The effects of providing personalized dietary feedback. A semi-computerized approach

There not only seems to be a trend for people to underestimate the dietary risks that they face, but it appears that this underestimation may be related to the difficulties they encounter when trying to assess their own dietary intake. A study (n = 118) examining the effects of providing people with information about their own dietary fat intake on their attitudes towards dietary change and their subsequent fat consumption is described. Participants in a group receiving feedback about their fat intake did not decrease their consumption of fat more than did those in a control group. No effects on subsequent fat consumption were observed in a group who had higher than average levels of fat consumption, higher perceived fat consumption than actual fat consumption and who received feedback information about their fat consumption. The results are discussed in relation to their implications for health promotion strategies that focus on the motivational effects of providing people with information about their fat consumption.     

Psychological Effects of Dietary Fat Analysis and Feedback: A Randomized Feedback Design

Excess consumption of dietary fat promotes chronic disease such as heart disease and cancer. Dietary analysis and feedback are often used to motivate dietary change; however, little is known about how people process, react to, and use this feedback to change behavior. This study used a randomized feedback design to examine psychological reactions to dietary fat feedback. Subjects were assessed for fat consumption and then randomly assigned to a high, moderate, or low percentage of calories from fat feedback group. Findings indicate that there are strong emotional, cognitive, and behavioral reactions to providing high-fat dietary feedback. Subjects that were told their diets were high in fat reported stronger negative emotional reactions and also reported they had stronger intentions to change than the other two feedback categories. These results are compared with studies providing nonrandomly assigned risk factor feedback.     

Modulation of oxidative DNA damage levels by dietary fat and calories

Decreased dietary intake of fat and/or calories generally results in a lower incidence of mammary gland tumors in rodents. Feeding of either low-fat or calorie-restricted diets to rats also has been shown to result in decreased levels of oxidative DNA damage. Since oxidative DNA damage is suggested to have a role in carcinogenesis, this may be one mechanism by which dietary change can reduce cancer risk. The effects of calorie-restricted diets on both oxidative DNA damage levels and mammary gland tumor incidence are generally more pronounced than that of low-fat diets. There is, however, some difficulty in defining what amount of fat should be used to prepare ‘low-fat’ and ‘high-fat’ rodent diets as well as what a suitable fat intake for control diets should be in studies that examine the effects of dietary fat and/or calories on tumorigenesis. In particular, the promoting effects of dietary fat may be exerted only up to a certain level of fat, above which no further effect is observed. Another difficulty in the interpretation of the results is that there may be a time-dependent effect of high fat diets on oxidative damage, with increased damage resulting only when the diets are fed for longer periods of time. The appropriate experimental approach to model human dietary exposures therefore remains to be determined. Although the effects of caloric intake on mammary gland tumorigenesis appear to be more pronounced than that of fat intake, low-fat diets still may be useful as a preventive measure in human populations to reduce breast cancer risk for individuals who cannot safely reduce their caloric intake.     

The unique merits of a low-fat diet for weight control

The virtual freedom from obesity enjoyed by many primitive societies may be traceable to the low fat content of their traditional diets. Recent studies indicate that humans have a very limited capacity for de novo lipogenesis from dietary carbohydrate; this implies that it should be easy to achieve negative fat balance if dietary fat intake is kept low and fat oxidation is promoted by regular exercise. Overfeeding with carbohydrate--but not with fat--provokes an insulin-mediated thermogenesis which acts to retard weight gain. Low-fat starchy foods have a relatively low caloric density, resulting in lower caloric consumption with meals. Once absorbed, carbohydrate has greater satiety value than fat. These considerations suggest that avoidance of dietary fat may be a more successful approach to weight control than "calorie counting". The efficacy of low-fat diets may be promoted by supplementary carnitine, which stimulates fat oxidation, and by chromium, which aids insulin-mediated thermogenesis. An unrefined low-fat diet, eaten to satiety and accompanied by regular exercise, may be the ideal means of maintaining a trim figure throughout life while minimizing one's risk for "Western" degenerative diseases.     

Dietary fat and obesity: a review of animal, clinical and epidemiological studies

The First Law of Thermodynamics provides a framework for understanding the imbalance between energy intake and expenditure that produces obesity, but it does not help understand the role of genetics, the regulation of food intake, the distribution of body fat, the mechanisms by which diets work or the mechanism by which portion control has gotten out of control. In animals, increasing dietary fat increases body fat, and it is unlikely that humans escape this important biological rule. In epidemiological studies, increasing dietary fat is associated with increased prevalence of obesity probably by increasing the intake of energy dense foods. In the National Weight Loss Registry, three things were associated with weight loss: continued monitoring of food intake, lowering dietary fat intake, and increased exercise. The relation of dietary fat is most evident when physical activity is low. The speed of adaptation to dietary fat is increased by exercise. When dietary fat is reduced, weight is lost, but weight loss eventually plateaus. The rate of weight loss during the initial phase is about 1.6 g/day for each 1% decrease in fat intake. When dietary fat is replaced with olestra to reduce fat intake from 33% to 25% in obese men, weight loss continues for about 9 months reaching a maximum of nearly 6% of body weight and a loss of 18% of initial body fat. In the control group with a 25% reduced-fat diet, weight loss stopped after 3 months and was regained over the next 6 months, indicating the difficulty of adhering to a conventional low-fat diet. Thus, dietary fat is an important contributor to obesity in some people.     

Protein selection, food intake, and body composition in response to the amount of dietary protein

Though not universally observed, moderately low-protein diets have been found to increase caloric intake and body fat. It appears that animals overeat in calories in order to obtain more dietary protein. For animals to control protein intake, they must be able to distinguish between two isocaloric diets containing different percentages of protein and make the appropriate dietary selection on the basis of their previous history of protein intake. Experiment 1 examined the 24-h diet selection (5 vs. 35% casein) of Sprague-Dawley rats that had been previously fed diets containing various percentages of dietary protein (5, 10, 20, 35, or 60% casein). Animals fed 5, 10, or 20% dietary protein showed a preference for the higher protein selection diet. In contrast, no significant diet preference was found in animals pre-fed the two higher levels of dietary protein (35 or 60% casein). In this study, daily food intake and body fat of rats fed the low-protein diets (5 and 10% casein) were similar to rats fed the 20% casein diet. Experiment 2 examined the effects of the level of methionine supplementation on rats fed 10% casein. In this study, food intake and body fat were increased by approximately 20% in rats fed 10% casein diets, regardless of the level of methionine supplementation (0.3 vs. 0.15%). Together, the results suggest that the presence of low-protein-induced hyperphagia helps maintain body protein levels in the face of moderately low dietary protein and promotes an increase in the amount of body fat and energy.     

Dietary self-selection,activity and carcass composition of rats fed thiouracil

The interaction of dietary self-selection and spontaneous running wheel activity as fat regulating mechanisms was studied in rats treated with thiouracil. Both hypothyroid and euthyroid rats were given the opportunity to either select their diets, engage in running activity or both. Thiouracil treated rats reduced carbohydrate intake while maintaining protein intake levels equal to those of controls. Thiouracil treatment reduced running activity levels when the rats were given the opportunity to select their diets, but did not affect the running levels of rats fed a control diet. All groups given access to running wheels were at the same carcass fat level except the control diet fed, thiouracil treated rats which were at a lower fat level. It was suggested that, at least for hypothyroid rats, the combination of dietary self-selection and running activity is a more efficient mechanism for regulating carcass composition than is either behavior alone.     

Effects of dietary fat feedback on behavioral and psychological variables

This paper reports on the immediate and delayed reactions to dietary fat consumption feedback. Subjects in our study received (1) personalized dietary fat feedback and (2) information about how to alter their fat consumption. Fat consumption was measured using a brief fat assessment instrument. Subjects were categorized into three risk groups: at or below, above, and significantly above the recommended level. Emotional, cognitive, and behavioral reactions were measured immediately after receiving feedback and at 1 month postfeedback. Subjects who received high fat feedback showed greater negative emotional distress in response to the feedback and stated that they knew less about high-fat foods than subjects receiving lower feedback. By the 1-month follow-up, subjects in the highest feedback condition were least likely to report intentions to lower their dietary fat. Interventions designed to alter dietary fat consumption should take into account the emotional and cognitive consequences of risk factor feedback.     

Effects of high and low dietary fat and indomethacin on tumour growth, hormone receptor status and growth factor expression in DMBA-induced rat breast cancer.

The effects of high and low dietary fat (20% vs. 0.5% corn oil), and of the prostaglandin synthetase inhibitor indomethacin (0.005% w/w), on tumour incidence, tumour growth, hormone-receptor status and growth-factor expression were examined in dimethylbenzanthracene (DMBA)-induced rat breast cancer. The high dietary-fat group showed a significantly higher tumour incidence, larger tumour size and larger number of bromodeoxyuridine(BrdU)-positive cells of tumours as compared with those in the low dietary-fat group. Indomethacin reduced tumour incidence significantly, but conversely increased the tumour size and the number of BrdU-positive cells in both the high and the low dietary-fat groups. No significant difference was noted in the hormone-receptor status of the tumours. Growth factors (TGF-alpha and IGF-II) were somewhat highly expressed in the high dietary-fat group as compared with the low dietary-fat group, but indomethacin rather reduced the growth-factor expression. It is concluded that high dietary fat stimulates tumour incidence and tumour proliferation, while indomethacin has dual effects: a stimulating effect on tumour proliferation, but an inhibiting effect on tumour incidence. It is also suggested that hormone-receptor status and growth-factor expression do not play an important role in their stimulating effects on tumour proliferation.     

A comparison of education methods and their impact on behavioral change in patients with hyperlipidemia

We sought to determine the efficacy of a hospital-based, professionally-taught program emphasizing cardiovascular health. Similar programs are in existence throughout the country without documentation of their long-term benefits. Thirty-six hyperlipidemic individuals were treated as a control group or participated in one of two intensive educational interventions. The educational program was based on information obtained from focus group methodology to elicit attitudes about dietary change and learning style preferences. Behavioral changes in smoking, dietary salt and saturated fat intake, stress and tension, physical activity, and departure from ideal body weight were documented using health questionnaires and Lifestyle Risk. Indices. At three months of follow-up, there was no change in serum lipids, total fat intake, or cardiovascular risk behavior in either the control or intervention group. We conclude that a one-day program, whether designed by the target population or experts, did not improve cardiovascular risk behaviors, suggesting that more innovative methods are required to address health behaviors in this high risk group.     

Selection of protein and fat by diabetic rats following separate dilution of the dietary sources

Diabetic and normal rats were allowed to select their diets from separate sources of protein, carbohydrate and fat. Following the determination of baseline intakes, diabetic and normal rats received dietary components in which either the protein (Experiment 1) or fat source (Experiment 2) was diluted by 25% or 50% by the addition of cellulose. Diabetic rats failed to maintain protein intake at both dilution levels, but made up for the loss of protein-derived calories by consuming more fat. Diabetic rats maintained fat intake at both dilution levels. Dietary dilutions had no effect on total caloric intakes or body weight gain of diabetic rats. Diabetic status, measured by fasting plasma glucose levels and urinary glucose excretion rates, also was unaffected by diet dilutions. These data suggest that diabetic rats maintain total caloric intake following dilution of either the protein or fat source of their diets, but defend intake of fat-derived calories more readily than protein-derived calories. Normal rats maintained both protein and fat intake at the 25% but not at the 50% dilution level. These findings are discussed in terms of the ability of diabetic rats to solve the metabolic problems associated with their diabetic condition.     

Dietary hyperphagia in rats: role of fat, carbohydrate, and energy content

Dietary energy, fat and carbohydrate content were varied to determine the nutritional factors responsible for hyperphagia induced by feeding rats high-fat diets. In the first experiment, rats were fed isoenergetic high-fat or high-carbohydrate diets for 2 weeks. Weight gain and energy intake were lower in rats given the high-fat diet. When some of the rats were switched to a diet that was high in fat, carbohydrate and energy, gram food intake was initially unchanged, resulting in a substantial increase in energy intake and weight gain. Energy intake gradually declined over the 4 weeks following the switch to the high-energy diet. In the second experiment, rats were fed high-fat diets that were either high or low in carbohydrate content and either high or low in energy content (kcal/g). Rats fed a high-fat diet that was high in energy and carbohydrate ate the most energy and gained the most body weight and carcass fat. In the third experiment, rats were fed high-carbohydrate diets varying in fat and cellulose content. Energy intake and body weight gain varied directly as a function of caloric density regardless of the fat or cellulose content of the diets. It is concluded that hyperphagia induced by feeding high-fat diets is not due to the high dietary fat content alone. Rather, high levels of fat, carbohydrate, and energy interact to produce overeating and obesity in rats fed high-fat diets.     

Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity

Amino acids modulate the secretion of both insulin and glucagon; the composition of dietary protein therefore has the potential to influence the balance of glucagon and insulin activity. Soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. Acting on hepatocytes, glucagon promotes (and insulin inhibits) cAMP-dependent mechanisms that down-regulate lipogenic enzymes and cholesterol synthesis, while up-regulating hepatic LDL receptors and production of the IGF-I antagonist IGFBP-1. The insulin-sensitizing properties of many vegan diets--high in fiber, low in saturated fat--should amplify these effects by down-regulating insulin secretion. Additionally, the relatively low essential amino acid content of some vegan diets may decrease hepatic IGF-I synthesis. Thus, diets featuring vegan proteins can be expected to lower elevated serum lipid levels, promote weight loss, and decrease circulating IGF-I activity. The latter effect should impede cancer induction (as is seen in animal studies with soy protein), lessen neutrophil-mediated inflammatory damage, and slow growth and maturation in children. In fact, vegans tend to have low serum lipids, lean physiques, shorter stature, later puberty, and decreased risk for certain prominent 'Western' cancers; a vegan diet has documented clinical efficacy in rheumatoid arthritis. Low-fat vegan diets may be especially protective in regard to cancers linked to insulin resistance--namely, breast and colon cancer--as well as prostate cancer; conversely, the high IGF-I activity associated with heavy ingestion of animal products may be largely responsible for the epidemic of 'Western' cancers in wealthy societies. Increased phytochemical intake is also likely to contribute to the reduction of cancer risk in vegans. Regression of coronary stenoses has been documented during low-fat vegan diets coupled with exercise training; such regimens also tend to markedly improve diabetic control and lower elevated blood pressure. Risk of many other degenerative disorders may be decreased in vegans, although reduced growth factor activity may be responsible for an increased risk of hemorrhagic stroke. By altering the glucagon/insulin balance, it is conceivable that supplemental intakes of key non-essential amino acids could enable omnivores to enjoy some of the health advantages of a vegan diet. An unnecessarily high intake of essential amino acids--either in the absolute sense or relative to total dietary protein--may prove to be as grave a risk factor for 'Western' degenerative diseases as is excessive fat intake.     

Adaptation to water restriction through dietary selection in weanling rats

For each of five pair of diets, 20 weanling rats were equally divided into ad lib and restricted water groups. Caloric density, palatability, as well as nutrient composition of the diet pairs were manipulated. Though lower in absolute food intake than controls, water-restricted rats took a larger proportion of their food from diets lower in protein content and higher in fat content, regardless of caloric content or palatability. The results demonstrate both a quantitative and qualitative dietary adaptation to water restriction.     

Effect of surfactant poloxalene 2930 on food intake, lipid absorption, and serum cholesterol in rats

Effect of hydrophobic surfactant, poloxalene 2930, on lipid absorption was studied in rats. Under acute conditions with surfactant infused intraduodenally with a lipid meal absorbed lipid accumulated abnormally in the enterocytes. This effect was quickly reversed after terminating treatment. Long-term administration of poloxalene given in semipurified diets resulted in changes in food intake, weight gain, fecal fat output, and serum cholesterol concentrations. The composition of the diet used as the vehicle for administration had a considerable effect on these results. When semipurified diets were used, food intake and weight gain were greatest when the dietary fat content was at the highest level. When the surfactant was given in ground chow, food intake was not affected and weight gain was only slightly, but significantly, less than the controls as a result of mild fat malabsorption. It is concluded that poloxalene 2930 affects lipid absorption, food intake, and serum cholesterol concentration but that results of this treatment are considerably affected by dietary factors.     

Difference in body weight between American and Italian women with polycystic ovary syndrome: influence of the diet

BACKGROUND: The study aim was to determine differences in body mass in two populations of women (USA and Italy) with polycystic ovary syndrome (PCOS), and to assess the effect of diet on body mass and cardiovascular risk factors. METHODS: Pools of women with PCOS from the USA (n = 343) and Italy (n = 301), seen between 1993 and 2001, were available for assessment. From these populations, 20 women who were seen consecutively in 2001 at each site had detailed analyses of diet and cardiovascular risk factors. RESULTS: In the entire group, American women had a significantly higher body mass compared with Italian women (P < 0.01). Also, the 20 women consecutively evaluated in the USA had a significantly higher mean (+/- SD) body mass index (40.3 +/- 1.0 kg/m(2)) than in Italy (29.7 +/- 1.0 kg/m(2)). US women had worse insulin resistance, lower levels of high-density lipoprotein-cholesterol (HDL-C) (P < 0.01) and higher levels of triglycerides (P < 0.01). Dietary analysis in the two groups indicated that the total daily calorific intake was similar (USA 2277 +/- 109; Italy 2325 +/- 68 Kcal), with no appreciable differences in dietary content of protein, carbohydrate and fat. However, the dietary saturated fat content was significantly higher in US women (31.9 +/- 3 versus 18.2 +/- 2 g/day, P < 0.01). Saturated fat intake correlated negatively with HDL-C (P < 0.01). CONCLUSIONS: Among women with PCOS, body mass was significantly higher in US women compared with Italian women. However, total calorie intake and dietary constituents were similar, except for a higher saturated fat in US women. It is hypothesized that diet alone does not explain differences in body mass; genetic and lifestyle factors likely contribute. An increased saturated fat intake may worsen the cardiovascular risk profile.     

Studies of the effects of high fat diets on cognitive function in a rat model

This research summarises a research program that is concerned with the effects of high fat diets on cognitive function in rats. The diets selected accurately represent current upper limits of human fat consumption in western societies. Rats fed with diets high in saturated or unsaturated fat for 3 months, were severely impaired on a range of learning and memory tasks. Related studies showed that these effects were modulated by concentration of fat, environmental influences, and treatment with glucose. More work is needed to identify the neurobiological mechanisms underlying this impairment but saturated fatty acid intake, as well as insulin resistance and glucose intolerance may be important factors. In demonstrating a clear relationship between obesity and cognitive impairment, this research has important implications for aging. Older adults are particularly vulnerable to the adverse effects of dietary fat and the present results underscore the importance of evidence that seniors with marginal levels of nutrient intake often perform poorly on tests of cognitive function, and are at increased risk for various forms of dementia.     

Dietary fat-induced hyperphagia in rats as a function of fat type and physical form

The influence of dietary fat on food intake and weight gain was assessed by feeding adult female rats diets that differed in the type and form of fat, as well as in the availability of other macro- and micronutrients. Compared to chow-fed controls, the various fat diets increased total food intake by 4% to 27%. Specifically, rats fed chow and a separate source of fat (fat option diet) consumed more fat and total calories, and gained more weight when the fat source was emulsified corn oil rather than pure corn oil or was vegetable shortening rather than corn oil. However, corn oil and shortening had similar effects on caloric intake and weight gain when presented as emulsified gels. Also, pure and emulsified-gel forms of shortening did not differ in their effects on caloric intake and weight gain. Supplementing the vegetable shortening with micronutrients, however, enhanced its hyperphagia-promoting effect. The results of two-choice tests revealed that the rats' preferences for the orosensory properties of the various fat sources did not account for the differential hyperphagias obtained. Rather, it appears that long-term fat selection and caloric intake are influenced primarily by postingestive factors. Fat selection and total intake were determined not only by the fat source itself, but also by the other diet options. That is, rats selected more fat and consumed more calories when chow was the alternative food than when separate sources of carbohydrate and protein were available.     

Effect of dietary macronutrients on food intake, body weight, and tail width in the marsupial S. crassicaudata

The role of dietary fat, as opposed to total energy intake, in the etiology of obesity is controversial. The aim of this study was to determine the effect of macronutrient content, specifically changes in dietary fat on body weight, fat stores, and food intake in S. crassicaudata, a marsupial that stores about 25% of total body fat in its tail. Female animals were divided into three groups (n = 7-9) matched for food intake per gram of body weight. Each group of animals was fed, ad lib an isocaloric diet (1.01 kcal/g), which contained either 10, 20, or 40% of calories from fat. Body weight, food intake, and tail width (an index of body fat stores) were measured daily. Over 21 days, cumulative energy intake was less (p = 0.026) in the 40% fat group compared to the 10% fat group. Despite the differences in food intake, body weight in each group remained stable throughout the study, so that at day 21 there were no differences in the body weights between the three groups. In contrast, tail width increased in the animals who received the 40% fat diet compared to either the 10% (p = 0.016) or 20% (p = 0.001) fat intake groups, whereas there was no significant change in tail width in either of these two groups. These observations indicate that macronutrient composition has a role, independent of total calories in the regulation of food intake and body fat stores, specifically that dietary fat promotes adiposity, independent of total caloric intake.