N. Zijlstra

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.

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.

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.

Effects of bite size and duration of oral processing on retro-nasal aroma release - features contributing to meal termination.

The brain response to a retro-nasally sensed food odour signals the perception of food and it is suggested to be related to satiation. It is hypothesised that consuming food either in multiple small bite sizes or with a longer durations of oral processing may evoke substantial oral processing per gram consumed and an increase in transit time in the oral cavity. This is expected to result in a higher cumulative retro-nasal aroma stimulation, which in turn may lead to increased feelings of satiation and decreased food intake. Using real-time atmospheric pressure chemical ionisation-MS, in vivo retro-nasal aroma release was assessed for twenty-one young, healthy and normal-weight subjects consuming dark chocolate-flavoured custard. Subjects were exposed to both free or fixed bite size (5 and 15 g) and durations of oral processing before swallowing (3 and 9 s) in a cross-over design. For a fixed amount of dark chocolate-flavoured custard, consumption in multiple small bite sizes resulted in a significantly higher cumulative extent of retro-nasal aroma release per gram consumed compared with a smaller amount of large bite sizes. In addition, a longer duration of oral processing tended to result in a higher cumulative extent of retro-nasal aroma release per gram consumed compared with a short duration of oral processing. An interaction effect of bite size and duration of oral processing was not observed. In conclusion, decreasing bite size or increasing duration of oral processing led to a higher cumulative retro-nasal aroma stimulation per gram consumed. Hence, adapting bite size or duration of oral processing indicates that meal termination can be accelerated by increasing the extent of retro-nasal aroma release and, subsequently, the satiation.

Eating behaviour and retro-nasal aroma release in normal-weight and overweight adults: a pilot study.

Eating rate and bite size are important factors affecting food intake, and we hypothesise the underlying role of oral sensory exposure in this. However, the latter currently lacks objective measuring parameters, but an interesting measure could be the extent of in vivo retro-nasal aroma release. Second, the literature is ambiguous about overweight subjects differing from normal-weight subjects in eating behaviour. Consequently, we investigated: (1) whether eating behaviour (food intake, eating rate, bite size, number of bites and meal duration) relates to weight status and (2) whether the extent of retro-nasal aroma release relates to eating behaviour and weight status. A matched group (sex, age and dietary restraint) of twenty-seven normal-weight (BMI 21.8 (SD 1.6) kg/m2) and twenty-seven overweight/obese subjects (BMI 30.5 (SD 5.8) kg/m2) consumed a spiced rice meal and apple pie yogurt on separate test days. The extent of retro-nasal aroma release was measured on a third test day. Mean bite size for spiced rice was significantly (P = 0.03) larger in overweight/obese (10.3 (SD 3.2) g) v. normal-weight subjects (8.7 (SD 2.1) g). There were no other significant differences in eating behaviour or retro-nasal aroma release between the groups. Eating behaviours were not correlated with BMI or retro-nasal aroma release. Subjects showed consistent eating behaviour for both test products. Eating behaviour might be a characteristic of an individual but not by definition a characteristic for a group of people based on their weight. Given the large sample sizes, necessary according to a posteriori sample size calculations, one needs to consider the relevance of finding a statistically significant difference in eating behaviour between the weight groups in a laboratory setting.

Texture and Diet Related Behavior: A Focus on Satiation and Satiety

In view of the increasing numbers in overweight and obesity, insight in food intake regulation is necessary. Food intake is regulated by sensory, cognitive, post-ingestive, and post-absorptive processes. Food properties, such as energy density, macronutrient composition, volume, and form, influence the satiating capacity of a food. This chapter focuses on the role of food texture in food intake regulation. Texture is an essential part of the whole spectrum of sensory properties of a food. Several studies showed that liquid foods elicit weaker suppressive appetite responses and a weaker compensatory response in energy intake than solid or semisolid foods. The mechanisms underlying the effect of texture on satiety are not well understood. Beverages might engage thirst mechanisms and not hunger mechanisms. Food properties such as viscosity and texture could affect chewing, oro-gastric handling of foods, and absorption. Other factors that play a role are beliefs about the satiating capacity of a food, sensory specific satiety, eating rate, gastric emptying, and learned associations between texture and metabolic consequences. One of the mechanisms involved could be the oral sensory exposure time. A longer oral exposure time gives the sensory receptors in the oral cavity more time to respond to the food. Liquid calories facilitate energy intake. This knowledge can be useful in both the overweight and underweight situation.

Liquid foods result in higher ad libitum food intake than semi-solid foods because of a higher eating rate and larger bite sizes

Enterostatin, the aminoterminal pentapeptide of procolipase, is produced in the GI tract and in specific brain regions. Enterostatin inhibits dietary fat intake and insulin secretion. The enterostatin receptor has been identified as the beta subunit of F1-ATPase complex present on plasma membranes. Since the anti-angiogenic agent angiostatin binds to the alpha subunit of F1-ATPase which is also present on plasma membranes complexed to the beta subunit, we examined the possibility that Enterostatin would also affect angiogenesis. Two angiogenesis assays were used, using either human fat cells or human placenta vein preparations. Enterostatin inhibited new blood vessel formation in human fat tissues in a dose response manner. Maximal inhibition was 50% at a dose of 1nM. The same dose responsive effect was observed in the human placental vein preparation where 10 nM and 100 nM enterostatin completely inhibited angiogenic growth at Day 16. Mouse oligo-microarray and subsequent Panther pathway analysis (Applied Biosystems) using RNA from GT1-7 and HepG2 cells incubated with or without enterostatin, identified 23 genes involved in the angiogenic response, which were confirmed using quantitative RT-PCR. These genes included fibroblast growth factor receptors 2 and 4, vascular endothelial growth factor, Raf1, fibroblast growth factor (acidic) intracellular binding protein, MAP kinases 12, 13, 14 and disheveled. These data provide the first evidence for an effect of enterostatin on angiogenesis. The role of this response in the long term ability of enterostatin to reduce body weight and body fat in rats remains to be determined. T2:OS1.2