Jenny H. Ledikwe

The influence of food portion size and energy density on energy intake: implications for weight management

The increase in the prevalence of obesity has coincided with an increase in portion sizes of foods both inside and outside the home, suggesting that larger portions may play a role in the obesity epidemic. Although it will be difficult to establish a causal relationship between increasing portion size and obesity, data indicate that portion size does influence energy intake. Several well-controlled, laboratory-based studies have shown that providing older children and adults with larger food portions can lead to significant increases in energy intake. This effect has been demonstrated for snacks and a variety of single meals and shown to persist over a 2-d period. Despite increases in intake, individuals presented with large portions generally do not report or respond to increased levels of fullness, suggesting that hunger and satiety signals are ignored or overridden. One strategy to address the effect of portion size is decreasing the energy density (kilojoules per gram; kilocalories per gram) of foods. Several studies have demonstrated that eating low-energy-dense foods (such as fruits, vegetables, and soups) maintains satiety while reducing energy intake. In a clinical trial, advising individuals to eat portions of low-energy-dense foods was a more successful weight loss strategy than fat reduction coupled with restriction of portion sizes. Eating satisfying portions of low-energy-dense foods can help to enhance satiety and control hunger while restricting energy intake for weight management.

Chefs’ Opinions of Restaurant Portion Sizes

Objectives: The objectives were to determine who establishes restaurant portion sizes and factors that influence these decisions, and to examine chefs’ opinions regarding portion size, nutrition information, and weight management.

A reliable, valid questionnaire indicates that preference for dietary fat declines when following a reduced-fat diet.

This study establishes the reliability and validity of the Fat Preference Questionnaire, a self-administered instrument to assess preference for dietary fat. Respondents select the food which tastes better and is eaten more frequently from 19 sets of food. Each set is comprised of related foods differing in fat content. The questionnaire was administered to women in laboratory-based (n=63), cross-sectional (n=150), and weight-loss (n=71) studies. The percentage of food sets in which high-fat foods were reported to taste better (TASTE score) and to be eaten more often (FREQ score) was determined. A measure of dietary fat restriction (DIFF) was created by subtracting TASTE from FREQ. Food intake was assessed by direct measure, 24-h recall, or food diary. Additionally, participants completed a standard survey assessing dietary restraint. Test-retest correlations were high (r=0.75-0.94). TASTE and FREQ scores were positively correlated with total fat intake (r=0.22-0.63). DIFF scores positively correlated with dietary restraint (r=0.39-0.52). Participants in the weight-loss trial experienced declines in fat consumption, TASTE and FREQ scores, and BMI values, and an increase in DIFF scores. Weight loss correlated with declines in FREQ (r=0.36) scores and increases in DIFF scores (r=-0.35). These data suggest that preference for dietary fat declines when following a reduced-fat diet and an increase in restraint for intake of dietary fat is important for weight loss. The Fat Preference Questionnaire is a stable, easily-administered instrument that can be used in research and clinical settings.

Reductions in Dietary Energy Density as a Weight Management Strategy

Reducing caloric intake is the cornerstone of dietary therapy for long-term healthy weight management. Strategies individuals have typically used include limiting portion sizes, food groups, or certain macronutrients. Although such restrictive approaches can lead to weight loss in the short term, they can result in feelings of hunger or dissatisfaction, which can limit their acceptability, sustainability, and long-term effectiveness. An alternative positive strategy to manage energy intake is for individuals to eat more foods that are low in calories for a given measure of food—that is, they are low in energy density (kcal/g). Data have shown that people eat a fairly consistent amount of food on a day-to-day basis; therefore, the energy density of the foods an individual consumes influences energy intake. Encouraging patients to eat more foods low in energy density and to substitute these foods for those higher in energy density allows them to decrease their energy intake while eating sati sfying portions, thereby controlling hunger and lowering energy intake. This type of diet fi ts with the current Dietary Guidelines for Americans in that it incorporates high quantities of fruits, vegetables, and fiber, which are often suboptimal in typical low-calorie diets, and it provides ample intakes of numerous micronutrients. Moreover, studies have found that individuals who consume lower-energy-dense diets consume more food by weight and have lower body weights compared with individuals who consume higher-energy-dense diets. This chapter reviews the evidence supporting the use of diets rich in low-energy-dense foods for weight management and provides practical approaches to lowering the energy density of the diet.