Halim Moore

Background While weight loss often triggers adaptations to prevent further weight loss, these remain understudied and under-considered in the context of pediatric obesity. This systematic review and meta-analysis is the first to provide a comprehensive synthesis of the available evidence regarding the adaptations of the components of total energy expenditure (EE) in response to weight loss in children and adolescents with overweight/obesity (OW/OB), considering the intervention types (e.g., dietary, multidisciplinary, pharmacotherapy, bariatric surgery, or physical activity-based). Methods Articles reporting on weight loss interventions of any type that included an assessment of EE based on indirect calorimetry were identified through a search of MEDLINE, EMBASE, and COCHRANE databases up to September 2024. Results Of the initial 1723 references found, 31 were included, representing 53 intervention arms. The meta-analysis revealed a small but non-significant decrease in resting EE (REE) after weight loss (Mean Change (MC) = −130.91 [−492.67, 230.86] kJ, p = 0.467), regardless of the intervention type. However, the systematic review suggests that the degree of weight loss and multidisciplinary studies (particularly those involving caloric restriction) appear to result in a greater decrease in REE, especially in girls, and during short-term interventions. REE relative to fat-free mass (FFM) (MC = −0.95 [−6.11, 4.21] kJ.kg⁻¹, p = 0.700) and physical activity-induced EE (PAEE) (MC = 45.47 [−22.93, 113.87] kJ, p = 0.155) were not meaningfully altered. The heterogeneity of the proposed intervention duration and the high inter-individual variability in body weight and composition changes could have contributed to these modifications. Conclusion The present results highlight the need for further well-controlled and designed studies, especially when it comes to the thermic effect of food, and the need to consider the patients’ individual profiles and responses to interventions.

Background: Low‐carbohydrate (CHO) or ketogenic diets have been proposed as alternative interventions to caloric restriction to address the childhood obesity epidemic. However, empirical support for this dietary strategy has remained inconclusive in youth. The objective was to test the hypothesis that consumption of a meal lower in the proportion of CHO relative to fat acutely elicits greater satiety, and lower preference for sweet and high‐fat foods and energy intake at the subsequent meal in adolescents with obesity. Methods: In a randomised crossover trial, 15 adolescents with obesity (7 females; 13.2 ± 1.8 years) consumed 3 isocaloric lunch meals on 3 different occasions: (i) moderate (52%), (ii) low (24%) or (iii) very low (7%) in CHO with commensurately adjusted fat content and matched for protein. Adolescents rated their appetite sensations at regular intervals throughout each test day (visual analogue scales). Food reward was recorded before and after the lunch meal, and prior to an ad libitum dinner (French version of the Leeds Food Preference Questionnaire [LFPQ‐fr]), from which energy and macronutrient intake was quantified. Results: No significant differences in energy or macronutrient intake at dinner or daily appetite sensations were found between conditions. Similarly, the proportions of CHO and fat had no effect on liking or wanting for high‐fat or sweet foods. Rather, choice frequency for sweet foods appeared to increase after consumption of each meal ( p = 0.048). Conclusion: In the context of isocaloric meals, lowering the CHO content with a commensurate increase in fat, does not significantly alter satiety, food reward or subsequent energy intake during a test meal in adolescents with obesity.

Summary: Background: A predisposition to elevated food reward may hinder weight loss success during multidisciplinary interventions. However, this has not been consistently demonstrated in adults, nor at all in children.Objective: To test the associations between explicit and implicit food reward and preference at baseline and prospective changes in weight and body composition in adolescents with obesity.Methods: A meta‐analysis of 6 clinical trials in adolescents with obesity was undertaken using frequentist and Bayesian linear mixed models. Participants from each study took part in similar 12‐week multidisciplinary interventions. Liking and wanting for foods varying in fat content and sweet taste were assessed at enrolment, and both anthropometrics were tracked from enrolment to post‐intervention.Results: In a grand sample of N = 132 adolescents with obesity, liking and wanting for high‐fat foods did not significantly predict changes in weight or fat mass. However, implicit wanting for sweet foods predicted changes in standardised body and lean mass, such that a greater wanting for sweet foods was associated with greater loss of body (p = 0.039, η²p = 0.05) and lean mass (p < 0.001, η²p = 0.13) in both frequentist and Bayesian analyses.Conclusions: Baseline implicit wanting for sweet (high carbohydrate, low protein), but not energy‐dense, foods may be more strongly related to prospective changes in lean mass than fat mass during weight loss in adolescents with obesity. Further research is needed to clarify whether low protein intake can account for this effect.

Context: Although low-carbohydrate (LC) diets have been shown to be beneficial for weight loss and improvements in cardiometabolic health in adults with obesity, their efficacy in youth has not yet been established. Objectives: A systematic review and meta-analysis was conducted to qualitatively and quantitively synthesize the evidence from clinical trials testing the efficacy of LC diets to improve anthropometric and cardiometabolic-related parameters in children and adolescents with obesity. Data Sources: Searches in Medline, EMBASE, and Cochrane databases were undertaken for LC interventions with or without control comparisons. Data Extraction and Analysis: Data before and after the LC intervention and control comparisons (if applicable) were extracted from 19 studies, 17 of which were pooled in random-effects meta-analyses. Results: Children on LC diets (Mean = 30 [IQR: 30-60] g/d), for approximately 3 months (IQR: 3-4 months) significantly reduced their weight (mean change [MC] = -7.09 [95% CI: -9.60, -4.58] kg; P < .001), body mass index (BMI) (MC = -3.01 [-3.71, -2.30] kg/m2; P < .001), and BMI z-score (MC = -0.27 [-0.48, -0.06]; P = .020), on average, with concomitant improvements in different metabolic biomarkers, such as serum triglycerides (MC = -29.16 [-45.06, -13.26] mg/dL; P = .002) and insulin (MC = -7.13 [-9.27, -4.99] µU/mL; P < .001). Evidence from 5 out of 7 controlled trials suggests that LC diets without caloric restriction may lead to similar or greater improvements in anthropometric and lipid-related outcomes relative to caloric-restricted or low-fat diets. However, meta-analyses demonstrated high between-study heterogeneity, indicative of a wide variety of methodologies, including intervention duration and degree of carbohydrate restriction. Conclusion: Overall, this review found that short-term LC diets can be beneficial for weight loss and improving cardiometabolic parameters with or without calorie restriction. However, the limited number of controlled trials and the demonstrable diversity in methods prevent firm conclusions regarding their efficacy relative to traditional approaches, such as energy restriction. Systematic Review Registration: PROSPERO registration no. CRD42023440835.

Background: Active breaks and very low- to low-intensity exercises such as walking or cycling at an active desk have been shown to significantly counteract the negative effect of prolonged sedentary behaviors. The objective was to investigate the effect of physical activity level (PAL) on changes in energy expenditure (EE), heart rate, and substrate oxidation from sit-to-stand and sit-to-light cycling. Methods: Fifty healthy young males and females (age: 23.9 [3.9] y, body mass index: 22.9 [2.3] kg/m²) were submitted to a fixed 1 hour session of different posture allocations: 15-minute sitting, 15-minute standing, 15-minute sitting, and 15-minute very low-intensity cycling. EE, substrate oxidation rates, and heart rate were continuously assessed throughout the experimental visit. Data were then compared between participants according to their PAL in tertiles (low, medium, or high). The high-PAL group showed lower sedentary time (P < .0001) and higher time spent in low (P < .0001), moderate (P < .0001), and vigorous physical activity (P = .0034). Results: ANOVA’s analysis showed that EE significantly increased when standing (+11%) and cycling (+94%) relative to the seated position (P < .05) without any differences between groups. There was also a significant increase in heart rate during standing and cycling compared with sitting (P < .05) without any differences between groups. Relative EE (in kilocalories per minute per kilogram) was significantly higher when seated (P < .05) independent of PAL but marginally higher in the high-PAL group when standing relative to the medium-PAL group (P = .06). Conclusion: The findings of this study suggest that people’s PAL does not impact energetic and metabolic adaptations during sit-to-stand and sit-to-very-light-intensity cycling exercise.

Background The implication of body composition and energy metabolism in the control of human energy intake (EI) has been well described in adults, remaining however unexplored in adolescents with obesity. The aim of this study was to question the role of body composition, energy expenditure (EE) and substrate metabolism in the control of EI of adolescents with obesity. Methods Ad libitum 24-h EI, body composition (Dual X-ray absorptiometry), Resting Metabolic Rate (RMR, indirect calorimeter) where measured and Total EE obtained during a 36-h stay in metabolic chambers in 26 adolescents (14.1 ± 1.5 years; 14 girls) with severe obesity. Results The mean body weight and Body Mass index were 92.2 ± 17.2 kg and 33.98 ± 4.14 kg.m^-2 respectively. 24-h EI was positively correlated with body weight (rho = 0.597, p = 0.014), Fat Free Mass (FFM) kg (rho = 0.576, p = 0.019), 24-h Total EE (TEE (rho =0.675, p < 0.001)), RMR (rho =0.632, p = 0.005), 24-h Carbohydrate (CHO) oxidation rates (rho = 0.716, p < 0.001), and urinary nitrogen excretion (rho =0.28, p < 0.001). According to the path analysis FFM (kg) but not Fat Mass (FM) (kg) was positively correlated with RMR, with direct effects of 0.87 (p < 0.001) and 0.027 (p = 0.74) respectively. The effect of FFM on 24-h EI was mediated by RMR (96% of the effect), while the effect of FM on 24-h EI was also mediated by RMR (67% of the effect). Conclusions The present study provides the first evidence regarding the role of RMR as a main tonic signal of appetite control mediating the effect of body composition and mainly FFM (over FM) on daily EI in adolescents with obesity. It also suggests for the first-time relationships between 24-h CHO and protein oxidation and daily EI in this population.

Background: It is essential to better characterize the energetic profile of individuals during very low-intensity physical activity. The objectives of the present study were to determine whether the saver profile from sit-to-stand persists during light physical activity and characterize patterns in substrate utilization from sit-to-stand and during very low-intensity physical activity in healthy men and women. Methods: Sixty-two healthy adults (38 women) performed an experimental sequence that corresponded to 15-minute sitting (SIT1), followed by 15-minute standing (STAND), 15-minute sitting again (SIT2), and finally 15 minutes of light cycling. Continuous indirect calorimetry was allowed to calculate energy expenditure (EE) and respiratory quotient through the entire sequence. Savers and nonsavers (Results: There was an interaction effect in EE between savers and nonsavers through the whole sequence (P = .008). Only nonsavers (71%) exhibited a significant increase in EE from SIT1 to STAND (P < .001). Nonsavers and savers significantly increased EE during 15 minutes of light cycling relative to sitting or standing (P < .001), without any difference between groups. The percentage of change in respiratory quotient from SIT1 to STAND was significantly different between the 2 groups, with increased values in savers and decreased values in nonsavers (P = .03). Significantly lower values in respiratory quotient and EE were found during 15 minutes of light cycling in women compared with men (P < .001). Conclusions: It is essential to determine individuals’ energetic phenotype to determine those who may benefit more from strategies such as standing or light physical activity. The sexual dimorphism in terms of substrate use during such exercise should be considered.

Summary: This systematic review and meta‐analysis synthesized evidence pertaining to consummatory and appetitive responses to acute exercise in children and adolescents with and without obesity (5–18 years). Articles reporting on supervised, controlled trials of any modality, duration, or intensity with laboratory‐measured food intake were found using MEDLINE, EMBASE, and Cochrane up to July 2023. Differences between conditions in laboratory energy and macronutrient intake, appetite sensations, and food reward were quantitatively synthesized using random‐effects meta‐analyses. Thirty‐five studies were eligible for the systematic review of energy intake, consisting of 60 distinct intervention arms with lean ( n = 374) and overweight/obesity participants ( n = 325; k = 51 eligible for meta‐analysis). Study quality as indicated by the Effective Public Healthy Practice Project tool was rated as low and moderate risk of bias for 80% and 20% of studies, respectively. Acute exercise had no significant effect on energy intake during an ad libitum test meal (mean difference [MD] = −4.52 [−30.58, 21.54] kcal, p = .729). Whilst absolute carbohydrate intake was lower after exercise (23 arms; MD = −6.08 [−11.26, −0.91] g, p = .023), the proportion of carbohydrate was not (30 arms; MD = −0.62 [−3.36, 2.12] %, p = .647). A small elevation in hunger (27 arms; MD = 4.56 [0.75, 8.37] mm, p = .021) and prospective food consumption (27 arms; PFC; MD = 5.71 [1.62, 9.80] mm, p = .008) was observed post‐exercise, but not immediately prior to the test meal (Interval: Mdn = 30 min, Range = 0–180). Conversely, a modest decrease in explicit wanting for high‐fat foods was evident after exercise (10 arms; MD = −2.22 [−3.96, −0.47] mm, p = .019). Exercise intensity ( p = .033) and duration ( p = .013) moderated food intake only in youth with overweight/obesity, indicating lower intake at high intensity and short duration. Overall, acute exercise does not lead to compensation of energy intake or a meaningful elevation of appetite or food reward and might have a modest benefit in youth with overweight/obesity if sufficiently intense. However, conclusions are limited by substantial methodological heterogeneity and the small number of trials employing high‐intensity exercise, especially in youth with overweight/obesity.