Monica Mars

Effects of dietary fibre on subjective appetite, energy intake and body weight: a systematic review of randomized controlled trials.

Dietary fibres are believed to reduce subjective appetite, energy intake and body weight. However, different types of dietary fibre may affect these outcomes differently. The aim of this review was to systematically investigate the available literature on the relationship between dietary fibre types, appetite, acute and long‐term energy intake, and body weight. Fibres were grouped according to chemical structure and physicochemical properties (viscosity, solubility and fermentability). Effect rates were calculated as the proportion of all fibre–control comparisons that reduced appetite (n = 58 comparisons), acute energy intake (n = 26), long‐term energy intake (n = 38) or body weight (n = 66). For appetite, acute energy intake, long‐term energy intake and body weight, there were clear differences in effect rates depending on chemical structure. Interestingly, fibres characterized as being more viscous (e.g. pectins, β‐glucans and guar gum) reduced appetite more often than those less viscous fibres (59% vs. 14%), which also applied to acute energy intake (69% vs. 30%). Overall, effects on energy intake and body weight were relatively small, and distinct dose–response relationships were not observed. Short‐ and long‐term effects of dietary fibres appear to differ and multiple mechanisms relating to their different physicochemical properties seem to interplay. This warrants further exploration.

The effect of viscosity on ad libitum food intake

Background:Energy-yielding liquids elicit weak suppressive appetite responses and weak compensatory responses, suggesting that liquid calories might lead to a positive energy balance. However, data is often derived from foods differing in many characteristics other than viscosity.Objective:To investigate the effect of viscosity on ad libitum food intake in real-life setting and to investigate whether a difference in ad libitum intake is related to eating rate and/or eating effort.Design:In real-life setting 108 nonrestrained subjects (26±7 years, BMI 22.7±2.4 kg m−2) received a chocolate flavored liquid, semi-liquid and semi-solid milk-based product, similar in palatability, macronutrient composition and energy density. In laboratory setting 49 nonrestrained subjects (24±6 years, BMI 22.2±2.3 kg m−2) received the liquid or semi-solid product. Effort and eating rate were controlled by means of a peristaltic pump.Results:In real-life setting the intake of the liquid (809±396 g) was respectively 14 and 30% higher compared to the semi-liquid (699±391 g) and semi-solid product (566±311 g; P<0.0001). In laboratory setting, removing eating effort, resulted in a 29% (P<0.0001) intake difference between liquid (319±176 g) and semi-solid (226±122 g). Standardizing eating rate resulted in 12% difference between liquid (200±106 g) and semi-solid (176±88 g; P=0.24). If not controlled, the difference in intake between liquid (419±216 g) and semi-solid (277±130 g) was comparable to the real-life setting (34%; P<0.0001).Conclusions:Products different in viscosity but similar in palatability, macronutrient composition and energy density lead to significant differences in intake. This difference is partially explained by the higher eating rate of liquids.

Effect of bite size and oral processing time of a semisolid food on satiation.

BACKGROUND Food texture plays an important role in food intake regulation. In previous studies we showed a clear effect of viscosity on ad libitum food intake and found indications that eating rate, bite size, and oral processing time (OPT) could play a role. OBJECTIVE The objective was to determine the effect of bite size and OPT of a food on satiation, defined as ad libitum food intake. DESIGN Twenty-two healthy subjects participated in all 7 test conditions. Bite sizes were free or fixed to small bite sizes ( approximately 5 g) or large bite sizes ( approximately 15 g). OPT was free (only in combination with free bite size) or fixed to 3 or 9 s. Subjects consumed chocolate custard through a tube, which was connected to a peristaltic pump. Sound signals indicated OPT duration. RESULTS Subjects consumed significantly more when bite sizes were large than when they were small (bite size effect: P < 0.0001) and when OPT was 3 s rather than 9 s (OPT effect: P = 0.008). Under small bite size conditions, mean (+/-SD) ad libitum intakes were 382 +/- 197 g (3-s OPT) and 313 +/- 170 g (9-s OPT). Under large bite size conditions, ad libitum intakes were much higher: 476 +/- 176 g (3-s OPT) and 432 +/- 163 g (9-s OPT). Intakes during the free bite size conditions were 462 +/- 211 g (free OPT), 455 +/- 197 g (3-s OPT), and 443 +/- 202 g (9-s OPT). CONCLUSION This study shows that greater oral sensory exposure to a product, by eating with small bite sizes rather than with large bite sizes and increasing OPT, significantly decreases food intake.

Gastrointestinal targets of appetite regulation in humans

The aim of this paper is to describe and discuss relevant aspects of the assessment of physiological functions – and related biomarkers – implicated in the regulation of appetite in humans. A short introduction provides the background and the present state of biomarker research as related to satiety and appetite. The main focus of the paper is on the gastrointestinal tract and its functions and biomarkers related to appetite for which sufficient data are available in human studies. The first section describes how gastric emptying, stomach distension and gut motility influence appetite; the second part describes how selected gastrointestinal peptides are involved in the control of satiety and appetite (ghrelin, cholecystokinin, glucagon‐like peptide, peptide tyrosin‐tyrosin) and can be used as potential biomarkers. For both sections, methodological aspects (adequacy, accuracy and limitation of the methods) are described. The last section focuses on new developments in techniques and methods for the assessment of physiological targets involved in appetite regulation (including brain imaging, interesting new experimental approaches, targets and markers). The conclusion estimates the relevance of selected biomarkers as representative markers of appetite regulation, in view of the current state of the art.

The effects of food viscosity on bite size, bite effort and food intake.

Two studies investigated the effect of a foods viscosity on bite size, bite effort and food intake using a standardized protocol in which subjects sipped through a straw every 20 s for a period of 15 min from one of two products, a chocolate-flavored dairy drink and a chocolate-flavored dairy semi-solid, matched for energy density. In the first study, subjects consumed 47% more from the liquid than from the semi-solid to reach the same degree of satiation, with larger bite sizes for the liquid throughout the 15 minute period (8.7+/-0.45 g) compared to the semi-solid (5.8+/-0.3 g, p<0.01). In the second study bite effort was eliminated by using a peristaltic pump to present the products every 20 s. Oral processing time before swallowing was set at 5 s (both products) or 8 s (semi-solid). With the elimination of bite effort and a standardized oral processing time, subjects consumed as much from the semi-solid as from the liquid to reach the same degree of satiation. Bite size for liquids started relatively small and grew gradually over successive bites, whereas the bite size for the semi-solid food started relatively large and became gradually smaller. The latter effect was even more pronounced when the oral processing time was increased from 5 to 8 s. In conclusion, semi-solids resulted in smaller bite sizes and lower intake than liquids, but these differences disappeared when differences in bite effort were eliminated.

Protein status elicits compensatory changes in food intake and food preferences

Background: Protein is an indispensable component within the human diet. It is unclear, however, whether behavioral strategies exist to avoid shortages. Objective: The objective was to investigate the effect of a low protein status compared with a high protein status on food intake and food preferences. Design: We used a randomized crossover design that consisted of a 14-d fully controlled dietary intervention involving 37 subjects [mean ± SD age: 21 ± 2 y; BMI (in kg/m2): 21.9 ± 1.5] who consumed individualized, isoenergetic diets that were either low in protein [0.5 g protein · kg body weight (BW)−1 · d−1] or high in protein (2.0 g protein · kg BW−1 · d−1). The diets were followed by an ad libitum phase of 2.5 d, during which a large array of food items was available, and protein and energy intakes were measured. Results: We showed that in the ad libitum phase protein intake was 13% higher after the low-protein diet than after the high-protein diet (253 ± 70 compared with 225 ± 63 g, P < 0.001), whereas total energy intake was not different. The higher intake of protein was evident throughout the ad libitum phase of 2.5 d. In addition, after the low-protein diet, food preferences for savory high-protein foods were enhanced. Conclusions: After a protein deficit, food intake and food preferences show adaptive changes that suggest that compensatory mechanisms are induced to restore adequate protein status. This indicates that there are human behavioral strategies present to avoid protein shortage and that these involve selection of savory high-protein foods. This trial was registered with the Dutch Trial register at http://www.trialregister.nl as NTR2491.

Effect of viscosity on appetite and gastro-intestinal hormones

In previous studies we showed that higher viscosity resulted in lower ad libitum intake and that eating rate is an important factor. In this study we aimed to explore the effect of viscosity on the gastro-intestinal hormones ghrelin, CCK-8 and GLP-1. Thirty-two subjects (22+/-2 y, BMI 21.9+/-2.2 kg/m(2)) participated in this cross-over study. Subjects received a fixed amount of a chocolate flavored milk-based liquid or semi-solid product similar in energy density and macronutrient composition. Before intake and 15, 30, 60 and 90 min thereafter, appetite was rated and blood was drawn to determine glucose, CCK-8, active ghrelin, desacyl ghrelin and GLP-1 concentrations. After the last blood withdrawal, subjects were offered a chocolate cake meal to consume ad libitum. In the appetite ratings we observed a small effect showing that the semi-solid product is apparently considered as more satisfying than the liquid. There was a significant product effect for fullness (p 0.03), desire to eat (p 0.04), appetite something sweet (p 0.002) and prospective consumption (p 0.0009). We observed no clear effect of viscosity on gastro-intestinal hormones. Only for desacyl ghrelin there was a significant product effect (p 0.004). Concentrations were consistently higher after intake of the semi-solid product. Ad libitum intake of the chocolate cake was 102+/-55 g after the liquid and 96+/-46 g after the semi-solid product (ns). The results of our study show a similar response of the gastro-intestinal hormones CCK-8, ghrelin and GLP-1 after a fixed preload of a liquid and semi-solid product similar in energy- and macronutrient composition.

Sweet preferences and sugar consumption of 4- and 5-year-old children: role of parents

We investigated the relationships in children between rules that restrict consumption of mono- and disaccharides (MDS), consumption of MDS and preferences for sucrose-containing orangeade. The background ideas of restriction rules we also investigated. To this end, 44 children (5.1+/-0.5 years) performed a rank-order and paired-comparison test of preference for five orangeades, which differed in sucrose concentration (0.14, 0.20, 0.29, 0.42, 0.61 M sucrose). Parents filled out a questionnaire concerning restriction rules and their childrens consumption of MDS-containing foods. Stronger restriction rules were related to a lower consumption of beverages that contained MDS and to a lower consumption of MDS-containing foods during breakfast and lunch. The most freedom to choose foods that contain MDS was given during the afternoon. Fifty-five percent of the children who were highly restricted showed a preference for the highest concentration of sucrose in orangeade. None of these children preferred the orangeade with the lowest concentration of sucrose. While 19% of the children who were little restricted preferred the beverage with the lowest concentration of sucrose, 33% preferred the beverage with the highest concentration. These parents generally believed that sugar has a bad effect on health and had similar background ideas concerning restriction rules.

Effect of viscosity on learned satiation

A higher viscosity of a food leads to a longer orosensory stimulation. This may facilitate the learned association between sensory signals and metabolic consequences. In the current study we investigated the effect of viscosity on learned satiation. In two intervention groups a low viscosity (LV) yogurt (n=24) and a high viscosity (HV) yogurt (n=22) was offered ad libitum for breakfast. In a learning period of 4 weeks, subjects consumed ad libitum a novel flavoured high energy density (HED) yogurt (150 kcal/100 g) or low energy density (LED) yogurt (50 kcal/100 g), with 10 exposures to each yogurt on alternate days. Over the repeated exposures, an interaction effect of exposure timeenergyviscosity on intake was seen (F(1,771)=4.12; p=0.04). In the HV intervention group a borderline significant interaction between exposure and energy density was observed (F(1,369)=3.61; p=0.06); after 10 exposures, the LED yogurt resulted in a 46+/-16 g higher intake compared with the HED yogurt. In the LV group, no significant interaction between exposure and energy density was seen (F(1,401)=1.04; p=0.31); after 10 exposures intake difference between the LED and HED yogurts was only 1.5+/-15 g. These results suggest that a higher viscosity facilitates learned satiation.

Fasting leptin and appetite responses induced by a 4-day 65%-energy-restricted diet

Objective:Animal studies show that the leptin decline after acute severe caloric restriction is a peripheral signal to increase food intake. However, most human studies have failed to observe such a relationship. We studied the acute effects of severe caloric restriction on the association between serum leptin concentrations and subjective appetite.Subjects:A total of 44 healthy adult men (aged: 43±5 years; BMI: 27.3±3.2 kg/m2).Measurements:Fasting serum leptin concentrations and self-perceived appetite levels were measured during a 4-day diet containing 36% of the estimated energy requirements. Appetite levels were assessed with a 10-point Likert scale, reflecting hunger, fullness, desire to eat, prospective consumption and total appetite.Results:After the 4-day energy deficit, fasting leptin concentrations decreased by 39.4% (95% CI: −43.6; −34.9%). This decline was associated with an increase in fasting hunger (r=−0.42; P<0.01), desire to eat (r=−0.39; P<0.05) and total appetite (r=−0.38; P<0.05). Furthermore, the association between fasting leptin concentrations and fasting appetite levels became stronger during the energy restriction period (for total appetite: day 0 r=−0.15, P=0.32; day 2 r=−0.31, P=<0.05; day 4 r=−0.41, P<0.01).Conclusions:The acute proportional reduction in fasting leptin after 4-day energy restriction is associated with an increase in self-perceived appetite. Additionally, the inverse association between proportional fasting leptin concentrations and self-perceived appetite response becomes stronger as energy restriction is prolonged. These findings suggest that leptin has an instrumental role in restoring energy balance in humans through the expression of appetite.