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Original Research |
1 Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana (H.J.R., M.M.M., A.S., J.C.L., J.V., G.A.B.)
2 Regulatory and Clinical Development, The Procter & Gamble Co., Cincinnati, Ohio (J.C.P.)
Address reprint requests to: Marlene M. Most, PhD, RD, FADA, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808. E-mail: mostmm{at}pbrc.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Methods: Ten healthy, lean young men participated in Study One that was a 22-day single blind, within-subject design. After a control diet (40% fat) for eight days Study One subjects received an Olestra-substituted diet (31% metabolizable fat) for 14 days. Study Two was a randomized parallel-arm clinical trial with 15 healthy, lean and overweight young women. These subjects were randomly assigned to receive a control diet (40% fat), an Olestra-containing diet (31% metabolizable fat) or a reduced-fat diet (31% fat) for 10 weeks. All foods were provided to the subjects, and energy intakes were not restricted. The primary endpoint in both studies was change from baseline in body weight. In Study Two, body composition was measured by dual energy x-ray absorptiometry. In both studies, food intake and nutrient compensation were assessed.
Results: In Study One fat substitution by Olestra resulted in a significant 1.7 kg weight loss from baseline. In Study Two, change in body weight and body fat from baseline were statistically significant in all groups, but the group with Olestra lost significantly more weight from baseline (-5.0 kg) than the other two groups. In Study One there was partial compensation for the decreased energy intake, while in Study Two, compensation was seen only for those on the reduced-fat diet.
Conclusion: Replacement of 
of dietary fat with Olestra in periods of up to 10 weeks results in weight loss in men and women.
Key words: body weight, dietary fat, energy intake, fat substitute
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Olestra provides a valuable tool with which to explore the changes in metabolism and food intake when energy density of the diet is covertly reduced without altering the mass or mouth-feel of the food. The replacement of dietary fat with Olestra produces an energy deficit that must be met by mobilizing fat reserves or by increasing food intake if weight loss is to be prevented. If the energy deficit produced by reducing metabolizable energy from fat is detected when other properties of the diet remain the same, then compensation might be expected to result in an increase in food intake. Previous studies examining the impact of Olestra on energy balance suggest that energy deficits on Olestra-containing diets are poorly compensated and could lead to weight loss [7]. However, previous studies were all short-term and investigations of effects of Olestra on substrate oxidation are lacking. We examined these concepts in two separate studies. In the first study, the effects of replacing dietary fat with Olestra were examined in young men who spent two periods of two days each in a metabolic chamber where the short-term effects of Olestra on fat oxidation and total energy expenditure could be measured. Only the weight change and food intake data are reported here. The observation of weight loss in the two-week interval between the two respiratory chamber stays in Study One prompted the second 12-week study of Olestra in a group of lean and obese females.
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METHODS |
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Study Two.
Eighteen healthy, young women, aged 18 to 30 years, with a BMI of 21 to 35 kg/m2 were recruited. They were weight stable for six months prior to the study, and regularly ate three meals a day. Women who were highly restrained eaters based on the Three Factor Eating Inventory [8] were excluded from the study. Additional factors for exclusion were diabetes, smoking, vegetarianism, athletic training, and medications other than oral contraceptives, gastrointestinal (GI) problems or surgery other than cholecystectomy or appendectomy, or a family history of obesity. Three women dropped out prior to completion of the study and were not used in the analyses. One subject experienced GI symptoms with consumption of Olestra, one had GI symptoms unrelated to Olestra, and one dropped out for personal reasons. This left 15 subjects who completed the study.
The Institutional Review Board of Louisiana State University approved both protocols and informed consent was obtained from all participants.
Experimental Design
Study One.
During the first eight days all subjects received a control diet prior to entering the respiration chamber. After the first 24 hours in the chamber, the diet was modified by the replacement of of the fat with Olestra. After an additional 24 hours, the subjects were discharged and given the Olestra-substituted diet as outpatients for an additional 14 days. For the final two days the subjects stayed in the respiration chamber to evaluate metabolic rate and fat oxidation (data not reported here). The energy needs for each subject were calculated before preparing their diets. The control diet brought all subjects to the same macronutrient composition prior to the experimental diet, so that each subject’s habitual diet would not confound the results. Body weight, without shoes and in light indoor clothing, was measured weekly in the morning, in the fasting state, and after voiding, using a calibrated electronic scale (National Control, model 3003, Santa Rosa, CA). Initial body composition was assessed by dual energy x-ray absorptiometry (Hologic, QDR2000, Waltham, MA). All subjects could eat as much of the Olestra-containing diet as they wished during the outpatient period, and no effort was made to modify their intake.
Study Two.
This was a randomized controlled trial with three parallel arms. During the first week all subjects consumed the control diet. They were then randomly assigned to one of three diets (the control diet, the Olestra-substituted diet or the reduced-fat diet containing the same metabolizable fat as in the Olestra-substituted diet) for 10 to 12 weeks. The variation in total study length for the women occurred due to the fact that the endpoint tests were performed at the same time of the menstrual cycle phase as baseline testing. Body weight was measured as in Study One, while lean body mass and fat mass were assessed at the beginning, middle and end of the study by dual energy x-ray absorptiometry (DXA). Although the subjects were randomly assigned to the diet arms, an imbalance in starting body weight occurred, and, as by chance, only lean subjects were randomized to the reduced-fat arm.
Diets
Study One.
The control diet provided 40% of the energy as fat, 45% as carbohydrate and 15% as protein [9]. The total fat level was near the average intake of the population at the time of the study. The Olestra diet had less absorbable fat than the control diet, but equal amounts of carbohydrate and protein (Fig. 1). Therefore, the metabolizable energy was approximately 13% less than the control diet, and the composition of the macronutrients changed, providing 31% of the metabolizable energy from fat, 52% from carbohydrate and 17% from protein. The Olestra diet was less energy dense than the control diet since the same volume provided 87% of the energy provided by the control diet. The subjects knew that Olestra was to be used during the study, but were unaware of what foods contained it.
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For both studies, foods in the Olestra-substituted diet matched those of the control diet, except that of the fat (24 to 50 g/day, depending on the energy level) in the diet was replaced by Olestra. Olestra replaced cooking oils and hydrogenated shortening in baked products and entrees. Menus were analyzed using the Moore’s Extended Nutrient (MENu) database (Pennington Biomedical Research Foundation, Baton Rouge, LA). Sample menus are shown in Table 1. All food was prepared by the Metabolic Kitchen staff of the Pennington Biomedical Research Center under the supervision of a research dietitian. The subjects were required to eat two meals a day, usually breakfast and dinner, at the center. Lunch, the evening snack and all weekend meals were packed for take-out.
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Use of a daily diary assessed adherence to the diet. All participants were asked to record study foods and beverages not consumed and non-study foods consumed. Although this is self-reported data, which depends on the honesty of the subjects, the dietary staff worked to establish an environment of trust to promote accurate reporting. Reported deviations were used to adjust dietary intake data.
To assess whether it was possible to detect the Olestra included in the food, prior to the study a panel of Pennington Biomedical Research Center staff conducted blinded paired-sample food tasting sessions. Sensory attributes and overall flavor acceptability for each Olestra and full-fat food product were rated. The taste panel members were asked to identify in each pair of foods the one they thought contained Olestra. The results showed that it was not possible to differentiate between the Olestra and the full-fat versions of the foods (data not shown).
Statistical Analysis of Data
Study One.
The response variables were analyzed using an analysis of variance (ANOVA) with repeated measures design, with two different types of repeated factor. One was the day (with five levels) and the other was the period (with two levels) referring to period one as a control and period two as treatment. In both cases the five dimensional covariance matrix of measurements was modeled as unstructured.
Study Two.
There were two types of analysis conducted. The repeated measures analysis was used for comparison of two periods (weeks 0 to 4 and weeks 5 to 10), adjusted for baseline body weight. For response variables that were taken at baseline, midpoint and end, such as fat mass and lean body mass, a simpler analysis was conducted, analyzing the change from baseline adjusted for baseline as a covariate with two levels of repeated factor.
In both studies, the baseline body weight was used as a covariate in body weight change analysis. Statistical analyses (Proc MIXED) were done on a personal computer using SAS for Windows, 6.12 (SAS, Inc. Cary, NC). An alpha <0.05 was considered significant.
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RESULTS |
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of the dietary fat, the expected fat intake was 79 g/day without any compensatory response. However, due to a partial compensation, metabolizable fat intake was significantly higher by 5 g/day (p < 0.002). Carbohydrate intake also was significantly higher than the calculated intake of 309 g/day (p < 0.03). However, there was no significant difference in carbohydrate intake between the control and Olestra diet periods (Table 3). Protein intake did not change. Within the control or Olestra diet periods, there was no significant effect of day on nutrient intakes (ANOVA, p > 0.6 for all variables).
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20 to 23 kg/m2) were randomized to the reduced-fat arm. Although the subjects were randomly assigned, this is never an assurance that the groups are not different on some traits as proved to be the case here. Nevertheless, at baseline, there were no significant differences among groups for weight or any other variable due to the larger variance with the small sample size. The average daily energy and nutrient intakes are shown in Table 4. Energy intakes, when adjusted for baseline body weight, for subjects consuming the Olestra and reduced-fat diets were significantly lower than intakes for those consuming the control diet. For those consuming the Olestra and reduced-fat diets, energy intake was less during weeks 5 to 10 than during the first half of the study. Energy intake did not change over time for the control subjects. Digestible fat intake differed among each of the diets and did not change over time. It was lowest for those on the Olestra diet, followed by that for the reduced-fat diet. Carbohydrate and protein intakes were significantly lower for those on the Olestra diet compared to the other diet groups.
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Mean weight loss (± standard error) for each diet group is shown in Fig. 4. All subjects lost weight during the study (p < 0.0001). From weeks 5 to 10, women in the control group had no further reduction in weight (p = 0.19). Women in the Olestra group lost significantly more weight (p < 0.0001) than did those on the reduced-fat diet (p = 0.01). The observed weight loss was due to significant loss of body fat over time (Table 5). From weeks 5 to 10 the Olestra group had a significant loss of fat mass (in kg), while the reduced-fat and control diet groups did not. There were no significant differences in lean body mass between groups or over time.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Reduction in the digestible fat by with Olestra in the diet of healthy men (approximately 13% of energy) resulted in a weight loss, which became statistically significant at the end of the 14-day intervention. A reduction of dietary fat from the control to the Olestra diet reduced energy intake by nearly 250 kcal/day. If this energy deficit was obtained from adipose tissue triglyceride stores, 36 g of fat would be metabolized each day (250 kcal divided by 7 kcal/g for adipose tissue). This would have produced during the 14 days of intervention a total loss of about 500 g or 0.5 kg. The mean weight loss was 1.0 kg, suggesting that some non-triglyceride stores and water were also lost.
The fact that the healthy men in the first experiment did not eat enough of the free choice foods to make up for the loss of metabolizable fat energy has two implications. First, it suggests, as have several other studies [21,22], that subjects eat to maintain the mass of food. Second, it suggests that in the short term, the calories lost as fat are not detected metabolically. The small, but significant weight loss in these healthy young men suggests that perhaps in the short run, gastric distention signals may be more important than those which arise from the hormonal signals generated in the intestinal milieu or from an energy deficit [22].
The second experiment extended the study of covert fat replacement to women over a longer period of time (10 weeks). The weight loss of the women eating the Olestra-substituted diet during the last six weeks of the study was significantly greater than the other two groups. As described above, if 36 g of fat from fat stores were needed each day to compensate for the energy deficit, one would anticipate over 10 weeks a loss of approximately 2.5 kg as adipose tissue triglyceride. Subjects in the Olestra group lost 5 kg of body weight by 10 weeks, similarly suggesting the loss of additional non-triglyceride stores and water. Again, free choice foods were not used to compensate for the lost calories from fat in the Olestra group. This leads us to conclude that covert replacement of fat by a fat substitute and the resulting daily withdrawal of small amounts of fat from body fat stores is not detected by the body. Conversely, compensation did occur for those consuming the reduced-fat diet, and their weight loss was less than that of the women consuming an Olestra diet. The fat substitute masked detection of daily changes in fat balance. The subjects may have been compensating for the volume of food, as suggested by Rolls et al. [23]. The compensation that occurred in Study Two is consistent with the compensation reported in other studies above.
It is possible that compensation was seen only for those on the reduced-fat diet because all subjects in that group were lean, whereas obese subjects were included in the other two diet groups. Additionally, we cannot overlook the inclusion of obese women in the Olestra group and the fact that the greatest weight loss occurred for this group. Although it might be tempting to believe these subjects had more incentive to lose weight, the control group also included obese women and energy intakes were not restricted. When comparing the weight loss of the Olestra group to that of the control group, the Olestra group lost significantly more during the last part of the study while the control group had no further reduction in weight.
The subjects selected for both studies had been weight stable for quite some time before the studies started. All subjects were assumed to be "good regulators" of their body weight. The basic hypothesis was that these subjects would detect easily the change in energy content of the food, or the change in their energy stores, and would then adjust their food intake accordingly. The study design, i.e., the presence of the freely available "free choice" foods, allowed them to do so. However, they did not fully compensate for the energy deficit when dietary fat was covertly replaced with Olestra.
A number of studies have examined diets differing in fat content on weight loss [10,24–31]. In many, fat content of the diet was reduced, resulting in an increased carbohydrate content, so that high fat diets were then compared to high carbohydrate diets. In this respect they differ from the fat substitution studies where a fat substitute contributes no energy to the food and can "hide" the lower energy content of the diet in terms of energy density and hedonic properties. The aforementioned studies have shown that high carbohydrate diets are associated with lower energy intake or loss of body weight. This is also supported by cross sectional studies showing a positive correlation between dietary fat intake and body fatness [32–35]. In reviews by Bray and Popkin [1] and Lissner and Heitman [2] cross-cultural comparisons and cross-sectional, prospective and randomized trials have all provided data consistent with the idea that higher dietary fat resulted in higher body fat. Lissner et al. [26] showed that simply reducing the fat content of the diet resulted in a loss of calories that was uncompensated, leading to weight loss. In a longer-term study where subjects had free choice to compensate, Kendall et al. [25] found that subjects compensated for only 35% of the reduced calories after 11 weeks. Thus, our studies showing weight loss and incomplete compensation for the reduction in metabolizable fat content of the diets are consistent with the findings of other studies of dietary fat reduction.
In summary, the present report indicates that reduction in dietary fat content through fat replacement with Olestra results in significant reduction in energy intake and body weight in both men and women.
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CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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of the dietary fat with Olestra in periods of up to 10 weeks results in loss of body weight and fat in both men and women. On average, only a minor adjustment of food intake was observed during covert fat substitution with Olestra. Greater compensation, but still incomplete, occurred with a more traditional reduced-fat diet.
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ACKNOWLEDGMENTS |
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The authors thank the study volunteers for their time and effort, without whom these studies would not have been possible. Additionally, we are indebted to Jana Ihrig, RN, for her coordination of the studies and to Helena Duplantis, RD, Camilla Ostrowe, Michelle Barkate, RD and the staff of the Pennington Center Metabolic Kitchen for the food preparation and the diet analysis. Finally, we are grateful to all the Clinical Trials staff members for their contributions to the research.
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FOOTNOTES |
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Received August 30, 2001. Accepted March 25, 2002.
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REFERENCES |
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