Increasing preload volume with water reduces rated appetite but not food intake in healthy men even with minimum delay between preload and test meal

Impact of energy density on energy intake in children and adults: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The energy density (ED) of a diet can be leveraged to prevent weight gain or treat overweight and obesity. By lowering the ED of the diet, energy intake can be reduced while maintaining portion size. However, a reliable meta-analysis of data from randomized controlled trials (RCTs) is missing. Therefore, this meta-analysis synthesized the evidence of ED manipulation on energy intake in RCTs.

METHODS

The systematic literature search of multiple databases according to PRISMA criteria considered RCTs investigating the objectively measured energy intake from meals with different ED (lower ED (median 1.1 kcal/g) versus higher ED (median 1.5 kcal/g)) under controlled conditions. Subgroup analyses for age (children versus adults), meal type (preload versus entrée design), and intervention length (1 meal versus > 1 meal) were performed to achieve the most homogeneous result.

RESULTS

The meta-analysis of 38 included studies demonstrated that lowering ED considerably reduced energy intake - 223 kcal (95% CI: - 259.7, - 186.0) in comparison to the higher ED interventions. As heterogeneity was high among studies, subgroup analyses were conducted. Heterogeneity decreased in subgroup analyses for age and meal type combined, strengthening the results. An extended analysis showed a positive linear relationship between ED and energy intake. Dietary ED did not affect the amount of food intake.

CONCLUSION

Manipulating ED substantially affects energy intake whereas food intake remains constant. Thus, this approach can be regarded as a powerful tool for weight management through nutrition therapy. Registration on 08/08/2021: CRD42021266653.

Αcute effects of essential amino acid gel-based and whey protein supplements on appetite and energy intake in older women

Deficiencies in protein and energy intakes are partly responsible for age-related sarcopenia. We investigated the effects of supplements matched in essential amino acid (EAA) content (7.5 g) on energy intake and appetite. Ten women aged 69.2 ± 2.7 years completed 3 trials in a randomised, crossover design. Composite appetite scores, peptide-YY (PYY), and insulin responses to a 200-mL whey protein (WP) isolate (275 kJ), a 50-mL EAA gel (GEL, 478 kJ), or nothing as the control (CON) condition were investigated over 1 h, followed by an ad libitum breakfast. Energy intake at breakfast (CON, 1957 ± 713; WP, 1413 ± 623; GEL, 1963 ± 611 kJ) was higher in CON and GEL than in WP (both P = 0.006). After accounting for supplement energy content, energy intake in GEL was higher than in CON (P = 0.0006) and WP (P = 0.0008). Time-averaged area under the curve for composite appetite scores (CON, 74 ± 20; WP, 50 ± 22; GEL, 60 ± 16 mm) was higher in CON than WP (P = 0.015). Time-averaged area under the curve for PYY (CON, 87 ± 13; WP, 119 ± 27; GEL, 97 ± 22 pg·mL−1) was higher in WP than CON (P = 0.009) and GEL (P = 0.012). In conclusion, supplementation with WP facilitated an increase in protein intake, whereas supplementation with GEL increases in both energy and protein intakes, when consumed before an ad libitum breakfast. Such findings highlight potential gel-based EAA supplementation intake for addressing age-related sarcopenia.

The effect of preload/meal energy density on energy intake in a subsequent meal: A systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review and meta-analysis of the effects of preload/meal energy density on energy intake in a subsequent meal(s).

METHODS

Multiple databases were searched for studies published through December 2016 on the effects of preload/meal energy density on energy intake in a subsequent meal(s). We extracted information on mean energy intake in a subsequent meal(s) and on variables that could contribute to between-subject heterogeneity.

RESULTS

Forty and Thirty nine eligible studies were identified for our systematic review and meta-analysis, respectively. The meta-analysis showed that preload/meal energy density did not affect energy intake in a subsequent meal(s) (95% CI:-21.21, 21.29). As heterogeneity was remarkable among studies, we stratified the studies by intervention type into "meal" or "preload" classifications. In the "preload" subgroup, studies used either fixed energy or fixed weight preloads. The results reveal that in comparison to a high energy-dense (HED) preload, consuming a low energy-dense (LED) preload with same weight resulted in higher energy intake in a subsequent meal (95% CI: 9.72, 56.19). On the other hand, decreased energy intake was observed after consuming an LED preload compared to after consumption of an HED preload with same energy content (95% CI: -138.71, -57.33). In the "meal" subgroup, studies were categorized by different subsequent meal (i.e., "afternoon or evening", "lunch" and "dinner or post-dinner"). Meta-analysis showed that an LED meal resulted in more energy intake only in afternoon or evening meals (95% CI: 14.82, 31.22).

CONCLUSION

In summary, the current analysis revealed that we can restrict the energy intake by consuming an LED preload. Moreover, consuming an LED preload could favorably affect preload+meal energy intake.

Energy-dense snacks can have the same expected satiation as sugar-containing beverages

Sugar-sweetened beverages (SSBs) are thought to be problematic for weight management because energy delivered in liquid form may be less effective at suppressing appetite than solid foods. However, little is known about the relative 'expected satiation' (anticipated fullness) of SSBs and solid foods. This is relevant because expected satiation is an important determinant of portion selection and energy intake. Here, we used a method of constant stimuli to assess the expected satiation of test meals that were presented in combination with different caloric and non-caloric beverages (500 ml) (Experiment 1 and 2), as well as with high-energy solid snack foods (Experiment 2). All energy-containing beverages and snack foods were presented in 210 kcal portions. Both experiments found that expected satiation was greater for meals containing caloric versus non-caloric beverages (201.3 ± 17.3 vs. 185.4 ± 14.1 kcal in Experiment 2; p < 0.05). Further, Experiment 2 showed that this difference was greater in participants who were familiar with our test beverages, indicating a role for learning. Notably, we failed to observe a significant difference in expected satiation between any of the caloric beverages and snack foods in Experiment 2 (range: 192.5-205.2 kcal; p = 0.87). This finding suggests that it may be more appropriate to consider beverages and solid foods on the same continuum, recognizing that the expected satiation of some solid foods is as weak as some beverages.

Effects of energy content and energy density of pre-portioned entrées on energy intake

Pre-portioned entrées are commonly consumed to help control portion size and limit energy intake. The influence of entrée characteristics on energy intake, however, has not been well studied. We determined how the effects of energy content and energy density (ED, kcal/g) of pre-portioned entrées combine to influence daily energy intake. In a crossover design, 68 non-dieting adults (28 men and 40 women) were provided with breakfast, lunch, and dinner on 1 day a week for 4 weeks. Each meal included a compulsory, manipulated pre-portioned entrée followed by a variety of unmanipulated discretionary foods that were consumed ad libitum. Across conditions, the entrées were varied in both energy content and ED between a standard level (100%) and a reduced level (64%). Results showed that in men, decreases in the energy content and ED of pre-portioned entrées acted independently and added together to reduce daily energy intake (both P < 0.01). Simultaneously decreasing the energy content and ED reduced total energy intake in men by 16% (445 ± 47 kcal/day; P < 0.0001). In women, the entrée factors also had independent effects on energy intake at breakfast and lunch, but at dinner and for the entire day the effects depended on the interaction of the two factors (P < 0.01). Simultaneously decreasing the energy content and ED reduced daily energy intake in women by 14% (289 ± 35 kcal/day; P < 0.0001). Both the energy content and ED of pre-portioned entrées affect daily energy intake and could influence the effectiveness of such foods for weight management.

Salad and satiety. The effect of timing of salad consumption on meal energy intake

In a previous study, consuming a fixed amount of low-energy-dense salad as a first course reduced meal energy intake. We investigated whether this effect depended on serving salad before rather than with the main course, or on compulsory rather than ad libitum consumption. On five occasions, 46 women consumed ad libitum a main course of pasta, accompanied four times by low-energy-dense salad (300 g; 100 kcal [418 kJ]). At two meals the salad was served 20 min before the pasta (once compulsory; once ad libitum), and at two meals the salad was served with the pasta (once compulsory; once ad libitum). Results showed that adding a fixed amount of salad to the meal reduced energy intake by 11% (57±19 kcal [238±79 kJ]). Ad libitum salad consumption was less than compulsory consumption and did not significantly affect energy intake. Across all participants, the timing of serving the salad did not significantly influence energy intake, but the effect of timing depended on participant scores for flexible dietary restraint. Consuming low-energy-dense salad before rather than with the main course increased vegetable consumption by 23%. To moderate energy intake, maximizing the amount of salad eaten may be more important than the timing of consumption.

Satiety: have we neglected dietary non-nutrients?

Satiety, which is the inhibition of eating following the end of a meal, is influenced by a number of food characteristics, including compositional and structural factors. An increased understanding of these factors and the mechanisms whereby they exert their effects on satiety may offer a food-based approach to weight management. Water and gas, which are often neglected in nutrition, are major components of many foods and contribute to volume, and to sensory and other characteristics. A review of previous short-term studies that evaluated the effects of water or gas in foods on satiety showed that while satiety was generally increased, effects on subsequent intakes were not always apparent. These studies were diverse in terms of design, timings and food matrices, which precludes definitive conclusions. However, the results indicate that solids may be more effective at increasing satiety than liquids, but gas may be as effective as water. Although increased gastric distension may be the main mechanism underlying these effects, pre-ingestive and ingestive impacts on cognitive, anticipatory and sensory responses also appear to be involved. Furthermore, there is limited evidence that water on its own may be effective at increasing satiety and decreasing intakes when drunk before, but not with, a meal. Longer-term extrapolation suggests that increasing food volumes with water or gas may offer weight-management strategies. However, from a practical viewpoint, the effects of water and gas on satiety may be best exploited by using these non-nutrients to manipulate perceived portion sizes, without increasing energy contents.

Familiarity changes expectations about fullness

Expected satiation (the extent to which a food is expected to deliver fullness) is an excellent predictor of self-selected portion size (kcal). Here, we explored the prospect that expected satiation changes over time. Fifty-eight participants evaluated expected satiation in eight test foods (including two 'candidate' foods: sushi and muesli) and reported how often they consumed each food. In one of the candidate foods (sushi), and across other test foods, expected satiation increased with familiarity. Together, these findings are considered in the context of 'satiation drift' - the hypothesis that foods are expected to deliver poor satiation until experience teaches us otherwise.

Hunger and thirst: issues in measurement and prediction of eating and drinking

Associations between hunger and eating and between thirst and drinking are generally weak. This stems, in part, from limitations in the measurement of these sensations which generally rely on temporal, motivational, metabolic and/or self-reported descriptive indices. Each is critically reviewed. Also problematic is the fact that the deterministic depletion-repletion concept of ingestive behavior fails to account for influences of a multitude of contravening cognitive, social, sensory and logistical factors. Although hunger and thirst serve some parallel purposes, sharp distinctions are also present with health implications. Of particular note are the observations that thirst ratings are higher and more stable over the day compared to hunger and thirst may be more motivating to drink than hunger is to eat. Coupling these observations with evidence that beverages have limited satiety value, they pose particular challenges and opportunities. Beverages can facilitate the delivery of nutrients to those desiring or requiring them, but also to those where they are not desired or required. The benefits and risks are a function of their use rather than their inherent properties.

Dopamine-related genotypes and the dose-response effect of methylphenidate on eating in attention-deficit/hyperactivity disorder youths

OBJECTIVE

There are individual differences in the effects of methylphenidate (MPH), a dopamine (DA) transport inhibitor, on appetite in children with attention-deficit/hyperactivity disorder (ADHD). One potential moderating factor is variation in brain DA activity, which is influenced by dopamine-related genes: the DA transporter (DAT) (SLC6A3), the DA D2 receptor (DRD2), and the DA D4 receptor (DRD4) genes. The purpose of this study was to explore the relationship between dopamine-related gene polymorphisms and food consumption in ADHD children receiving varying doses of MPH.

METHODS

In a randomized, within-subject, double-blind design, 58 ADHD children (ages 6-12 years) received placebo, 0.15, 0.3, or 0.6 mg/kg of MPH three times daily over 9 weeks. Observations of percent lunch consumed as a function of dopamine-related genotypes and MPH dose were analyzed using mixed effects regression models.

RESULTS

A significant dose-response reduction in eating was observed across all genotypes (p < 0.001). There was an interaction of DAT SLC6A3 and DRD2 genotypes and dose, because 9/9 DAT children showed a stronger effect of dose when compared with the 9/10 and 10/10 children (p < 0.001) and DRD2 A2/A2 children showed a stronger effect of dose when compared with A1/A1 and A1/A2 children combined (p = 0.007). There was no significant interaction of dose by DRD4 genotype.

CONCLUSIONS

Lunch consumption decreased as a function of MPH dose. DA-related genotypes associated with greater brain DA signaling moderated the influence of drug on consumption. These results provide information relevant to predicting which children are likely to experience the greatest appetite suppression when taking MPH.

The relationship between dietary energy density and energy intake

Much of the research in ingestive behavior has focused on the macronutrient composition of foods; however, these studies are incomplete, or could be misleading, if they do not consider the energy density (ED) of the diet under investigation. Lowering the ED (kcal/g) by increasing the volume of preloads without changing macronutrient content can enhance satiety and reduce subsequent energy intake at a meal. Ad libitum intake or satiation has also been shown to be influenced by ED when the proportions of macronutrients are constant. Since people tend to eat a consistent weight of food, when the ED of the available foods is reduced, energy intake is reduced. The effects of ED have been seen in adults of different weight status, sex, and behavioral characteristics, as well as in 3- to 5-year-old children. The mechanisms underlying the response to variations in ED are not yet well understood and data from controlled studies lasting more than several days are limited. However, both population-based studies and long-term clinical trials indicate that the effects of dietary ED can be persistent. Several clinical trials have shown that reducing the ED of the diet by the addition of water-rich foods such as fruits and vegetables was associated with substantial weight loss even when patients were not told to restrict calories. Since lowering dietary energy density could provide effective strategies for the prevention and treatment of obesity, there is a need for more studies of mechanisms underlying the effect and ways to apply these findings.

Food volume effects on intake and appetite in women with binge-eating disorder and weight-matched controls

OBJECTIVE

Our study examined the effect of food volume on later intake and appetite ratings in 15 women with binge eating disorder (BED) and 15 healthy control women.

METHOD

On nonconsecutive days, lower-volume (250 ml/171 kcal) and higher-volume milk-based preloads (500 ml/171 kcal) were served in counterbalanced order. Thirty minutes later, appetite ratings and intake at a buffet-style test-lunch were assessed.

RESULTS

Higher-volume preloads decreased hunger, desire to eat, excitement about eating, desire for dessert, and loss of control over eating at test meals, relative to lower-volume preloads. Test-meal intake was greater among BED participants than controls; intake did not differ by preload volume. BED participants' desire to eat, prospective consumption, excitement about eating, and desire for meals and desserts were higher than controls' ratings.

CONCLUSION

Higher-volume foods decreased hunger and related appetite ratings. Differences in food intake and appetite between BED and control participants provide further evidence for the validity of test meals to assess binge eating.

Relationships between human thirst, hunger, drinking, and feeding

There is a widely held view that hunger prompts feeding to ensure energy needs are met, while thirst cues drinking to address hydration requirements. However, recent changes in the nature of the food supply and eating patterns have raised questions about the functionality of these relationships with respect to maintaining energy balance. The increasing consumption of energy-yielding beverages and foods with diluted energy density, through the use of ingredients such as high-intensity sweeteners and fat replacers, poses new challenges to presumed homeostatic energy regulatory mechanisms. This review draws on findings from a recent observational study and other published evidence to explore whether shifts of food composition and use patterns may be disrupting relationships between thirst, hunger, drinking, and eating, resulting in positive energy balance (e.g., drinking low satiety, energy-yielding beverages in response to hunger). The observational study entailed collecting hourly appetitive ratings and dietary recalls from 50 adults for seven consecutive days. These data reveal a clear bimodal daily hunger pattern, whereas thirst is stronger and more stable throughout the day. Further, approximately 75% of fluid intake occurs peri-prandially, with the majority derived from energy-yielding beverages. While there is published evidence that drinking is responsive to feeding, support for the view that drinking is the more tightly regulated behavior is stronger. Our data indicates that, due to a number of plausible factors, neither absolute values nor changes of hunger or thirst are strong predictors of energy intake. However, it is proposed that stable, high thirst facilitates drinking, and with the increased availability and use of energy-yielding beverages that have low satiety properties, can promote positive energy balance. There are marked individual differences in mean daily hunger and thirst ratings with unknown implications for energy balance.

Acquired flavor acceptance and intake facilitated by monosodium glutamate in humans

Monosodium glutamate (MSG) is known to enhance liking for the flavor of savory foods, but whether associations between flavors and effects of MSG lead to changes in subsequent liking and intake for the flavor alone is unclear. To test this, 32 volunteers evaluated and consumed a novel savory soup with no added MSG before and after four training sessions where the same soup was consumed either unchanged (Control) or with added MSG. The addition of MSG during training increased both pleasantness and savory character of the soup and resulted in a larger increase in rated pleasantness of the soup in the MSG-trained relative to control condition when the soup was re-evaluated Post-training without MSG. There was also a significant increase in voluntary soup intake Post-training after the soup had been paired with MSG but not in the Control condition, and rated hunger increased more after tasting the soup Post-training in the MSG-trained but not Control condition. These findings demonstrate that co-experience of a savory flavor and MSG can result in increased subsequent liking and intake for the flavor in the absence of MSG, and possible explanations for how MSG reinforces learning are discussed.

Flavor-nutrient learning in restrained and unrestrained eaters

After we consume a novel food an association can form between its sensory characteristics (e.g., taste properties) and the effect it has on the body (rewarding). Associations of this kind underpin much of our everyday dietary behavior because they mediate both the affective quality of food (flavor-preference learning) and the amount that we choose to consume (learning satiation). Notwithstanding this fact, very few studies have successfully demonstrated the process of dietary learning in human adults. In addition, based on evidence from related research, we explored whether learning is less likely to occur in individuals who have high scores on a measure of dietary restraint. Female participants (N = 44) consumed two differently flavored desserts. Each was presented three times on separate days. One was formulated with a high-energy content (1882 kJ) and the other with a low-energy content (226 kJ). After training, we found little evidence for learned satiation. However, we did observe flavor-preference learning. Specifically, participants acquired a greater liking and desire-to-eat the dessert flavor that was paired with a higher energy density during training. Further analysis revealed that this effect on liking is qualified by dietary restraint. As predicted, unrestrained eaters demonstrated greater differential responding to the two desserts than did restrained eaters. These data provide further evidence for flavor-nutrient learning in adults and they highlight a hitherto unexplored and potentially important difference between restrained and unrestrained eaters.

Volume and variety: Relative effects on food intake

Volume has been shown to be an important direct control of food intake, since larger volumes of food consumed prior to a meal can inhibit subsequent intake. Variety of food is known to stimulate food intake. The present study was designed to examine the relative effects of manipulating the volume of a soup preload in the context of providing either a single or a variety of sandwich fillings. Thirty participants (15 females; 15 males) attended the laboratory on 4 occasions to receive a low (f=240 ml, 3.6 kJ/g; m=300 ml, 3.6 kJ/g) or high (f=480 ml, 1.8 kJ/g; m=600 ml, 1.8 kJ/g) volume tomato soup preload 30 min before a sandwich lunch with either single or a variety of fillings. Overall, subjects reported significant differences in hunger and fullness as a function of volume manipulations but the satiety quotient (SQ: change in ratings divided by weight of soup) calculated just before lunch indicated a smaller SQ for high than for the low volume soup. Therefore, although subjective ratings were influenced by volume this was not sufficient to affect intake at lunch. Variety (2344+/-200 kJ) increased food intake at lunch compared to the single filling condition (2062+/-171 kJ), an enhancement by variety of 14%. In conclusion, lowering energy density and increasing volume by adding water failed to reduce intake at lunch. Clearly volume effects on intake rely both on amount consumed and energy density. As predicted, variety stimulated food intake and this occurred across volume conditions.

Alcohol and food intake

PURPOSE OF REVIEW

Alcohol is commonly consumed around mealtimes, and both the immediate pharmacological actions of ethanol and the energy generated by metabolism of alcohol have the potential to modify food intake. Effects of moderate alcohol consumption on food intake in humans will be reviewed, and potential mechanisms considered.

RECENT FINDINGS

Unlike other macronutrients, there is minimal evidence for any reduction in food intake to compensate for the potential energy in alcohol. In contrast, moderate alcohol consumption prior to a test meal leads to a short-term increase in food intake. This stimulatory effect of alcohol is not apparent beyond acute administration, but the inability to reduce voluntary energy intake in response to energy from alcohol metabolism is evident over extended periods. Alcohol suppresses fatty acid oxidation, increases short-term thermogenesis and stimulates a number of neurochemical and peripheral systems implicated in appetite control, including inhibitory effects on leptin, glucagon-like peptide-1, and serotonin, and enhancement of gamma-aminobutyric acid, endogenous opioids and neuropeptide Y. All of these effects could lead to overeating, and mechanisms underlying appetite stimulation through alcohol require further substantiation.

SUMMARY

Alcohol is a complex component of the diet, and appears to have multiple effects on appetite. Failure to reduce food intake in response to energy from alcohol makes moderate alcohol consumption a risk factor for obesity. Further integration of evidence from nutrition and neuroscience will be crucial to our understanding of effects of alcohol on appetite.