Diet texture, moisture and starch type in dietary obesity

The Effects of Gelatinized Wheat Starch and High Salt Diet on Gut Microbiota and Metabolic Disorder

Diets high in gelatinized starch and high in gelatinized starch supplemented with salt-induced metabolic disorders and changes in gut microbiota have scarcely been studied. In this study, mice on wheat starch diets (WD) exhibited significantly higher body weight, white adipose tissue (WAT), and gut permeability compared to those on normal diet (ND). However, gelatinized wheat starch diet (GWD) and NaCl-supplemented gelatinized wheat starch diet (SGW) mice did not increase body and WAT weights or dyslipidemia, and maintained consistent colon pH at ND levels. WD mice showed higher levels of Desulfovibrio, Faecalibaculum, and Lactobacillus and lower levels of Muribaculum compared to ND mice. However, GWD and SGW mice showed a significantly different gut microbial composition, such as a lower proportion of Lactobacillus and Desulfovibrio, and higher proportion of Faecalibaculum and Muribaculum compared to WD mice. High starch diet-induced dysbiosis caused increase of lipid accumulation and inflammation-related proteins' expression, thereby leading to non-alcoholic fatty liver disease. However, GWD and SGW showed lower levels than that, and it might be due to the difference in the gut microbial composition compared to WD. Taken together, diets high in gelatinized starch and high in gelatinized starch supplemented with salt induced mild metabolic disorders compared to native starch.

Food Viscosity Influences Caloric Intake Compensation and Body Weight in Rats

OBJECTIVE

To determine the effects of food viscosity on the ability of rats to compensate for calories in a dietary supplement.

RESEARCH METHODS AND PROCEDURES

In a series of four experiments, rats consumed dietary supplements equated for caloric and nutritive content but differing in viscosity. Experiments 1 to 3 examined the ability of the rats to compensate for the calories consumed in low- compared with high-viscosity premeals by reducing intake of a subsequent test meal. Caloric compensation was assessed with a wide range of premeal viscosity levels and with two different non-nutritive thickening agents. Experiment 4 assessed the effects of consuming daily a low-viscosity compared with an equicaloric high-viscosity dietary supplement on longer term body weight gain.

RESULTS

Consuming a lower viscosity premeal was followed by significantly more caloric intake (i.e., less caloric compensation) compared with consuming premeals with higher viscosity levels. This effect was not specific to one thickening agent. Furthermore, rats given a low-viscosity supplement daily gained significantly more weight over a 10-week period compared with rats given a high-viscosity supplement.

DISCUSSION

The results of these experiments suggest that food viscosity may be an important determinant of short-term caloric intake and longer term body weight gain.

Eating for pleasure or just wanting to eat? Reconsidering sensory hedonic responses as a driver of obesity

Pleasure from foods can stimulate "non-homoeostatic" eating, and might therefore also potentially contribute toward obesity. However, obesity is not reliably associated with heightened hedonic responses to foods. This apparent discrepancy may reflect the differentiation between "liking" and "wanting". Supporting this, behavioural and neurophysiological data on responsiveness to food-related cues indicate that obesity may be associated with increased motivation for food consumption, without necessarily any greater explicit pleasure derived from the orosensory experience of eating. This distinction may have important implications for further research, and applications in commercial and public health approaches to modifying energy intakes.

Effects of food texture change on metabolic parameters: short- and long-term feeding patterns and body weight

A complete diet was prepared with cooked pieces of meat, beans, cream starch, and water and presented to the rats in two different textures: a blended purée and a rough mixture that required a lot of chewing. We hypothesized that this texture modification might change both anticipatory reflexes and feeding behavior. Feeding rate, meal size, intermeal intervals, and their correlation were monitored in response to each texture. The long-term (6 wk) effect on body weight was assessed. Periprandial plasma glucose, insulin, glucagon, and lipid concentrations were assayed. Whole and background metabolism, respiratory quotient, and locomotion were measured using a computerized calorimeter of original design. In the short term, rats preferred the mixture. However, after 3 wk, they ingested more purée than mixture and gained more body weight per gram of food ingested as purée. Insulin response declined earlier with the mixture. During meals, glycerol and free fatty acid increased earlier with purée, whereas in the postprandial period, glycerol increased earlier with mixture. The metabolic rate, however, was not significantly affected. We concluded that texture, an everyday manipulation performed on food for human consumption, affects not only palatability of ingestants but also their metabolic management in the short and long term.

Nutrient preference and diet-induced adiposity in C57BL/6ByJ and 129P3/J mice

Purified carbohydrates and fats are usually palatable to humans and other animals, and their consumption often induces weight gain and accumulation of fat. In this study, we examined consumption of complex carbohydrates (cornstarch and Polycose) and fats (soybean oil and margarine) in mice from two inbred strains, C57BL/6ByJ and 129P3/J. At lower concentrations of liquid nutrients tested using two-bottle tests, when the amounts consumed had negligible energy content, the C57BL/6ByJ mice had higher acceptance of Polycose and soybean oil. This was probably due to strain differences in chemosensory perception of Polycose and oil. At higher concentrations, the mice consumed a substantial part of their daily energy from the macronutrient sources, however, there were no or only small strain differences in nutrient consumption. These small differences were probably due to strain variation in body size. The two strains also did not differ in chow intake. Despite similar energy intakes, access to the nutrients resulted in greater body weight (BW) gain in the C57BL/6ByJ mice than in the 129P3/J mice. The diet-induced weight gain was examined in detail in groups of 2-month-old C57BL/6ByJ and 129P3/J mice given ether chow, or chow and margarine to eat. Access to margarine did not increase total energy consumption of either strain. It increased BW and adiposity of the C57BL/6ByJ mice, but only after they reached the age of approximately 3 months. There were no differences in BW and adiposity between control and margarine-exposed 129P3/J mice. The results suggest that diet-induced adiposity in the B6 mice depends on age and does not depend on hyperphagia.

Preferential fat intake increases adiposity but not body weight in Sprague-Dawley rats

It is not known whether an inherent preference for dietary fat promotes obesity in animals allowed to self-select the proportions of fat and carbohydrate consumed. To address this question, Sprague-Dawley rats were given a choice between two diets containing either 78% fat (by energy) or 78% carbohydrate; both diets were equicaloric for protein (22%). The entire study lasted 12 weeks. After an adaptation period, macronutrient preferences were determined by measuring 24 h intake of the two diets for 5 days; fat-preferring animals were classified as those that consumed greater than 60% of total energy from the fat/protein source, and carbohydrate-preferring rats as those that consumed less than 40%. Rats with intermediate macronutrient intakes were excluded. Initial body weight was not different between preference groups. Caloric intakes and body weights were then recorded at approximate weekly intervals, and fat depots were weighed at the time of sacrifice. Measures of energy intake and body weight did not differ between the two preference groups over time. In addition, baseline macronutrient preferences remained stable across the study period. Despite similar body weights, mean epididymal fat depot weight was significantly higher in fat-preferring rats than in carbohydrate-preferring rats (12.6 vs. 10.0 g); also, mean inguinal fat depot weight in fat-preferrers was greater although not reliably different compared to carbohydrate-preferring rats (12.9 vs. 10.9 g). Thus, the preferential intake of fat led to a greater deposition of both subcutaneous and visceral fat without an increase in body weight. These data lead us to conclude that the increased fat deposition was due primarily to the ingestion of fat rather than to excess caloric intake.

Chemoreception for fat: do rats sense triglycerides directly?

Rats given a choice between fluid containing 0.1-0.5% triglyceride oil and the same fluid without oil, generally preferred the fluid containing oil. Several experiments indicate that this preference is based on the detection of impurities rather than triglycerides per se. Rats preferred crude triolein to a greater degree than they did highly purified triolein or corn oil. Rats did not show any preference for or aversion to tristearin, a fat that does not decompose as readily as triolein. Rats that have been trained to avoid a dilute suspension of triolein, also avoided an aqueous extract of triolein. Since rats that had been trained to avoid triolein oil also avoided corn oil, it seems likely that different oils may possess similar impurities. Since training rats to avoid mineral oil did not reduce preference for triolein, these substances may have different flavors. It is proposed that rats use fat decomposition products to detect the presence of fats in foods.

Thresholds for starch and Polycose are lower than for sucrose in rats

Detection thresholds for corn starch, Polycose and sucrose in water were assessed by a new technique. Rats were trained to avoid these carbohydrates by giving them fluid containing carbohydrate mixed with lithium chloride on some days, and fluid containing sodium chloride with no carbohydrate on other days. Rats trained by this procedure avoided the substance that they were trained to avoid, but did not avoid other substances. Thus rats trained to avoid starch avoided mixtures containing as little as 0.025% starch, but did not avoid Polycose, sucrose or sodium chloride. Rats trained to avoid Polycose avoided fluids containing as little as 0.01% Polycose, but did not avoid fluids containing starch or sucrose. Finally, rats trained to avoid sucrose avoided fluids containing as little as 0.05% sucrose, but did not avoid fluids containing starch or Polycose. Therefore, rats possess a keen sensitivity for starch, a substance that is commonly thought to be tasteless. Furthermore, starch, Polycose and sucrose are discriminable from each other.

High-fat diet preference in developing and adult rats

Diet preference tests in rats have yielded equivocal results, as some investigators have reported a strong preference for diets high in fat over those containing less fat, while others have failed to see this preference. To further explore this unresolved problem, two diet preference experiments were conducted. In Experiment 1, adult rats were maintained for at least three months on one of three powdered diets (control, high-carbohydrate or high-fat). Rats were then given a preference test with all three diets available. Animals from each group overwhelmingly preferred the high-fat diet. To determine whether this preference was also present in younger, developing rats, in Experiment 2, weanling animals were tested with the same three diets as in Experiment 1. As observed with adult animals, weanling rats also showed a strong preference for the high-fat diet. The idea that rats prefer a diet with a relatively high level of fat is supported. Possible explanations for these findings are discussed.

Does dietary hyperphagia contradict the lipostatic theory?

It has frequently been suggested that body weight or fat somehow exerts an inhibitory influence on food intake in a way that acts to maintain a stable body weight or fat. The principal evidence supporting this idea is that animals that have been induced to overeat and become overweight by various means, eat less than control rats when they are permitted to eat freely. If the degree of suppression of appetite by overweight is as large as several experiments suggest, then dietary hyperphagia should be self-limiting. Any overeating induced by dietary treatments should disappear after animals become moderately overweight. Animals fed some kinds of hyperhagia-promoting diets do show this pattern. However, animals fed other kinds of diets do not show this pattern, and with most diets, dietary hyperphagia continues for extended periods. This implies that either 1) overweight does not suppress appetite as much as suggested by various authorities, 2) dietary manipulations can override normal regulatory mechanisms, or 3) certain diets induce irreversible changes in body fat that are not evident from changes in body weight.

Dietary hyperphagia and obesity: what causes them?

Diets that cause animals to overeat and become obese have been used in many investigations of obesity. Most of this research, however, has concentrated on the consequences rather than the causes of overeating. Furthermore, in most studies, several nutritional variables were manipulated simultaneously, making cause and effect relationship impossible to disentangle. Consequently, progress has been slow. Diets could alter energy intake by virtue of their effects on oral-sensory, gastrointestinal or postabsorptive effects. Palatability is the most popular oralsensory hypothesis but the empirical basis for this hypothesis is particularly weak. A substantial body of evidence is consistent with the possibility that the osmotic effects of diets in the gastrointestinal tract and metabolic postabsorptive factors may play a major role in dietary hyperphagia and obesity. Suggestions for future research directions are offered.

Experimental obesity: a homeostatic failure due to defective nutrient stimulation of the sympathetic nervous system

The basic hypothesis of this review is that studies on models of experimental obesity can provide insight into the control systems regulating body nutrient stores in humans. In this homeostatic or feedback approach to analysis of the nutrient control system, we have examined the afferent feedback signals, the central controller, and the efferent control elements regulating the controlled system of nutrient intake, storage, and oxidation. The mechanisms involved in the beginning and ending of single meals must clearly be related to the long-term changes in fat stores, although this relationship is far from clear. Changes in total nutrient storage in adipose tissue can arise as a consequence of changes in the quantity of nutrients ingested in one form or another or a decrease in the utilization of the ingested nutrients. A change in energy intake can be effected by increased size of individual meals, increased number of meals in a 24-hour period, or a combination of these events. Similarly, a decrease in utilization of these nutrients can develop through changes in resting metabolic energy expenditure which are associated with one of more of the biological cycles such as protein metabolism, triglyceride for glycogen synthesis and breakdown, or maintenance of ionic gradients for Na+ + K+ across cell walls. In addition, differences in energy expenditure related to the thermogenesis of eating or to the level of physical activity may account for differences in nutrient utilization.

Overeating, overweight and obesity induced by an unpreferred diet

Rats fed diets containing 50-71% added water (liquid diets) eat more energy and gain more weight than rats fed the same diets without added water (solid diets). The present experiments examined the effects of making a liquid diet less palatable. The first experiment examined the effects of sucrose octaacetate on diet preference. Rats, given a choice of a liquid diet containing 0.5% sucrose octaacetate and a plain solid diet, preferred the plain solid diet for three weeks. When the concentration of sucrose octaacetate was reduced to 0.05%, the rats did not show a reliable preference for either the sucrose octaacetate liquid or plain dry diet. In subsequent experiments, each rat was given only one diet at a time. In the second experiment, rats were fed 0.5% sucrose octaacetate liquid diet for three weeks followed by 0.05% sucrose octaacetate liquid diet for another four weeks. The rats fed the sucrose octaacetate liquid diet overate and became obese compared to the rats fed plain solid diet throughout. In the third experiment, rats fed 0.5% sucrose octaacetate liquid diet for six weeks became obese compared to rats fed plain solid diet throughout. Thus, the overeating and obesity induced by liquid diets cannot be attributed solely to their high palatability.