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Department of Nutrition, University of California, Davis, CA 95616
3To whom correspondence should be addressed. E-mail: bbfreeman{at}ucdavis.edu.
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ABSTRACT |
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 TOP ABSTRACT SUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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40% walnut or safflower fat or 4% fat did not differ; however, walnut consumption may promote food patterns consistent with consuming diets higher in fiber.
KEY WORDS: • walnuts • (n-3) fatty acids • insulin • cholecystokinin • food intake
Preliminary evidence suggests that walnuts may be differentiated from other high-fat, energy-dense foods for their effects on body weight (1,2). The mechanisms by which walnuts may act to regulate body weight are unclear. Walnuts have a unique composition of nutrients combined in a complex food structure that offer multiple means to affect short- and long-term mechanisms controlling food intake and energy homeostasis. Among these, walnuts may impart greater hunger and appetite control, i.e., enhance satiety. Walnuts are a rich source of fat, fiber, and protein (3), each of which was shown to modulate satiety. Fat, in particular, was shown to have an important role in satiety in animals and humans (4–8). Fat is a potent stimulator of cholecystokinin (CCK),4 a gastrointestinal peptide involved in satiety and food intake regulation (9–12). Walnuts are high in both linoleic and 
-linolenic fatty acids (3). The effect of foods predominant in these fatty acids on fat-sensitive gastrointestinal peptides, such as CCK, as well as behavioral outcomes, is not clear. The combination of walnut fat with inherent fibers may augment satiety. In a study by Burton-Freeman et al. (13), fiber included in a low-fat (20% energy) meal resulted in greater hunger suppression and overall satiety compared with a low-fat, low-fiber meal equivalent in energy density.
Satiety-related reductions in subsequent food intake and dietary compensation are among the possible explanations for the apparent low risk of weight gain reported previously with frequent nut, including walnut, consumption. To our knowledge, no study has directly investigated the effects of an acute load of walnut or its extracted oil on outcomes of short-term food intake regulation. Therefore, the present study was designed using the preload paradigm to evaluate acute outcomes of energy intake at a test meal, subjective satiety, and hormonal markers/mediators of satiety. The primary objective of the study was to determine whether walnut fat incorporated into a semisolid liquid preload at a level of 40% energy would reduce energy intake at a test meal compared with an energy-equivalent low-fat (4%) control. Secondary objectives included the following: to determine whether variation in fatty acid composition or the delivery form in which walnut fat was provided in a semisolid liquid preload would impart differential effects on test meal intake; to examine the subjective satiety response as measured by visual analog scales (VAS) to preloads differing in fat type/composition, content and delivery/form; to examine the stimulatory effect of the preloads on CCK and insulin release and their relation to the subjective satiety response and test meal intake; and last, explore the influence of gender and restraint on study outcome measures.
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SUBJECTS AND METHODS |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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10 were considered restrained, those scoring <10, unrestrained. The inclusion criteria were men and women with BMI 22–27 kg/m2, who were 21–50 y old, moderate to light exercisers, consuming diets with dietary fat intake of 30–35% of total energy, normal plasma glucose and insulin, and able to meet the time and effort requirements required for study participation; 13 women and 12 men met the study criteria and were invited to participate in the study. Of these, all completed the study.
The study was a single-blind, 4-arm, 4-period, 4-sequence randomized crossover design utilizing the preload paradigm. Four study-specific preloads differing in fat content and fat source were tested for effects on subsequent (test meal) intake, satiety, and hormone release, randomly, 1 wk apart. Preloads were prepared as semisolid shakes using varying proportions of frozen, sweetened, whole strawberries, dry nonfat milk solids, water/ice, soybean lecithin, and either walnut or safflower as a source of fat (Table 1). Three preloads contained 39% energy from fat; high-oleic safflower oil (SAFF), walnut oil (WOL) or finely ground whole walnuts (WNT) and 1 preload contained 4% fat energy, low-fat control (LFC). Preloads contained 0.98 kcal/g (4.10 kJ/g), 14% energy from protein, and 47 or 82% energy from carbohydrate, depending on preload fat content (Table 1). The higher fat-containing preloads (SAFF, WOL, WNT) had a similar proportion of saturated fat, whereas the ratio of monounsaturated fatty acids (M) to PUFA (P) differed; M:P for SAFF, WOL and WNT was 3.85, 0.35 and 0.35, respectively. Additionally, the 2 walnut-containing preloads contained 20 times more -linolenic acid than the SAFF preload (1.37 and 1.43 g vs. 0.07 g, respectively). Men consumed 300 g and women consumed 225 g of each preload, 1254 and 941 kJ, respectively. Preloads were rated by subjects as not different and acceptable in palatability, texture, and flavor. Sweetness was the exception, in that the low-fat control was rated sweeter than the higher-fat preloads.
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On the day of each study session, subjects arrived at the laboratory 2 h before their usual lunch time, which corresponded to 4 h (±30 min) after breakfast. Subjects were instructed to maintain their breakfast habits during the study and to eat the same breakfast at the same time on each test day. Subjects were also instructed to consume a meal the night before (d –1) each study session that was similar in energy and macronutrient content, i.e., within 836 kJ of the usual evening meal and within 5% of usual macronutrient composition. For simplicity, most subjects consumed the same evening meal before each study session. Upon subjects’ arrival, body weight and food records were checked to ensure compliance on both measures [change in weight <1.0 kg and food intake (d –1 evening meal and study day breakfast) consistencies]. After the initial study day screening for compliance, subjects were provided 100 mL of water to drink while an indwelling catheter was placed in the nondominant arm of each subject for multiple blood sampling. After the initial fasting blood draw, subjects rested for a few minutes, acquainted themselves with their dining area and completed their first set of VAS, assessing hunger, fullness, desire to eat, prospective consumption, and appetite satisfaction. After completing the first VAS, subjects were given 1 of the 4 test preloads to consume in 15 min. Subsequent blood samples were collected and VAS booklets were completed at 15, 30, and 45 min after preload ingestion. After the 45-min blood sample, subjects were offered lunch, which consisted of a tray of preweighed lunch food items. The tray contained more food than subjects would be expected to eat; however, additional food was provided if requested. Foods provided on the tray included: white and wheat bread, deli-style meats and cheeses, condiments of leafy lettuce, tomato, and pickles, potato salad, mayonnaise, mustard, ranch dressing, grapes, bananas, and apple slices, bite-size Snicker® bars, cookies, chips, diet and regular cola, and water.
VAS booklets were given to each subject to assess appetite and satiety in response to the 4 preloads as described above. Assessments of hunger, fullness, desire to eat, prospective consumption, appetite satisfaction, pleasantness of preload, and sweetness were rated on 100-mm line scales. Questions such as "How hungry do you feel right now?" or "How strong is your desire to eat right now?" preceded a 100-mm line anchored by opposing phrases "not at all hungry" and "extremely hungry" or "very weak" and "very strong." Other anchors consisted of the phrases "not at all full" and "extremely full" or "a large amount" and "nothing at all" or "very pleasant" and "not at all pleasant" to access fullness, prospective consumption, and meal like/dislike. The use and value of these scales for assessing motivation to eat and food preference were reported previously (12,13,15).
Blood samples were collected in EDTA-coated vacutainer tubes, immediately cooled in ice, and plasma was obtained by centrifugation at 2000 x g for 15 min at 23°C. Aliquots of plasma (2 mL, n = 2) were extracted onto Sep-Pak cartridges containing octadecylsilysilica and frozen at –70°C for determination of CCK concentrations by RIA. Another portion (2 mL) of plasma was stored in microcentrifuge tubes and frozen at –20°C for subsequent analysis of glucose and insulin concentrations. Plasma glucose was analyzed in the University of California, Davis Clinical Nutrition Research Unit, analytical core laboratory, NIH#DK35747, according to approved protocols. Plasma CCK was measured by RIA using a highly specific and selective antibody, Ab-92128 (gift from Dr. Jens Rehfeld, Rigshospitalet, Copenhagen, Denmark) (16). Plasma insulin was measured by RIA according to the basic method described by Yalow and Berson modified by using 0.05 mol/L phosphate buffer containing 0.4% human serum albumin and the precipitation method described by Desbuquois and Aurbach, using polyethylene glycol to separate free and antibody-bound insulin (17,18).
Statistical analysis. Data were analyzed by repeated-measures ANOVA using PC-SAS (version 6; SAS Institute) General Linear Model and MIXED procedures with preload, time, gender, and restraint as main factors and subject as the blocking variable. Test meal intake was assessed by difference from preweighed food on each subject’s tray. Energy and macronutrient intakes among subjects were compared across treatments. Adjustment in food intake after test meals was assessed by analyzing the subjects’ food records after leaving the laboratory until midnight of the study day (i.e., poststudy food records). Total intake on study days, including the energy from preloads and test meals, was compared with usual intake defined by mean energy intake on days –1 and +1, respectively. Data analyzed from the VAS were first converted to increments above baseline to account for relative baseline variability among subjects. Substrate metabolites not conforming to expected distributional assumptions were log transformed. Significant differences among treatment means were analyzed by pairwise t test and Tukey’s honestly significant test for appropriate comparisons. The level used to determine statistical significance was P < 0.05. Power analysis indicated that a sample size of 24 subjects was sufficient to detect a minimum difference of 523 kJ between control and fat-containing preloads, with a power of 80% at this alpha level (0.05). Values in the text are LSmeans ± SEM, unless otherwise noted.
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RESULTS |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Food records/usual intake.
Food records were collected to provide information about the usual diets of the men and women participating in the study as well as information related to the consumption of the preloads. The food records indicated that energy intakes differed between men and women but not within gender. In general, men consumed more total energy than women. However, energy intake before coming to the laboratory for a study visit (breakfast) did not differ between men and women (2006 ± 247 and 1576 ± 234 kJ, respectively) or among visit days (range 1760 ± 176 to 1797 ± 176 kJ), including macronutrient composition. Additionally, breakfast energy intake did not differ between subjects characterized as restrained or unrestrained eaters (restrained 1835 ± 284 kJ, unrestrained 1726 ± 222 kJ). Energy intake the day before (d –1) did not differ from energy consumed the day after (d +1), but both were less than the study day intake (P < 0.05, Fig. 1). The macronutrient composition of diet determined from food records completed on the days before (d –1) and after (d +1) study test days showed that the diets consumed on those days did not differ, i.e., 28 ± 2%, 57 ± 2%, and 15 ± 1% energy from fat, carbohydrate, and protein, respectively.
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45 min after preload consumption. Men and women differed (P < 0.04) in energy consumed at the lunch test meal. Men consumed more energy than women (3812 ± 326 and 2817 ± 314 kJ, respectively). In general, men consumed more carbohydrate (P < 0.01) and protein (P < 0.04) energy than women and tended to consume more fat energy (P = 0.14) at the test meal. The effects of each preload on energy intake at the lunch test meal by the subjects did not differ (LFC, 3014 ± 134 kJ; SAFF, 3198 ± 134 kJ; WNT, 3340 ± 134 kJ; and WOL, 3457 ± 138 kJ; P = 0.12). However, when each of the fat-containing preloads was compared with the LFC, energy intake at the test meal tended to be higher after WNT (P = 0.09) and was higher after WOL (P = 0.02) preloads. Preload affected carbohydrate (P = 0.05) and fiber intake (P = 0.02) and tended to affect fat (P = 0.08) but not protein intake at the test meal. Carbohydrate and fiber intakes were greater after consumption of preloads with walnut (WNT, P = 0.005) or walnut oil (WOL, P = 0.07) compared with the LFC preload. Fat intake tended to decrease with increasing carbohydrate and fiber intake (P = 0.09). Energy intake relative to preload was not affected by subjects’ characteristic restraint level; however, there was a gender x restraint interaction (P < 0.001) (Fig. 2). Women who were characterized as unrestrained eaters consumed less energy than their restrained female counterparts (2529 ± 222 kJ and 3152 ± 238 kJ, respectively). In contrast, the men characterized as unrestrained eaters consumed more energy at lunch than those characterized as restrained eaters (4276 ± 205 and 2884 ± 293 kJ, respectively). Energy intake of restrained men and women did not differ.
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Subjective satiety (VAS). Statistical analysis of VAS-based ratings of hunger, fullness, desire to eat, prospective consumption, and satisfaction of appetite as a function of preload revealed a significant time effect (P < 0.001) for all variables tested. However, only appetite satisfaction was affected by the preload (P = 0.01). The SAFF and WNT preloads suppressed appetite the most (21.6 ± 2.1and 18.1 ± 2.1, respectively) followed by LFC and WOL (14.5 ± 2.1 and 12.2 ± 2.1, respectively) (Table 2). In addition to the main effects of time and preload for appetite satisfaction, significant preload x gender interactions were observed for hunger (P < 0.0002) and desire to eat (P < 0.05). In men, hunger suppression did not differ between the LFC and SAFF preloads nor between the WNT and WOL preloads, and the former (LFC, SAFF) were significantly more hunger suppressive than the latter 2 preloads. Men reported that the SAFF preload had the greatest effect on the desire to eat. This effect of the SAFF preload tended to differ from that of the WNT preload (P = 0.07) and did differ from those of the WOL and LFC preloads. In women, the SAFF preload was the least hunger suppressive compared with the WNT, WOL and LFC preloads, which were rated as not different. The preloads did not differ for women on ratings of desire to eat. Variables of the subjective satiety response sensitive to restraint included prospective consumption and appetite satisfaction. A main effect of preload and a preload x restraint interaction was apparent (preload; P < 0.05 and P = 0.01, preload x restraint; P = 0.03 and P = 0.02) for prospective consumption and appetite satisfaction, respectively. For both prospective consumption and appetite satisfaction, the SAFF preload was reported to be more suppressive on the amount subjects thought they could eat and more satisfying than the LFC preload, which appears to be driven by restraint. The subjects characterized as unrestrained did not show a differential response to preloads compared with the LFC preload, but within the fat-containing preloads, the SAFF and WNT preloads were rated as more satisfying for unrestrained subjects. For prospective consumption, ratings were higher for the SAFF preload in restrained subjects and higher for the WNT preload in unrestrained subjects.
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DISCUSSION |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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40% energy would reduce energy intake at a test meal compared with an energy-equivalent low-fat (4%) control. Secondary objectives included determining the significance of fatty acid composition and delivery/form on test meal intake, subjective satiety, and the stimulated release of CCK and insulin. We were also interested in examining the influence of gender and restraint on study outcome measures. In this study, subjects consumed 1 of 4 preloads, on 4 different occasions, beginning 45 min before an all-you-can-eat deli-style lunch tray was served. The preloads did not affect test meal energy intake overall. Food intake tended to be greater when walnut fat replaced carbohydrate energy in the low-fat preload (LFC vs. WNT P = 0.09, LFC vs. WOL P = 0.02). However, when walnut fat was compared with another source of fat, safflower oil, for replacing carbohydrate energy in the LFC, test meal food intake was not affected. Our findings suggest that macronutrient composition, fatty acid distribution, and delivery form of fat do not differentially influence energy intake at a subsequent meal when preloads 
1254 kJ and <600 mL are provided <1 h before the next meal. Several studies have suggested that fat is less satiating than carbohydrate (19–22), whereas others suggest that they are not different (23–26) or that fat is more satiating than carbohydrate (5,6,27). The reason(s) for the discrepancy of results is not entirely clear; however, study design mechanics, including the time delay between preload and test meal as well as aspects of the preload and test meal themselves, influence study outcomes and conclusions.
In the present study, the time delay between the preload and test meal was 30 min. In general, preloads that are liquid in form are best studied with a short time delay (20–60 min), whereas for solid preloads, 2–4 h is more appropriate for detecting differences at a subsequent meal (28). Dynamics in cephalic, gastric, and intestinal phases of eating, particularly the latter 2 relating to gastric emptying, digestion, and absorption, are in large part due to this timing differential for solid vs. liquid preloads. In a study such as ours, in which the preload is semisolid in nature, the time frame may shift to an intermediate time frame (e.g., 1–2 h). However, in both a pilot study in our laboratory using preloads similar to those of the present study and in a study of yogurt consumption by Rolls et al. (29), the time course for detecting differences at a test meal was between 30 and 45 min and as the interval lengthened, compensation for preload was less precise. Thus, the time frame of 20–60 min appears to be appropriate for testing semisolid preparations using the preload paradigm.
Recent studies showed that energy density is an important variable in determining how fat affects satiety and food intake outcomes. When energy density is held constant, fat content does not affect energy intake (30–32). Therefore, to study the potential differences among specific types of fats and their ability to satiate and reduce subsequent food intake, energy density must be held constant. In the present study, preloads were maintained at an energy density of 4.1 kJ/g. This level of energy density is 2 times the energy density of 1% milk or a soft drink (33) and about half the energy density of a mixed-food diet in which the percentage of energy from fat is 34% (34). Our results indicate that under controlled and reasonable levels of energy density, differences by fatty acid composition on short-term food intake measures are not apparent. Walnut fat in the study preloads provided 4 times more polyunsaturated fat [predominantly linoleic, 18:2 (n-6) and 20 times more -linolenic acid, 18:3 (n-3)] than the safflower-based preload, a source of monounsaturated fat [18:1 (n-9)]. Rates of fatty acid oxidation favor -linolenic and linoleic over oleic acid (35) in young lean men. Based on the theory in which fats that are preferentially oxidized are more satiating than those that are preferentially stored (36,37), the results might be expected to have shown a difference according to preload, i.e., walnut fat would be more satiating and reduce test meal intake relative to the safflower preload. The fact that we did not detect a difference may refute this theory or suggest that the effects of the different fats tested in this study on measures of food intake were not evident in short-term regulation of satiety. Effects on long-term regulation of food intake cannot be ruled out, however. Anecdotal data suggest that walnuts provide a certain level of satiety when incorporated into the diet daily (38,39).
The 3 fat-containing preloads had the same energy density as the low-fat control but differed in macronutrient composition and sweetness. Informal, prestudy panel testing during preload development did not reveal a sweetness difference among the preloads. In contrast, however, subjects participating in the study did score the LFC preload as sweeter than the 3 fat-containing preloads. A limitation of the study is delineating the effect of this difference on study results. All other sensory qualities tested, including texture and palatability, were rated as not different by subjects. Accounting for the sweetness difference in the statistical model was unremarkable. The enhanced sweetness of the LFC preload would have been expected to augment reductions in food intake and hunger (40), although the effect of sweeteners and flavorings on satiety are inconsistent and hence, unclear.
Energy intake at the test meal did not differ by preload. Total energy intake for the study day was higher (approximating the energy provided by the preload) than the usual daily energy intake, as assessed by food records on the days before (d –1) and after (d +1) the study days. Whether this is a general phenomenon of in-laboratory studies in which a "free," all-you-can-eat lunch is provided (potentially overriding physiologic signals) or a lack of compensation for preloads is not clear. Test meals that consist of multiple food types (variety) that are palatable may also influence test meal intake, resulting in higher levels of energy intake. Incorporation of a nonenergy-containing negative control into the study design might have aided in determining the dominant factor(s) influencing energy intake at the test meal in this study. Substituting fat for carbohydrate energy in energy- and volume-matched preloads did not have a remarkable effect on subsequent test meal intake under the conditions tested.
A specific aim of this study was to examine the effects of fat type and form of delivery on satiety outcomes. Moreover, we were interested in determining whether the satiety produced would be greater than what we might see with energy alone. Energy itself produces a level of satiety. Therefore, to answer the questions of this study and to control for the confound(s) of energy that exist when energy-containing preloads are compared with no energy preloads, we incorporated an energy matched preload with minimal (4%) fat as a control. A limitation of the study might be the inability to determine compensation relative to a no-load condition; however, a strength of the study is the finding that when energy and volume are constant, fat content, fatty acid composition, and fat delivery form did not affect energy intake compared with a low-fat, energy-matched control at a test meal. Future studies will be required to address questions related to energy on these outcomes.
Despite the lack of an effect on energy intake at the test meal according to preloads, analysis of test meal intake for macronutrient selection at the test meal revealed differences among preloads. Carbohydrate and fiber intakes were higher (P < 0.05) after walnut fat–containing preloads that after the LFC preload. This difference was an effect that persisted through the rest of the day, offset by a tendency for a reduced fat intake (P = 0.08). Argument for a sensory- or nutrient-specific effect may be apparent here. Subjects chose foods that were higher in carbohydrate and lower in fat after the high-fat walnut preloads. However, if a sensory- or nutrient-specific effect was operant, the safflower preload would have been expected to induce a similar effect on food choice, which was not apparent. Additionally, the observation that subjects continued this choice pattern over a 10- to12-h period postpreload consumption, well beyond the temporal effect of a sensory- or nutrient-specific effect, further argues for an alternative explanation/operant mechanism.
In a 6-h postprandial study with almonds in which whole almonds compared with almond oil were incorporated into a mixed whole food solid meal providing approximately one-third the daily energy of men and women, CCK and subjective satiety were strongly associated (12). CCK was shown in other studies to be an important mediator of fat-induced satiety (12,17–20). In the present study, the CCK response was indicative of the preload fat content. For men, the apparent availability of fat to interact with CCK mechanisms required for its release was also important. The CCK response to the preload with ground walnuts was blunted compared with the response induced by the 2 oil-containing preloads. This effect was not observed in women. Despite the differential responses observed for CCK, these responses did not correspond directly to subjective satiety or food intake at the test meal. There are 3 main differences between the studies showing an association between subjective satiety and CCK and the present study. These include the presentation/form of the challenge food/preload (solid vs. liquid/shake-like), the energy content of the challenge food ( 2 to 3-fold energy difference), and the duration of measured satiety (30 min vs. 6 h), all of which significantly affect study results and potentially, correlative patterns. Collectively, based on the data from this study and others, CCK is not a dominant modulator of satiety within the first 30–40 min after consumption of a liquid/shake-like food with an energy content 1254 kJ.
Alternatively, insulin may be playing a role in the satiety response among men under these study conditions. Higher insulin levels with the LFC and SAFF preloads corresponded to greater suppression of hunger in men. Recent data in rats suggest that men may be more sensitive to changes in insulin than women. Small incremental changes in insulin concentrations in the brain significantly reduced food intake in male rats but not female rats (41). Insulin in cerebral spinal fluid increases within minutes in response to a meal (42), suggesting that the actions of insulin in food intake regulation, at least in part, may be apparent in the present study through the suppression of hunger in men. An important implication of these findings is the need for continual research into the gender differences that may reflect a fundamental difference in the metabolic control system.
Dietary restraint refers to the extent to which individuals control food intake based on knowledge or experience with food and its perceived effect on body weight. We were interested in determining whether dietary restraint would influence study outcomes. Our findings revealed that dietary restraint did not alter subjects’ energy intake at a test meal relative to preload under the conditions of the study in which subjects were unaware of treatment. However, as a function of gender, energy intake was influenced by dietary restraint. Interestingly, women who were characterized as unrestrained eaters consumed less energy than their restrained female counterparts, whereas for men, the opposite occurred; men characterized as unrestrained eaters consumed more energy at lunch than men characterized as restrained. In examination of these results in terms of biological response, a marginal restraint by preload interaction was detected for CCK. More noteworthy is the finding that the CCK response in restrained subjects was blunted, whereas the CCK response in unrestrained eaters had a greater sensitivity to the level and availability of fat in the preloads. It is unclear whether this finding indicates a behavioral pattern of food intake (restrained eating), altering physiologic signaling, or alternatively, that restraint as an eating behavior arises from alterations in CCK and potentially, other gastrointestinal signaling physiology. The potential importance of these findings is highlighted by findings documenting a blunted CCK response in subjects with bulimia nervosa compared with control subjects after consuming a test meal (43–45). This blunted response was particularly pronounced after consumption of larger meals (45). Thus, progression and persistence of an eating disorder may have roots in the regulatory pathways controlling food intake, in addition to or in conjunction with the described psychological aberrations. These findings warrant replication as well as future research in both men and women to more thoroughly identify patterns of released satiety signals that may correspond to food intake patterns associated with dietary eating patterns such as those observed in restrained eaters.
In summary, the results of this study indicate that walnuts, as a source of dietary fat, do not have effects on test meal energy intake that differ from the effects observed with a preload containing an alternative fat, or a preload containing 10 times less fat (40% vs. low fat control of 4% energy). Our results show that subjects chose carbohydrate, fiber-rich foods at subsequent meals 10–12 h after walnut consumption. This observation suggests that walnut (fat) consumption may promote food choices that are consistent with consuming diets higher in fiber, and possibly less energy dense overall, which has implications for long-term body weight regulation. Additional studies are warranted to fully understand the importance of these results with daily walnut consumption in the regulation of short- and long-term food intake and energy balance.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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2 Funded by the California Walnut Commission, Sacramento, CA.
4 Abbreviations used: CCK, cholecystokinin,; LFC, low-fat control; SAFF, safflower oil as source of fat in preload; VAS, visual analog scales; WNT, ground walnuts as source of fat in preload; WOL, walnut oil as source of fat in preload.
Manuscript received 30 August 2004. Initial review completed 22 October 2004. Revision accepted 28 March 2005.
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LITERATURE CITED |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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