Understanding fat preference and consumption: applications of behavioural sciences to a nutritional problem

Cell mechanisms of gustatory lipids perception and modulation of the dietary fat preference

Dietary lipids are usually responsible of several metabolic disorders. Recent compelling evidences suggest that there is a sixth taste modality, destined for the detection of oro-gustatory fats. The lipid-binding glycoprotein CD36, expressed by circumvallate papillae (CVP) of the mouse tongue, has been shown to be implicated in oro-gustatory perception of dietary lipids. We demonstrate that linoleic acid (LA) by activating sPLA2, cPLA2 and iPLA2 via CD36, produced arachidonic acid (AA) and lyso-phosphatidylcholine (Lyso-PC) which triggered Ca(2+) influx in CD36-positive taste bud cells (TBC), purified from mouse CVP. LA induced the production of Ca(2+) influx factor (CIF). CIF, AA and Lyso-PC exerted different actions on the opening of store-operated Ca2+ (SOC) channels, constituted of Orai proteins and regulated by STIM1, a sensor of Ca(2+) depletion in the endoplasmic reticulum. We observed that CIF and Lyso-PC opened Orai1 channels whereas AA-opened Ca(2+) channels were composed of Orai1/Orai3. STIM1 was found to regulate LA-induced CIF production and opening of both kinds of Ca(2+) channels. Furthermore, Stim1(-/-) mice lost the spontaneous preference for fat, observed in wild-type animals. Our results suggest that fatty acid-induced Ca(2+) signaling, regulated by STIM1 via CD36, might be implicated in oro-gustatory perception of dietary lipids and the spontaneous preference for fat. Other cell types are involved in, and external factors can influence this preference.

Children's knowledge of packaged and fast food brands and their BMI. Why the relationship matters for policy makers

Studies regarding the advancing challenges of obesity in many countries are beginning to converge on the importance of early food exposure and consumption patterns. Across two studies (Study 1, 34 boys, 35 girls; Study 2, 40 boys, 35 girls, ages 3-6), child knowledge of brands offering products high in sugar, salt and fat was shown to be a significant predictor of child BMI, even after controlling for their age and gender and when also considering the extent of their TV viewing. Additionally, two different collage measures of brand knowledge (utilized across the two studies) performed similarly, suggesting that this measure may be serving as a surrogate indicator of an overall pattern of product exposure and consumption. Policy implications are discussed.

Apical CD36 immunolocalization in human and porcine taste buds from circumvallate and foliate papillae

CD36 is the receptor for long chain fatty acids (LCFA), and is expressed in lingual taste cells from rodents. In these animals, CD36 has been proposed to play an important role in oral detection of LCFA, and subsequently, determines their dietary fat preference. Humans also seem to detect LCFA in the oral cavity, however, information on the molecular mechanism of this human orosensory LCFA recognition is currently lacking. The aim of our study was to investigate whether CD36 is also expressed in lingual human and porcine taste buds cells. Using fluorescence immunohistochemistry, apical CD36 expression was revealed in human and porcine taste bud cells from circumvallate and foliate papillae. These data suggest CD36 as the putative orosensory receptor for dietary LCFA in human, and, therefore, may be involved in our preference for fatty foods.

Food neophobia and associations with cultural diversity and socio-economic status amongst rural and urban Australian adolescents

Exposure to diverse cultures and higher socio-economic status (SES) may increase knowledge of a wide variety of stimuli, including food, and be negatively associated with food neophobia. We contrasted questionnaire responses from two groups of Australian high school students (aged 12-18 years) from remote rural (rural, n=243) and cosmopolitan urban (city, n=696) locations to the food neophobia scale (FNS), familiarity with certain foods and willingness to try those foods. Cultural diversity measures and two SES scales were created. City students were less food neophobic than rural students (mean FNS scores 29.35 versus 34.68, p<0.001). City students were also significantly more familiar with different foods and more willing to try unfamiliar foods, were of higher SES and had greater exposure to cultural diversity. However, the association between the FNS and familiarity with foods, willingness to try unfamiliar foods, SES, and exposure to cultural diversity, were only weak or moderate for both city and rural students. Greater exposure to cultural diversity and higher SES has some influence on adolescents' responses to unfamiliar foods, but the relationship between these factors and the FNS score is tenuous.

Bottle-choice tests in Sprague-Dawley rats using liquid diets that differ in oil and sucrose contents

Bottle choice tests using liquid diets were done with Sprague-Dawley (SD) rats. SD rats ingested more oil-and-sucrose-enriched milk (hi-fat) and less oil-enriched milk (hi-fat-no-carb) than sucrose-enriched (hi-carb) milk by two-bottle choice tests after they were habituated to liquid diets for 4 days. Chronic food restriction didn't increase hi-fat ingestion but hi-fat-no-carb. Rats ingested less without habituation, and overnight food deprivation increased intake. This increment was maintained after rats were free-fed. The difference in fat content of the maintenance diet had little effect on fat preference. These results showed SD rats prefer a sweet and fatty liquid diet than a sweet and lean liquid diet. Habituation and food restriction were more important than the composition of the maintenance diet to demonstrate a clear preference for the fatty liquid diet.

What do users of reduced-fat dairy products know about the fat in their diets?

OBJECTIVES

To assess the fat intake and knowledge about the fat content of foods consumed by a sample of self reported users of reduced-fat dairy products.

DESIGN

Cross-sectional study of a population-based sample of women shoppers.

SETTING

A small, rural town (population approximately 6000) in central Victoria, Australia.

SUBJECTS

Seventy-eight women aged 25-50 years, who regularly used at least one reduced-fat dairy product.

RESULTS

Mean reported intake of total fat was lower while intake of dairy fat was similar to that of a national sample of women of the same age both in the whole sample and when under-reporters were excluded. The ability to identify major sources of fat in the diet as reported appeared to be limited. Less than half of the subjects were able to correctly estimate the fat content of reduced-fat dairy products relative to regular products and about one quarter of subjects reported replacing one kind of oil or fat with another as a strategy to reduce fat intake. Subjects were generally aware of the need to 'eat less fat' but few could articulate specific recommendations. A number of subjects reported using low fat diets to control their weight but few subjects appeared to understand the connection between fat intake and energy intake.

CONCLUSIONS

The findings of this study raise important questions about how nutrition advice is understood and implemented by consumers, particularly the message to reduce fat intake and the role of energy balance in weight management. They also highlight the difficulty of interpreting information on food intake, in subjects who have modified their diet by reducing intake of specific foods.

Long-term optional ingestion of corn oil induces excessive caloric intake and obesity in mice

Corn oil is well tolerated by mice but tolerance may decrease with excessive ingestion. In the present study, we compared the effects of optional ingestion of excessive corn oil with ingestion of water (control) or a 20% sucrose solution in mice. During the entire study, mice consistently ingested 100% corn oil and incrementally ingested 20% sucrose. Food intake in the corn-oil group was approximately constant but that in the sucrose group was slightly decreased. Body-weight gains in the corn-oil group were higher than those in the control and sucrose groups. At the end of the study, hepatic hypertrophy and fatty liver were present, especially in the corn-oil group, and the visceral fat of mice fed corn oil increased significantly compared with the other two groups. These results suggest that mice, when given a choice, will continue to overeat corn oil over the long term, inducing excessive caloric intake and obesity.

Food choice and intake: the human factor

Human perceptions and selection of food are derived from the prevailing and momentary food, agro-economic and cultural environment, cognitive and biological characteristics of individuals, and the real and perceived intrinsic and extrinsic attributes of foods themselves. The range of items typically chosen and consumed within a given population is largely determined by interaction of the external environmental context with guiding sets of implicit and explicit social and psychobiological 'rules'. Within the rather broad limits of biology, individual food choices and intake behaviours relate to and reflect aspects of food availability, existing habitual behaviours, learning mechanisms, and individual beliefs and expectations. Many of the relevant features of these variables are uniquely human, together determining what is 'food', when, how, by and with whom it is chosen and eaten, and in what quantities. They also provide the opportunities for individuals to establish and maintain a relatively stable set of culturally and biologically determined affective responses ('likes') and intake behaviours. Understanding of the potential contribution of these influences under different conditions can serve to explain many of the observed characteristics of human eating, and highlight potential avenues for intervention.

Macronutrient preference, dietary intake, and substrate oxidation among stable cirrhotic patients

Anorexia in liver disease is common; however, its association with aberrant metabolism and the type of cirrhosis has not been considered. Dietary intake, nutritional status, fasting substrate oxidation, and macronutrient preference were examined in controls (n = 18) and 65 patients with hepatocellular (n = 31) or biliary cirrhosis (n = 34). Energy intakes were lowest in hepatocellular patients (controls: 9.0 +/- 0.48 megajoules/day compared with biliary: 7.0 +/- 0.40 MJ/day, P <.05; controls compared with hepatocellular 6.5 +/- 0.39 megajoules/day, P <.01). Triceps skinfold was lower only in hepatocellular patients (controls: 109 +/- 9.2% compared with hepatocellular 79 +/- 5.6%, P <.05). The fasting rate of lipid oxidation was elevated in hepatocellular patients when compared with controls and biliary patients (controls: 40.9 +/- 15.1 mg/min compared with hepatocellular 62.8 +/- 16.8 mg/min, P <.001, and biliary : 45.5 +/- 17.0 mg/min compared with hepatocellular, P <.001). Control subjects exhibited a greater preference for the high fat, moderate carbohydrate food (controls: median 7.0 IQR 2.0 compared with biliary: median 5.0 interquartile range [IQR] 4.7, P <.01) (controls compared with hepatocellular: median 6.0 IQR 4.0, P <.01). Cirrhotic patients' spontaneous dietary intake is lower than that of controls and recommended intakes. Although macronutrient preference ratings were different within cirrhotic patient groups it remains unclear whether associated nutrient deficits are metabolically driven and dictated by primary cause.

Taste preferences and food intake

Sensory responses to the taste, smell, and texture of foods help determine food preferences and eating habits. However, sensory responses alone do not predict food consumption. The view that a "sweet tooth" leads to obesity through excess sugar consumption is overly narrow. In reality, there are multiple links between taste perceptions, taste preferences, food preferences, and food choices and the amount of food consumed. Taste responses are influenced by a range of genetic, physiological, and metabolic variables. The impact of taste factors on food intake further depends on sex and age and is modulated by obesity, eating disorders, and other pathologies of eating behavior. Food preferences and food choices of populations are further linked to attitudinal, social, and--probably most important--economic variables such as income. Nutrition education and intervention strategies aimed at improving population diets ought to consider sensory pleasure response to foods, in addition to a wide range of demographic and sociocultural variables.