Metabolic, Psychological, and Health Correlates of Dietary Restraint in ...

Journal of Gerontology: MEDICAL SCIENCES 2001, Vol. 56A, No. 4, M206–M211

Copyright 2001 by The Gerontological Society of America

Metabolic, Psychological, and Health Correlates of Dietary Restraint in Healthy Postmenopausal Women Gaston P. Bathalon, Nicholas P. Hays, Simin N. Meydani, Bess Dawson-Hughes, Ernst J. Schaefer, Ruth Lipman, Miriam Nelson, Andrew S. Greenberg, and Susan B. Roberts Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.

Background. Dietary restraint, a term used to describe the intentional control of food intake to prevent weight gain or promote weight loss, is commonly practiced by older adults, but little is known about its effects on physiology and metabolism. Methods. We therefore compared a wide range of parameters between groups of healthy non-obese postmenopausal women classified psychometrically as unrestrained eaters (body mass index [BMI] 23.8 ⫾ 0.6 [SEM] kg/m2, n ⫽ 28) or restrained eaters (BMI 24.5 ⫾ 0.5, n ⫽ 39). Measurements were made of reported micronutrient intakes, cardiopulmonary function, hematology, body temperature, skin thickness, bone mass, and immune function; in addition, self-perceived health, mood, and some dimensions of eating behavior were assessed by questionnaire. Results. Macronutrient and micronutrient intakes were not significantly different between restrained and unrestrained eaters reporting energy intake to within 30% of predicted total energy expenditure. Restrained eaters had significantly lower hemoglobin (12.9 ⫾ 0.1 [SEM] vs 13.2 ⫾ 0.1 g/dl; p ⬍ .05), but values were within the normal range in both groups. In addition, restrained eaters scored significantly higher on the Eating Attitudes Test ( p ⬍ .01) and drivefor-thinness ( p ⬍ .001) and maturity fears ( p ⬍ .05) subscores of the Eating Disorders Inventory, but values were again within the normal range. No other parameter differed significantly between groups. Conclusions. In this normal-weight population, restrained eating was not associated with detrimental effects in a wide range of physiological, metabolic, and health characteristics. Further work is needed to determine the relevance of these results to the general population.

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HE psychological construct “dietary restraint” was introduced by Herman and Mack (1) to describe the high degree of self-control in eating exhibited by some women attempting to suppress weight gain or promote weight loss. The instrument most commonly used to quantify dietary restraint is the Eating Inventory of Stunkard and Messick (2), and dietary restraint is typically defined as a score of ⱖ10 on a scale of 0 to 21, a cut-off demarcating the upper 25th percentile of restraint scores in a reference population of German women (3). Restrained eaters typically report trying to avoid eating foods that might encourage weight gain and eating fewer calories than they would like to eat, although the effect of these reported behaviors on measurements of energy intake remains controversial, with some studies reporting no effect of dietary restraint on the accuracy of dietary records, and others identifying significant undereporting (3–5). Of relevance to this controversy, Mela and Aaron (6) recently reported that restrained eaters are more likely than unrestrained eaters to anticipate eating differently when recording dietary intake and are also more likely to eat less than usual of some foods and more of others. In a recent survey of healthy U.S. women aged 55 to 65 years (7), more than 50% of the subjects were classified as restrained eaters, a prevalence which is substantially higher than in both the German reference population (3) and a large U.S. population also examined in the late 1980s (8). It

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is not known whether the difference between the studies might be due to changes in dietary restraint over time or to the fact that the recent study was conducted in older individuals. Nevertheless, such a high prevalence of dietary restraint in an older population highlights the fact that relatively little is known about the long-term physiological, metabolic, and health effects of what now appears to be a very widespread dietary practice (3,9–11). Previous studies have suggested a high prevalence of ovulatory disturbances in restrained eaters, which are thought to accelerate bone loss over time (10,11), as well as alterations in such basic physiological processes as the cephalic phase response to food (12), taste preferences (13), and cognitive function (14). However, almost all work to date has been performed in young women, and the long-term effects of dietary restraint are not known. Moreover, the animal literature on dietary restriction suggests that, if dietary restraint is accompanied by a persistent reduction in energy intake, there might potentially be beneficial long-term effects of dietary restraint, for example, reduced blood pressure and improved blood lipid profile (15). However, to our knowledge there is no published information relevant to the long-term positive and negative effects of dietary restraint. We therefore conducted a cross-sectional study to test the hypothesis that reported that habitual dietary restraint is associated with alterations in a broad range of biological parameters in postmenopausal women.

DIETARY RESTRAINT IN HEALTHY WOMEN

METHODS Subjects Sixty-seven healthy postmenopausal women aged 55 to 65 years were recruited for the study by local advertisement and mailing lists to the target population. Subjects were classified as either highly unrestrained or highly restrained eaters on the basis of Eating Inventory scores (2). The scores defining the groups were ⱕ5 and ⱖ13, which are the 25th and 75th percentiles of dietary restraint determined in a recent U.S. survey of healthy women in the same age range as those recruited for this study (7). In addition to being categorized by level of dietary restraint, all women reported stable body weight and dietary restraint over the past 10 years. Subjects were judged to be free from known disorders that might affect energy regulation, including obesity (body mass index [BMI] ⬎31 kg/m2), underweight (BMI ⬍18 kg/ m2), diabetes, cancer, coronary heart disease, eating disorders, depression, alcoholism, inflammatory disorders, and endocrine, hepatic, renal, and thyroid dysfunction. Individuals were also excluded from the study if they reported that they were currently smoking, participating in endurance training (sports or athletic training) of ⬎6 hours per week, being on a weight loss diet during the past year, or having a history of hypertension, psychiatric disorders, or the use of medications known to affect energy intake or expenditure. In addition, groups were matched for BMI. The study was conducted in the Metabolic Research Unit at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University with ethical approval from the New England Medical Center/Tufts University Human Investigations Review Committee. Prior to participation in this study, each subject gave written informed consent Study Protocol The study was conducted over an 18-day period. Subjects arrived at the research center on the morning of Day 1 after an overnight fast. Measurements were made of body fat and fat-free mass, bone mineral content (BMC), and cardiopulmonary function. In addition, blood samples were obtained for the assessment of standard hematologic parameters and immune function, and questionnaires were administered to assess eating behavior, perceived health status, and mood. Subjects then returned home and came back to the center on the morning of Day 9 to provide a second blood sample, to repeat measurements of vital signs and anthropometry, and to start a measurement of delayed-type hypersensitivity (DTH). They came back to the center a third time on the morning of Day 11 to complete the DTH test and to repeat anthropometric and cardiopulmonary function measurements. Sixty-one subjects also weighed and recorded all foods and beverages consumed during study Days 11 through 17, as described elsewhere (5). On Day 18 they returned the 7-day food records to the center and were discharged from the study. Body Fat, Fat-Free Mass, and Anthropometry Body density was determined by hydrostatic weighing with repeated measurements taken until at least three values

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for total body fat agreed within 1% (16–18). Total body fat was calculated using the Siri equation (19). Two volunteers were unable to complete the hydrostatic weighing procedure, and results from dual-energy x-ray absorptiometry (Lunar DPX; software version 3.6Z, Lunar Corporation, Madison, WI) were used because there were no significant differences between data from the two methods (data not shown). Body weight was measured to ⫾0.01 kg (8138 Toledo Weight-Plate; Bay State Scale Co., Cambridge, MA), with the subject wearing a preweighed gown. Height and waist and hip circumferences were measured in triplicate using standard techniques (20). Skin thickness was measured in tripicate on the back of each hand over the second, third, and fourth metacarpals with Harpenden calipers, using the method of Need and colleagues (21). Cardiopulmonary Function Subjects were asked to sit quietly for 5 minutes prior to having their blood pressure measured using standardized indirect auscultation (22). Heart rate was also determined in triplicate by manual monitoring of the radial pulse. Mean arterial pressure was calculated as brachial systolic pressure ⫹ (2 ⫻ brachial diastolic pressure)/3, and pulse pressure was calculated as brachial systolic pressure ⫺ brachial diastolic pressure. Oral temperature was also taken at the time of blood pressure measurement with a handheld digital thermometer. Forced vital capacity (FVC) and forced expiratory volume in the first second of the FVC maneuver (FEV1) were measured on Days 1 and 11 using standard procedures (23,24). Measurements were taken in triplicate, with the subject wearing a nose clip and sitting in a good position, using a Water Seal Survey Spirometer, which was calibrated using a 3.0-l syringe and an Eagle II Microprocessor (Warren E. Collins, Inc., Braintree, MA). FVC and FEV1 were corrected to body temperature pressure saturated, assuming a body temperature of 37⬚C, and taken from the best curve, which was defined as the test meeting the recommended acceptability criteria and giving the largest values of FVC and FEV1 (23), regardless of which curve the values come from. Spirometric measurements were standardized for height using the method of Burr and colleagues (25). Blood Parameters Fasting blood samples obtained on Days 1 and 9 were centrifuged, and plasma and serum were stored at ⫺80⬚C prior to analysis. Plasma lipid and lipoprotein cholesterol concentrations were measured by standardized automated enzymatic methods as previously described (26). Hemoglobin was measured using a Baker 9000/DF (Biochem Immunosystems, Allentown, PA), and glucose was measured by enzymatic methodology with an automated analyzer (Cobas Mira; Roche Diagnostic Systems, Somerville, NJ). Insulinlike growth factor 1 (IGF-1) was measured by radioimmunoassay with an IGF-1 100T kit (Nichols Institute Diagnostics, San Juan Capistrano, CA). Serum free triiodothyronine (FT3), thyroxine (FT4), reverse triodothyronine (rT3), and thyroid stimulating hormone (TSH) levels were also measured by radioimmunoassay (kits from Bayer Diagnostics,

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Walpole, MA; Biodata Diagnostics, Cortland Manor, NY; and Nichols Institute Diagnostics, San Juan Capistrano, CA). Immune Function Assessed by DTH DTH was assessed with multitest CMI (Merieux Institute, Inc., Miami, FL), a single-use disposable application with eight heads, each loaded with glycerine control or one of seven recall antigens (tetanus toxoid, diphtheria toxoid, streptococcus group C, mycobacterium tuberculosis, candida albicans, tricophyton metagrophytes, and proteus mirabilis). A trained study nurse, who was blinded to the eating pattern of the volunteer, applied the skin plant on the volar aspect of the forearm. The diameter of each reaction was taken as the mean of induration measurements determined across two diameters at right angles 48.0 ⫾ 1.0 hours after administration of the test. A mean induration of ⱖ2 mm was considered positive. If a positive reaction to the glycerine control was observed, the diameter of its induration was subtracted from the mean diameter of each positive reaction. The antigen score was calculated as the total number of positive antigens, and the cumulative score was calculated as the sum of induration diameters for positive reactions (27). BMC Bone mineral density (BMD) and BMC were measured in a total body scan by dual-energy x-ray absorptiometry (Lunar Corp.) as described elsewhere (28). Psychological Parameters Self-administered questionnaires were completed by a subset of the subjects (between 62 and 67, depending on the questionnaire): the Eating Attitude Test and the Eating Disorders Inventory (29), which predict the risk of anorexia and bulimia (note: actual diagnosis of either of these disorders was an exclusion criterion for the study), the Profile of Mood States questionnaire (30) for assessment of different dimensions of mood, the Geriatric Depression Scale (31) for specific quantification of symptoms of depression in older individuals, and the MOS short-form health survey (32) for determination of self-reported health status. Statistical Analysis Values are expressed as the mean ⫾ SEM. The Kolmogorov-Smirnov statistic was used to test the normality of each variable. Differences between groups were analyzed using Student’s independent t test (normal distribution) or Mann-Whitney U test (non-normal distribution), and a onesample t test was used for comparing nutrient intakes against dietary recommendations. Levene’s test for equality of group variances was used to assess equal variances with the reported p value reflecting whether the assumption of equal variances was achieved. Differences between groups were considered significant at p ⬍ .05 for single variables unrelated to other variables (e.g., hemoglobin). A Bonferroni correction was used to adjust for multiple comparisons within a family of variables (e.g., pulmonary function, dietary intake). The calculations were performed using SPSS 8.0 for Windows (SPSS Inc., Chicago, IL).

RESULTS The general characteristics of the subjects are summarized in Table 1. By design, the groups were similar in mean age, BMI, and body fatness but different in dietary restraint score. In addition, the groups were similar in waist-to-hip circumference, fat-free mass, age of menopause, and reported disinhibition, hunger, and weight history. Cardiopulmonary measurements, oral temperature, and skin thickness data are shown in Table 2. None of the parameters differed significantly between groups. There were also no significant differences in plasma lipids, fasting glucose, IGF-1, thyroid hormone parameters, or DTH between groups, but hemoglobin levels were significantly lower in the restrained eaters (Table 3). The restrained eaters tended to have higher BMD of than unrestrained eaters, but group differences did not reach statistical significance (Table 4). Concerning psychological profiles, the restrained eaters reported significantly higher EAT ( p ⬍ .01) and EDI drive for thinness ( p ⬍ .001) and maturity fears subscores ( p ⬍ .05) (Table 5). Other subscale scores of the EDI were not significantly different between the two groups. Similarly, there were no differences between the groups in self-reported physical function, mood, or symptoms of depression (Table 6). The reported macronutrient and micronutrient intakes of the subjects who accurately reported dietary intake [defined as energy intake within 30% of energy requirements predicted by the equation 1 of Vinken and colleagues (33)] are summarized in Table 7, which shows there was no significant difference between the groups in any dietary variable. DISCUSSION Dietary restraint is a widespread dietary practice, but relatively little is known about its effect on physiology and Table 1. Subject Characteristics

General Characteristics Age, y Age at menopause, y Weight, kg Height, cm BMI, kg/m2 Waist/hip ratio Fat-free mass, kg Fat, % by weight Psychometric Scores Cognitive restraint Hunger Disinhibition Weight History Maximum weight, kg Maximum BMI, kg Maximum weight loss, kg Time since maximum weight loss, y Previous Dieting Attempts Never 1 to 3 times 4 to 15 times ⬎15 times

Unrestrained

Restrained

60.0 ⫾ 0.6 49.7 ⫾ 1.0 63.9 ⫾ 1.6 163.9 ⫾ 1.2 23.8 ⫾ 0.6 0.81 ⫾ 0.01 40.9 ⫾ 0.8 35.5 ⫾ 1.2

59.2 ⫾ 0.6 48.7 ⫾ 1.0 63.6 ⫾ 1.3 161.1 ⫾ 1.0 24.5 ⫾ 0.5 0.80 ⫾ 0.01 40.2 ⫾ 0.8 36.2 ⫾ 1.4

4⫾0 6⫾1 6⫾1

16 ⫾ 0* 5⫾1 7⫾1

65.9 ⫾ 1.5 24.6 ⫾ 0.5 5.7 ⫾ 0.9 18.2 ⫾ 3.0

67.2 ⫾ 1.4 26.0 ⫾ 0.5 9.0 ⫾ 1.2 20.1 ⫾ 2.1

11 13 4 0

5 7 18 9

Notes: Data are means ⫾ SEM. BMI ⫽ body mass index. *Significantly different from unrestrained eaters, p ⬍ .01.


Table 2. Cardiopulmonary Measures, Oral Temperature, and Skin Thickness in Postmenopausal Women Classified as Unrestrained or Restrained Eaters

Heart rate, beats/min Systolic blood pressure, mm Hg Diastolic blood pressure, mm Hg Mean arterial pressure, mm Hg* Pulse pressure, mm Hg† Oral temperature, ⬚F Skin thickness, mm Pulmonary function FVC, l FVC corrected for height, l FEV1, l FEV1 corrected for height, l FEV1/FVC Residual volume, l

Unrestrained

Restrained

68 ⫾ 1 121 ⫾ 3 74 ⫾ 2 171 ⫾ 3 47 ⫾ 2 96.8 ⫾ 0.1 1.9 ⫾ 0.1

66 ⫾ 1 118 ⫾ 2 73 ⫾ 1 166 ⫾ 3 45 ⫾ 2 96.7 ⫾ 0.1 1.9 ⫾ 0.1

3.24 ⫾ 0.09 3.24 ⫾ 0.07 2.47 ⫾ 0.07 2.47 ⫾ 0.6 0.76 ⫾ 0.01 2.01 ⫾ 0.06

3.03 ⫾ 0.09 3.01 ⫾ 0.07 2.37 ⫾ 0.07 2.36 ⫾ 0.06 0.78 ⫾ 0.01 1.96 ⫾ 0.08

Notes: Data are means ⫾ SEM. FVC ⫽ forced vital capacity; FEV1 ⫽ forced expiratory volume in one second. *Calculated as brachial systolic pressure ⫹ [(2 ⫻ brachial diastolic pressure)/3]. †Calculated as brachial systolic pressure ⫺ brachial diastolic pressure. Differences between groups are not significant.

metabolism. In the late 1980s, two large surveys conducted in Germany and the United States (3,8) indicated that 20% to 25% of adults had dietary restraint scores ⱖ10 points on the 21-point scale of the Eating Inventory (2), and more recent work suggests an even higher prevalence among some population groups in the United States currently (7). In the present study we examined the association of dietary restraint with a range of variables in older women, specifically to test the hypothesis that long-term dietary restraint is associated with a range of metabolic and health Table 3. Hematologic and Immune Characteristics of Postmenopausal Women Classified as Unrestrained or Restrained Eaters

Total cholesterol, mg/dl Triacylglycerol, mg/dl VLDL-cholesterol, mg/dl LDL-cholesterol, mg/dl HDL-cholesterol, mg/dl Glucose IGF-1 Hemoglobin, g/dl TSH, ␮U/ml Free T3, pg/ml Free T4, ng/dl Reverse T3, ng/ml Antigen score Cumulative DTH score, mm

Unrestrained

Restrained

206 ⫾ 7 105 ⫾ 9 25 ⫾ 5 119 ⫾ 8 61 ⫾ 3 88 ⫾ 2 144 ⫾ 11 13.2 ⫾ 0.1 3.31 ⫾ 0.55 2.90 ⫾ 0.08 1.49 ⫾ 0.03 0.17 ⫾ 0.01 3⫾0 15 ⫾ 2

200 ⫾ 5 118 ⫾ 9 26 ⫾ 3 109 ⫾ 5 65 ⫾ 3 89 ⫾ 1 164 ⫾ 11 12.9 ⫾ 0.1* 2.62 ⫾ 0.22 2.99 ⫾ 0.29 1.59 ⫾ 0.08 0.19 ⫾ 0.01 3⫾0 14 ⫾ 2

Notes: Data are means ⫾ SEM. VLDL ⫽ very low-density lipoprotein; LDL ⫽ low-density lipoprotein; HDL ⫽ high-density lipoprotein; IGF-1 ⫽ insulin-like growth factor 1; TSH ⫽ thyroid stimulating hormone; T3 ⫽ triiodothyronine; T4 ⫽ thyroxine; DTH ⫽ delayed-type hypersensitivity. Antigen score is the total number of positive reactions. Cumulative DTH score is the sum of induration. *Significantly different from unrestrained eaters; p ⬍ .05.

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Table 4. Regional Bone Mineral Density and Bone Mineral Content Measurements of Unrestrained and Restrained Eaters Region

Unrestrained

Restrained

0.794 ⫾ 0.012 1.102 ⫾ 0.015 1.059 ⫾ 0.015

0.811 ⫾ 0.014 1.104 ⫾ 0.032 1.087 ⫾ 0.014

g/cm2

Bone Mineral Density, Arms Legs Total Bone Mineral Content, g Arms Legs Total

270.2 ⫾ 7.3 828.7 ⫾ 24.5 2137.5 ⫾ 53.4

267.3 ⫾ 8.6 850.0 ⫾ 25.3 2194.7 ⫾ 53.8

Notes: Data are means ⫾ SEM. Differences between groups are not significant.

outcomes, some negative and some positive. The subjects were normal-weight, postmenopausal women who were currently restrained or unrestrained eaters and reported stable body weight and dietary restraint for at least 10 years. The groups were matched for BMI at the screening examination, so that we could examine the correlates of dietary restraint independent of group differences in body composition, and were subsequently shown to have comparable mean values for percent body fat and intakes of macronutrients and micronutrients. To our knowledge, this is the first study that has taken into account the likely effect of body composition on the relationship between dietary restraint and metabolic and health outcome variables. It should be noted that our matching of groups for BMI was also appropriate from the perspective of applicability to the general population because previous work has indicated no independent effect of dietary restraint on body fatness (34). Both groups had a lower mean BMI than normative data for this age group from the most recent U.S. national survey (35), and, therefore, further work is needed to determine the extent to which the results of this study are relevant to the general population. The primary finding of this study was that there were very few differences between the groups. A range of parameters including heart rate, blood pressure, body temperature, skin thickness, blood lipids, fasting glucose, thyroid hormone, total BMC, immune function as assessed by DTH, and psychological and self-assessed health variables did not Table 5. Mean Eating Attitudes Test and Eating Disorders Inventory Scores in Postmenopausal Women Classified as Unrestrained or Restrained Eaters

Eating Attitudes Test Eating Disorders Inventory Body dissatisfaction Bulimia Drive for thinness Interoceptive awareness Interpersonal distrust Ineffectiveness Maturity fears Perfectionism

Unrestrained

Restrained

8⫾1

14 ⫾ 1*

8⫾2 3⫾0 0⫾0 0⫾0 1⫾0 1⫾0 1⫾0 5⫾1

9⫾1 3⫾0 3 ⫾ 1* 0⫾0 1⫾0 1⫾0 2⫾0 4⫾1

Note: Data are means ⫾ SEM. *Significantly different from unrestrained eaters; p ⬍ .01.

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Table 6. Mean MOS 36-Item Short-Form Health Survey Health Concepts Scores and Mood State Scores From the Profile of Mood States in Postmenopausal Women Classified as Unrestrained or Restrained Eaters

MOS 36-Item Short Form Physical functioning Role functioning—physical Role functioning—emotional Social functioning Bodily pain Mental health Vitality General health perceptions Profile of Mood State Tension-anxiety Depression-dejection Anger-hostility Vigor-activity Fatigue-inertia Confusion-bewilderment Total mood disturbance Geriatric Depression Scale

Unrestrained

Restrained

29 ⫾ 0 8⫾0 6⫾0 10 ⫾ 0 11 ⫾ 0 27 ⫾ 0 20 ⫾ 0 22 ⫾ 0

29 ⫾ 0 8⫾0 6⫾0 10 ⫾ 0 10 ⫾ 0 27 ⫾ 0 19 ⫾ 1 22 ⫾ 0

31 ⫾ 0 34 ⫾ 0 40 ⫾ 1 72 ⫾ 1 37 ⫾ 1 32 ⫾ 1 102 ⫾ 2 2⫾1

31 ⫾ 0 34 ⫾ 0 40 ⫾ 0 69 ⫾ 1 40 ⫾ 1 31 ⫾ 0 106 ⫾ 2 2⫾0

Notes: Data are means ⫾ SEM. Differences between groups are not significant.

differ significantly between the restrained and unrestrained eaters, and mean values were generally very similar. Restrained eaters did have significantly lower blood hemoglobin despite comparable mean reported micronutrient intakes, but group means for hemoglobin were within normal ranges. Similarly, restrained eaters differed from unrestrained eaters in some of the psychological variables; in particular, they had higher Eating Attitude Test scores and higher drive-for-thinness and maturity fears subscores in the Eating Disorders Inventory, both suggesting a theoretical trend toward eating disorders as documented in several (36) but not all (37) previous studies of younger restrained eaters. It should be noted, however, that these apparent trends may simply reflect the fact that restrained eating is part of a normal spectrum of eating behavior that leads to an eating disorder in extreme cases. Moreover, all individual values

Table 7. Reported Dietary Intake in Postmenopausal Women Classified as Unrestrained or Restrained Eaters Nutrient

Unrestrained (n ⫽ 24)

Restrained (n ⫽ 20)

Energy, MJ/d Protein, g/d Fat, g/d Carbohydrate, g/d Ethanol, g/d Calcium, mg/d Iron, mg/d Zinc, mg/d Vitamin A (retinol equivalents), ␮g/d Vitamin D, ␮g/d Vitamin E (␣-tocopherol equivalent), mg/d Vitamin C, mg/d

8.6 ⫾ 0.2 73 ⫾ 3 73 ⫾ 4 274 ⫾ 11 8⫾2 1165 ⫾ 122 19 ⫾ 2 13 ⫾ 1 1755 ⫾ 177 9⫾1 27 ⫾ 9 185 ⫾ 19

8.0 ⫾ 0.2 78 ⫾ 4 59 ⫾ 4 260 ⫾ 8 10 ⫾ 3 1049 ⫾ 72 21 ⫾ 2 12 ⫾ 1 1482 ⫾ 179 8⫾1 17 ⫾ 4 159 ⫾ 19

Note: Data are means ⫾ SEM.

in the present study were low, and means were well within the normal range. The combination of these results on diverse outcome measures suggests that dietary restraint is not associated with significantly adverse metabolic, physiologic, psychological, or health characteristics in older women without major chronic diseases and who report stable body weight and dietary restraint over a 10-year period. Thus, our results are consistent with those previous reports that have suggested minimal or benign differences between restrained and unrestrained eaters in hormonal parameters such as fasting thyroid hormone, cortisol, insulin, norepinephrine, and growth hormone (9,38,39). In contrast, some previous work has suggested the potential for negative long-term effects of dietary restraint. Most notably, Barr and colleagues (11) observed a shorter luteal phase of the menstrual cycle among 40-year-old women practicing dietary restraint, a finding consistent with the observation of Schweiger and colleagues (10), who noted shorter menstrual cycles and reduced luteal phase progesterone production in restrained eaters compared with unrestrained eaters. These changes could theoretically put women at risk of accelerated bone demineralization over time, but low bone mineral density was not observed in our group of older long-term restrained eaters. Indeed, mean total mineral density was 3% higher in restrained eaters compared with unrestrained eaters, although the difference did not reach statistical significance. It should be noted that there were no significant differences in dietary macronutrients or micronutrients between restrained and unrestrained eaters providing apparently accurate dietary reports [defined as energy intake within 30% of values predicted using equations predicting total energy expenditure (33)]. Presumably, this helped to minimize differences in health characteristics between groups. If there are cultural influences on the nutrition knowledge and the types of foods that restrained eaters attempt to restrict, this may influence the extent to which the positive or negative effects of dietary restraint are seen in studies of other populations of restrained eaters. In summary, this cross-sectional study of healthy postmenopausal women of normal body weight and reporting stable weight and dietary restraint over the past 10 years showed no detrimental effect of dietary restraint on a wide range of parameters. Our results thus suggest that dietary restraint is consistent with health in older women. Further studies are needed to confirm this possibility in a population followed longitudinally and to explore a wider range of parameters than possible in this investigation. Acknowledgments We thank the volunteers for participating in the study and the nursing and recruitment staff of the Metabolic Research Unit for their expert help with data collection. This study was funded with NIH Grants AG12829 and B2A600209, USDA Contract 53-3K06-5-10, and an Army Medical Department Long Term Civilian Training Scholarship to GPB. Contents of this publication do not necessarily reflect the views or policies of the U.S. Department of Agriculture or Department of Defense, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. Gaston P. Bathalon’s current affiliation is U.S. Army Research Institute of Environmental Medicine, Natick, MA.


Address correspondence to Susan B. Roberts, Energy Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington St., Boston, MA 02111. E-mail: [email protected]

20. 21.

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Received July 1, 1999 Accepted September 20, 2000 Decision Editor: John E. Morley, MB, BCh