Astrid J. Smeets

Protein-induced satiety: Effects and mechanisms of different proteins

Relatively high protein diets, i.e. diets that maintain the absolute number of grams of protein ingested as compared to before dieting, are a popular strategy for weight loss and weight maintenance. Research into multiple mechanisms regulating body weight has focused on the effects of different quantities and types of dietary protein. Satiety and energy expenditure are important in protein-enhanced weight loss and weight maintenance. Protein-induced satiety has been shown acutely, with single meals, with contents of 25% to 81% of energy from protein in general or from specific proteins, while subsequent energy intake reduction was significant. Protein-induced satiety has been shown with high protein ad libitum diets, lasting from 1 to 6 days, up to 6 months. Also significantly greater weight loss has been observed in comparison with control. Mechanisms explaining protein-induced satiety are nutrient-specific, and consist mainly of synchronization with elevated amino acid concentrations. Different proteins cause different nutrient related responses of (an)orexigenic hormones. Protein-induced satiety coincides with a relatively high GLP-1 release, stimulated by the carbohydrate content of the diet, PYY release, while ghrelin does not seem to be especially affected, and little information is available on CCK. Protein-induced satiety is related to protein-induced energy expenditure. Finally, protein-induced satiety appears to be of vital importance for weight loss and weight maintenance. With respect to possible adverse events, chronic ingestion of large amounts of sulphur-containing amino acids may have an indirect effect on blood pressure by induction of renal subtle structural damage, ultimately leading to loss of nephron mass, and a secondary increase in blood pressure. The established synergy between obesity and low nephron number on induction of high blood pressure and further decline of renal function identifies subjects with obesity, metabolic syndrome and diabetes mellitus II as particularly susceptible groups.

Sensory and gastrointestinal satiety effects of capsaicin on food intake

BACKGROUND:Decreased appetite and increased energy expenditure after oral consumption of red pepper has been shown.OBJECTIVE:The aim of the present study was to assess the relative oral and gastrointestinal contribution to capsaicin-induced satiety and its effects on food intake or macronutrient selection.METHODS:For 24 subjects (12 men and 12 women; age: 35±10 y; BMI: 25.0±2.4 kg/m2; range 20–30), 16 h food intake was assessed four times during 2 consecutive days by offering macronutrient-specific buffets and boxes with snacks, in our laboratory restaurant. At 30 min before each meal, 0.9 g red pepper (0.25% capsaicin; 80 000 Scoville Thermal Units) or a placebo was offered in either tomato juice or in two capsules that were swallowed with tomato juice. Hunger and satiety were recorded using Visual Analogue Scales.RESULTS:Average daily energy intake in the placebo condition was 11.5±1.0 MJ/d for the men and 9.4±0.8 MJ/d for the women. After capsaicin capsules, energy intake was 10.4±0.6 and 8.3±0.5 MJ/d (P<0.01); after capsaicin in tomato juice, it was 9.9±0.7 and 7.9±0.5 MJ/d, respectively (compared to placebo: P<0.001; compared to capsaicin in capsules: P<0.05). En % from carbohydrate/protein/fat (C/P/F): changed from 46±3/15±1/39±2 to 52±4/15±1/33±2 en% (P<0.01) in the men, and from 48±4/14±2/38±3 to 42±4/14±2/32±3 en% (P<0.01) in the women, in both capsaicin conditions. Satiety (area under the curve) increased from 689 to 757 mmh in the men and from 712 to 806 mmh in the women, both (P<0.01). Only in the oral exposure condition was the reduction in energy intake and the increase in satiety related to perceived spiciness.CONCLUSION:In the short term, both oral and gastrointestinal exposure to capsaicin increased satiety and reduced energy and fat intake; the stronger reduction with oral exposure suggests a sensory effect of capsaicin.

Acute effects on metabolism and appetite profile of one meal difference in the lower range of meal frequency

A gorging pattern of food intake has been shown to enhance lipogenesis and increase body weight, which may be due to large fluctuations in storage and mobilisation of nutrients. In a state of energy balance, increasing meal frequency, and thereby decreasing inter-meal interval, may prevent large metabolic fluctuations. Our aim was to study the effect of the inter-meal interval by dividing energy intake over two or three meals on energy expenditure, substrate oxidation and 24 h satiety, in healthy, normal-weight women in a state of energy balance. The study was a randomised crossover design with two experimental conditions. During the two experimental conditions subjects (fourteen normal-weight women, aged 24.4 (SD 7.1) years, underwent 36 h sessions in energy balance in a respiration chamber for measurements of energy expenditure and substrate oxidation. The subjects were given two (breakfast, dinner) or three (breakfast, lunch, dinner) meals per d. We chose to omit lunch in the two meals condition, because this resulted in a marked difference in inter-meal-interval after breakfast (8.5 h v. 4 h). Eating three meals compared with two meals had no effects on 24 h energy expenditure, diet-induced thermogenesis, activity-induced energy expenditure and sleeping metabolic rate. Eating three meals compared with two meals increased 24 h fat oxidation, but decreased the amount of fat oxidised from the breakfast. The same amount of energy divided over three meals compared with over two meals increased satiety feelings over 24 h. In healthy, normal-weight women, decreasing the inter-meal interval sustains satiety, particularly during the day, and sustains fat oxidation, particularly during the night.

Satiety and substrate mobilization after oral fat stimulation.

The aim of the study was to provoke cephalic and metabolic responses by oral fat stimulation with different high-fat meals in the postprandial state. A randomized parallel design was executed with three groups of subjects (twenty-six women and ten men; twelve subjects per group). Oral fat stimulation was achieved by the modified sham feeding (MSF) technique. Five hours after a high-fat breakfast, the subjects were given one of three test meals in random order: a high-fat lunch, water or the same lunch as the MSF. The main fat sources in the high-fat lunch and MSF were olive oil, linoleic oil and oleic oil. For 3 h after the test meal, blood samples were taken for analysis of metabolite, and visual analogue scales of appetite profile were completed. A cephalic response appeared to be achieved by MSF in that we observed a relative increase in insulin and glucose; this response lasted up until 90 min, indicating possible vagal stimulation. NEFA increased significantly after MSF compared with water ingestion in the case of olive oil (P<0.0001) and linoleic oil (P<0.05), but not with oleic oil. MSF provoked a significantly higher increase in triacylglycerol and glycerol levels compared with water ingestion in the case of linoleic oil (P<0.05). Satiety was significantly increased in the eating condition and in the MSF condition (P<0.0002, all oils) compared with water ingestion. We conclude that cephalic and perhaps vagal stimulation by different fats increased the concentrations of the metabolites and stimulated satiety, with linoleic oil showing the strongest response.

Pooled-data analysis identifies pyloric pressures and plasma cholecystokinin concentrations as major determinants of acute energy intake in healthy, lean men

BACKGROUND The interaction of nutrients with the small intestine modulates gastropyloroduodenal motility, stimulates the release of gut hormones, and suppresses appetite and energy intake. OBJECTIVE We evaluated which, if any, of these variables are independent determinants of acute energy intake in healthy, lean men. DESIGN We pooled data from 8 published studies that involved a total of 67 healthy, lean men in whom antropyloroduodenal pressures, gastrointestinal hormones, and perceptions were measured during intraduodenal nutrient or intravenous hormone infusions. In all of the studies, the energy intake at a buffet lunch was quantified immediately after the infusions. To select specific motor, hormone, or perception variables for inclusion in a multivariable mixed-effects model for determination of independent predictors of energy intake, we assessed all variables for collinearity and determined within-subject correlations between energy intake and these variables by using bivariate analyses adjusted for repeated measures. RESULTS Although correlations were shown between energy intake and antropyloroduodenal pressures, plasma hormone concentrations, and gastrointestinal perceptions, only the peak number of isolated pyloric-pressure waves, peak plasma cholecystokinin concentration, and area under the curve of nausea were identified as independent predictors of energy intake (all P < 0.05), so that increases of 1 pressure wave, 1 pmol/L, and 1 mm . min were associated with reductions in energy intake of approximately 36, approximately 88, and approximately 0.4, respectively. CONCLUSION We identified specific changes in gastrointestinal motor and hormone functions (ie, stimulation of pyloric pressures and plasma cholecystokinin) and nausea that are associated with the suppression of acute energy intake.

Oral exposure and sensory-specific satiety

Satiety has been shown after oral exposure to food that was chewed but not eaten (Modified Sham Feeding (MSF)). The aim of the study was to explore the role of sensory-specific satiety (SSS) in satiety development with MSF. Subjects were studied on three test days in a randomized crossover design; they received, in random order, water, MSF, or a meal. At the start and the end of each course of the lunch condition subjects evaluated appetite sensations, taste perception and pleasantness of taste using Visual Analogue Scales. SSS was present when eating soup and salad. SSS also occurred with MSF of salad. When eating the soup no significant changes in appetite ratings occurred. Hunger decreased and satiety increased while the salad was eaten (p<0.0004). In this condition taste perception did not change significantly and a decrease in pleasantness coincided with an increase in satiety. During the MSF salad taste perception changed, i.e. creaminess and intensity increased (p<0.05 and p<0.02, respectively). When the salad was eaten satiety increased and hunger and desire to eat (DTE) decreased. Chewing the salad resulted only in a decrease in DTE. In this experiment merely chewing a salad produced SSS. We conclude that when SSS takes place during feeding, it is related to an increase in satiety, and a decrease in hunger and DTE. With SSS during MSF, satiety does not increase, nor does hunger decrease, yet DTE decreases. Thus MSF is sufficient for a sensory decrease in DTE despite of lack of satiety.

Sex differences in energy homeostatis following a diet relatively high in protein exchanged with carbohydrate, assessed in a respiration chamber in humans

CONTEXT Obesity prevalence is generally higher in women than in men, and a paucity of research with sex-specific approaches exists. The question arises whether current weight loss programmes, largely developed and tested on women, are appropriate for men. OBJECTIVE Investigate 24 h energy metabolism, satiety and related hormones during a diet relatively high in protein (HP), exchanged with carbohydrate compared to an adequate-protein (AP) diet, in a respiration chamber in men, in comparison with previous outcomes in women. DESIGN Ten healthy males (BMI: 22.5+/-1.6 kg/m(2), age: 25+/-3.5 y) were fed in energy balance with an AP (10/60/30% of energy of protein/carbohydrate/fat) or a HP (30/40/30% of energy of protein/carbohydrate/fat) diet in a randomized cross-over design. RESULTS During the HP diet, 24 h Energy Expenditure (10.5+/-0.5 vs 10.0+/-0.5 MJ/d; p<0.05), Sleeping Energy Expenditure (7.1+/-0.3 vs 6.9+/-0.2 MJ/d; p<0.05), protein balance (0.5+/-0.02 vs 0.0+/-0.01 MJ/d; p<0.05), satiety (AUC) p<0.05, and plasma GLP-1 concentrations (42+/-23 vs 28+/-16 AUC; p<0.005) were significantly higher and 24 h RQ (0.80 vs 0.85; p<0.01), fat balance (-0.85+/-0.03 vs 0.05 vs 0.03 MJ/d; p<0.01) and hunger (AUC) p<0.05, were significantly lower. Comparisons reveal a stronger reaction in men in energy expenditure and substrate oxidation, whereas satiety reacted stronger in the women. CONCLUSIONS Effects of a diet relatively high in protein exchanged with carbohydrate, vs an adequate protein diet are a stronger increased energy expenditure, fat oxidation, protein anabolism in men, and a stronger increased satiety in women, thereby creating sex-specific conditions for long-term use for body-weight management.

The addition of monosodium glutamate and inosine monophosphate-5 to high-protein meals: effects on satiety, and energy and macronutrient intakes

In a fed and orally stimulated state, whether the addition of monosodium glutamate (MSG) (alone or in combination with inosine monophosphate-5 (IMP-5)) to a high-protein (HP) meal leads to early satiety and a difference in energy intake at a second course was investigated. Ten men and twelve women consumed, in random order, a first-course meal consisting of: (1) water (control); (2) a HP meal with 0.6% MSG and 0.25% IMP-5; (3) a HP meal with no additives; (4) a HP meal with MSG only; (5) a sham-fed meal 2 (oral-stimulation). Appetite perceptions, plasma concentrations of glucagon-like peptide 1 (GLP-1), glucose and insulin, and energy intake at a buffet (i.e. a second course) were measured before and after each condition. Changes in appetite, and in GLP-1, glucose and insulin, were similar for the three fed HP conditions and all were greater (post hoc all P < 0.01) than the control and sham conditions. Energy intake was not different following the HP+MSG+IMP (1.86 (SEM 0.3) MJ) as compared with the HP+MSG-only (2.24 (SEM 0.28) MJ) condition (P = 0.08), or for the HP+MSG+IMP compared with the HP no-additives condition (1.60 (SEM 0.29) MJ) (P = 0.21). Following the HP+MSG-only condition, 0.64 (SEM 0.20) MJ more energy was consumed compared with the HP no-additives condition (P = 0.005). We conclude that the addition of MSG to a HP meal does not influence perceptions of satiety and it may increase energy intake at a second course. Cephalic responses after the sham condition were of similar magnitude to the control and therefore just tasting food is not enough to influence appetite and energy intake.

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/m2). 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.

Addition of Capsaicin and Exchange of Carbohydrate with Protein Counteract Energy Intake Restriction Effects on Fullness and Energy Expenditure

Energy intake restriction causes a yo-yo effect by decreasing energy expenditure (EE) and decreasing fullness. We investigated the 24-h effect of protein and capsaicin, singly or combined, on fullness and EE during 20% energy intake restriction. The 24 participants (12 male, 12 female; BMI, 25.2 ± 0.4 kg/m(2); age, 27 ± 4 y; body fat, 25.6 ± 5.7%; 3-factor eating questionnaire, F1: 6 ± 2, F2: 4 ± 2, F3: 3 ± 2) underwent eight 36-h sessions in a respiration chamber. The study had a randomized crossover design with 8 randomly sequenced conditions. The participants were fed 100 or 80% of their daily energy requirements. There were 2 control (C) conditions: 100%C and 80%C; 2 conditions with capsaicin (Caps): 100%Caps and 80%Caps; 2 conditions with elevated protein (P): 100%P and 80%P; and 2 conditions with a mixture of protein and capsaicin (PCaps): 100%PCaps and 80%PCaps. Appetite profile, EE, and substrate oxidation were monitored. Compared with 100%C, the 80%C group had expected negative energy-balance effects with respect to total EE, diet-induced thermogenesis, and fullness, whereas the 80%Caps diet counteracted these effects, and the 80%P and 80%PCaps diets exceeded these effects (P < 0.01). In energy balance and negative energy balance, fat balance was more negative in the 80%Caps, P, and PCaps groups than in the 80%C group (P < 0.05) and respiratory quotient values were lower. A negative protein balance was prevented with the 80%P and 80%PCaps diets compared with the 80%C diet. Our results suggest that protein and capsaicin, consumed singly or mixed, counteracted the energy intake restriction effects on fullness and EE. During energy restriction, protein and capsaicin promoted a negative fat balance and protein treatments also prevented a negative protein balance.