Effects of a high-protein intake on metabolic targets for weight loss in children with obesity: a randomized trial.

OBJECTIVE: The objective of this research is to study effects of a 4-week high-protein (HP) diet on energy intake, resting energy expenditure (REE), protein turnover and body composition in children with obesity. METHODS: In this randomized placebo-controlled single-blind crossover study, children with obesity (n = 14; mean age: 10.1 years ± 1.2 standard deviation; body mass index-standard deviation score [BMI-SDS]: 2.8 ± 0.5) received an ad libitum HP (+50 g protein per day) or normal-protein (NP) diet for 4 weeks with a washout period of ≥2 weeks. Energy intake, REE, protein turnover, weight, BMI-SDS and body composition were measured. RESULTS: No differences were found in energy intake or REE between HP and NP. There was an increased urea production and phenylalanine hydroxylation after HP compared with NP (p < 0.05). There was an increased rise in fat-free mass after HP compared with NP (∆HP: 0.8 ± 0.8 kg vs. ∆NP: 0.1 ± 0.6 kg, p < 0.05). BMI and BMI-SDS increased during the study (BMI-SDS start: 2.8 ± 0.5, end: 2.9 ± 0.5, p < 0.05) without a difference between groups. CONCLUSIONS: A 4-week HP diet with ad libitum food intake did not affect energy intake and energy expenditure in children with obesity. BMI increased, although that could be partly explained by an increase in fat-free mass.

The effects of protein ingestion on GH concentrations in visceral obesity.

Growth hormone (GH), a hormone originating from the anterior pituitary gland, is an important regulator of metabolism and body composition. Low GH secretion is associated with features of the metabolic syndrome, in particular increased visceral body fat and decreased lean body mass. It has been shown that GH release can be promoted by ingestion of protein, in particular gelatin protein. The question remains; is the GH-promoting effect of gelatin protein also present in a population with blunted GH response, such as visceral obesity? 8 lean women (age: 23+/-3 years, BMI: 21.6+/-2.0 kg/m (2)) and 8 visceral obese women (age: 28+/-7 years, BMI: 33.8+/-5.5 kg/m (2)) were compared with regard to their 5-h GH response after oral ingestion of gelatin protein (0.6 g protein per kg bodyweight), placebo (water), or injection of growth hormone releasing hormone (GHRH) (1 mu/kg body weight), in a randomized crossover design. GH response after placebo, gelatin protein, or GHRH was higher in lean subjects than in visceral obese subjects (p<0.05). Ingestion of gelatin protein increased GH response compared with placebo in both visceral obese (182.1+/-81.6 microg/l.5 h vs. 28.4+/-29.8 microg/l.5 h) and lean (631.7+/-144.2 microg/l.5 h vs. 241.0+/-196.8 microg/l.5 h) subjects (p<0.05). GH response after ingestion of gelatin protein in visceral obese did not differ from that in lean, placebo-treated subjects (p=0.45). GH concentrations after GHRH injection correlated significantly with GH concentrations after gelatin ingestion (AUC; r=0.71, p<0.01, Peak; r=0.81, p<0.01). Further research is needed to investigate if gelatin protein is able to improve metabolic abnormalities in hyposomatotropism in the long term or to investigate the relevance of protein as diagnostic tool in hyposomatotropism.

The effects of dietary protein on the somatotropic axis: a comparison of soy, gelatin, alpha-lactalbumin and milk.

BACKGROUND/OBJECTIVES: Growth hormone (GH) is an important regulator of growth and body composition. It has been shown that GH release can be promoted by administration of various amino acids (AAs), such as arginine and lysine, that are present in soy protein. We previously showed that oral ingestion of soy protein stimulates the GH release, it is not known however to which extent other proteins stimulate the GH secretion. SUBJECTS/METHODS: Ingestion of soy protein (soy), gelatin protein (gelatin), alpha-lactalbumin protein (alpha-lactalbumin) and milk protein (milk) were compared on their GH-stimulating capacity. After oral ingestion of protein (0.6 g protein per kg bodyweight), blood was sampled every 20 min for 5 h to analyze GH, AA, insulin and glucose concentrations. The study was performed in eight healthy women (aged 19-26 years; body mass index 19-26 kg/m(2)) in a randomized, single blind, placebo-controlled crossover design. RESULTS: GH responses were more increased after ingestion of gelatine (8.2+/-1.1 microg/l) compared with ingestion of soy, alpha-lactalbumin and milk (5.0+/-0.8, 4.5+/-0.6 and 6.4+/-1.0 microg/l, respectively) (P<0.05). After ingestion of each protein, GH responses were higher compared with placebo ingestion (P<0.05). Simultaneously ingestion of gelatin resulted in the highest serum-arginine concentrations (ARG) compared with after ingestion of the other proteins (P<0.05). Insulin as well as glucose concentrations were not different after ingestion of the various proteins (P<0.05). CONCLUSIONS: The GH-promoting activity of protein depends on the protein source, in that, gelatin protein is the most potent GH stimulator. Arginine may be the responsible AA in the GH-promoting effect of gelatin, although each protein may have its own specific AA-spectrum involved in the stimulation of the somatotropic axis.

SNP analyses of postprandial responses in (an)orexigenic hormones and feelings of hunger reveal long-term physiological adaptations to facilitate homeostasis.

BACKGROUND: The postprandial responses in (an)orexigenic hormones and feelings of hunger are characterized by large inter-individual differences. Food intake regulation was shown earlier to be partly under genetic control. OBJECTIVE: This study aimed to determine whether the postprandial responses in (an)orexigenic hormones and parameters of food intake regulation are associated with single nucleotide polymorphisms (SNPs) in genes encoding for satiety hormones and their receptors. DESIGN: Peptide YY (PYY), glucagon-like peptide 1 and ghrelin levels, as well as feelings of hunger and satiety, were determined pre- and postprandially in 62 women and 41 men (age 31+/-14 years; body mass index 25.0+/-3.1 kg/m(2)). Dietary restraint, disinhibition and perceived hunger were determined using the three-factor eating questionnaire. SNPs were determined in the GHRL, GHSR, LEP, LEPR, PYY, NPY, NPY2R and CART genes. RESULTS: The postprandial response in plasma ghrelin levels was associated with SNPs in PYY (215G>C, P<0.01) and LEPR (326A>G and 688A>G, P<0.01), and in plasma PYY levels with SNPs in GHRL (-501A>C, P<0.05) and GHSR (477G>A, P<0.05). The postprandial response in feelings of hunger was characterized by an SNP-SNP interaction involving SNPs in LEPR and NPY2R (668A>G and 585T>C, P<0.05). Dietary restraint and disinhibition were associated with an SNP in GHSR (477G>A, P<0.05), and perceived hunger with SNPs in GHSR and NPY (477G>A and 204T>C, P<0.05). CONCLUSIONS: Part of the inter-individual variability in postprandial responses in (an)orexigenic hormones can be explained by genetic variation. These postprandial responses represent either long-term physiological adaptations to facilitate homeostasis or reinforce direct genetic effects.