Dietary energy density and weight regulation

Trends and dietary determinants of overweight and obesity in a multiethnic population

OBJECTIVES

To describe trends in BMI among different ethnic groups in Hawaii and to explore the relation of nutrient and food intake with excess weight.

RESEARCH METHODS AND PROCEDURES

We pooled demographic, anthropometric, and nutritional data derived from a detailed diet history for 159,683 participants of 18 population-based epidemiological studies conducted in Hawaii over a 25-year period. The age-adjusted prevalence of excess weight (BMI > or = 25 kg/m(2)) was estimated for 5-year intervals. To explore dietary determinants of excess weight, we computed odds ratios using logistic regression.

RESULTS

During the study period, the prevalence of excess weight increased considerably among all ethnic groups. Native Hawaiians had the highest and Asian Americans had the lowest prevalence of excess weight at all times. Although the percentage of calories consumed from carbohydrates increased, the percentage of calories from fat decreased over time. On an individual level, fat and protein consumption predicted a higher BMI, and dietary fiber intake predicted a lower BMI. Similarly, a higher consumption of meat, poultry, and fish was related to excess weight, whereas fruit and vegetable intake were inversely associated with excess weight. After stratification by ethnicity, the associations were not materially altered among women, but carbohydrates seemed to have a stronger association with excess weight among Native Hawaiian and Japanese men than among white men.

DISCUSSION

In this large ethnically diverse population, plant-based foods and dietary fiber emerged as a potential protective factor against excess weight regardless of ethnicity.

Popular weight reduction diets

The percentage of people who are overweight and obese has increased tremendously over the last 30 years. It has become a worldwide epidemic. This is evident by the number of children are being diagnosed with a body mass index >85th percentile, and the number of children begin diagnosed with type 2 diabetes mellitus, a disease previously reserved for adults. The weight loss industry has also gained from this epidemic; it is a billion dollar industry. People pay large sums of money on diet pills, remedies, and books, with the hope of losing weight permanently. Despite these efforts, the number of individuals who are overweight or obese continues to increase. Obesity is a complex, multifactorial disorder. It would be impossible to address all aspects of diet, exercise, and weight loss in this review. Therefore, this article will review popular weight loss diets, with particular attention given to comparing low fat diets with low carbohydrate diets. In addition, the role that the environment plays on both diet and exercise and how they impact obesity will be addressed. Finally, the National Weight Control Registry will be discussed.

Predictors of weight gain in a Mediterranean cohort: the Seguimiento Universidad de Navarra Study 1

BACKGROUND

High consumption of sugar-sweetened drinks has been associated with weight gain and obesity in the United States. This trend may also be affecting populations with different eating patterns who increasingly are adopting typical US dietary patterns.

OBJECTIVE

We assessed whether the consumption of sweetened drinks and other food items increased the likelihood of weight gain in a Mediterranean population.

DESIGN

This was a prospective cohort analysis of 7194 men and women with a mean age of 41 y who were followed-up for a median of 28.5 mo with mailed questionnaires. Dietary exposure was assessed with a previously validated semiquantitative food-frequency questionnaire.

RESULTS

During follow-up, we observed that 49.5% of the participants increased their weight (x weight gain: 0.64 kg; 95% CI: 0.55, 0.73 kg). In the participants who had gained > or =3 kg in the 5 y before baseline, the adjusted odds ratio of subsequent weight gain for the fifth quintile compared with the first quintile of sugar-sweetened soft drink consumption was 1.6 (95% CI: 1.2, 2.1; P for trend = 0.02). This association was absent in the participants who had not gained weight in the 5-y period before baseline. The consumption of hamburgers, pizza, and sausages (as a proxy for fast-food consumption) was also independently associated with weight gain (adjusted odds ratio for the fifth compared with the first quintile = 1.2; 95% CI: 1.0, 1.4; P for trend = 0.05). We also found a significant, but weaker, association between weight gain and both red meat and sweetened fruit juice consumption.

CONCLUSION

In a Mediterranean cohort, particularly in the participants who had already gained weight, an increased consumption of sugar-sweetened soft drinks and of hamburgers, pizza, and sausages was associated with a higher risk of additional subsequent weight gain.

A twin study of the effects of energy density and palatability on energy intake of individual foods

The relative effects of energy density and palatability on energy intake, and whether there are familial influences on these effects, are not known. We investigated this issue in 7 pairs of healthy, male monozygotic twins (mean+/-SD age 26.3+/-8.6 years, BMI 23.7+/-3.2 kg/m(2)) in a clinical study involving covert ad libitum feeding of high-fat (HF, approximately 40%) and low-fat (LF, approximately 20%) diets in two 9-day phases. Diets were matched for average energy density, protein, fiber, and initial reported taste pleasantness, but these factors varied among the individual foods. Relationships between energy density, palatability, and energy intake were explored using regression and path analyses. Food energy density was positively associated with average taste pleasantness (r=0.46, P=0.03) independent of fat content, while energy intake from individual foods was positively associated with both energy density (r=0.56, P=0.007) and taste pleasantness (r=0.73, P<0.0001). In path analysis, both energy density and taste pleasantness directly influenced energy intake, and energy density also indirectly influenced energy intake by influencing taste pleasantness. In addition, there were significant within-twin pair similarities for the energy density-taste pleasantness and energy density-energy intake relationships (P<0.03) with the result that some twin pairs but not others identified foods high in energy density as more pleasant tasting and consumed relatively more energy from them compared to foods low in energy density. These results suggest that there are familial influences on the extent to which high energy density foods are preferred and contribute to total energy intake.

Low- and high-carbohydrate diets: body composition differences in rats

OBJECTIVE

To determine differences in adipose tissue mass, cell size, and lipid metabolism transcripts and differences in composition of body weight loss and energy expenditure (EE) after isoenergetic, energy-restricted intake of low-carbohydrate/high-fat/high-protein (LC) and high-carbohydrate/low-fat/moderate-protein (HC) diets.

RESEARCH METHODS AND PROCEDURES

Ten-week old female Sprague-Dawley rats were fed a high-fat diet ad libitum for 8 weeks to induce weight gain and fat deposition. Weight-matched rats were then assigned to isoenergetic LC (Atkins) and HC (American Dietary Association Exchange) diets for 10 weeks at 65% of ad libitum energy intake.

RESULTS

There was no significant difference in the serum lipid profiles or amount of body weight lost between the HC and LC groups, whereas a higher insulin sensitivity index (p < 0.01) resulted from the HC compared with the LC diet. Compared with the post-restriction LC group, the HC group demonstrated (p < 0.05) higher EE during active hours, lower mRNA levels for the lipogenic genes peroxisome proliferator-activated receptor gamma2, lipoprotein lipase, and, adipocyte fatty acid binding protein, decreased adipocyte cell volume, and decreased fat mass.

DISCUSSION

Results indicated down-regulation of lipogenic genes, decreased fat mass, and, therefore, improved body composition in the post-restriction HC compared with the LC group. The small mean differences between the two diet groups (p = 0.11) in 24-hour EE over the 10 weeks of diet intervention would account for the majority of the lower mean body weights in the post-restriction HC group. These data suggest that macronutrient composition of the diet influences body composition and indicate a distinction between HC and LC diets.

Reductions in portion size and energy density of foods are additive and lead to sustained decreases in energy intake

BACKGROUND

When the portion size and energy density (in kcal/g) of a food are varied simultaneously in a single meal, each influences energy intake independently.

OBJECTIVE

We aimed to determine how the effects of portion size and energy density combine to influence energy intake and satiety over multiple meals for 2 d.

DESIGN

In a crossover design, 24 young women were provided with meals and snacks for 2 consecutive days per week for 4 wk; all foods were consumed ad libitum. Across the 4 sessions, the subjects were served the same 2 daily menus, but all foods were varied in portion size and energy density between a standard level (100%) and a reduced level (75%).

RESULTS

Reducing the portion size and energy density of all foods led to significant and independent decreases in energy intake over 2 d (P < 0.0001). A 25% decrease in portion size led to a 10% decrease in energy intake (231 kcal/d), and a 25% decrease in energy density led to a 24% decrease in energy intake (575 kcal/d). The effects on energy intake were additive and were sustained from meal to meal. Despite the large variation in energy intake, there were no significant differences in the ratings of hunger and fullness across conditions over the 2 d.

CONCLUSIONS

Reductions in portion size and energy density independently decreased ad libitum energy intake in women when commonly consumed foods were served over 2 d. Reductions in both portion size and energy density can help to moderate energy intake without increased hunger.

Effects of Flax Fiber on Laxation and Glycemic Response in Healthy Volunteers

We investigated whether a flax supplement taken orally or baked in a bakery product would effect the physiological responses characteristic of soluble and insoluble fiber, i.e., laxation and glycemic response, respectively. In Study 1, 26 healthy young adults consumed up to 15 g of fiber from a proprietary flax fiber supplement or as a psyllium supplement for 2 weeks once usual fecal weights were established. Changes in dietary fiber intake and acceptability of both products were evaluated. An increase in fecal weight was found with both fiber treatments. Supplemental fiber at intakes of 9.0 g/day (flax) and 10.4 g/day (psyllium) gave fecal bulking capacity of about 2.9 and 4.8 g of fecal weight/g of fiber, respectively. In Study 2, the effect of flax bread versus control white bread on glycemic response was studied. Eleven fasting subjects completed four test periods (duplicate trials of each bread) under standardized glycemic testing conditions. Paired t tests were used to analyze test compared with control peak blood glucose values (6.6 +/- 0.9 mmol/L compared with 6.9 +/- 0.7 mmol/L, P < .05, respectively) and area under the curve (AUC) (669 +/- 53 compared with 693 +/- 57, P = .015, respectively). Peak blood glucose values and AUC were improved by ingestion of flax fiber in healthy subjects. In conclusion, a flax fiber supplement provides the benefits of soluble and insoluble fiber.

Energy density of diets reported by American adults: association with food group intake, nutrient intake, and body weight

OBJECTIVE

Recent reports suggest that dietary energy density may play a role in regulation of food intake. However, little is known about the energy density of diets consumed by free-living populations; therefore, the purpose of this study was to examine demographic, health, and nutritional correlates of energy density of self-reported diets.

RESEARCH METHODS AND PROCEDURES

Using data from the NHANES III (n=13 400), dietary energy density was defined three ways: (1) energy content (kJ/g) of all foods and beverages reported or ED1, (2) energy content (kJ/g) of all foods and energy yielding beverages or ED2, and (3) energy content (kJ/g) of all foods (no beverages) or ED3. Multiple linear or logistic regression methods were used to examine the association of energy density with intake of energy, nutrients, food groups, and body mass index (BMI). We computed the ratios of within- to between-person variance for the three energy density variables using the second recall obtained from the second exam subsample of NHANES III (n=1037).

RESULTS

The mean ED1, ED2, and ED3, respectively, were 3.84+/-0.02, 5.45+/-0.03, and 8.03+/-0.03. Dietary intakes of energy, fat, and low-nutrient-density foods were related positively, but amounts of micronutrients, fruit, and vegetables were related inversely with all types of energy density (P<0.0001). ED2 and ED3 were modest positive predictors of BMI in both men and women (P< or =0.03). The ratios of within- to between-person components of variance for ED1, ED2, and ED3 were 1.34, 2.05, and 1.53, respectively.

DISCUSSION

High-energy-density diets in the US were characterized by low fruit and vegetable intake, and high BMI.

Stereotypical thinking about foods and perceived capacity to promote weight gain

The modern health media as well as the food and diet industries praise certain foods and food nutrients as being healthful while at the same time criticizing other foods and nutrients as promoters of obesity and disease. Do the categorical messages that much of the general public has assimilated concerning food influence judgements of the weight-enhancing properties of foods? In the present study a sample of adult participants (mostly middle-aged) rated the weight-enhancing characteristics of a group of snack names that possess positive health reputations (e.g. a banana) along with snack names that were more disreputable in terms of wholesomeness (e.g. bacon). The results indicated that lower-calorie (and in some cases lower-fat) disreputable snacks were generally perceived to promote greater weight gain than much higher-calorie (and in some cases higher-fat) reputable snacks. Beliefs about particular foods' goodness or badness as well as fat content were most often emphasized. The good versus bad message that Americans have assimilated concerning foods may be contributing to tendencies toward obesity.

Dietary fiber and body weight

OBJECTIVE

This review provides an update of recent studies of dietary fiber and weight and includes a discussion of potential mechanisms of how dietary fiber can aid weight loss and weight maintenance.

METHODS

Human studies published on dietary fiber and body weight were reviewed and summarized. Dietary fiber content of popular low-carbohydrate diets were calculated and are presented.

RESULTS

Epidemiologic support that dietary fiber intake prevents obesity is strong. Fiber intake is inversely associated with body weight and body fat. In addition, fiber intake is inversely associated with body mass index at all levels of fat intake after adjusting for confounding factors. Results from intervention studies are more mixed, although the addition of dietary fiber generally decreases food intake and, hence, body weight. Many mechanisms have been suggested for how dietary fiber aids in weight management, including promoting satiation, decreasing absorption of macronutrients, and altering secretion of gut hormones.

CONCLUSION

The average fiber intake of adults in the United States is less than half recommended levels and is lower still among those who follow currently popular low-carbohydrate diets, such as Atkins and South Beach. Increasing consumption of dietary fiber with fruits, vegetables, whole grains, and legumes across the life cycle is a critical step in stemming the epidemic of obesity found in developed countries. The addition of functional fiber to weight-loss diets should also be considered as a tool to improve success.

Dietary Fiber and Fat Are Associated with Excess Weight in Young and Middle-Aged US Adults

OBJECTIVE

To examine relative associations of dietary composition variables with body mass index (BMI; calculated as kg/m2) among young and middle-aged US adults. We hypothesized that in subjects with physiologically plausible reported energy intakes, fiber intake would be inversely associated with BMI, independent of other dietary composition and sociodemographic variables.

SUBJECTS AND DESIGN

Data from adults age 20 to 59 years in the Continuing Survey of Food Intakes by Individuals (CSFII) 1994-1996 were used. Exclusions were pregnancy or lactation, food insecurity, missing weight or height data, or having only one dietary recall. Based on our previously published methods, a physiologically plausible reported energy intake was calculated as being within +/-22% of predicted energy requirements for the mean of two 24-hour recalls.

RESULTS

Reporting plausibility ([reported energy intake/predicted energy requirements]x100) averaged 83% in the total sample (N=4,539) and increased to 96% in the plausible sample (n=1,932). Only approximately 5% of the plausible sample consumed the Adequate Intake for fiber. In plausibly reporting women, fiber, its interaction with percentage energy from fat, and energy density were independently associated with BMI. Only percentage energy from fat was associated with BMI in men reporting plausibly. Compared with the total sample, stronger relationships between diet and BMI were observed among the plausible reporters. In women, a low-fiber (< 1.5 g/MJ), high-fat (> or = 35% energy) diet was associated with the greatest increase in risk of overweight or obesity compared with a high-fiber, low-fat diet.

CONCLUSIONS

Weight control advice for US women should place greater emphasis on consumption of fiber.

Changing the energy density of the diet as a strategy for weight management

A growing body of laboratory-based, clinical, and epidemiological data suggests that low-energy-dense diets are associated with better diet quality, lower energy intakes, and body weight. Dietary energy density can be lowered by adding water-rich fruits, vegetables, cooked grains, and soups to the diet, and by reducing the diet's fat content. Low-energy-dense diets can be successfully incorporated into clinical dietetics since they help lower energy intake without reducing food volume and thus help individuals avoid feeling hungry and deprived. There are multiple steps that could be taken by nutrition professionals and food manufacturers to encourage the consumption of low-energy-dense diets. The goal is to develop reduced-calorie eating plans that meet personal food preferences and also provide satisfying food portions. Since using energy density to guide food choices leads to food patterns consistent with dietary guidelines, policy level initiatives should be devised to help ensure that low-energy-dense diets are affordable and accessible to all.

Overweight among low-income preschool children associated with the consumption of sweet drinks: Missouri, 1999-2002

OBJECTIVE

To examine the association between sweet drink consumption and overweight among preschool children.

METHODS

A retrospective cohort design was used to examine the association between sweet drink consumption and overweight at follow-up among 10904 children who were aged 2 and 3 years and had height, weight, and Harvard Service Food Frequency Questionnaire data collected between January 1999 and December 2001 and height and weight data collected 1 year later. Sweet drinks included vitamin C-containing juices, other juices, fruit drinks, and sodas as listed on the Harvard Service Food Frequency Questionnaire. Logistic regression was used to adjust for age; gender; race/ethnicity; birth weight; and intake of high-fat foods, sweet foods, and total calories. Results were stratified by baseline BMI.

RESULTS

Among children who were normal or underweight at baseline (BMI <85th percentile), the association between sweet drink consumption and development of overweight was positive but not statistically significant. Children who were at risk for overweight at baseline (BMI 85th-<95th percentile) and consumed 1 to <2 drinks/day, 2 to <3 drinks/day, and > or =3 drinks/day were, respectively, 2.0 (95% confidence interval [CI]: 1.3-3.2), 2.0 (95% CI: 1.2-3.2), and 1.8 (95% CI: 1.1-2.8) times as likely to become overweight as the referent (<1 drink/day). Children who were overweight at baseline (BMI > or =95th percentile) and consumed 1 to <2 drinks/day, 2 to <3 drinks/day, and > or =3 drinks/day were, respectively, 2.1, 2.2, and 1.8 times as likely to remain overweight as the referent.

CONCLUSIONS

Reducing sweet drink consumption might be 1 strategy to manage the weight of preschool children. Additional studies are needed to understand the mechanism by which such consumption contributes to overweight.

Acid–base balance may influence risk for insulin resistance syndrome by modulating cortisol output

Frank metabolic acidosis is known to promote renal excretion of hydrogen ion by induction of glutaminase and other enzymes in the renal tubules. This induction, at least in part, reflects an increase in pituitary output of ACTH and a consequent increased production of cortisol and aldosterone; these latter hormones act on the renal tubules to promote generation of ammonia, which expedites renal acid excretion. Recent evidence suggests that the moderate metabolic acidosis associated with a protein-rich diet low in organic potassium salts - quantifiable by net acid output in daily urine - can likewise evoke a modest increase in cortisol production. Since cortisol promotes development of visceral obesity, and has a direct negative impact on insulin function throughout the body, even a modest sustained up-regulation of cortisol production may have the potential to increase risk for insulin resistance syndrome and type 2 diabetes. This thesis appears to be consistent with previous epidemiological reports correlating high potassium consumption, or a high intake of fruits and vegetables, with reduced risk for diabetes and coronary disease. Future prospective epidemiology should assess whether the estimated acid-base balance of habitual diets - calculated from the ratio of dietary protein and potassium - correlates with risk for insulin resistance syndrome and diabetes.

Dietary Energy Density and Body Weight: Is There a Relationship?

The energy density of foods and beverages is defined as the available energy per unit weight (kJ/g). Energy density of the diet is usually calculated excluding non-caloric beverages and drinking water. Because water contributes more to the weight of foods than any macronutrient, energy-dense foods are not necessarily those high in sugar or fat, but those that are dry. Evidence linking dietary energy density with body weight is critically evaluated in this review. Existing reports of a positive association between dietary energy density, higher energy intakes, and weight gain are based on laboratory and clinical studies. Although some cross-sectional epidemiological studies have linked dietary energy density with higher body mass index (BMI) values, the data are not consistent. At this time, there are no longitudinal cohort data linking dietary energy density with higher obesity risk.

Diet, insulin resistance, and obesity: zoning in on data for Atkins dieters living in South Beach

Insulin resistance is a central pathogenic factor for the metabolic syndrome and is associated with both generalized obesity and the accumulation of fat in the omental and intramyocellular compartments. In the context of the current obesity epidemic, it is imperative to consider diets in terms of their ability to both promote weight loss and ameliorate insulin resistance. Weight loss under any dietary formulation depends on hypocaloric intake, and only moderate weight loss (5-10%) is sufficient to augment insulin sensitivity. However, increments in insulin sensitivity may be more directly related to loss of intramyocellular or omental fat rather than loss of total body weight per se. The widespread acceptance of popular low-carbohydrate high-fat diets (e.g. Atkins Diet, Zone Diet, South Beach diet) further underscores the need to evaluate dietary interventions regarding their safety and metabolic effects. These high-fat diets have been shown to be safe in the short term; however, their long-term safety has not been established. With respect to insulin sensitivity, diets enriched in saturated fats can induce insulin resistance, whereas fat substitution with monounsaturated fats can enhance insulin sensitivity. On the other hand, high-fiber, high-carbohydrate diets comprised of foods with low caloric density can similarly be used for effective weight reduction and to ameliorate insulin resistance. Although some data suggest that low-glycemic index diets are most advantageous in this regard, these effects may have more to do with increments in dietary fiber than differences in available carbohydrates. Popular low-carbohydrate, high-fat diets are being fervently embraced as an alternative to challenging modifications in lifestyle and intentional calorie reduction. Current data do not support such unbridled enthusiasm for these diets, particularly in relationship to high-fiber, high-carbohydrate diets emphasizing intake of fresh vegetables and fruits. Long-term studies to determine the efficacy and safety of both popular and experimental diets are warranted.

Ballaststoffe: Mehr als ein Diätmittel

A nutrition rich in fibre has a preventive effect against constipation, colon diverticulosis, carcinoma of the large bowel and stomach, type 2-diabetes, metabolic syndrome and cardiovascular disease. In case of constipation, diverticulosis and diabetes this effect solely depends on dietary fibre. Regarding carcinomas and cardiovascular diseases, so far unknown factors integrated in or associated with fibre-rich food may also contribute to the preventive effect. Therapy with dietary fibre is indicated for constipation, colon diverticulosis, diarrhea, diabetes, and hypercholesterinemia. The individual dietary fibres differ substance-specifically. Food-integrated dietary fibre such as whole-grain bread, vegetables and fruit have their place in prevention. Dietary fibre preparations such as wheat bran, flax seed or sugar-beet fibre are useful in the treatment of constipation, colon diverticulosis and adiposity. Oat bran is preferentially used in hypercholesterinemia. Purified dietary fibres such as cellulose, guar, psyllium, and beta-glucan have an anti-diabetic, all viscous fibres an anti-lipaemic effect. The therapeutic dosages of dietary fibre preparations are 20-40 g/day and of purified fibres substances 10-20 g/day respectively.

Diet composition and the risk of type 2 diabetes: epidemiological and clinical evidence

In the last 10 years nutritional research on diabetes has improved dramatically in terms of both number of studies produced and quality of methodologies employed. Therefore, it is now possible to attempt to provide the evidence on which nutritional recommendations for the prevention of type 2 diabetes could be based. We therefore performed a literature search and, among the papers published in indexed journals, we selected relevant epidemiological (mostly prospective) and controlled intervention studies. Lifestyle factors that have, so far, been consistently associated with increased risk of type 2 diabetes are overweight and physical inactivity. However, recent evidence from epidemiological studies has shown that the risk of type 2 diabetes is also associated with diet composition, particularly with: (1) low fibre intake; (2) a high trans fatty acid intake and a low unsaturated:saturated fat intake ratio; (3) absence of or excess alcohol consumption. All these factors are extremely common in Western populations and therefore the potential impact of any intervention on them is large: indeed, >90 % of the general population has one or more of these risk factors. The ability to correct these behaviours in the population is estimated to reduce the incidence of diabetes by as much as 87 %. Recent intervention studies have shown that type 2 diabetes can be prevented by lifestyle changes aimed at body-weight reduction, increased physical activity and multiple changes in the composition of the diet. Within this context, the average amount of weight loss needed is not large, about 5 % initial weight, which is much less than the weight loss traditionally considered to be clinically significant for prevention of type 2 diabetes. In conclusion, new emphasis on prevention by multiple lifestyle modifications, including moderate changes in the composition of the habitual diet, might limit the dramatic increase in incidence of type 2 diabetes envisaged worldwide.

Clarifying concepts about macronutrients’ effects on satiation and satiety

It seems that many people, including dietetics professionals and other nutrition experts, are unclear about some of the fundamental yet complex concepts behind the influence of dietary macronutrients (ie, protein, carbohydrate, and fat) on appetite regulation. Recent research has begun to unravel some of the more complicated physiological processes of appetite control and regulation generated by hormones such as leptin, ghrelin, and the gut hormone peptide YY3-35. Although the processes by which the macronutrients in our foods influence appetite regulation have been a topic of study for decades, they remain confusing and are often misunderstood. The objective of this article is to define the terminology commonly used to discuss the macronutrients' roles in appetite regulation and to discuss the interrelated concepts and roles of taste, palatability, and energy density.

Effects of food unit size and energy density on intake in humans

The effects of food unit size (FU) and energy density (ED) on food consumption were explored in 20 adults using a within subjects 2 x 2 design study. The four food treatment combinations were provided in the laboratory in random order on four non-consecutive days. The foods differed in FU (small food unit (SFU) or customary food unit (CFU)) and energy density, by manipulating fat content (low (LED) or high (HED)). Appetitive responses and total grams and kilocalories consumed were monitored. Hunger, fullness, desire to eat and prospective consumption ratings were not significantly different between treatments. Gram weight of food consumed was constant across all treatments. Energy intake of HED foods was greater than LED foods independent of food unit size for breakfast (F(1,17) = 11.77, p < 0.001), lunch (F(1,17) = 4.70, p < 0.05) and the 24 h period (F(1,17) = 8.99, p < 0.001) but only tended to be increased at dinner. In summary, appetitive sensations were not markedly altered by food unit size or energy density. The daily gram weight of food consumed and appetitive ratings were relatively consistent across treatments resulting in higher energy intake with HED foods.

Is a calorie a calorie?

The aim of this review was to evaluate data regarding potential thermodynamic mechanisms for increased rates of weight loss in subjects consuming diets high in protein and/or low in carbohydrate. Studies that compared weight loss and energy expenditure in adults consuming diets high in protein and/or low in carbohydrate with those in adults consuming diets low in fat were reviewed. In addition, studies that measured the metabolizable energy of proteins, fats, and carbohydrates were reviewed. Diets high in protein and/or low in carbohydrate produced an approximately equal to 2.5-kg greater weight loss after 12 wk of treatment. Neither macronutrient-specific differences in the availability of dietary energy nor changes in energy expenditure could explain these differences in weight loss. Thermodynamics dictate that a calorie is a calorie regardless of the macronutrient composition of the diet. Further research on differences in the composition of weight loss and on the influence of satiety on compliance with energy-restricted diets is needed to explain the observed increase in weight loss with diets high in protein and/or low in carbohydrate.

Diet, nutrition and the prevention of excess weight gain and obesity

OBJECTIVES

To review the evidence on the diet and nutrition causes of obesity and to recommend strategies to reduce obesity prevalence.

DESIGN

The evidence for potential aetiological factors and strategies to reduce obesity prevalence was reviewed, and recommendations for public health action, population nutrition goals and further research were made.

RESULTS

Protective factors against obesity were considered to be: regular physical activity (convincing); a high intake of dietary non-starch polysaccharides (NSP)/fibre (convincing); supportive home and school environments for children (probable); and breastfeeding (probable). Risk factors for obesity were considered to be sedentary lifestyles (convincing); a high intake of energy-dense, micronutrient-poor foods (convincing); heavy marketing of energy-dense foods and fast food outlets (probable); sugar-sweetened soft drinks and fruit juices (probable); adverse social and economic conditions-developed countries, especially in women (probable). A broad range of strategies were recommended to reduce obesity prevalence including: influencing the food supply to make healthy choices easier; reducing the marketing of energy dense foods and beverages to children; influencing urban environments and transport systems to promote physical activity; developing community-wide programmes in multiple settings; increased communications about healthy eating and physical activity; and improved health services to promote breastfeeding and manage currently overweight or obese people.

CONCLUSIONS

The increasing prevalence of obesity is a major health threat in both low- and high income countries. Comprehensive programmes will be needed to turn the epidemic around.

Parents are key players in the prevention and treatment of weight-related problems

There is growing agreement among experts that an obesogenic environment, which encourage excess food intake and idealizes thinness, plays a crucial role in the epidemic of childhood obesity and eating disorders. Because parents provide a child's contextual environment, they should be considered key players in interventions aimed at preventing or treating weight-related problems. Parenting style and feeding style are crucial factors in fostering healthy lifestyle and awareness of internal hunger and satiety cues and de-emphasizing thinness. Effective interventions for prevention and treatment of weight-related problems should be approached from a health-centered rather than a weight-centered perspective, with the parents as central agents of change. This paper reviews the environmental risk factors and parents' role in the prevention and treatment of children's weight-related problems.

Self-regulation of energy intake in the prevention and treatment of obesity: is it feasible?

The prevalence of obesity in developed countries has been steadily increasing. Comprehensive lifestyle change programs for the treatment of obesity have garnered considerable empirical support, but most weight lost in lifestyle interventions is regained within several years. The outcome of obesity prevention programs has also been disappointing. One reason for this state of affairs may be that most weight control programs are based on an assumption of equipotentiality of their intervention components. That is, obesity prevention and treatment programs consist of a multitude of behavioral, cognitive, nutritional, physical activity, and interpersonal techniques, all of which are assumed to be of roughly equal importance in weight control. However, there is considerable evidence that our evolutionary heritage has made most humans highly sensitive to the availability and nature of food in the environment. It therefore may be unrealistic to expect that enhancing self-regulatory skills will be sufficient to overcome the combined influence of our appetitive predispositions and the obesigenic environment. However, there is growing evidence that weight control interventions that focus on the availability, structure, composition, and portion size of foods in the diet improve long-term weight control. Concerted efforts to change the availability and nature of foods at both the individual and population level may hold considerable promise for the treatment and prevention of obesity.

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.

Dietary energy density is associated with increased intake in free-living humans

Dietary energy density markedly influences the daily dietary intake of humans. The present study examined the relation of energy density to dietary intake and body size in 371 male and 581 female adults. The subjects were free-living and provided a detailed record of their everyday food and drink intake in 7-d food diaries. The reported diets were analyzed for the relation of energy density to body size and to per-meal, daily, and weekly dietary intake. High energy density was associated with greater (P < 0.001) total intake, especially of fat, when intake was correlated with energy density (r = 0.26, P < 0.001) and when the daily intake of individual participants was correlated with their daily dietary density (r = 0.66, P < 0.001). These results occurred regardless of sex, low reporting, or the inclusion of drinks in the energy density calculations. High energy density was also associated with a high rate of intake (r = 0.46, P < 0.001) and large meal sizes (r = 0.61, P < 0.001). However, energy density was not correlated with body size, height, weight, or body mass index. High energy density appears to be related to greater overall intake in the short-term, but there may be compensation over the long term, with no net effect on body size.

The time of day of food intake influences overall intake in humans

Circadian and diurnal rhythms affect food intake, and earlier research has suggested that meal sizes increase, whereas the after-meal intervals and satiety ratios decrease over the day. We hypothesized that the time of day of food intake would be related to total intake such that intake early in the day would tend to reduce overall intake, whereas intake later in the day would tend to increase intake over the entire day. The intakes of 375 male and 492 female free-living individuals, previously obtained via 7-d diet diaries, were reanalyzed. The total and meal intakes of food energy, the amounts of the macronutrients ingested and the density of intake occurring during five 4-h periods (0600-0959, 1000-1359, 1400-1759, 1800-2159 and 2200-0159 h) were identified and related to overall and meal intakes during the entire day. The proportion of intake in the morning was negatively correlated with overall intake (r=-0.13, P<0.01), whereas the proportion ingested late in the evening was positively correlated with overall intake (r=0.14, P<0.01). The energy densities of intake during all periods of the day were positively related to overall intake (range, r=0.13-0.23, P<0.01). The results suggest that low energy density intake during any portion of the day can reduce overall intake, that intake in the morning is particularly satiating and can reduce the total amount ingested for the day, and that intake in the late night lacks satiating value and can result in greater overall daily intake.

What Can Intervention Studies Tell Us about the Relationship between Fruit and Vegetable Consumption and Weight Management?

Given the recent surge in obesity, effective dietary strategies for weight management are required. Because fruits and vegetables are high in water and fiber, incorporating them in the diet can reduce energy density, promote satiety, and decrease energy intake. Although few interventions have specifically addressed fruit and vegetable consumption, evidence suggests that coupling advice to increase intake of these foods with advice to decrease energy intake is a particularly effective strategy for weight management. This approach may facilitate weight loss because it emphasizes positive messages rather than negative, restrictive messages.

Behavioral treatment of obesity

Behavioral treatment for obesity seeks to identify and modify eating, activity, and thinking habits that contribute to patients' weight problems. This approach recognizes that body weight is affected by factors other than behavior, which include genetic, metabolic, and hormonal influences. Behavioral treatment helps obese individuals develop a set of skills (eg, a low-fat diet, a high-activity lifestyle, realistic expectations) to regulate weight, even though patients may remain overweight after treatment. This article describes the behavioral treatment of obesity, its short- and long-term results, and methods to improve long-term weight loss.

Effect of hypocaloric meals with different macronutrient compositions on energy metabolism and lung function in obese women

OBJECTIVE

We investigated the effect of hypocaloric mixed diets with different proportions of carbohydrate, protein, and fat on resting metabolic rate and the thermic effect of food in obese women.

METHODS

Three mixed hypocaloric diets were consumed in random order during separate periods lasting 7 d each. Between each dietary period there was a washout period of 10 d. Diet 1 had a higher proportion of energy from carbohydrate (72%), diet 2 had a higher proportion of energy from protein (43%), and diet 3 had a higher proportion of energy from fat (68%). Indirect calorimetry and lung function tests were done after the completion of each 7-d diet. Seven obese women, ages 22 to 45 y and with body mass indexes of 32 to 59 kg/m(2), participated in the study. Oxygen consumption, carbon dioxide production, resting metabolic rate, and the thermic effect of food by indirect calorimetry were measured. Lung function tests included spirometry in the seated and upright positions, arterial blood gas analysis, and maximal inspiratory and expiratory pressures.

RESULTS

There were no statistically significant differences in the resting metabolic rate and the thermic effect of food resulting from the three diets. The mean resting metabolic rates (kJ/d) were 7453 +/- 1446 for diet 1, 7461 +/- 1965 for diet 2, and 7076 +/- 2048 for diet 3. The mean thermic effects of food (kcal/min) were -0.02 +/- 0.07 for diet 1, -0.01 +/- 0.25 for diet 2, and 0.05 +/- 0.13 for diet 3. Lung function tests were normal before and after the hypocaloic diets: partial pressure of oxygen (mmHg) values were 81 +/- 13, 77 +/- 8, and 78 +/- 11 for diets 1 to 3, respectively; and partial pressure of carbon dioxide (mmHg) were 37 +/- 4, 37 +/- 3, and 37 +/- 4 for diets 1 to 3, respectively.

CONCLUSIONS

Obese women with normal lung function tests and consuming mixed hypocaloric diets showed no alteration in resting metabolic rate and a reduced or absent thermic effect of food independently of the macronutrient composition.

Sustaining dietary changes for preventing obesity and diabetes: lessons learned from the successes of other epidemic control programs

A degree of success has been achieved in controlling several epidemics of infectious and non-infectious causes of death in countries, such as, Australia and New Zealand. Using the epidemiological triad (host, vector, environment) as a model, the key components of the control of these epidemics have been identified and compared to the current status of interventions to prevent obesity and its main disease consequence, type 2 diabetes. Reductions in mortality from tobacco, cardiovascular diseases, road crashes, cervical cancer and sudden infant death syndrome have been achieved by addressing all corners of the triad. Similarly, prevention programs have minimized the mortality from HIV AIDS and melanoma mortality rates are no longer rising. The main lessons learned from these prevention programs that could be applied to the obesity/diabetes epidemic are: taking a more comprehensive approach by increasing the environmental (mainly policy-based) initiatives; increasing the 'dose' of interventions through greater investment in programs; exploring opportunities to further influence the energy density of manufactured foods (one of the main vectors for increased energy intake); developing and communicating specific, action messages; and developing a stronger advocacy voice so that there is greater professional, public and political support for action. Successes in the other epidemics have been achieved in the face of substantial barriers within individuals, society, the private sector and government. The barriers for preventing obesity/diabetes are no less formidable, but the strategies for surmounting them have been well tested in other epidemics.

Relative influence of diet and physical activity on body composition in urban Chinese adults

BACKGROUND

The relative influence of diet and physical activity on body fatness remains uncertain.

OBJECTIVE

The objective of the study was to investigate associations of dietary variables and physical activity with body fatness in urban Chinese adults.

DESIGN

We conducted a cross-sectional study in 130 weight-stable men and women aged 35-49 y. Subjects were selected from upper and lower tertiles of dietary fat and physical activity on the basis of screening questionnaires. Dietary intake was assessed by weighed food intake, physical activity level (PAL) was calculated as the ratio of predicted total energy expenditure (TEE) to predicted resting energy expenditure, and body composition was measured with the use of (2)H(2)O. Reported energy intake and predicted TEE were validated against TEE determined with the use of (2)H(2)(18)O (n = 73).

RESULTS

Body fatness was positively associated with dietary variety (ie, variety of ingredients) (partial r = 0.186, P = 0.039) and frequency of consuming restaurant foods (partial r = 0.237, P = 0.001) and negatively associated with PAL (partial r = -0.307, P = 0.001) in a multiple regression analysis that controlled for sex and confounders. The combined variance accounted for by dietary variety and restaurant food consumption (9.1%) was equivalent to that for PAL (9.4%). Neither dietary fat nor energy density predicted body fatness, but dietary energy density predicted within-subject day-to-day variation in reported energy intake (P < 0.001).

CONCLUSIONS

Dietary variety, frequency of restaurant food consumption, and PAL significantly predicted body fatness in urban Chinese adults, but dietary fat did not. These findings support previous studies in US adults and suggest that dietary variables other than fat have an important influence on adult body composition.

Effect of food on gastrointestinal transit of liquids in cynomolgus monkeys

We investigated the gastrointestinal transit of liquids, as well as various gastric pH profiles, in fed cynomolgus monkeys. Twelve grams of a biscuit-type solid food were provided 1 h before the test. The acetaminophen method was used to determine the gastric half-emptying time (t(50%)), which provided an estimate of the gastric emptying rate. The gastric emptying rate of liquids was significantly reduced after food intake in monkeys. The mean t(50%) value was 143.5 min and comparable to that of humans after eating. However, there was a large variability in the t(50%) between individual animals as shown by the coefficient of variance of approximately 80%. Next, the median oro-caecal transit time in fed monkeys was determined to be 1.8 h, using the sulfasalazine-sulfapyridine method. There was no significant difference in oro-caecal transit time between unfed and fed monkeys; thus, food intake has no significant effect on the oro-caecal transit time of liquids in either monkeys or humans. However, the oro-caecal transit time in humans is about 2 h longer than that in monkeys. Our experiments using several different foods suggested that the typical human gastric pH profile could not be simulated in fed monkeys.

Dietary fat and cardiovascular disease risk: quantity or quality?

When considering dietary fat quantity, there are two main factors to consider, impact on body weight and plasma lipoprotein profiles. Data supporting a major role of dietary fat quantity in determining body weight are weak and may be confounded by differences in energy density, dietary fiber, and dietary protein. With respect to plasma lipoprotein profiles, relatively consistent evidence indicates that under isoweight conditions, decreasing the total fat content of the diet causes an increase in triglyceride and decrease in high-density lipoprotein (HDL) cholesterol levels. When considering dietary fat quality, current evidence suggests that saturated fatty acids tend to increase low-density lipoprotein (LDL) cholesterol levels, whereas monounsaturated and polyunsaturated fatty acids tend to decrease LDL cholesterol levels. Long-chain omega-3 fatty acids, eicosapentaenoic acid (EPA) (20:5n-3) and docosahexaenoic acid (DHA) (22:6n-3), are associated with decreased triglyceride levels in hypertriglyceridemic patients and decreased risk of developing coronary heart disease (CHD). Dietary trans-fatty acids are associated with increased LDL cholesterol levels. Hence, a diet low in saturated and trans-fatty acids, with adequate amounts of monounsaturated and polyunsaturated fatty acids, especially long-chain omega-3 fatty acids, would be recommended to reduce the risk of developing CHD. Additionally, the current data suggest it is necessary to go beyond dietary fat, regardless of whether the emphasis is on quantity or quality, and consider lifestyle. This would include encouraging abstinence from smoking, habitual physical activity, avoidance of weight gain with age, and responsible limited alcohol intake (one drink for females and two drinks for males per day).

The role of energy density

Dietary energy density (ED) appears to have a major influence on the regulation of food intake and body weight. If people consume a fixed weight of food each day, then high-ED diets should be associated with high energy intakes and with overweight. In contrast, low-ED diets should result in lower daily energy intakes and therefore weight loss. For this approach to work, low-ED foods must be as palatable as high-ED foods and, calorie for calorie, have a greater satiating power. Each of those assumptions is debatable. Dietary ED depends chiefly on the water content of foods. As a rule, high-ED foods are more palatable but less satiating, whereas low-ED foods are more satiating but less palatable. Consumer preferences for high-ED foods can be explained in terms of good taste, low cost, and convenience. Low-ED foods, such as fresh produce, provide less energy per unit cost than do high-ED foods, which often contain added sugars and fats. Poverty and obesity may well be linked through the habitual consumption of a low-cost, high-ED diet.

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.

Preventive strategies against weight gain and obesity

A well-resourced, comprehensive, population-based set of strategies is needed to attenuate and eventually reverse the current trends of increasing obesity prevalence now apparent in most countries. The Epidemiological Triad (host, vector, environment) has proven to be a robust model for other epidemics and is applied to obesity. Host-based strategies are primarily educational and these tend to be most effective among people with higher incomes and higher educational attainment. The main vectors for a high-energy intake are energy-dense foods and drinks and large portion sizes and, for low energy expenditure, machines that promote physical inactivity. Vector-based strategies that alter food formulation can have a significant impact, particularly through influencing common, high-volume foods. The increasingly 'obesogenic' environments are probably the main driving forces for the obesity epidemic. There are many environmental strategies that can influence the physical, economic, policy or socio-cultural environments, but the evidence base for these potentially powerful interventions is small. Children should be the priority population for interventions, and improving the general socio-economic conditions for disadvantaged, marginalized or poor population sectors is also a central strategy for obesity prevention. The key settings for interventions are schools, homes, neighbourhoods, primary health care services and communities. The key macroenvironments for interventions are the transport and infrastructure sector, the media and the food sector.