Acute decrease in plasma testosterone and appetite after either glucose or protein beverages in adolescent males.

OBJECTIVE: Chronic testosterone blood concentrations associate with food intake (FI), but acute effects of testosterone on appetite and effect of protein and glucose consumption on testosterone response have had little examination. METHODS: In a randomized, crossover study, twenty-three adolescent (12-18 years old) males were given beverages containing either: (a) whey protein (1 g/kg body weight), (b) glucose (1 g/kg body weight) or (c) a calorie-free control (C). Plasma testosterone, luteinizing hormone (LH), GLP-1 (active), ghrelin (acylated), glucose, insulin and subjective appetite were measured prior (0) and at 20, 35 and 65 minutes after the consumption of the beverage. FI at an ad libitum pizza meal was assessed at 85 minutes. RESULTS: Testosterone decreased acutely to 20 minutes after both protein and glucose with the decrease continuing after protein but not glucose to 65 minutes (P = 0.0382). LH was also decreased by both protein and glucose, but glucose had no effect at 20 minutes in contrast to protein (P < 0.001). Plasma testosterone concentration correlated positively with LH (r = 0.58762, P < 0.0001) and negatively with GLP-1 (r = -0.50656, P = 0.0003). No associations with appetite, ghrelin or glycaemic markers were found. Food intake was not affected by treatments. CONCLUSION: Protein or glucose ingestion results in acute decreases in both plasma testosterone and LH in adolescent males. The physiological significance of this response remains to be determined as no support for testosterone's role in acute regulation of food intake was found.

The role of IL-6 in exercise-induced anorexia in normal-weight boys.

Our previous study showed that interleukin-6 (IL-6) is associated with suppression of appetite after high-intensity exercise (HIEX), but an independent role in food intake (FI) was not defined. We hypothesized that IL-6 suppresses appetite and FI, independently of appetite hormones, after HIEX in normal-weight (NW) boys. We investigated the effect of HIEX, with and without the inflammation inhibitor ibuprofen (IBU), on IL-6, other biomarkers of inflammation and appetite, FI, and ratings of appetite in NW boys. Fifteen NW boys (aged 13-18 years) were randomly assigned in a crossover design to 4 sessions: (i) water and rest, (ii) IBU and rest, (iii) water and HIEX, and (iv) IBU and HIEX. HIEX consisted of three 10-min bouts of exercise at 75% of maximal oxygen uptake with 90 s of active rest between bouts. IBU (300 mg) was given as a liquid suspension. FI, ratings of appetite, and plasma biomarkers of appetite, inflammation, stress, and glucose control were measured. FI was not affected by HIEX or IBU. Appetite increased over time (p = 0.002) but was lower after HIEX (p < 0.001) and not affected by IBU. HIEX, but not IBU, resulted in higher levels of IL-6 (p < 0.001) and cortisol (p < 0.001) and lower active ghrelin (p < 0.001). IL-6 correlated with active ghrelin (r = 0.37; p = 0.036) and cortisol (r = 0.26; p = 0.049). An independent role for IL-6 in appetite suppression was not supported. However, IL-6 was correlated with active ghrelin and cortisol, thus potentially mediating appetite via these interactions.

Decreased Appetite after High-Intensity Exercise Correlates with Increased Plasma Interleukin-6 in Normal-Weight and Overweight/Obese Boys.

Background: High-intensity exercise (HIEX) suppresses appetite in adults and is thought to be mediated by appetite-regulating hormones. However, the effects of HIEX-induced inflammatory and stress biomarkers on appetite control and body weight have not been reported in children or adults. Objective: The objective of this study was to describe the effects of acute HIEX at 70% peak oxygen consumption (VO2peak) on postexercise appetite and selective biomarkers of inflammation, stress, and appetite regulatory hormones in normal-weight (NW) and in overweight/obese boys. Methods: NW (n = 11) and overweight/obese (n = 11) boys aged 10-18 y were randomly assigned in a crossover design to either rest or HIEX. Visual analog scale appetite ratings and plasma biomarkers of appetite, inflammation, stress, and glucose control were measured after HIEX or rest. Results: Appetite increased from baseline to 110 min (P < 0.001), but was lower after HIEX (P = 0.04), with no difference between body weight groups. HIEX also resulted in lower active ghrelin (P < 0.001) and increased interleukin-6 (IL-6; P < 0.001), tumor necrosis factor-α (P < 0.001), and cortisol (P < 0.001) concentrations, independent of body weight. It increased blood glucose (P = 0.002) and insulin (P = 0.028) concentrations in NW but not overweight and obese boys. Leptin, glucagon-like peptide 1, peptide tyrosine tyrosine, C-reactive protein, and cortisol were not affected by HIEX. An inverse correlation was found between IL-6 and appetite (r = -0.379; P = 0.012), but not any other biomarkers. Conclusions: HIEX resulted in reduced appetite that correlated with an increase in IL-6 in both NW and overweight/obese boys. However, although a role for IL-6 in the response can be suggested, the suppression of appetite was potentially mediated by the decrease in active ghrelin and/or increase in cortisol. This trial was registered at clinicaltrials.gov as NCT02619461.

Physiology of Food Intake Control in Children.

The purpose of this review is to draw attention to the limited information available on food intake (FI) control in children and adolescents 7-17 y of age, which is essential for developing food policies and guidelines in this population. Although environmental factors have been the overwhelming focus of research on the causative factors of obesity, research focusing on the physiologic control of appetite in children and adolescents is a neglected area of research. To present this message, a review of FI regulation and the role of food and food components in signaling processes are followed by an examination of the role of hormones during puberty in intake regulation. To examine the interaction of environment and physiology on FI regulation, the effects of exercise, television programs, and food advertisements are discussed. In conclusion, although limited, this literature review supports a need for children and adolescents to be a greater focus of research that would lead to sound nutrition policies and actions to reduce chronic disease. A focus on the environment must be balanced with an understanding of physiologic and behavioral changes associated with this age group.

Acute changes in substrate oxidation do not affect short-term food intake in healthy boys and men.

The acute relationship between substrate oxidation as measured by respiratory exchange ratio (RER) and food intake (FI) has not been defined. The purpose of the study was to determine acute relationships between RER, modified by exercise and a glucose load, and FI and net energy balance (NEB) in physically active normal-weight boys and men. In a crossover design, 15 boys (aged 9-12 years) and 15 men (aged 20-30 years) were randomly assigned to 4 conditions: (i) water and rest, (ii) glucose-drink and rest, (iii) water and exercise, and (iv) glucose-drink and exercise. Indirect calorimetry was used to determine RER, energy expenditure, and carbohydrate and fat oxidation. Subjective appetite and blood glucose were also measured. RER was higher after glucose (0.91 ± 0.01) compared with water (0.87 ± 0.01) (p < 0.0001), and after exercise (0.91 ± 0.01) compared with rest (0.88 ± 0.01) (p = 0.0043) in men (0.91 ± 0.01) compared with boys (0.88 ± 0.01) (p = 0.0002). FI (kcal·m(-2)) did not differ between boys and men. Glucose (582 ± 24 kcal·m(-2)) reduced FI compared with water (689 ± 25 kcal·m(-2)) (p < 0.0001), and further decreased FI when combined with exercise (554 ± 34 kcal·m(-2)) (p = 0.0303). NEB was reduced with exercise (573 ± 25 kcal·m(-2)) compared with the sedentary condition (686 ± 24 kcal·m(-2)) (p < 0.0001), but was higher after the glucose drink (654 ± 27 kcal·m(-2)) compared with water (605 ± 25 kcal·m(-2)) (p = 0.0267). No correlations were found between RER and FI or NEB in boys and men, except in the control condition of resting with water. In conclusion, the short-term modification of substrate oxidation by glucose and/or exercise in normal weight and active boys and men did not affect FI and NEB.