US) in obese adolescents. Methods. Thirty-five postpubertal obese boys were randomized into two groups: one receiving metformin in combination with a multidisciplinary lifestyle intervention versus a placebo group, which also received the same intervention. The visceral, subcutaneous fat and degree of steatosis were measured by ultrasonography. Fasting blood samples were collected to analyze glucose, insulin, insulin resistance, and aminotransferases. Repeated ANOVA measures were used to compare changes over time and between groups, and Spearman's correlations were used to identify an association between insulin and the degree of steatosis at US. Results. There was a positive correlation between the degree of steatosis at US with insulin concentrations and HOMA-IR. Long-term therapy plus metformin significantly reduced body weight, body mass index, insulin, HOMA-IR, and visceral fat. Conclusions. Metformin was more effective than the placebo in improving clinical parameters associated with obesity and steatosis.

Intraperitoneal fat and insulin resistance in obese adolescents

Obesity is epidemic among adolescents in the United States. We sought to analyze the anthropometric measures of adiposity and fasting indices of insulin resistance, including insulin-like growth factor-binding protein-1 (IGFBP-1), and to provide a clinical estimate of intraperitoneal (IP) fat in obese adolescents (BMI > or =95th percentile), between ages 13 and 17 years. Subjects had baseline testing to determine eligibility for a subsequent randomized, placebo-controlled trial of metformin XR therapy. Anthropometry and dual-energy X-ray absorptiometry (DXA) were used to quantify total body fat while abdominal computed tomography (CT) was used to measure IP (CT-IP) and subcutaneous (CT-SQ) fat. Using anthropometry and fasting laboratory data, we constructed regression models for both CT-IP and CT-SQ. A total of 92 subjects, 33 males, were evaluated. Of the 92 subjects, 19 were black. Fasting insulin concentrations were highly associated with other measures of insulin resistance. Median percent body fat across all subjects, as measured by DXA, was 41%. Using CT measures, 67% of abdominal cross-sectional area was fat, 14% of which was IP fat. In multiple regression analysis, waist circumference (WC) and BMI, jointly and independently, were strongly associated with both CT-IP and CT-SQ fat. BMI and WC explained 62% of variance of CT-SQ fat, but only 26% of variance of CT-IP fat. Adding triglyceride:high-density lipoprotein (TG:HDL) ratio and IGFBP-1 (among nonblacks) to the regression model increased the explained variance for estimating CT-IP fat to 45%. When evaluating the metabolic morbidity of an obese adolescent, a model using fasting IGFBP-1, TG:HDL, BMI, and WC may be worthwhile as an estimate of IP fat.

Metformin in combination with structured lifestyle intervention improved body mass index in obese adolescents, but did not improve insulin resistance

This study assessed the efficacy of adding metformin to a structured lifestyle intervention in reducing BMI in obese adolescents with insulin resistance. Obese adolescents (25) aged 10-16 years with a body mass index (BMI) > 95th percentile and insulin resistance (Homeostasis Model Assessment-HOMA) > 3.0 were assessed in a community clinic. A structured lifestyle intervention comprising nutritional and exercise education and motivational support in both individual and group sessions was delivered over 6 months. Subjects were randomized to lifestyle intervention alone or with metformin (1500 g daily). The primary outcome measures were a change in BMI and modification of metabolic risk factors, including insulin resistance, plasma lipids and adipocytokines. Eleven adolescents receiving lifestyle and metformin intervention and 14 receiving lifestyle alone completed the study. BMI decreased by 1.8 kg/m(2) with lifestyle and metformin but did not change with lifestyle alone. HOMA was significantly decreased in the lifestyle intervention group, but not following metformin, while the adiponectin/leptin ratio improved significantly in both groups. Dyslipidemic profiles improved most significantly with metformin. We conclude that metformin in combination with a 6-month structured lifestyle intervention is effective in reducing BMI in obese adolescents but did not improve insulin resistance. Lifestyle intervention, with or without metformin, improved metabolic risk factors such as plasma lipids and adipocytokines.

Use of somatostatin analogues in obesity

Obesity is a condition that results from dysregulation of energy balance. Insulin, a component of the efferent pathway of the energy-regulatory circuit, promotes storage of energy substrates in adipose tissue and is, therefore, a potential target for pharmacotherapy. Somatostatin and its analogues (octreotide and lanreotide) bind to somatostatin subtype 5 receptors on the beta-cell membrane, which limits insulin release and, consequently, may decrease adipogenesis. Somatostatin and its analogues have been used in trials in patients with paediatric hypothalamic obesity. These children have hypothalamic dysfunction, mainly due to brain tumours such as craniopharyngiomas, which are thought to generate increased vagal output, leading to hyperinsulinaemia and weight gain. Two small trials, each of 6 months' duration, in children with paediatric hypothalamic obesity showed either a minimal weight loss or stabilization of bodyweight. In children with Prader-Willi syndrome, the most common genetic hypothalamic disorder associated with hyperphagia, hyperghrelinaemia, massive obesity and other endocrine disturbances, somatostatin failed to control hyperphagia and weight gain in a small number of patients, although it lowered the levels of the anorexigenic hormone ghrelin. Long-acting release octreotide was recently used in hyperinsulinaemic obese adults without cranial pathology. Insulin suppression was associated with small decreases in the body mass indexes of obese subjects receiving the higher dosages of the drug, with an acceptable safety profile, similar to that in previous studies. In conclusion, somatostatin and its analogues, by suppressing beta-cell insulin secretion, can retard weight gain in children with hypothalamic obesity and induce a small amount of weight loss in some adults with hyperinsulinaemic obesity.

Age at menarche in the Canadian population: secular trends and relationship to adulthood BMI

PURPOSE

Studies from around the world indicate a trend toward younger ages of menarche. The extent of this trend in the Canadian population is unknown, and the relationship to later-life health indicators has not yet been fully elucidated. The objective of this study is to estimate the trend in age at menarche (AAM) in the Canadian population and evaluate the relationship between AAM and adult body mass index (BMI).

METHODS

Our data source was a nationally representative survey (the Canadian Community Health Survey, 2.2), and analyses included 8080 women, aged 15 and older, who self-reported AAM. Height and weight were measured by the interviewers for the calculation of current BMI. We modeled the secular trend in AAM over time, and the relationship between current BMI and AAM.

RESULTS

We found a statistically significant decline in AAM in successive age cohorts, indicating a 0.73-year (8.8-month) decrease in AAM between the oldest and youngest age cohorts in the sample. A 1-year increase in AAM was associated with a decrease in mean BMI of approximately 0.5 kg/m(2), after adjustment for covariates. A current age-AAM interaction term was nonsignificant, indicating that the relationship was stable throughout increasing temporal separation from puberty.

CONCLUSION

The observed trend toward earlier menarche could be an indicator of a change in insulin-related metabolism, possibly mediated by behavioral and environmental variables. This study suggests that AAM may be an important clinical and public health indicator of susceptibility to overweight and obesity and attendant morbidity.

Prevention and treatment of pediatric obesity: an endocrine society clinical practice guideline based on expert opinion

OBJECTIVE

Our objective was to formulate practice guidelines for the treatment and prevention of pediatric obesity.

CONCLUSIONS

We recommend defining overweight as body mass index (BMI) in at least the 85th percentile but < the 95th percentile and obesity as BMI in at least the 95th percentile against routine endocrine studies unless the height velocity is attenuated or inappropriate for the family background or stage of puberty; referring patients to a geneticist if there is evidence of a genetic syndrome; evaluating for obesity-associated comorbidities in children with BMI in at least the 85th percentile; and prescribing and supporting intensive lifestyle (dietary, physical activity, and behavioral) modification as the prerequisite for any treatment. We suggest that pharmacotherapy (in combination with lifestyle modification) be considered in: 1) obese children only after failure of a formal program of intensive lifestyle modification; and 2) overweight children only if severe comorbidities persist despite intensive lifestyle modification, particularly in children with a strong family history of type 2 diabetes or premature cardiovascular disease. Pharmacotherapy should be provided only by clinicians who are experienced in the use of antiobesity agents and aware of the potential for adverse reactions. We suggest bariatric surgery for adolescents with BMI above 50 kg/m(2), or BMI above 40 kg/m(2) with severe comorbidities in whom lifestyle modifications and/or pharmacotherapy have failed. Candidates for surgery and their families must be psychologically stable and capable of adhering to lifestyle modifications. Access to experienced surgeons and sophisticated multidisciplinary teams who assess the benefits and risks of surgery is obligatory. We emphasize the prevention of obesity by recommending breast-feeding of infants for at least 6 months and advocating that schools provide for 60 min of moderate to vigorous daily exercise in all grades. We suggest that clinicians educate children and parents through anticipatory guidance about healthy dietary and activity habits, and we advocate for restricting the availability of unhealthy food choices in schools, policies to ban advertising unhealthy food choices to children, and community redesign to maximize opportunities for safe walking and bike riding to school, athletic activities, and neighborhood shopping.

Pre-teen insulin resistance predicts weight gain, impaired fasting glucose, and type 2 diabetes at age 18-19 y: a 10-y prospective study of black and white girls

BACKGROUND

Identifying early pre-teen predictors of adolescent weight gain and the development of impaired fasting glucose (IFG) and type 2 diabetes (T2DM) at age 18-19 y could provide avenues for prevention.

OBJECTIVE

We evaluated possible pre-teen predictors for development of IFG, T2DM, and changes in body mass index at age 18-19 y in black and white girls.

DESIGN

In a prospective cohort study, body habitus and fasting insulin and glucose were measured at ages 9-10 and 18-19 y, and multiple 3-d diet records were collected. Factors predicting 10-y change in body mass index and development of IFG and T2DM together were assessed.

RESULTS

In multivariate analyses, 10-y change in homeostatic model assessment of insulin resistance (HOMA-IR) and the age 9-10 y HOMA-IR x percentage of calories from fat interaction were positive predictors of 10-y changes in body mass index. At age 18-19 y, there were 5 incident cases of T2DM, 37 cases of IFG, and 597 noncases. Age 9-10 y IFG and HOMA-IR (or insulin), 10-y change in HOMA-IR (or insulin), and the age 9-10 y insulin x total caloric intake interaction predicted IFG and T2DM at age 18-19 y.

CONCLUSIONS

Pre-teen IFG, insulin resistance (and insulin), and rapidly increasing insulin resistance during adolescence identifies girls who are at greater risk of future IFG and T2DM. In addition, insulin resistance, interacting with high-fat diets, identifies girls who are at risk of greater weight gain. These findings could open avenues to primary prevention of obesity, IFG, and T2DM in children.

Addition of metformin to a lifestyle modification program in adolescents with insulin resistance

OBJECTIVE

To evaluate whether metformin, when added to a program of personal goal setting, improves weight loss and clinical status in obese adolescents.

STUDY DESIGN

In a randomized double-blind placebo controlled trial, 85 adolescents with insulin resistance were randomized to receive metformin (70%) or placebo (30%), along with monthly goal setting for diet and exercise modification. Anthropometric measures, fasting blood analysis, and glucose tolerance tests were performed at baseline and 6 months.

RESULTS

Mean age was 15.7 years. Mean body mass index (BMI) was 39.7 kg/m(2). 71% were female, 58% were Hispanic, and 34% were African-American. 76% of participants completed the study. Goal setting alone did not result in significant weight loss. In addition, there were no group differences between metformin and placebo in weight loss or measures of glucose metabolism. However, among females taking metformin, there was a significant decrease in BMI not seen in the placebo group. Furthermore, metformin adherence, when accompanied by lifestyle change, was a predictor of BMI decrease of 5% or more. 60% of 10 subjects who adhered to metformin and decreased portion size decreased BMI by >5%.

CONCLUSIONS

In this group of predominately minority adolescents, monthly goal setting alone did not lead to weight loss. Although the addition of metformin had no effect on weight loss overall, the agent did significantly increase weight loss among females and weight loss was predicted by degree of metformin adherence. However, weight loss was only found in those participants also reporting lifestyle change, particularly a decrease in portion sizes. These results suggest that metformin may be a useful agent to promote short-term weight loss among girls making modest lifestyle changes.

Role of metformin for weight management in patients without type 2 diabetes

OBJECTIVE

To evaluate the efficacy and safety of metformin for weight management in overweight and obese patients without type 2 diabetes.

DATA SOURCES

Literature was obtained through MEDLINE Ovid (1950-February week 3, 2008), EMBASE (all years), and a bibliographic review of relevant articles. Key words included metformin, obesity, overweight, and weight loss.

STUDY SELECTION/DATA EXTRACTION

All studies published in the English language that evaluated the effects of metformin on weight in obese or overweight individuals were critically analyzed. Relevant articles were selected for inclusion in this review.

DATA SYNTHESIS

Metformin is first-line pharmacotherapy in the treatment of overweight or obese patients with type 2 diabetes, with beneficial effects on weight in this population. Multiple trials have evaluated the effect of metformin on weight and other metabolic parameters in adults and adolescents without diabetes. Five of 12 trials in adults evaluated weight loss as a primary endpoint. Significant weight reduction was found in 4 of these studies; however, the trials were small and of weak design. Weight reduction was significant in 5 of the 6 adolescent trials; similarly, these studies were limited by weak study design and small patient population. Metabolic parameters (blood pressure, waist circumference, cholesterol parameters, insulin/glucose levels) often showed varying results. Metformin was well tolerated; gastrointestinal effects were the most frequently reported adverse effects.

CONCLUSIONS

The weight loss effects of metformin in overweight or obese adults and adolescents without diabetes appear promising; however, trials have been limited by small patient populations and weak design. Metformin may also have a positive effect on metabolic parameters such as waist circumference, fasting insulin and glucose levels, and triglycerides. Further research involving large-scale trials that evaluate weight loss as a primary outcome is necessary to firmly establish the role of metformin in this population.

Insulin resistance, hyperinsulinemia, and energy intake in overweight children

OBJECTIVE

To examine the relationship between energy intake during a buffet meal and indexes of insulin dynamics in overweight children.

STUDY DESIGN

Ninety-five nondiabetic, overweight (body mass index > or = 95th percentile) children (age 10.3 +/- 1.4 years) selected lunch from a 9835-kcal buffet eaten ad libitum after an overnight fast. The associations between energy intake and measures of insulin dynamics, in the postabsorptive state and during a 2-hour hyperglycemic clamp, were determined. Covariates in the statistical model included race, sex, skeletal age, fat-free mass, fat mass, socioeconomic status, and number of foods in the buffet rated as acceptable.

RESULTS

Energy intake was positively associated with the fasting homeostasis model assessment for insulin resistance index (beta = 0.24, P = .042), fasting insulin/glucose ratio (beta = 0.24, P = .044), first-phase insulin (beta = 0.23, P = .032), and first-phase C-peptide (beta = 0.21, P = .046); energy intake was negatively associated with clamp-derived insulin sensitivity (beta = -0.29, P = .042). Each 10% decrease in clamp-derived insulin sensitivity predicted a 27-kcal greater energy intake.

CONCLUSIONS

Insulin resistance and hyperinsulinemia are associated with greater energy intake after an overnight fast in overweight children. These associations suggest mechanisms whereby insulin resistance may contribute to excessive weight gain in children.

Management approaches for pediatric obesity

Childhood obesity is a worldwide problem that has reached epidemic proportions, resulting in an increased prevalence of premature obesity-related morbidities, and, thus, probable increased health-care costs to treat children. The development of viable approaches to manage this epidemic is crucial. Most experts in the field of childhood obesity agree that the prevention of obesity in children should be the first line of management. Pediatricians must be adept at recognizing children at risk of obesity, calculating and plotting the BMI at all visits, using a change in the BMI to identify excessive weight gain, and monitoring for comorbidities associated with obesity. If obesity is present, the cornerstone of treatment is modification of dietary and exercise habits. Practice-based counseling and community-based programs that support and encourage lifestyle modifications have yielded promising short-term results. Children with severe comorbidities who are unable to achieve lifestyle modifications can be considered for either pharmacologic therapy or surgery, but these options should be considered as a last resort. Early intervention and prevention strategies are the most cost-effective methods of dealing with this issue.

Effects of lifestyle intervention and metformin on weight management and markers of metabolic syndrome in obese adolescents

PURPOSE

The purposes of this study are threefold: to determine what components of the metabolic syndrome are present in obese adolescents, to determine what differences exist in the effects of lifestyle intervention versus lifestyle intervention plus metformin on weight management and select markers of metabolic syndrome in obese adolescents, and to determine which factors predict weight loss in obese adolescents treated with lifestyle changes and metformin.

DATA SOURCES

The study was a secondary data analysis utilizing a retrospective chart review of 63 obese adolescents aged 11 through 18 who were treated for obesity at the LeBonheur Youth Lifestyle Clinic from January 1, 2000, through June 30, 2005. Lifestyle interventions included diet, exercise, and counseling. The medication utilized was metformin. Outcomes evaluated included body mass index, relative body mass index (RBMI), weight, waist and hip circumference, blood pressure, serum lipid levels, fasting plasma glucose, 2-h oral glucose tolerance tests, and insulin levels. Changes in mean values between groups were evaluated using the General Linear Models procedure. Logistic regression was utilized to determine which factors might predict weight loss.

CONCLUSIONS

The metformin group (N= 37) tended to be heavier, older, and had more components of the metabolic syndrome than the nonmetformin group (N= 26). All components of the metabolic syndrome were present in both groups (overall prevalence 55%). Both groups had a downward trend in RBMI, a surrogate marker for weight loss, but only the metformin group had a significant loss in RBMI points from baseline to end. There was a trend toward better diastolic blood pressure at 6 months in the metformin group (p= 0.06), which was not seen in the nonmetformin group. The only predictors of weight loss were higher RBMI (those who were heavier lost more) and the absence of type 2 diabetes mellitus (type 2 DM) (those with type 2 DM were less likely to lose 10 or more points in RBMI).

IMPLICATIONS FOR PRACTICE

All components of the metabolic syndrome are present in obese adolescents. The use of lifestyle changes and lifestyle changes plus metformin both produce some degree of weight loss, but subjects on metformin in this study lost significantly more RBMI points than those on lifestyle changes alone. Subjects with type 2 DM are less likely to lose weight than those without type 2 DM. Larger studies and studies with subjects more representative of the general population need to be carried out to assist in the development of evidence-based practice guidelines.

Insulin resistance in children and adolescents

IR is hypothesized to be the important pathophysiologic link between adiposity and future development of type 2 diabetes and cardiovascular disease. A variety of methods for measuring IR have been validated in children, from the gold-standard hyperinsulinemic euglycemic clamp, to simple fasting measures based on fasting insulin and glucose levels. Studies have shown that there are a number of important risk factors for IR in children, including adiposity and visceral adiposity, race/ethnicity, puberty, a family history of type 2 diabetes, sex, and being small for gestational age or prematurity. However, obesity represents the critical risk factor for IR in children. Greater than 50% of obese adolescents in the US have IR. Formal assessment of IR in obese children may represent an important strategy for improving the efficacy of pharmacologic therapy for weight loss and chronic disease prevention.