The role of energy density in the overconsumption of fat

Growth of children at high risk of obesity during the first 6 y of life: implications for prevention

BACKGROUND

The contribution of familial factors to adiposity in children is poorly understood.

OBJECTIVE

The objective was to assess differences in growth in the first 6 y of life in children born to either overweight or lean mothers.

DESIGN

The body size and composition of 33 children at high risk and 37 children at low risk of obesity on the basis of the mother's overweight [body mass index (BMI; in kg/m(2)) of 30.2 +/- 4.2 and 19.5 +/- 1.1, respectively] were measured repeatedly from 3 mo to 6 y of age at the Children's Hospital of Philadelphia.

RESULTS

At year 2, no significant differences in any measure were observed between the high- and low-risk groups. By year 4, weight, BMI, and lean body mass were greater in the high-risk than in the low-risk children. By year 6, weight was even greater in the high-risk than in the low-risk children (23.4 +/- 6.4 compared with 20.4 +/- 2.1 kg; P < 0.02), and, for the first time, fat mass was greater in the high-risk than in the low-risk children (6.7 +/- 5.7 compared with 3.8 +/- 1.2 kg; P < 0.02). Ten of 33 high-risk children exceeded the 85th percentile of BMI at year 6 compared with 1 of 37 low-risk children (odds ratio = 15.7). Accelerated weight gain was predicted by high-risk group status, greater weight at year 2, and lower family income.

CONCLUSION

Anthropometric measures were not significantly different between groups at year 2; weight and lean body mass were greater at years 4 and 6, and fat mass was greater at year 6 in high-risk children.

Effects of a low-fat diet compared with those of a high-monounsaturated fat diet on body weight, plasma lipids and lipoproteins, and glycemic control in type 2 diabetes

BACKGROUND

An important therapeutic goal for patients with type 2 diabetes is weight loss, which improves metabolic abnormalities. Ad libitum low-fat diets cause weight loss in nondiabetic populations. Compared with diets higher in monounsaturated fat, however, eucaloric low-fat diets may increase plasma triacylglycerol concentrations and worsen glycemic control in persons with type 2 diabetes.

OBJECTIVE

We investigated whether, in type 2 diabetes patients, an ad libitum low-fat diet would cause greater weight loss than would a high-monounsaturated fat diet and would do this without increasing plasma triacylglycerol concentrations or worsening glycemic control.

DESIGN

Eleven patients with type 2 diabetes were randomly assigned to receive an ad libitum low-fat, high-carbohydrate diet or a high-monounsaturated fat diet, each for 6 wk. The diets offered contained 125% of the estimated energy requirement to allow self-selection of food quantity. The response variables were body weight; fasting plasma lipid, lipoprotein, glucose, glycated hemoglobin A(1c), and fructosamine concentrations; insulin sensitivity; and glucose disposal.

RESULTS

Body weight decreased significantly (1.53 kg; P < 0.001) only with the low-fat diet. Plasma total, LDL-, and HDL-cholesterol concentrations tended to decrease during both diets. There were no interaction effects between diet and the lipid profile response over time. Plasma triacylglycerol concentrations, glycemic control, and insulin sensitivity did not differ significantly between the 2 diets.

CONCLUSION

Contrary to expectations, the ad libitum, low-fat, high-fiber diet promoted weight loss in patients with type 2 diabetes without causing unfavorable alterations in plasma lipids or glycemic control.

Insulin resistance as a modifier of the relationship between dietary fat intake and weight gain

OBJECTIVE

To investigate whether insulin resistance modifies the rate of weight gain associated with a high percent of energy intake from dietary fat.

DESIGN

Longitudinal, observational population study.

SUBJECTS

A total of 782 nondiabetic Hispanic and non-Hispanic white free-living adult residents of the San Luis Valley in Colorado.

MEASUREMENTS

Subjects were seen up to three times over a 14-y period. Weight, height, fasting insulin and glucose, diet by 24 h recall, and self-reported physical activity were collected at each visit.

RESULTS

Percentage of energy intake from dietary fat was positively associated with weight gain over time (P=0.0103). High intake of dietary fat was more strongly related to weight gain in women than in men, and in those with lower total energy intake levels. The relationship between weight change and relative macronutrient intake also varied by baseline insulin sensitivity (P=0.0025). Weight gain over time in individuals with relative insulin resistance at baseline, as measured by QUICKI, was the greatest among those who consumed a higher percent of energy from fat.

CONCLUSION

Percentage of total intake from dietary fat predicts weight change independent of total energy intake. Nondiabetic, insulin-resistant individuals are particularly susceptible to the weight gain associated with high levels of dietary fat intake. Further investigation into the relationship between insulin resistance, diet, and weight gain is warranted.

Diet and obesity

PURPOSE OF REVIEW

Obesity continues to increase in the United States and worldwide. There is controversy surrounding different dietary patterns used to promote weight loss, and none has emerged as clearly more effective. This paper briefly reviews the factors that influence energy intake and dietary treatments used to promote weight loss.

RECENT FINDINGS

Increasing portion size, eating away from home, and consuming a variety of high-energy dense foods appear to increase energy intake. Hormonal influences on diet continue to be explored. Very-low-calorie diets and low-carbohydrate diets lead to greater initial weight loss, but long-term results are no better than more moderate calorie-restricted diets. A program using meal replacements appears to lead to weight loss slightly greater than calorie-restricted diets and offers one option to treat obesity. Dietary patterns low in energy density and glycemic index have potential in treating obesity and should be studied further.

SUMMARY

Clearly, a dietary pattern that prescribes a lower total energy intake is necessary for weight loss, and this pattern should be sustainable to maintain weight loss. Although many dietary programs can achieve short-term loss of weight, dietary treatment should be recommended that emphasizes lifestyle changes and is consistent with other dietary guidelines to promote long-term health. Features consistent with this are a dietary pattern low in total calories, saturated fat, and refined carbohydrate; moderate in whole grains; and high in low-energy dense vegetables and fruits. Future studies should explore dietary strategies and combination therapies that contribute to weight loss, long-term weight maintenance, and improved health.

Effects of fast-food consumption on energy intake and diet quality among children in a national household survey

BACKGROUND

Fast food has become a prominent feature of the diet of children in the United States and, increasingly, throughout the world. However, few studies have examined the effects of fast-food consumption on any nutrition or health-related outcome. The aim of this study was to test the hypothesis that fast-food consumption adversely affects dietary factors linked to obesity risk.

METHODS

This study included 6212 children and adolescents 4 to 19 years old in the United States participating in the nationally representative Continuing Survey of Food Intake by Individuals conducted from 1994 to 1996 and the Supplemental Children's Survey conducted in 1998. We examined the associations between fast-food consumption and measures of dietary quality using between-subject comparisons involving the whole cohort and within-subject comparisons involving 2080 individuals who ate fast food on one but not both survey days.

RESULTS

On a typical day, 30.3% of the total sample reported consuming fast food. Fast-food consumption was highly prevalent in both genders, all racial/ethnic groups, and all regions of the country. Controlling for socioeconomic and demographic variables, increased fast-food consumption was independently associated with male gender, older age, higher household incomes, non-Hispanic black race/ethnicity, and residing in the South. Children who ate fast food, compared with those who did not, consumed more total energy (187 kcal; 95% confidence interval [CI]: 109-265), more energy per gram of food (0.29 kcal/g; 95% CI: 0.25-0.33), more total fat (9 g; 95% CI: 5.0-13.0), more total carbohydrate (24 g; 95% CI: 12.6-35.4), more added sugars (26 g; 95% CI: 18.2-34.6), more sugar-sweetened beverages (228 g; 95% CI: 184-272), less fiber (-1.1 g; 95% CI: -1.8 to -0.4), less milk (-65 g; 95% CI: -95 to -30), and fewer fruits and nonstarchy vegetables (-45 g; 95% CI: -58.6 to -31.4). Very similar results were observed by using within-subject analyses in which subjects served as their own controls: that is, children ate more total energy and had poorer diet quality on days with, compared with without, fast food.

CONCLUSION

Consumption of fast food among children in the United States seems to have an adverse effect on dietary quality in ways that plausibly could increase risk for obesity.

Fast foods, energy density and obesity: a possible mechanistic link

Fast foods are frequently linked to the epidemic of obesity, but there has been very little scientific appraisal of a possible causal role. Here we review a series of studies demonstrating that the energy density of foods is a key determinant of energy intake. These studies show that humans have a weak innate ability to recognise foods with a high energy density and to appropriately down-regulate the bulk of food eaten in order to maintain energy balance. This induces so called 'passive over-consumption'. Composition data from leading fast food company websites are then used to illustrate that most fast foods have an extremely high energy density. At some typical outlets the average energy density of the entire menus is approximately 1100 kJ 100 g(-1). This is 65% higher than the average British diet (approximately 670 kJ 100 g(-1)) and more than twice the energy density of recommended healthy diets (approximately 525 kJ 100 g(-1)). It is 145% higher than traditional African diets (approximately 450 kJ 100 g(-1)) that probably represent the levels against which human weight regulatory mechanisms have evolved. We conclude that the high energy densities of many fast foods challenge human appetite control systems with conditions for which they were never designed. Among regular consumers they are likely to result in the accidental consumption of excess energy and hence to promote weight gain and obesity.

Fats and food intake

PURPOSE OF REVIEW

Given the global rates of obesity and the potential link to dietary fat intake, understanding the role of fat in the regulation of food intake is critical. Some short-term, laboratory-based studies demonstrate poor compensation for manipulation of fat content, leading to passive overconsumption, while others demonstrate compensation to levels similar to other macronutrients. The observation of compensation in the short term does not concur with long-term rates of obesity increase. This review discusses factors that may explain at a physiological level these discrepancies, in particular fat structure, dietary adaptation, and palatability.

RECENT FINDINGS

Medium-chain triglycerides have been demonstrated to be more satiating and promote weight loss. Recent data suggest different gastrointestinal transduction mechanisms elicit vagal afferent firing for fatty acids of different chain length. Dietary adaptation to fat can influence the sensitivity of the feedback response, which appears to be nutrient specific and relate to gastric emptying rates and hormonal feedback. Fat content has been found to influence palatability of foods. Recently it has been demonstrated that increasing palatability can partially override the satiating effects of covertly manipulated macronutrient preloads. Recent data suggest that hormonal influences may also affect the palatability response.

SUMMARY

It is becoming increasingly clear that although energy density of diets is a major factor determining intake, macronutrient structure, subject, dietary and taste differences can all play an important modulatory influence on the final response on food intake. Further understanding of these factors and interactions may provide strategies to help aid weight regulation.

Dynamics of the Nutrition Transition toward the Animal Foods Sector in China and its Implications: A Worried Perspective

Many changes in diet and in physical activity are occurring simultaneously in the developing world. These diet shifts include large increases in energy density, in the proportion of the population consuming a high fat diet and in animal product intake. Animal source foods (ASF) play a major role in these diet shifts. This article documents the large shifts in the composition of diets and obesity across the developing world and notes that these changes are accelerating. Using China as a case study, evidence of the speeding up of this process is presented in descriptive and more rigorous dynamic longitudinal analysis. The implications of these changes for dietary and obesity patterns and cardiovascular disease are great. Indeed, developing countries are at a point where the prevalence of obesity is greater than that of undernutrition and concerns related to intake of saturated fat and energy imbalance must be considered more seriously by the agriculture sector. Current agriculture development policy in many developing countries focuses on livestock promotion and does not consider the potential adverse health consequences of this strategy. Although linkages between ASF intake and obesity cannot be established as clearly as they are for high ASF intakes, heart disease and cancer, the potential adverse health effects linked with an increased ASF intake should no longer be ignored.

Attaining Successful Weight Loss With an Ideal Macronutrient Balance

A dramatic increase in the number of people who are overweight or obese in this country presents a growing public health problem. Successful weight loss requires diet, physical activity, and behavior modification interventions. Weight loss diets with distinctively different macronutrient profiles have resulted in short-term weight loss. There is great interest in identifying the most effective strategies to achieve long-term weight loss. Individualizing weight loss interventions, including diet, will be important to facilitate significant weight loss on a population basis. Nurses and nurse practitioners can play an integral role in supporting their patient's weight loss efforts.

The relationship between eating behaviors and obesity in African American and Caucasian women

The primary goal of this study was to determine the relevance of four self-reported eating behaviors (eating before bedtime, eating between meals, feeling hungry within 3 h of eating, and eating beyond satiation) as risk factors for overweight and obesity. The sample consisted of 35- to 49-year-old, premenopausal African American (n=580) and Caucasian (n=398) women, randomly selected from the membership of a large urban prepaid health plan. Eating beyond satiation was the only behavior associated with body mass index (BMI). The odds of becoming obese increased 6-fold for Caucasian women and 15-fold for African American women who ate beyond satiation everyday compared to those who rarely or never ate beyond satiation. Additionally, eating beyond satiation was also the only eating behavior associated with the age of obesity onset. Focusing on this eating behavior in weight loss programs may be important.

Nonexercise muscle tension and behavioral fidgeting are positively correlated with food availability/palatability and body weight in rats

While certain measures of energy expenditure such as respiratory quotient and thermogenesis are readily quantifiable using existing animal models, the mechanism for and measurement of energy expenditure via nonexercise activity have not been thoroughly characterized. This low intensity form of physical exertion, associated with involuntary fidgeting and postural changes in man, was quantified in the present studies using passive measurement of muscle tension in rats. In particular, long-term weight loss and gain were induced using diet yoking and feeding of preferred foods in order to assess corresponding changes in locomotor activity and radiotelemetered measures of muscle tension, temperature and global activity. Hind limb muscle tension, but not body temperature, was increased 30-60% by enhancing the availability or palatability of food relative to the decreased muscle tension resulting from limited food availability. Enhancing food availability or palatability also produced a relative 5-15% increase in the amount of telemetered global activity. Importantly, neither diet yoking nor provision of a highly preferred diet altered a precise measure of behavioral locomotor activity. These results suggest that muscle tension and activity-in-place are positively correlated with weight change in the present studies and that these mechanisms of energy expenditure are mobilized by environmental changes in diet composition and meal pattern.

Effects of dietary carbohydrate on the development of obesity in heterozygous Zucker rats

Rats carrying one copy of the fa allele are predisposed to diet-induced metabolic disturbances which contribute to hyperinsulinemia, obesity and dyslipidemia. To investigate the role of dietary carbohydrate and fat in the development of these conditions, we fed 6-week old male heterozygous (fa/+) lean rats carbohydrate-free diets containing primarily saturated fat either ad libitum or pair-fed. These diets were compared to standard chow and to a high saturated fat mixed diet containing 10% energy from sucrose for 4 weeks. The carbohydrate-free diet resulted in significantly lower circulating glucose levels compared to all other groups (p = 0.006). Weight gain was negligible in the carbohydrate free groups compared to standard diet and 10% sucrose diet (p = 0.03). This was reflected in energy efficiency which was markedly reduced (90%) in the carbohydrate-free groups compared to the other groups (p = 0.04). Corresponding changes were noted in fat pad mass. The subscapular and epididymal fat pads were increased 42% and 44%, respectively, in animals consuming the 10% sucrose diet compared to all other groups (p < 0.01). Comparable changes in fatty acid synthase (FAS) mRNA were observed in response to the carbohydrate-free diet, which resulted in a 53% decrease in adipocyte FAS mRNA (p < 0.001). Addition of 10% sucrose to the diet completely reversed this effect resulting in a 69% increase in adipocyte FAS mRNA compared to the carbohydrate-free groups (p = 0.01). Similarly, hepatic FAS mRNA was elevated by 51% and 66% in the 10% sucrose and standard diet groups respectively, compared to the carbohydrate-free groups. Therefore, diets that contain minimal carbohydrate may minimize net lipid storage and adiposity.

Understanding the nutrition transition: measuring rapid dietary changes in transitional countries

OBJECTIVE

To understand methodological concerns related to dietary intake collection in transitional societies.

DESIGN

Three days of household weighing and measurement of all food used and repeated 24-hour recalls.

SETTING

Eight Chinese provinces.

SUBJECTS

Five thousand nine hundred and fifty-two and 5152 adults aged 20-45 years in 1989 and 1997, respectively.

RESULTS

Great variance exists in the types and quantity of animal products used in common recipes. For example, the proportion of pork from lean cuts in 'stir-fried fresh pepper and pork' varies between 14 and 24% in urban and rural areas and the total pork content for 100 g (dish) varies by 15 to 19 g between rural and urban areas in each of eight provinces. Another challenge relates to the variation in the edible vegetable oil content added during food preparation. Reliance on standard recipes for each fried dish would miss the variations in oil use over time, space and socio-economic status.

CONCLUSIONS

Dietary change is rapid in transitional countries. Reliance on recipes standardised for animal food and edible oil contents will lead to very large systematic errors in the measurement of energy, fat and protein intakes.

Biobehavioral influences on energy intake and adult weight gain

U.S. adults are now gaining more weight and becoming obese at an earlier age than in previous years. The specific causes of adult weight gain are unknown, but may be attributed to a combination of factors leading to positive energy balance. U.S. food supply data indicate that Americans have had a gradual increase in energy intake since 1970, and that per capita energy intake was 1.42 MJ/d (340 kcal/d) higher in 1994 than that in 1984. In contrast, self-reported physical activity remained constant between 1990 and 1998. Taken together, these data indicate that the increasing trend in U.S. adult weight gain is primarily attributable to overconsumption of energy. Epidemiological and experimental studies in animals and humans provide strong evidence that biobehavioral factors such as dietary variety, liquid (vs. solid) energy, portion size, palatability (taste), snacking patterns, restaurant and other away-from-home food, and dietary restraint and disinhibition influence hunger, satiety and/or voluntary energy intake. When these eating behaviors are consistently experienced either separately or in combination over the long term, they are likely to facilitate overeating. We provide a brief overview of the evidence to date for the role of these biobehavioral factors in contributing to excess energy intake and increases in body weight over time.

Childhood obesity: public-health crisis, common sense cure

During the past two decades, the prevalence of obesity in children has risen greatly worldwide. Obesity in childhood causes a wide range of serious complications, and increases the risk of premature illness and death later in life, raising public-health concerns. Results of research have provided new insights into the physiological basis of bodyweight regulation. However, treatment for childhood obesity remains largely ineffective. In view of its rapid development in genetically stable populations, the childhood obesity epidemic can be primarily attributed to adverse environmental factors for which straightforward, if politically difficult, solutions exist.

Influence of dietary carbohydrates and glycaemic response on subjective appetite and food intake in healthy elderly persons

Increased satiety and decreased food intake are reported following the consumption of low glycaemic index (GI) foods, which gradually increase blood glucose. This observation, however, is not uniformly supported and few studies have examined the impact of different GI foods on satiety and intake in the elderly. After an overnight fast, 10 men and 10 women (aged 60-82 years) consumed similar amounts of available carbohydrate as high (glucose drink or potatoes) or low (barley) GI foods or a non-energy placebo drink on four mornings. Blood glucose and subjective appetite were measured throughout a 120 min post-ingestion period, followed by consumption of an ad libitum lunch. Differences in plasma glucose after test food ingestion (glucose > potatoes > barley > placebo; P < 0.03) did not predict subjective appetite or lunch intake. Potatoes increased subjective satiety the most, followed by barley, then glucose, which trended towards greater satiety than placebo. Potatoes led to less hunger than placebo (P = 0.0023) and less prospective consumption than the other three foods (P < 0.0083), and potatoes and barley led to greater fullness than glucose and placebo (P < 0.0001). Lunch intake was decreased, compared with placebo (502 +/- 47 kcal, P < 0.031), by potatoes (405 +/- 40 kcal) and barley (441 +/- 41 kcal); however, only potatoes (41.9 +/- 12.3%) led to greater compensation at lunch for test food ingestion compared with glucose (11.9 +/- 9.5%, P = 0.016). These results suggest that elderly subjects are sensitive to the effects of different foods on subjective appetite and food intake, and that the GI of the foods tested did not predict their effects on satiety and food intake.

Pharmacological approaches for the treatment of obesity

The high incidence of obesity, its multifactorial nature, the complexity and lack of knowledge of the bodyweight control system, and the scarcity of adequate therapeutics have fuelled anti-obesity drug development during a considerable number of years. Irrespective of the efforts invested by researchers and companies, few products have reached a minimum level of effectiveness, and even fewer are available in medical practice. As a consequence of anti-obesity research, our knowledge of the bodyweight control system increased but, despite this, the pharmacological approaches to the treatment of obesity have not resulted yet in effective drugs. This review provides a panoramic of the multiple different approaches developed to obtain workable drugs. These approaches, however, rely in only four main lines of action: control of energy intake, mainly through modification of appetite;control of energy expenditure, essentially through the increase of thermogenesis;control of the availability of substrates to cells and tissues through hormonal and other metabolic factors controlling the fate of the available energy substrates; andcontrol of fat reserves through modulation of lipogenesis and lipolysis in white adipose tissue. A large proportion of current research is centred on neuropeptidic control of appetite, followed by the development of drugs controlling thermogenic mechanisms and analysis of the factors controlling adipocyte growth and fat storage. The adipocyte is also a fundamental source of metabolic signals, signals that can be intercepted, modulated and used to force the brain to adjust the mass of fat with the physiological means available. The large variety of different approaches used in the search for effective anti-obesity drugs show both the deep involvement of researchers on this field and the large amount of resources devoted to this problem by pharmaceutical companies. Future trends in anti-obesity drug research follow closely the approaches outlined; however, the increasing mass of information on the molecular basis of bodyweight control and obesity will in the end prevail in our search for effective and harmless anti-obesity drugs.

Energy from fat is associated with obesity in U.S. men: results from the Prostate Cancer Prevention Trial

BACKGROUND

Diets high in fat have been proposed as one cause of obesity, primarily because fat is more energy-dense than other macronutrients. However, the literature on fat consumption and human obesity is inconclusive. This research examines associations between dietary fat intake and obesity in men participating in the Prostate Cancer Prevention Trial.

METHODS

Data in this cross-sectional study are from 15,266 men (55-79 years) who completed questionnaires on usual diet, physical activity, and health-related characteristics. Height and weight were collected by clinic personnel. Obesity was defined as body mass index (BMI) greater than or equal to 30 kg/m2.

RESULTS

In this healthy cohort, 23.3% were obese. Younger age, a sedentary lifestyle, lower education, and black race were positively associated with obesity (all P < 0.001). Using two statistical approaches, both total energy and energy from fat, but not total energy from other macronutrients, increased linearly and significantly with increasing BMI. Mean fat intake increased from 691 kcal (31.4% energy) among normal-BMI men to 797 kcal (34.3% energy) among the obese (P for trend <0.001). After controlling for demographic and health-related characteristics in regression models, BMI increased by 0.53 and 0.14 kg/m(2) for every 500 kcal of fat and total energy consumed, respectively. Energy underreporting, based on estimated basal metabolic rate and physical activity, was fourfold higher among obese compared to normal-weight men.

CONCLUSIONS

In this large cohort of healthy older men, energy from fat was associated with obesity, suggesting that high-fat dietary patterns are contributing to the high rates of obesity in U.S. men.

Stimulation of appetite by alcohol

To investigate the effects of alcohol on appetite and food intake, 26 males attended the laboratory on three occasions. On each occasion, they were given a standard breakfast. Visual analog scale ratings of hunger, desire to eat and fullness (appetite ratings) were recorded from before breakfast until their return to the laboratory for lunch. Thirty minutes before lunch, subjects either rested (baseline), were given 330 ml of a no-alcohol lager (264 kJ: no-alcohol condition) or 330 ml of the same lager spiked with 3 units of alcohol (24 g ethyl alcohol; total energy=969 kJ: alcohol condition). Ratings of appetite were taken before and after the preload or baseline rest period and again before and hourly after lunch. The test meal at lunch consisted of a buffet-style array of foods and chilled water. Ad libitum intake at lunch (excluding energy from alcohol) was significantly higher following alcohol (7301+/-442 kJ) compared to both baseline (6365+/-334 kJ) and the no-alcohol conditions (6479+/-289 kJ). Appetite ratings failed to demonstrate any differences between alcohol and the no-alcohol condition. Total energy intake (including energy from alcohol) was enhanced in the alcohol condition by 30%, suggesting that energy from alcohol is not compensated in the short-term and may even have a stimulatory effect on food intake.

Effect of high-fat diet on body mass and energy balance in the bank vole

We tested the hypothesis that animals that reduce their body mass in response to decreased photoperiod do not develop diet-induced obesity (DIO) when fed a high-fat diet (HFD). Bank voles (Clethrionomys glareolus) fed a diet with fat content of 13.5% by mass and 28.2% by energy, for 5 weeks, did not develop hyperphagia and were resistant to DIO, consistent with predictions. There was no significant difference between food (g/day) or energy intake (kJ/day) between the experimental or control group (fed a standard diet with fat content of 5.4% by mass and 12.3% by energy) over the duration of the experiment. However, as a result of a higher apparent energy assimilation efficiency (AEAE), voles fed the HFD assimilated significantly more energy over the 5-week period. Furthermore, they consumed twice as much fat per day as controls. There were no significant differences in resting metabolic rate (RMR) over time or between groups over the 5-week period. In conclusion, bank voles achieved resistance to DIO despite assimilating more energy than control animals fed the standard diet and taking in twice as much fat. Resistance did not occur by modification of RMR, implicating differences in activity levels.

High-Energy Diets, Fatty Acids and Endothelial Cell Function: Implications for Atherosclerosis

Diets high in fat and/or calories can lead to hypertriglyceridemia and postprandial lipemia and thus are considered a risk factor for the development of atherosclerosis. Plasma chylomicron levels are elevated in humans after consuming a high-fat meal, and hepatic synthesis of VLDL is increased when caloric intake is in excess of body needs. High lipoprotein lipase activity and subsequent hydrolysis of triglyceride-rich lipoproteins may be an important source of elevated concentrations of fatty acid anions in the proximity to the endothelium and hence a major risk factor for atherosclerosis. We have shown that selected fatty acids, as well as lipoprotein lipase-derived remnants of lipoproteins isolated from hypertriglyceridemic subjects, can activate vascular endothelial cells and disrupt endothelial integrity. Our studies suggest that omega-6 fatty acids, and especially linoleic acid, cause endothelial cell dysfunction most markedly as well as can potentiate TNF-mediated endothelial cell injury. We propose that high-energy diets, and especially diets rich in linoleic acid, are atherogenic by contributing to an imbalance in cellular oxidative stress/antioxidant status of the endothelium, which can lead to activation of oxidative stress-responsive transcription factors, inflammatory cytokine production and the expression of adhesion molecules. Our data also suggest that nutrients, which have antioxidant and/or membrane stabilizing properties, can protect endothelial cells. These findings contribute to the understanding of the interactive role of high fat/calorie diets and subsequent hypertriglyceridemia with inflammatory components and nutrients that exhibit antiatherogenic properties in the development of atherosclerosis. Moreover, results from our research further support the concept that high-fat/calorie diets and associated postprandial hypertriglyceridemia are significant risk factors for atherosclerosis.

Dietary determinants of energy intake and weight regulation in healthy adults

Until recently, the percentage of energy from dietary fat has been considered a primary determinant of body fatness. This review covers recent studies from our laboratory that challenge this notion. High and low fat diets matched for energy density, palatability and fiber resulted in similar mean voluntary energy intakes over 9 d; analysis of the individual foods in these diets showed that energy density and palatability were significant determinants of energy intake, independent of fat content. Path analysis further revealed that the influence of energy density on energy intake was in part direct, and in part indirect and mediated by palatability. In another study, dietary variety within food groups was shown to be an important predictor of body fatness, and the direction of the association depended on which food groups provided the variety, i.e., the variety of sweets, snacks, condiments, entrees and carbohydrates consumed was positively associated with body fatness, whereas the variety of vegetables was negatively associated. Last, a study of restaurant food and body fatness showed that the frequency of consumption of restaurant food was positively associated with body fatness, independent of education level, smoking status, alcohol intake and physical activity. Restaurant meals tend to be high in fat and low in fiber, and thus energy dense. Restaurants also typically serve a variety of palatable foods in large portions. The increasing variety of high energy foods available and the increasing proportion of household income spent on foods consumed away from home may help explain the U.S. national rising prevalence of obesity.