Whey protein (WP) has been heavily appreciated as a rich source of bioactive peptides, with potential benefits for cardiovascular health. This study constitutes a systematic review and meta-analysis summarising the effects of WP consumption on vascular reactivity, arterial stiffness and circulatory biomarkers of vascular function. We searched electronic databases, including PubMed, SCOPUS and Web of science for relevant articles from inception to July 2020. Original clinical trials published in English-language journals that investigated the effects of WP on vascular function were eligible. A total of 720 records were identified in the initial search; from these, sixteen were included in our systematic review and thirteen in meta-analysis. The pooled analysis of six studies showed a significant increase in flow-mediated dilation (FMD) after WP consumption (weighted mean differences (WMD): 1·09 %, 95 % CI: 0·17, 2·01, P= 0·01). Meta-analysis of available data did not show any significant reduction in arterial stiffness measures including augmentation index (effect sizes: 7, WMD: −0·29 %, 95 % CI: −1·58, 0·98, P= 0·64) and pulse wave velocity (effect sizes: 4, WMD: −0·72 m/s, 95 % CI: −1·47, 0·03, P= 0·06). Moreover, the pooled analysis of six effect sizes showed no significant effects on plasma levels of nitric oxide following WP supplementation (WMD: 0·42 μmol/l, 95 % CI: −0·52, 1·36, P= 0·38). The overall results provided evidence supporting a protective effect of WP on endothelial function measured by FMD, but not for arterial stiffness measures and circulatory biomarker of vascular function. Further research is required to substantiate the benefits of WP on vascular function.

Protein quality has an important role in increasing satiety. Evidence suggests that whey protein (WP) provides satiety via gastrointestinal hormone secretion. Hydrolysed collagen supplementation can also stimulate the production of incretins and influence satiety and food intake. Thus, we sought to compare the effect of acute supplementation of WP or hydrolysed collagen on post-intervention appetite and energy consumption. This was a randomised, double-blind, crossover pilot study with ten healthy adult women (22·4 years/old) who were submitted to acute intake (single dose) of a beverage containing WP (40 g of concentrated WP) or hydrolysed collagen (40 g). Subjective appetite ratings (feelings of hunger, desire to eat and full stomach) were measured using the Visual Analog Scale (VAS), energy intake was quantified by ad libitum cheese bread consumption 2 hours after supplementation and blood was collected for leptin and glucose determination. There was no difference between treatment groups in the perception of hunger (P = 0·983), desire to eat (P = 0·326), full stomach feeling (P = 0·567) or food consumption (P = 0·168). Leptin concentrations at 60 min post supplementation were higher when subjects received hydrolysed collagen (P = 0·006). Acute supplementation with hydrolysed collagen increased leptin levels in comparison with WP, but had no effect on appetite measured by feelings of hunger, desire to eat, full stomach feeling (VAS) or energy consumption.

Postprandial hyperglycaemia is recognised as an important target in type 2 diabetes management. Dietary pattern, meal composition, and amount of food intake are major factors for maintaining postprandial blood glucose levels. The aim of this study was to investigate the effect of consuming a whey protein-based multi-ingredient nutritional drink (WD) on postprandial glycaemic, insulinaemic, and active glucagon-like peptide-1 (GLP-1) responses in comparison to a typical breakfast, which is boiled white rice with chicken (BC) in patients with type 2 diabetes mellitus (T2DM). Fifteen subjects with T2DM participated in a randomised, controlled, cross-over study. Two isocaloric diets with similar nutrient composition were randomly tested with at least 7 d in between. Glucose, insulin, and active GLP-1 were measured by standard methods with blood samples collected with a venous catheter for 240 min during a kinetic test. The incremental area under the curve (iAUC0–240 min) for plasma glucose was significantly lower after the consumption of WD (WD: 3551 ± 546; BC: 9610 ± 848 mg min/dl; P < 0⋅01), while insulinaemic response tended to be lesser (iAUC0–240 min) than those of BC. In addition, higher iAUC0–240 min for active GLP-1 was obtained with WD diet (WD: 2230 ± 441; BC: 925 ± 183 pM min/ml; P < 0⋅01). This study showed that WD can be used to replace a regular breakfast for improving postprandial glucose response and active GLP-1 levels in people with T2DM. Further studies are required to elucidate the clinical efficacy of WD on long-term glycaemic control in people with T2DM.

Essential amino acids (EAA) promote the process of regulating muscle synthesis. Thus, whey protein that contains higher amounts of EAA can have a considerable effect on modifying muscle synthesis. However, there is insufficient evidence regarding the effect of soya and whey protein supplementation on body composition. Thus, we sought to perform a meta-analysis of published randomised clinical trials that examined the effect of whey protein supplementation and soya protein supplementation on body composition (lean body mass, fat mass, body mass and body fat percentage) in adults. We searched PubMed, Scopus and Google Scholar, up to August 2020, for all relevant published articles assessing soya protein supplementation and whey protein supplementation on body composition parameters. We included all randomised clinical trials that investigated the effect of whey protein supplementation and soya protein supplementation on body composition in adults. Pooled means and standard deviations were calculated using random effects models. Subgroup analysis was applied to discern possible sources of heterogeneity. After excluding non-relevant articles, ten studies, with 596 participants, remained in this study. We found a significant increase in lean body mass after whey protein supplementation (weighted mean difference (WMD: 0·91; 95 % CI 0·15, 1·67; P = 0·019). We observed no significant change between whey protein supplementation and body mass, fat mass and body fat percentage. We found no significant change between soya protein supplementation and body composition parameters. Whey protein supplementation significantly improved body composition via increases in lean body mass, without influencing fat mass, body mass and body fat percentage.

This work aimed to evaluate the effects of whey protein concentrate (WPC) admixtured of curcumin on metabolic control, inflammation and oxidative stress in Wistar rats submitted to exhaustive exercise. A total of forty-eight male rats were divided into six experimental groups (n 8): standard diet group (AIN-93M), standard diet submitted to exhaustion test group (AIN-93M ET), WPC admixtured of curcumin group (WPC + CCM), WPC + CCM submitted to exhaustion test group (WPC + CCM ET), CCM group and CCM subjected to exhaustion test group (CCM ET). The swimming exhaustion test was performed after 4 weeks of experiment. The consumption of WPC + CCM as well as isolated CCM did not alter the biometric measurements, the animals’ food consumption and the hepatic and kidney function, as well as the protein balance of the animals (P > 0·05), but reduced the glycaemia and the gene expression of TNF-α and IL-6 and increased the expression of IL-10 (P < 0·05). The animals that were submitted to the exhaustion test (AIN-93M ET) showed higher aspartate aminotransferase values when compared to the animals that did not perform the exercise (AIN-93 M) (P < 0·05). WPC + CCM reduced the concentration of nitric oxide, carbonylated protein and increased the concentration of catalase (P < 0·05). Both (WPC + CCM and CCM) were able to increase the concentrations of superoxide dismutase (P < 0·05). We concluded that the WPC admixtured of CCM represents a strategy capable of decreasing blood glucose and oxidative and inflammatory damage caused by exhaustive physical exercise in swimming.

This research communication relates to the hypothesis that the consumption of raw or unprocessed cow's milk contributes to lowered prevalence of allergies. Thermal pasteurization of bovine milk can result in denaturation of minor whey proteins and loss of their bioactivity. Denaturation of bovine serum albumin (BSA), immunoglobulin G (IgG) and lactoferrin (LF) in skim milk was studied under different temperature (72, 75 or 78°C) and time (0–300 s) combinations. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) results revealed that denaturation of all 3 proteins occurred at 72°C and progressed with increase in temperature and holding time. About 59% of LF and 12% of IgG denatured under high-temperature short-time (72°C/ 15 s) pasteurization, while BSA was least impacted. To assess modulation of milk immunogenicity, secretion of selected T helper (Th)-type cytokines by human peripheral blood mononuclear cells (PBMCs) was studied in vitro in response to different concentrations of BSA (0.4–1.0 mg/ml) and IgG (0.8–1.6 mg/ml) in unheated skim milk. Addition of IgG at 1.6 mg/ml induced a prominent Th1-skewed cytokine profile that may not trigger a Th2-skewed allergic reaction. BSA did not appear to modulate milk immunogenicity to any significant extent.

Casein glycomacropeptide (CGMP) is a bioactive milk-derived peptide with potential anti-inflammatory effects. Animal studies suggest that CGMP may work by altering gut microbiota composition and enhancing butyrate production. Its effects on intestinal homoeostasis, microbiota and metabolites in humans are unknown. The aim of the present study was to assess both the intestinal and systemic immunomodulatory effects of orally ingested CGMP. We hypothesised that daily oral CGMP intake would reduce high-sensitive C-reactive protein (hsCRP) in healthy adults. In a single-centre limited but randomised, double-blinded, reference-controlled study, we compared the effects of a 4-week intervention of either 25 g of oral powder-based chocolate-flavoured CGMP or a reference drink. We included twenty-four healthy adults who all completed the study. CGMP had no systemic or intestinal immunomodulatory effects compared with a reference drink, with regard to either hsCRP or faecal calprotectin level, faecal microbiota composition or faecal SCFA content. CGMP ingestion did not affect satiety or body weight, and it caused no severe adverse events. The palatability of CGMP was acceptable, and adherence was high. CGMP did not induce or change gastrointestinal symptoms. In conclusion, we found no immunomodulatory effects of CGMP in healthy adults. In a minor group of healthy adults, oral ingestion of 25 g of CGMP during 4 weeks was safe, well tolerated, had acceptable palatability and was without any effects on body weight.

Protein supplementation may be beneficial for patients with chronic liver disease (CLD). This study compared the effects of whey protein isolate (WP) and casein (CA) supplementation on nutritional status and immune parameters of CLD patients who were randomly assigned to take 20 g of WP or CA twice per d as a supplement for 15 d. Body composition, muscle functionality and plasmatic immunomarkers were assessed before and after supplementation. Patients were also classified according to the model for end-stage liver disease (MELD) into less (MELD < 15) and more (MELD ≥ 15) severe disease groups. Malnutrition, determined by the Subjective Global Assessment at baseline, was observed in 57·4 % and 54·2 % of patients in the WP and CA groups, respectively (P = 0·649). Protein intake was lower at baseline in the WP group than in the CA group (P = 0·035), with no difference after supplementation (P = 0·410). Both the WP and CA MELD < 15 groups increased protein intake after supplementation according to the intragroup analysis. No differences were observed in body composition, muscle functionality, most plasma cytokines (TNF, IL-6, IL-1β and interferon-γ), immunomodulatory proteins (sTNFR1, sTNFR2, brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor) or immunomodulatory hormones (adiponectin, insulin and leptin) after supplementation in the WP groups at the two assessed moments. WP supplementation increased the levels of interferon-γ-induced protein-10/CXCL10 (P = 0·022), eotaxin-1/CCL11 (P = 0·031) and monocyte chemoattractant protein-1/CCL2 (P = 0·018) and decreased IL-5 (P = 0·027), including among those in the MELD ≥ 15 group, for whom IL-10 was also increased (P = 0·008). Thus, WP consumption by patients with CLD impacted the immunomodulatory responses when compared with CA with no impact on nutritional status.

The effects of dietary fibre (DF) and protein on insulin response, lipidaemia and inflammatory biomarkers were studied in a model experiment with juvenile obese Göttingen minipigs. After 20 weeks feeding on a high-fat fructose-rich low-DF diet, forty-three 30-week-old minipigs (31·3 (sem 4·0) kg body weight) were allocated to low- or high-DF and -protein diets for 8 weeks in a 2 × 2 factorial design. High DF contents decreased (P = 0·006) while high protein increased (P < 0·001) the daily gain. High protein contents increased fasting plasma concentrations of glucose (P = 0·008), NEFA (P = 0·015), ghrelin (P = 0·008) and non-fasting LDL:HDL ratios (P = 0·015). High DF increased ghrelin (P = 0·036) and C-peptide levels (P = 0·011) in the non-fasting state. High protein increased the gene expression of fructose-bisphosphatase 1 in liver tissue (P = 0·043), whereas DF decreased fatty acid synthase expression in adipose tissue (P = 0·035). Interactions between DF and protein level were observed in the expression of leptin receptor in adipose tissue (P = 0·031) and of PPARγ in muscle (P = 0·018) and adipose tissue (P = 0·004). In conclusion, high DF intake reduced weight gain and had potential benefit on β-cell secretory function, but without effect on the lipid profile in this young obese model. High dietary protein by supplementing with whey protein did not improve insulin sensitivity or lipidaemia, and combining high DF with high protein did not alleviate the risk of metabolic abnormalities.

Although glucose is the best-known nutrient to stimulate glucagon-like peptide-1 (GLP-1) secretion, dietary peptides also potently stimulate GLP-1 secretion. Certain peptide fragments derived from dietary proteins possess dipeptidyl peptidase-4 (DPP-4) inhibitory activity in vitro. Hence, we hypothesised that dietary peptides protect GLP-1 from degradation through attenuating DPP-4 activity in vivo. Here, we compared GLP-1 responses with dietary proteins, a carbohydrate and a lipid (Intralipos) in rats having or not having plasma DPP-4 activity. Plasma GLP-1 concentrations clearly increased by oral administration of whey protein (2–4 g/kg), but not by that of dextrin (2–4 g/kg), in control rats (untreated Sprague–Dawley rats and F344/Jcl rats), having DPP-4 activity. In contrast, dextrin administration increased the plasma GLP-1 concentrations as the whey protein administration did, in rats having reduced or no DPP-4 activity (a DPP-4 inhibitor, sitagliptin-treated Sprague–Dawley rats or DPP-4-deficient F344/DuCrl/Crlj rats). DPP-4 inhibition by sitagliptin treatment also enhanced GLP-1 response to Intralipos, and casein, but the treatment did not further enhance GLP-1 response to whey protein. Intestinal GLP-1 content and gastric emptying rate were not associated with differences in GLP-1 responses to test nutrients. The luminal contents from rats administered whey protein decreased DPP-4 activity in vitro. These results suggest that GLP-1 released by dextrin, Intralipos and casein was immediately degraded by DPP-4, while GLP-1 released by whey protein was less degraded. Our study provides novel in vivo evidence supporting the hypothesis that dietary peptides not only stimulate GLP-1 secretion but also inhibit DPP-4 activity to potentiate GLP-1 response.

A feeding trial involving growing piglets was undertaken to establish whether feed supplemented with whey protein concentrate (WPC), exhibiting antioxidant properties, had any effects on welfare and meat quality. For that purpose, 48 weaned piglets (20-days-old) were assigned to two experimental groups receiving standard or experimental diet for 30 days. Blood and tissue collection were performed at various time-points. The following oxidative stress markers were assessed: reduced glutathione (GSH), catalase activity, total antioxidant capacity (TAC), thiobarbituric acid reactive substances (TBARS), protein carbonyls (CARB) and hydrogen peroxide (H2O2) decomposition activity. The effects on bacterial growth and the fatty acid profile of meat were also assessed. Results showed that piglets fed with the WPC-supplemented diet had significantly increased antioxidant mechanisms in almost all tissues tested, as indicated by increases in GSH, H2O2 decomposition activity and TAC compared with the control group. Piglets fed with the experimental diet exhibited decreased oxidative stress-induced damage to lipids and proteins, as shown by decreases in TBARS and CARB in the WPC group compared with the control group. In addition, the experimental diet enhanced growth of facultative probiotic bacteria and lactic acid bacteria and inhibited growth of pathogen populations. In addition, WPC inclusion in piglets' diet increased n-3 fatty acids significantly and decreased n-6/n-3 ratio significantly compared with the control group. The current study showed that WPC inclusion in the diet had a significant effect on welfare and meat quality of growing piglets.

This Research Communication describes the adaptation and testing of an RP-HPLC method, previously tested for the determination of lactoferrin (LF) in whey, for its applicability to determine milk lactoferrin content. Milk samples of various species, namely, ovine, caprine, bovine, donkey and human milk, were tested. The advantage of this RP-HPLC method includes speed and convenience, as it does not include extensive pretreatment or separation steps. A simple pre-treatment step was added in order to remove fat and proteins of the casein family and the samples were tested. The results varied in terms of elution of the LF peak both between the milk of the different species as well as from the initial application on whey. The peak resolution was satisfactory in the cases of ovine, bovine and donkey milk samples while for caprine and human milk an interference with other peaks was observed. Nevertheless, quantification of LF was found possible for all samples. This new application of the modified method will allow the determination of LF in milk samples of the tested species either for everyday analysis or as a useful qualitative screening for presence or absence of LF.

Consuming whey protein before a meal may reduce postprandial glucose excursions, however, optimising timing of supplementation is important to improve its clinical utility. A total of thirteen centrally obese, insulin-resistant males (waist circumference: 121 (sem 3) cm; homeostasis model assessment for insulin resistance (HOMA-IR): 6·4 (sem 1·2)) completed four experimental conditions in a single-blind, crossover design. Participants consumed mixed-macronutrient breakfast and lunch meals on all occasions, with 20 g whey protein consumed 15 min before (PRE), alongside (DUR) or 15 min post-breakfast (POST) or omitted (CON). Capillary glucose and plasma concentrations of insulin, TAG and NEFA, in addition to subjective appetite ratings, were collected for 180 min after each meal. PRE and DUR reduced post-breakfast glucose peak by 17·0 (sem 1·9) % (P<0·001) and 9·2 (sem 2·9) % (P=0·046), respectively, compared with CON. Post-breakfast glucose AUC was lower following PRE compared with POST and CON (PRE: 982 (sem 30) v. POST: 1031 (sem 36) and CON: 1065 (sem 37) mmol/l×180 min; P≤0·042) but similar to DUR (1013 (sem 32) mmol/l×180 min; P=0·77). Insulin was lower during PRE, when compared with POST and DUR (both P≤0·042) but similar to CON. There were no between-condition differences in measures of postprandial lipaemia or appetite, and no effect of condition post-lunch. Consumption of whey protein as a preload or alongside a mixed-macronutrient breakfast reduces postprandial glucose excursions in centrally obese, insulin-resistant males. Whey consumed as a preload has superior glycaemic-lowering effects. Supplementation at breakfast does not alter glycaemic responses to subsequent meals.

Non-fasting TAG – postprandial lipaemia (PPL) – are to a higher degree associated with cardiovascular risk compared with fasting TAG. Dietary protein, especially whey proteins (WP), may lower PPL. We hypothesised that a WP pre-meal (17·6 g protein) consumed 15 v. 30 min before a fat-rich meal reduces the PPL response in subjects with the metabolic syndrome (MetS) and that a WP pre-meal has more potent effects than casein and gluten pre-meals. A total of sixteen subjects with the MetS completed an acute, randomised, crossover trial. WP pre-meals were consumed 15 and 30 min, and casein and gluten 15 min before a fat-rich meal. Blood samples were drawn 360 min postprandially to determine metabolite and hormone responses, S-paracetamol (for assessment of gastric emptying) and amino acids. Insulin and glucagon responses were affected by both timing and protein type (for all P <0·01), with significantly higher concentrations for WP given at –15 min than WP at –30 min and higher responses compared with gluten for the first 30 min after pre-meal consumption (for all P <0·05). The PPL responses changed neither by timing nor by protein type. Glucose-dependent insulinotropic peptide but not glucagon-like peptide 1 responses differed between the three protein types. S-paracetamol concentration was higher for WP (–30 min) than for WP (–15 min) 15 min after the main meal (P = 0·028), and higher for casein and gluten than for WP at time point 30 min (for all P <0·05). In conclusion, the PPL response was not changed by ingestion of a 17·6 g protein pre-meal, whereas both timing and protein quality affected hormone secretion (insulin and glucagon).

Epidemiological studies demonstrate that poor glycaemic control is an independent risk factor for CVD. Postprandial glycaemia has been demonstrated as a better predictor of glycated Hb, the gold standard of glycaemic control, when compared with fasting blood glucose. There is a need for more refined strategies to tightly control postprandial glycaemia, particularly in those with type 2 diabetes, and nutritional strategies around meal consumption may be effective in enhancing subsequent glycaemic control. Whey protein administration around meal times has been demonstrated to reduce postprandial glycaemia, mediated through various mechanisms including an enhancement of insulin secretion. Whey protein ingestion has also been shown to elicit an incretin effect, enhancing the secretion of glucose-dependent insulinotropic peptide and glucagon-like peptide-1, which may also influence appetite regulation. Acute intervention studies have shown some promising results however many have used large dosages (50–55 g) of whey protein alongside high-glycaemic index test meals, such as instant powdered potato mixed with glucose, which does not reflect realistic dietary strategies. Long-term intervention studies using realistic strategies around timing, format and amount of whey protein in relevant population groups are required.

Dietary protein is considered more satiating than carbohydrate, and whey protein is more satiating than other protein sources. The purported satiating effect of whey protein may be due to direct effects of the unique mixture of proteins in whey, due to the effects of peptides released upon digestion and/or its amino acid composition. The objective of the present study was to compare the satiating effects of intact whey protein isolate (WPI) or a free amino acid mixture (AAM) simulating the amino acid composition of the WPI. A single-blind completely randomised block design included twenty, healthy, adult women (age 24·2 (sem 0·8) years) of normal weight (BMI 22·7 (sem 0·4) kg/m2). Following consumption of isoenergetic (approximately 1800 kJ) preload meals enriched (52 g amino acid equivalent) with WPI or AAM, consumption of an ad libitum test meal 120 min later and subjective feelings of appetite using visual analogue scales (VAS) were determined. There were no significant differences (P=0·24) in the ad libitum test meal intakes between the WPI (268·5 (sem 27·3) g) and the AAM (238·4 (sem 22·7) g) preload meals. Subjective VAS ratings of appetite did not differ significantly between the WPI and the AAM preload meals (P>0·05). Intact whey protein and a free AAM simulating the whey protein showed similar effects on satiety. This suggests that the satiating effect of whey protein may be related to its specific amino acid composition.

The aim of this Research Communication was to investigate the changes in physicochemical, colour, apparent viscosity and texture properties in low-fat goat milk yogurts prepared with cupuassu pulp by the addition of inulin (SI), maltodextrin (SM), whey protein (SW) and skim milk powder (SP). Three batches of each cupuassu goat milk yogurt were prepared and analysed on the 1st day of storage by pH, proximate composition, colour, apparent viscosity, and texture. In comparison to yogurts from whole (W) or skimmed milk (S), all of the fat replacers improved the physicochemical properties (P < 0·05). The addition of the carbohydrates (inulin and maltodextrin) and proteins (whey protein and skim milk powder) also influenced the colour of the low-fat cupuassu goat milk yogurt (P < 0·05). All fat replacer treatments (SI, SM, SW and SP) presented a higher (P < 0·05) apparent viscosity than W and S yogurts. However, only the addition of skim milk powder increased the texture parameters (firmness and consistency) (P < 0·05). These results suggest that skim milk powder can be used to improve the texture properties of low-fat cupuassu goat milk. Furthermore, inulin, maltodextrin, and whey protein can potentially be applied in the goat dairy industry to increase the viscosity of yogurts.

Increasing evidence suggests that the source of dietary protein can have an impact on weight gain and fat mass during high-fat feeding in both humans and rodents. The present study examined whether dietary bovine serum albumin (BSA) as the dominant source of protein alters energy balance and adiposity associated with high-fat feeding. C57/BL6J mice were given a diet with 10 % of energy from fat and 20 % of energy from casein or a diet with 45 % of energy from fat and either 20 % of energy from casein (HFD) or BSA (HFD+BSA) for 13 weeks. The HFD+BSA diet did not significantly alter daily energy expenditure, locomotor activity and RER, but did increase cumulative energy intake and percentage of lean mass while reducing feed efficiency and percentage of fat mass when compared with the HFD (P< 0·05). In subcutaneous adipose tissue (SAT), the HFD+BSA diet increased the mRNA levels of PPARα (PPARA), carnitine palmitoyltransferase 1b (CPT1b) and uncoupling protein 3 (UCP3), but reduced the mRNA level of leptin when compared with the HFD (P< 0·05). The SAT mRNA levels of PPARA, CPT1b and UCP3 were negatively correlated (P< 0·05) with SAT mass, which was reduced in HFD+BSA mice compared with HFD controls (P< 0·01). No differences in epididymal fat mass existed between the groups. The HFD+BSA diet normalised plasma leptin and corticosterone levels compared with the HFD (P< 0·05). While differences in leptin levels were associated with the percentage of fat mass (P< 0·01), changes in corticosterone concentrations were independent of the percentage of fat mass (P< 0·05). The data suggest that the HFD+BSA diet influences plasma leptin levels via SAT mass reduction where mRNA levels of genes linked to β-oxidation were increased, whereas differences in plasma corticosterone levels were not related to fat mass reduction.

Digestive kinetics are believed to modulate satiety through the modulation of nutrient delivery. We hypothesised that the duration of satiety could be extended by modulating the kinetics of dietary amino acid delivery in overweight subjects, using snacks containing casein and whey protein. In the present study, eighty-two subjects underwent a first satiety test where they received a control snack containing 60 g maltodextrin. For the next 5 d, the subjects consumed a liquid protein snack containing 30 g carbohydrates and 30 g proteins (casein, whey protein or an equal mix of the two; n 26–28 per group). The subjects then underwent a second satiety test after ingesting the protein snack. The time period elapsing between the snack and request for lunch, food intake at lunch and satiety scores were recorded. A subgroup of twenty-four subjects underwent a digestive and metabolic investigation after ingesting their protein snack. Gastric emptying times were 2·5, 4 and 6 h for whey protein, mix and casein, respectively, displaying different kinetics of appearance of dietary N in plasma but without affecting pancreatic and gastrointestinal hormones. Compared with the control snack, proteins extended the duration of satiety (+17 min, P= 0·02), with no difference between the protein groups. The satiating effect of proteins was greater in subjects who ate their lunch early after the snack (below the median value, i.e. 2 h) at the control test (+32 min, P= 0·001). Energy intake at lunch was not modulated by proteins. The satiating effect of proteins is efficient in overweight subjects, especially when the duration of satiety is short, but independently of their digestive and plasma amino acid kinetics.