Megan L. Gow

Optimal Macronutrient Content of the Diet for Adolescents With Prediabetes; RESIST a Randomised Control Trial

CONTEXT Prediabetes and clinical insulin resistance in adolescents are rapidly emerging clinical problems with serious health outcomes. OBJECTIVE The objective of this study was to determine the efficacy of 2 structured lifestyle interventions, both differing in diet macronutrient composition, on insulin sensitivity. DESIGN This study was a randomized controlled trial, known as Researching Effective Strategies to Improve Insulin Sensitivity in Children and Teenagers, in 2 hospitals in Sydney, Australia. PARTICIPANTS Participants included overweight or obese 10- to 17-year-olds with either prediabetes and/or clinical features of insulin resistance. INTERVENTION At baseline adolescents were prescribed metformin and randomized to a structured diet, which was either high carbohydrate or moderate carbohydrate with increased protein. The program commenced with a 3-month dietary intervention, with the addition of an exercise intervention in the next 3 months. OUTCOMES The outcomes included an insulin sensitivity, anthropometry, and cardiometabolic profile at 6 months. RESULTS One hundred eleven subjects (66 girls) were recruited and 98 subjects (58 girls) completed the 6-month intervention. After 3 months the mean insulin sensitivity index increased by 0.3 [95% confidence interval (CI) 0.2-0.4]. After 6 months the mean insulin (picomoles per liter) to glucose ratio (millimoles per liter) decreased by 7.2 [95%CI -12.0 to -2.3], body mass index, expressed as a percentage of the 95th centile, decreased by 9% (95% CI -3 to -15), but there was no significant change in the lipids. There were no significant differences in outcomes between the diet groups at any time point. CONCLUSIONS These results are in contrast with our hypothesis that adolescents randomized to the increased protein diet would have better outcomes. Further strategies are required to better address prediabetes and clinical features of insulin resistance in adolescents.

Impact of dietary macronutrient distribution on BMI and cardiometabolic outcomes in overweight and obese children and adolescents: a systematic review

The present systematic review examined the effectiveness of weight management interventions comparing diets with varying macronutrient distributions on BMI and cardiometabolic risk factors in overweight or obese children and adolescents. A systematic search of seven databases for the period 1975-2013 identified 14 eligible randomized or quasi-randomized controlled trials conducted with 6-18-year-old subjects. Seven trials compared a low-fat (≤ 33% energy or < 40 g/day) to an isocaloric (n = 2) or ad libitum (n = 5) low-carbohydrate diet (< 20% energy or < 60 g/day). Meta-analysis indicated a greater reduction in BMI in the low-carbohydrate group immediately after dietary intervention; however, the quality of the studies was limited and cardiometabolic benefits were inconsistent. Six trials compared increased-protein diets (19-30% energy) to isocaloric standard-protein diets (15-20% energy) and one compared an increased-fat diet (40% energy) to an isocaloric standard-fat diet (27% energy); there were no differences in outcomes in these studies. Current evidence suggests that improved weight status can be achieved in overweight or obese children and adolescents irrespective of the macronutrient distribution of a reduced-energy diet. Tailoring the macronutrient content to target specific cardiometabolic risk factors, such as a low-carbohydrate diet to treat insulin resistance, may be possible, but further research is needed before specific recommendations can be made.

Improved insulin sensitivity and body composition, irrespective of macronutrient intake, after a 12 month intervention in adolescents with pre-diabetes; RESIST a randomised control trial

BackgroundA higher protein to carbohydrate ratio in the diet may potentiate weight loss, improve body composition and cardiometabolic risk, including glucose homeostasis in adults. The aim of this randomised control trial was to determine the efficacy of two structured lifestyle interventions, differing in dietary macronutrient content, on insulin sensitivity and body composition in adolescents. We hypothesised that a moderate-carbohydrate (40-45% of energy), increased-protein (25-30%) diet would be more effective than a high-carbohydrate diet (55-60%), moderate-protein (15%) diet in improving outcomes in obese, insulin resistant adolescents.MethodsObese 10–17 year olds with either pre-diabetes and/or clinical features of insulin resistance were recruited at two hospitals in Sydney, Australia. At baseline adolescents were prescribed metformin and randomised to one of two energy restricted diets. The intervention included regular contact with the dietician and a supervised physical activity program. Outcomes included insulin sensitivity index measured by an oral glucose tolerance test and body composition measured by dual-energy x-ray absorptiometry at 12 months.ResultsOf the 111 adolescents recruited, 85 (77%) completed the intervention. BMI expressed as a percentage of the 95th percentile decreased by 6.8% [95% CI: −8.8 to −4.9], ISI increased by 0.2 [95% CI: 0.06 to 0.39] and percent body fat decreased by 2.4% [95% CI: −3.4 to −1.3]. There were no significant differences in outcomes between diet groups at any time.ConclusionWhen treated with metformin and an exercise program, a structured, reduced energy diet, which is either high-carbohydrate or moderate-carbohydrate with increased-protein, can achieve clinically significant improvements in obese adolescents at risk of type 2 diabetes.Trial registrationAustralian New Zealand Clinical Trail Registry ACTRN12608000416392. Registered 25 August 2008.

The Effectiveness of Different Diet Strategies to Reduce Type 2 Diabetes Risk in Youth

Type 2 diabetes in children and adolescents has become a prominent clinical issue in recent decades. Increasing numbers of young people have risk factors for type 2 diabetes, particularly obesity, indicating the need for effective type 2 diabetes prevention strategies. The aim of this review was to identify specific dietary strategies that optimize improvements in risk factors for type 2 diabetes in youth and hence reduce the risk of type 2 diabetes development. Our review of the current literature indicates that dietary interventions lead to weight loss when intervention adherence is high. However, in addition to weight loss, a diet that is reduced in carbohydrates may optimize improvements in other type 2 diabetes risk factors, including insulin resistance and hyperglycemia. While further research is needed to confirm this finding, reduced carbohydrate diets may include a very low-carbohydrate diet, a very low-energy diet, a lower-glycemic-index diet, and/or an intermittent fasting diet. This array of dietary strategies provides a suite of intervention options for clinicians to recommend to young people at risk of type 2 diabetes. However, these findings are in contrast to current guidelines for the prevention of type 2 diabetes in adults which recommends a low-fat, high-carbohydrate diet.

Can early weight loss, eating behaviors and socioeconomic factors predict successful weight loss at 12- and 24-months in adolescents with obesity and insulin resistance participating in a randomised controlled trial?

BackgroundLifestyle interventions in adolescents with obesity can result in weight loss following active intervention but individual responses vary widely. This study aimed to identify predictors of weight loss at 12- and 24-months in adolescents with obesity and clinical features of insulin resistance.MethodsAdolescents (n = 111, 66 girls, aged 10–17 years) were participants in a randomised controlled trial, the RESIST study, examining the effects of two diets differing in macronutrient content on insulin sensitivity. Eighty-five completed the 12-month program and 24-month follow-up data were available for 42 adolescents. Change in weight was determined by BMI expressed as a percentage of the 95th percentile (BMI95). The study physician collected socioeconomic data at baseline. Physical activity and screen time, and psychological dimensions of eating behavior were self-reported using the validated CLASS and EPI-C questionnaires, respectively. Stepwise multiple regressions were conducted to identify models that best predicted change in BMI95 at 12- and 24-months.ResultsMean BMI95 was reduced at 12-months compared with baseline (mean difference [MD] ± SE: -6.9 ± 1.0, P < 0.001) but adolescents had significant re-gain from 12- to 24-months (MD ± SE: 3.7 ± 1.5, P = 0.017). Participants who achieved greater 12-month weight loss had: greater 3-month weight loss, a father with a higher education, lower baseline external eating and parental pressure to eat scores and two parents living at home. Participants who achieved greater 24-month weight loss had: greater 12-month weight loss and a lower baseline emotional eating score.ConclusionsEarly weight loss is consistently identified as a strong predictor of long-term weight loss. This could be because early weight loss identifies those more motivated and engaged individuals. Patients who have baseline factors predictive of long-term weight loss failure may benefit from additional support during the intervention. Additionally, if a patient does not achieve early weight loss, further support or transition to an alternate intervention where they may have increased success may be considered.Trial registrationAustralian New Zealand Clinical Trial Registration Number (ACTRN) 12608000416392 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=83071

Dietary glycemic load, insulin load, and weight loss in obese, insulin resistant adolescents: RESIST study

BACKGROUND & AIMS The optimal dietary approach for weight loss and improving insulin sensitivity in adolescents is unknown. This study aimed to explore the association between the estimated insulin demand of the diet, as measured by glycemic and insulin load, weight loss, percentage body fat and insulin sensitivity index (ISI) in obese adolescents with clinical features of insulin resistance and/or prediabetes after a 3 month lifestyle and metformin intervention. METHODS Secondary data analysis of 91 adolescents (median age 12.7 years (range 10.1-17.4) participating in a randomized controlled trial, known as RESIST; ACTRN12608000416392. Weight change between baseline and 3 months was measured by BMI expressed as percentage of the 95th centile (BMI %95). Body composition was measured by dual energy X-ray absorptiometry and ISI was determined by an oral glucose tolerance test. RESULTS Higher dietary glycemic load and insulin load were associated with less weight loss (BMI %95), adjusted for sex and pubertal stage, β = 0.0466, P = 0.007 and β = 0.0124, P = 0.040, respectively. Inclusion of total energy intake in the model explained observed associations between dietary glycemic load and insulin load and change in BMI %95. Neither dietary glycemic load nor insulin load were associated with changes in percentage body fat or ISI. Dietary glycemic index and macronutrient content (% of total energy) were not associated to changes in BMI %95, percentage body fat or ISI. CONCLUSION Reduced energy diet contributes to weight loss in obese, insulin resistant adolescents. Diets with a lower insulin demand were associated with a lower energy intake and may hence assist with weight loss.

Vitamin B12 in Obese Adolescents with Clinical Features of Insulin Resistance

Emerging evidence indicates an association between obesity, metformin use and reduced vitamin B12 status, which can have serious hematologic, neurologic and psychiatric consequences. This study aimed to examine B12 status in obese adolescents with pre-diabetes and/or clinical features of insulin resistance. Serum B12 was measured using chemiluminescence immunoassay in 103 (43 male, 60 female) obese (mean body mass index (BMI) z-score ± SD (2.36 ± 0.29)), adolescents aged 10 to 17 years, median (range) insulin sensitivity index of 1.27 (0.27 to 3.38) and 13.6% had pre-diabetes. Low B12 (<148 pmol/L) was identified in eight (7.8%) and borderline status (148 to 221 pmol/L) in an additional 25 (24.3%) adolescents. Adolescents with borderline B12 concentrations had higher BMI z-scores compared to those with normal concentrations (2.50 ± 0.22 vs. 2.32 ± 0.30, p = 0.008) or those with low B12 concentration (2.50 ± 0.22 vs. 2.27 ± 0.226, p = 0.041). In conclusion, nearly a third of obese adolescents with clinical insulin resistance had a low or borderline serum B12 status. Therefore, further investigations are warranted to explore the cause and the impact of low B12 status in obese pediatric populations.

Effect of fat loss on arterial elasticity in obese adolescents with clinical insulin resistance: RESIST study

CONTEXT Reduced arterial elasticity contributes to an obesity-related increase in cardiovascular risk in adults. OBJECTIVE To evaluate the effect of fat loss on arterial elasticity in obese adolescents at risk of type 2 diabetes. DESIGN A secondary data analysis of the RESIST study was performed in two hospitals in Sydney, Australia. PARTICIPANTS The study included 56 subjects (ages, 10 to 17 y; 25 males) with prediabetes and/or clinical features of insulin resistance. INTERVENTION A 12-month lifestyle plus metformin intervention. OUTCOMES Arterial elasticity and systemic vascular resistance were measured using radial tonometry pulse contour analysis, percentage body fat (%BF) was measured by dual-energy x-ray absorptiometry, and insulin sensitivity index was derived from an oral glucose tolerance test and lipids. RESULTS Adolescents (n = 31) with decreased %BF (mean change [range], -4.4% [-18.3 to -0.01%]) after the intervention had significant increases in the mean large arterial elasticity index (mean change [95%CI], 5.1 [1.9 to 8.2] mL/mm Hg * 10; P = .003) and insulin sensitivity index (0.5 [0.1 to 0.9]; P = .010) and a decrease in systemic vascular resistance (-82 [-129 to -35] dyne * s * cm(-5); P = .001). There were no significant changes in these parameters in adolescents who increased their %BF. Nor was there any significant change in the mean small arterial elasticity index in either group. CONCLUSION Long-term follow-up of these adolescents is warranted to assess whether the observed changes in vascular elasticity will lead to a clinical benefit including reduced cardiovascular morbidity and mortality.

Sustained improvements in fitness and exercise tolerance in obese adolescents after a 12 week exercise intervention

A 12 week exercise program was evaluated for its effect on aerobic fitness, anaerobic threshold, physical activity and sedentary behavior levels in obese insulin resistant adolescents post intervention and at follow up. 111 obese insulin resistant 10-17 year olds were recruited to a 12 month lifestyle intervention, known as RESIST. From months 4 to 6, adolescents participated in supervised exercise sessions twice per week (45-60min/session). Aerobic fitness and anaerobic threshold were measured by gas analysis at baseline, 6 months (post intervention) and 12 months (follow up). Self-reported physical activity and sedentary behavior was measured using the CLASS questionnaire. At 6 months aerobic fitness and time to reach the anaerobic threshold had improved by 5.8% [95% CI: 0.8-11.3] and 19.7% [95% CI: 10.4-29.0], respectively compared with baseline. These improvements were maintained at 12 months. Compared to baseline, 6 month physical activity levels increased by 19min/day [95% CI: 5-33] and screen time decreased by 49min/day [95% CI: 23-74] but returned to baseline levels by 12 months. Improved fitness and anaerobic threshold can be sustained up to 6 months following completion of an exercise program possibly enhancing capacity to perform daily functional tasks.

Nutritional adequacy of diets for adolescents with overweight and obesity: considerations for dietetic practice

Background/Objectives:Adolescents have unique nutrient requirements due to rapid growth and development. High rates of obesity in adolescents require a variety of diet interventions to achieve weight loss under clinical supervision. The aim of this study is to examine the nutritional adequacy of energy-restricted diets for adolescents.Subjects/Methods:Three popular diets were modelled for 7 days and assessed by comparing the nutrient profile to the Australian Nutrient Reference Values. Three diets were: (1) a standard energy restricted diet based on current dietary guidelines; (2) a modified carbohydrate diet; and (3) a modified alternate day fasting diet.Results:Initial modelling revealed limiting nutrients (that is, not meeting the recommended intakes) across the diets. Subsequent modelling was required to achieve nutritional adequacy for all three diets. The dietary guidelines diet design met most nutrient targets except essential fatty acids before subsequent modelling, however this diet also provided the highest energy (8.8 vs 8.0 MJ and 6.8 MJ for the modified carbohydrate and modified alternate day fasting diet, respectively).Conclusions:Energy-restricted diets need careful consideration to meet nutritional requirements of adolescents. A variety of eating patterns can be adapted to achieve nutritional adequacy and energy restriction, however health practitioners need to consider adequacy when prescribing diet interventions for weight loss during adolescence.