Lifestyle Factors Related to Postpartum Weight Gain and Body Image in Bottle- and Breastfeeding Women

JOGNN

CLINICAL STUDIES

Lifestyle Factors Related to Postpartum Weight Gain and Body Image in Bottle- and Breastfeeding W o m e n Lorraine 0. Walker, RN, EdD, Jeanne Freeland-Graves, RD, PhD

=

Objective: To explore the relationship of lifestyle variables to postpartum weight gain and body image attitudes of bottle- and breastfeeding women. Design: Mail survey of new mothers at approximateiy 4 months postpartum. Setting: Southwestern community. Participants: One hundred one bottle-feeding women (69%white, 20% Hispanic, 1 1 % other) and 106 breastfeeding women (76%white, 19% Hispanic, 5% other)without diabetes. Bottle- and breastfeeding women did not differ on gestational weight gain or weight gain sustained postpartum. Main Outcome Measures: Postpartum weight gain (relative to prepregnancy weight) and body image attitudes. Results: Feeding method (breast or bottle) was not associated with postpartum weight gain in the sample a s a whole. Bottle-feeding mothers with higher postpartum gains exercised less, had higher fat intake habits, and were more dissatisfied with body image than mothers with lower gains. Breastfeeding mothers with higher and lower gains did not differ on any lifestyle factors. Overall lifestyle and psychologic skill in managing emotions were related negatively to postpartum body image dissatisfaction in both groups of women. Conclusions: Breastfeeding women did not differ from bottle-feeding women in sustained postpartum weight gain. In bottle-feeding women, lifestyle factors were associated with levels of weight gain. Lifestyle-focused programs for weight management would potentially benefit these women. JOGNN, 27, 151-1 60; 1998.

Accepted: July 1997

MarchlApril 1998

After giving birth, women have persistently expressed concerns about returning to a normal weight (Fairburn & Welch, 1990; Hiser, 1987). Similar concerns have been voiced about regaining a desirable body appearance (Gruis, 1977; Hiser, 1987). Experts now recognize the importance of these concerns. Obesity is epidemic in the United States where more than one third of women are overweight (Kuczmarski, Flegal, Campbell, & Johnson, 1994). Thus, the National Task Force on Prevention and Treatment of Obesity (1994) has advocated studying critical periods, such as childbearing, for weight gain. The current study focuses on postpartum weight gain. Excessive postpartum weight gain (i.e., gain above prepregnancy weight) currently is attributed to lifestyle rather than reproductive biology (Lederman, 1993). Lactation may influence the relationship between weight and lifestyle variables, such as dietary patterns (Murphy, & Abrams, 1993). Because childbearing may affect attitudes toward body image, this psychologic dimension of weight also is important to understanding postpartum weight gain. The purpose of the current study was to explore relationships among lifestyle factors, weight gain, and body image attitudes of women who were bottle- and breastfeeding during the early postpartum months.

R ;I ckg r ou nd R m g e arid Sipiificnrzce A ftrr. Cbildbir?b

of

Weight Gain

The Institute of Medicine (IOM) (1990) estimates that with e x h birth, women in the United States experience J permanent weight gain of 2.2 JOG"

151

Ib ( 1 kg). This estimate generally agrees with two recent national surveys that compared women who did and those who did not give birth during the survey period. Women in one survey had average (adjusted) weight gains of -2.0 to 6.6 Ib (-0.9 to 3.0 kg), depending on parity and ethnicity (calculated from Smith et al., 1994, p. 1750). In the other survey, gains of 3.7 to 4.9 lb (1.7 to 2.2 kg) were reported (Williamson et al., 1994).These modest average gains are deceptive, however. Williamson et al. (1994)reported that childbearing carried a risk of 40-60% for a major weight gain of more than 28.7 Ib (13 kg). Such gain is of concern because the amount of weight retained from pregnancy at 6 months postpartum predicts excessive weight gain 4 to 5 years later (Rooney & Schauberger, 1995). Other studies corroborate that women d o not always return to near their prepregnant weights (Greene, Smiciklas-Wright, Scholl, & Karp, 1988; Rossner, 1992; Schauberger, Rooney, & Brimer, 1992). For example, Greene et al. (1988) reported that 1 2 % of women carry gains of 15 Ib (6.8 kg) or more to the start of their next pregnancies.

pregnancy IS expected to support part of the energy demands of lactation (Illingworth, Jung, & Howie, 1987; IOM, 1991). Yet no evidence has been found of a direct effect of breastfeeding (versus bottle-feeding) on postpartum weight (Walker, 1995). Still, choice of infant feeding method may affect weight regulation in other ways, such as moderating lifestyle. Women usually lose the majority of weight they carry over from pregnancy during the first 3 postpartum months, and losses between 3 to 6 months postpartum average only about 2.2 lb (1 kg) (Brewer, Bates, & Vannoy, 1989). In women from racially diverse groups, gains of 10.6 Ib (4.8 kg) above prepregnancy weight were observed at 3 to 6 months postpartum (Parhani, Astrom, & King, 1990). By 6 months, white women average only 3.1 Ib (1.4 kg) more than their prepregnancy weight (Schauberger et al., 1992). Women who retain excessive weight at 3 to 6 months after childbirth may be at risk of developing chronic obesity (Rooney & Schauberger, 1995).

Lifestyle and Weight After C h i l d b i d

W e i g h t gains sustained after childbirth may be potential health risks for women of childbearing age.

Recent research challenges the view that weight gains incurred during the childbearing years are benign. For example, weight gains of 11 Ib (5 kg) or more in women after age 18 have been linked to elevated risk of coronary heart disease, as have higher body mass indices within the “normal” range (Willett et al., 1995). Similar increased risks for breast cancer have been associated with weight gains of 15 Ib (6.8 kg) or more (Kumar, Lyman, Allen, Cox, & Schapira, 1995). Collectively, these findings suggest that weight gains of 11 to 15 Ib or more (5 to 6.8 kg) sustained after childbirth may be potential health risks for women of childbearing age.

Origins and Trajectory of Weight Changes After C h i l d b i d Fat storage appears to be a normal physiologic adaptation of pregnancy. For example, a gain of 7.7 Ib (3.5 kg) of fat is expected in a comparative standard pregnancy with a 27.5 Ib (about 12.5 kg) weight gain (Hytten, 1991). An explanation for this obligatory gain in fat is that it forms a “nutrient reserve during times of food deprivation” (Pipe et al., 1979, p. 939). Fat stored during 152 JOG”

Weight generally is regulated by powerful forces such as genetics (Bouchard, 1991). However, it is important to know what part lifestyle may play in postpartum weight in order to plan effective weight management interventions. Lifestyle behaviors such as exercise, diet, and smoking contribute to the environmental components of weight regulation in the postpartum period. For example, reductions in exercise and activity after childbirth may decrease energy expenditure (ManningDalton & Allen, 1983; Sternfeld, Sidney, Jacobs, Anderssen, & Bild, 1992) and thus prohibit weight loss. However, two studies found no significant relationships between exercise and postpartal weight (Schauberger et al., 1992; Walker, 1996). The reason for this is unclear. The impact of dietary changes during the postpartum period may be another powerful influence on weight retention. Studies by Manning-Dalton and Allen ( 1983) and Ohlin and Rossner (1996) suggest that high postpartal energy intake and irregular eating habits may be significant factors contributing to postpartal weight status. Less healthy dietary patterns may be reactions to time pressures and conflicting demands of spouse, children, and employment (Devine & Olson, 1992; Walker & Best, 1991). Other components of lifestyle also are likely to be altered by stress during the early postpartum months (Walker, 1989). One example is smoking. Smoking during the postpartum period is associated with lower postpartal weight gains (Schauberger et al., 1992), whereas a stop to smoking during pregnancy is associated with greater postpartal weight gain (Ohlin & Rossner, 1990). Thus, the effect of smoking should be considered in studies of lifestyle influences on postpartum weight. Volume 27, Number 2

Finally, maternal skill in self-regulating emotions under stress may be important during the demanding ~ n labor-intensive d period of caring for a n infant (Walker, Walker, & Walker, 1994). The extent to which a woman can modulate her emotional reactions to stressti11 stimuli m a y help her integrate self-care needs with care of a newborn and family and household demands. The relationship of such skill to either lifestyle behaviors o r weight gain after childbirth has not been investigated.

Body Image and Childbearing The changes in body image that accompany biologic changes constitute a key psychologic aspect of childbearing (Rubin, 1984). These perceptual and attitudinal body image changes have been well documented (Drake, Verhulst, Fawcett, & Barger, 1988; Fawcett, Bliss-Holtz, Haas, Leventhal, & Rubin, 1986; Strang & Sullivan, 1985).Although attitudes of dissatisfaction toward postpartum body image (Strang & Sullivan, 1985) may be affected by weight (Brodie & Slade, 1988) and may contribute to changes in lifestyle behaviors related to diet and exercise, the association between body image and postpartal weight has been explored only in a small study with nonsignificant findings (Drake et al., 1988). However, the lack of a correction for weight-for-height makes it difficult to interpret the results. Thus, further study on the relationship of body image and weight is needed to understand the psychologic context of weight gain after childbirth.

Study Questions The current study focused on the following questions: 1. Do bottle- and breastfeeding women differ on postpartum weight gain, body image attitudes, or lifestyle? 2. Within feeding-method groups, are weight gain (as a continuous variable) and body image attitudes related to lifestyle factors, such as aerobic exercise, fat intake habits, smoking, overall lifestyle, and self-regulation? 3. Within feeding-method groups, d o women with higher (more than 7.7 Ib) and lower (7.7 Ib or less) postpartum weight gains differ on lifestyle factors?

Methods Design and Sample After human subjects’ approval was obtained, an eight-page questionnaire was mailed to a cross-sectional sample of 513 new mothers (Walker, 1998). Names of mothers were obtained from newspaper birth announcements, and participants were selected if they resided in MarchlApril 1998

Austin, Texas; had a singleton birth; and had a published mailing address. Ethnic composition of the survey region was 65% white; 21% Hispanic; 11% black; and 3% Native American, Asian, and other (Greater Austin Chamber of Commerce, personal communication, January, 1995). Responses were returned by 245 women, and the adjusted response rate was 52% after correction for questionnaires returned as undeliverable ( n = 39). Of the 245 respondents, 19 who did not meet inclusion criteria were excluded for the following reasons: health conditions (polyhydramnios, multiple sclerosis, HIV infection) that might interact with weight ( n = 3), age younger than 18 years ( n = 5 ) , newborn birth weight under 2,500 g ( n = 6), incomplete or unusable height or weight data ( n = 5), multiple birth ( n = l), and missing data on feeding method ( n = 1).Two respondents fell into more than one category. In addition, respondents ( n = 19) reporting diabetes (gestational or pregestational) were excluded. Thus, the final sample consisted of 207 women. Of these, 150 ( 7 3 % )were white, 40 ( 1 9 % ) Hispanic, and 16 ( 8 % )of other ethnicity. Median time since delivery was 4 months. (Findings from a follow-up at 1 year postpartum are in Walker, 1997). Table 1 shows demographic and anthropometric data for bottle- and breastfeeding mothers. No significant differences were found for prepregnancy body mass index, gestational weight gain, time since delivery, or social variables, such as number of children and ethnicity. Breastfeeding mothers were more educated and more likely to be living with their infants’ fathers.

Variables and Measurement Items on the survey questionnaire included anthropometric variables (e.g., height and weight), reproductive variables (e.g., mode of delivery), and social and demographic variables (e.g., maternal age). Parity was assessed by the number of children at home. The body image and exercise measures in the questionnaire were pretested and shown to be suitable for use with ethnically diverse women. (See Table 2 for an overview of psychometric instruments.) Prepregnant weight-for-height was indexed by body mass index (BMI),which was computed as weight (kg)/height (m)’. Gestational weight gain was computed from weight at the end of pregnancy minus prepregnant weight. Postpartal weight gain was calculated as postpartal weight minus prepregnant weight. Postpartum gains were classified as lower gains if they were equal to or less than the theoretical estimate of 7.7 Ib (3.5 kg) of fat stored during pregnancy and as higher gains if they exceeded this estimate (Hytten, 1991). All weight measures were based on self-reported data. Stevens-Simon, Roghmann, and McAnarney (1992)concluded that “for most pregnant adolescents and women, self-reported JOGNN

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TABLE 1

Social and Anthropometric Characteristics of Bottle- and Breastfeeding Mothers Bottle-Feediizg (11 = 101)

Variables Number of children (%) One Two or more Education (%) High school or less Some college Family incomea (YO) <$30,000 >$30,000 Ethnicityb (YO) White Hispanic Other Living with infant’s father (Yo) Yes No Time since delivery (median in months)c Age of mother (median in years) Gestational weight gain (median in Ib) Prepregnancy body mass index (median) a

Breastfeeding (n = 106)

47 53

47 53

31 69

13 87”*

36 64

26 74

69 20 11

76 19 5

89 11 4.0 29.0 32.0 22.6

97“ 3 4.0 31.0 32.0 21.6

Data missing for 7 cases. Data missing for 1 case. Data missing for 2 cases.

* p < .05.* * p < .01. (x2test)

prepregnant weight is a valid estimate [Y = .96] of their body weight before their pregnancy” (p. 86). However, bias is more likely at extremely high and low weights. Body image attitudes were measured by a shortened version of the Body Cathexis Scale (BCS),a 46-item

summated rating scale of satisfaction with one’s body (Secord & Jourard, 1953). Persons express how positively or negatively they feel about various parts and functions of their bodies named in the scale. Reliability of the original scale is .83 with females. Its validity is

TABLE 2

Summary of lnstrurneiits lnstnrmerrt

What Is Measured

Score Range and Interpretation

Body Cathexis Scale Wang et al. Scale Food Habits Questionnaire Personal Lifestyle Questionnaire

Dissatisfaction with body Level of aerobic exercise Eating high-fat foods Overall lifestyle, which includes nutrition, safety, substance use, exercise, health monitoring, etc. Psychologic skill in managing distress, problem solving, etc.

29-145: High scores = high dissatisfaction with body 1-7: High scores = high level of aerobic exercise 1-4: High scores = often eat high fat foods 20-80: High scores = positive overall health behaviors

Self-Control Schedule

154 JOG”

35-210: High scores = high skill in managing distress, etc.

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based on expected significant correlations with esteem measures and weight loss (Wineman, 1980), and its sensitivity to body image changes is related to reproduction (Strang Ly: Sullivan, 1985). For brevity in the current study, the BCS was shortened to 30 body parts or functions relevant to postpartum such as appetite, physical stamina, waist, breasts, hips, and weight. One item on elimination was omitted from data analysis because a number of women indicated that it was unclear. The final 29-item scale used in this study had an internal consistency of .91. High scores indicate body image dissatisfaction. Current activity level was assessed by the Wang, Eddy, and Fitzhugh (1992) scale for aerobic activity. In the Wang et al. scale, persons select one of seven levels of progressively more demanding activity that best describes their activity level. These levels range from 1 (essentially no physical activity above minimum demands of daily living) to 7 (one or more dynamic activities with large muscle groups at 40 to 60 minutes per session for 5 or 6 sessions per week ar 65% or more maximal heart rate). Furthermore, at each activity level, corresponding examples of specific activities are given to aid users in determining their activity level. The Wang et al. scale is recommended for health promotion research and is applicable to survey designs. In postpartal women, scores o n the Wang et al. (1992) scale have been shown to correlate significantly ( r = 3 6 , p < .001) with another activity index measured 12 months earlier (Walker, 1996). Dietary behaviors were measured by the Food Habits Questionnaire (FHQ) (Kristal, Shattuck, & Henry, 1990). The FHQ captures dietary fat intake habits for the last month and includes behaviors aimed a t avoiding, altering, substituting, and replacing foods to lower dietary fat intake. Modified from its initial 28-item version, the 20-item version developed by Kristal et al. was tested by Beerman and Dittus (1994) and showed a test-retest reliability of .83. The latter also reported that for women, the FHQ correlated significantly with percentage of calories from fat in the diet ( r = 5 5 ) . The FHQ differentiated those with high fat intakes from those with medium or low intakes. It also had a more favorable responsiveness index in a clinical trial than either 4-day food records or food frequency questionnaires (Kristal, Beresford, & Lazovich, 1994). Response choices range from 1 (usually or always) to 4 (rarely or never as well as not applicable). The 20-item version used in this study had an internal consistency of .83. Two items were compressed in scoring. Average item mean scores were computed to accommodate nonapplicable items, and high scores indicated habits favoring a high-fat diet. Overall health-related lifestyle was assessed on the Personal Lifestyle Questionnaire (PLQ) (Brown, Muhlenkamp, Fox, & Osborn, 1983), a 24-item, four-point

MarchlApril 1998

scale about behaviors related to iititrition, substance use and smoking, exercise, relaxation, safety, and health promotion. A sample item reads, “See a hcalth care provider for a checkup a t least yearly.” Two items (keeping emergency telephone numhers near the phone and driving over the speed limit) were omitted from analysis hecause several women indicated that they had no phone or did not drive. An item about weight was deleted s o that it would not confound lifestyle and weight, and one about smoking was treated separately as an indicator of smoking status. Respondents indicated how frequently they engaged in behaviors by responses ranging from 4 (regularly) to 1 (never). Test-retest reliability for the PLQ is .78 to .88 (Brown et al., 1953). Validity is supported by expected correlations with self-esteem and social support measures (Muhlenkamp Ly: Sayles, 1986). Internal consistency was .64 for the 20-item version of the scale used in this analysis. Higher scores indicate a healthier lifestyle. Self-regulation was measured by the Self-Control Schedule (SCS) (Rosenbaum, 1980), a measure of selfmanagement capabilities that individuals use when confronted with cues or situations that interfere with effective behavior. This 36-item summated rating scale addresses cognitive control of responses, problem solving, gratification delay, and self-efficacy. A sample item reads, “When I find it difficult to settle down and do a certain job, I look for ways to help me settle down.” One item on smoking cessation was omitted from analysis because a number of women who were nonsmokers left it blank. The SCS has a test-retest reliability of .86 and an internal consistency reliability that ranges from .78 to .84. The validity of the SCS is supported by significant correlations with related constructs, such as locus of control. The 35-item scale version used in this study had an internal consistency of .78. In stress experiments, those scoring high on the SCS responded with greater capability for tolerating stress (Rosenbaum, 1980). A higher score indicates higher self-regulation.

Data Anulysis Preliminary inspection of the data indicated that several variables (particularly weight variables) were skewed in distribution. Thus, for consistency, medians were reported as measures of central tendency, and statistical analyses were conducted using nonparainetric tests. The chi-square test and Mann-Whitney U test were used to compare bottle- and breastfeeding mothers on weight, body image, and lifestyle-related factors. The Spearman correlation tested relationships among lifestyle factors, weight, and body image. The Mann-Whimey U test was used to compare bottle- and breastfeeding mothers separately on lifestyIe-reIated factors associated with lower and higher postpartum weight gains. For ease of interpretation in these analyses, mediilns (scores at the mid-point of ranked data) are presented instead of mean ranks.

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TABLE 3

Medians of Weight, Body Image Dissatisfaction, and Lifestyle-Related Factors in Bottle- and Breastfeeding Women Bottle-Feeding Breastfeeding (n = 101) (n = 106)

trend for bottle-feeding mothers to be more likely to report smoking ( n = 13) than breastfeeding mothers ( n = 6), x' = 3.07, p = .08.

Body Image, Weight, and Lifestyle Relationships Witbin Feeding-Methods Gvottps

Results

Table 4 presents correlations between variables for each feeding-method group. In the bottle-feeding group ( n = 101), body image dissatisfaction, fat intake habits, and smoking were related to postpartum weight gain. Aerobic exercise was negatively related to weight gain, whereas higher gain accompanied lower level of exercise. Body image was significantly and negatively related to aerobic exercise, overall lifestyle, and self-regulation. That is, greater body image dissatisfaction occurred with less vigorous exercise, less healthy lifestyle, and less self-regulatory capabilities. Within the breastfeeding group ( n = 106),neither body image dissatisfaction nor lifestyle variables were related to weight gain. Dissatisfaction with body image was significantly and negatively related to overall lifestyle and self-regulatory capabilities. Gestational weight gain was significantly related to postpartum weight gain in both bottle- and breastfeeding groups.

Comparing Bottle- and Breastfeeding Women on Weight Gain, Body Image, and Lifestyle

Lifestyle Differences Associated witb Higher Weight Gain Within Feeding-Method Groups

The method of feeding (bottle versus breast) was not associated with significant differences in postpartum weight gain or body image dissatisfaction (see Table 3 ) . Breastfeeding mothers reported healthier overall lifestyles on the Personal Lifestyle Questionnaire and had lower fat intake habits than did bottle-feeding mothers. N o statistically significant differences were found in the areas of aerobic exercise or self-regulation. There was a

Next, bottle-feeding women were divided into those who had higher (more than 7.7 lb) or lower (7.7 lb or less) weight gains based on Hytten's (1991) estimate of fat gain. Medians for weight gain were 12 lb (5.4 kg) and 0 Ib (0 kg), respectively. Table 5 shows that the two weight-gain groups did not differ on the length of time since giving birth. Bottle-feeding mothers with higher gains had greater dissatisfaction with their body

Variables

Postpartum weight gain (median in Ib) Body image dissatisfaction" Aerobic exerciseb Fat intake habits" Overall lifestyle' SeIf-regulationd

5.0

6.0

77.0

79.0

2.00 2.80 59.0 144.5

3.00 2.56' 62.0*'* 145.0

Data missing for 1 case. Data missing for 4 cases. ' Data missing for 2 cases. Data missing for 7 cases. * p c .05.* * p < .01. * * * p < ,001.

a

TABLE 4

Correlation Between Weight, Body Image Dissatisfaction, and Lifestyle-Related Variables Breastfeeding Womenb (n = 106)

Bottle-Feeding Women' ( n = 101)

Body image dissatisfaction Fat intake habits Aerobic exercise Smoking Overall lifestyle Self-regulation Gestational gain

Postpartum Gain

Body lmage

.22* .20* -.21* .17* -.16 -.12 .52'**

.08 -.25** .12 -.32*'* -.39* '' -.02

Postpartum Gain

-

.13 .05 .10

-.15 -.11 .08 .46'**

Body lmage

-

.oo -.09

.oo -.33* '' -.28*'

.15

Note. Postpartum gain is indexed to prepregnancy weight. a n varies from 96 to 101 because of missing data. n varies from 103 to 106 because of missing data. * p < .05.* * p < .01. * * * p < .001.

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TABLE 5

Medians of Variables by Lower and Higher Postpartum Weight Gain in Bottle- and Breastfeeding Groups Medians for Bottle-Feeding Group Variables

Months since birth Body image Fat intake habits Aerobic exercise Overall lifestyle Self-regulation Gestational gain (Ib) Prepregnant body mass

Medians for Breastfeeding Group

Lower Gain n = 57

Higher Gain n = 44

U Test

Lower Gain n = 61

Higher Gain n = 45

U Test

4.0 71.0 2.69 3.00 59.0 147.5 28.0 22.9

4.0 81.0 2.94 2.00 58.0 140.5 38.5 22.0

1212.5' 886.5* 866.5' * 877b * 1056 903.5' 591*** 1186

3.5 78.0 2.56 3.00 62.0 145.5 30.0 21.3

4.0 80.0 2.56 3.00 62.0 144.5 38.0 21.9

1332" 1166" 1335.5 113Sb 128 2.5 1259Sb 687*** 1351

Note. Lower gains = 57.7 Ib and higher gains = >7.7 Ib. Missing data for 1 case. Missing data for 2 cases. ' Missing data for 5 cases. * p < .05.* * p i.01. * * * p < .001.

a

image, higher fat intake habits, and lower levels of aerobic exercise than bottle-feeding mothers with lower gains. Eight of the 13 bottle-feeding mothers who smoked were in the higher weight gain group, but this difference was not significant, xz = 1.96, p > .05. Table 5 shows that women with higher weight gain in the postpartum period had gained more weight in pregnancy. Bottle-feeding women with lower or higher gains in postpartum did not differ in their prepregnancy BMIs. Because differences were found for overall fat intake habits for bottle-feeding women, a comparison of individual fat intake items was undertaken to identify specific areas of difference (data not shown). Women with lower postpartum gains reported more frequent use of meatless sauces on pasta, vegetarian meals, fish or chicken instead of meat, fruit for dessert, and vegetables substituted for high-fat snacks compared with women who reported higher gains. When breastfeeding women were divided into those with higher and lower weight gains, group medians for weight gain were 13 Ib (5.9 kg) and 2 Ib (0.9 kg), respectively. Table 5 shows that breastfeeding women with higher and lower postpartum gain did not differ regarding the length of time since giving birth, body image dissatisfaction, or any lifestyle-related variables. Five of the six breastfeeding mothers who smoked were in the lower weight gain group. Breastfeeding women who had higher postpartum weight gain had gained more weight in pregnancy. However, they did not differ in prepregnancy BMI compared with women who reported lower gains.

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Discussion lnfluence of Feeding Method on Lifestyle and Weight Gain After Childbirtb This study challenges the common belief that breastfeeding mothers lose more weight in the early months of postpartum than do mothers who bottle-feed their infants. The reason for a lack of beneficial effect on weight is puzzling because lactation requires more energy than the nonlactating state. However, the results of this study are consistent with others that show negligible effects of lactation on women's weight (Ohlin & Rossner, 1996). This study is the first to suggest that lifestyle patterns in the postpartum period have differing effects on weight depending on feeding method. This was most evident when lifestyle variables were considered separately for bottle- and breastfeeding women according to the degree of weight gain (higher versus lower). In bottle-feeding women, higher postpartum weight gains were associated with less vigorous exercise patterns and higher fat intake ha bits than lower weight gains. No such effect was present in the women who breastfed.

T h e r e was evidence that choice of feeding method may moderate the relationship between lifestyle and weight gain after childbirth.

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The findings of this study support the importance of emphasizing lifestyle factors in weight management for women who bottle-feed. The beneficial effect of vigorous exercise in the postpartum period is not surprising because it is well known that increased exercise improves energy expenditure and can lead to weight loss, provided appetite is not stimulated. A decline in fat intake also can promote weight reduction if fat calories are substituted in equal weights by carbohydrates and protein, which have less than half the energy (caloric) equivalents. Lowering of fat intake by increases in dietary fiber would have an even more profound effect because there is minimal digestion of this dietary component (Freeland-Graves & Peckham, 1996). It is of interest that bottle-feeding mothers who smoked had a tendency to be heavier postpartum. It is conceivable that this pattern may have resulted from smoking cessation during pregnancy, which may lead to higher gestational and postpartum weight gains. Because only postpartum smoking habits were assessed, the extent of smoking cessation during pregnancy and relapse in the postpartum period is unclear. Still, the postpartum period may be a critical time for supporting women in maintaining smoking cessation, especially if they are overweight. There is no clear explanation for the lack of association between lifestyle factors and weight gain among breastfeeding women. We propose several possibilities. First, it is plausible that women who breastfeed generally have a greater interest in health and nutrition than d o women who choose to bottle-feed. This may lead to a more careful selection of a nutritionally adequate, wellbalanced diet and fewer variations in total energy intake. Second, as Dewey, Heinig, and Nommsen (1993) have speculated, higher prolactin levels in the early months of lactation may stimulate appetite, thereby delaying the mobilization of fat stores. Consequently, the increased caloric demands of lactation may be offset by the greater ingestion of energy in the diet. Third, vigorous exercise during the early postpartum months may not effect weight loss in breastfeeding women because of compensatory decreases in other activities and increases in energy intake (Dewey, Lovelady, Nommsen-Rivers, McCrory, & Lonnerdal, 1994). The current study supports the need for further study of biologic and behavioral factors in weight regulation in breastfeeding women.

Body Image Dissatisfaction, Weight, and Lifestyle Factors In bottle-feeding women, a greater dissatisfaction with body image was associated with higher weight gains. The differences for breastfeeding women with higher and lower postpartum weight gains were in the expected direction but were not significant. Analysis of text data provided by this sample and reported elsewhere 158 JOG”

(Walker, 1998) suggests that some women who are breastfeeding niay temper their feelings about their weight. This, in turn, may cause a weakened relationship between body image dissatisfaction and weight during 1acta ti on. For both b o tt I e - and breast f eed i ng w o in e 11, greater dissatisfaction with body image was related to less self-regulatory capabilities and less healthful overall lifestyle. Although these relationships were unexpected, women with more dissatisfaction may be less able to use cognitive processes such as reappraisal to manage the stress of bodily changes inherent in the post pa r t u m experience . Converse I y , ma i n t a in i ng a healthier lifestyle may give mothers something positive to focus on regarding their bodies. Body image was also enhanced among bottle-feeding women who exercised more vigorously.

Limitations and Future Directions The limitations of the current study should be considered when the findings are interpreted. The response rate was just over 5 0 % , and respondents were predominantly white. Women’s weights in this study were self-reported, so it would be desirable to repeat this study using measured prepregnancy and postpartum weights. I t also would be of interest to collect diet surveys on these participants in order to calculate actual fat and energy intakes. Finally, the extent to which breastfeeding women may have used supplemental formula was not measured. The unexpected finding of this study was that bottle- and breastfeeding women were remarkably similar except for a few social variables (maternal education and marital status). Future research should focus o n the two lifestyle differences associated with women’s choice of feeding method: overall lifestyle and fat intake habits. Yet the role of lifestyle in weight regulation may be a more complex phenomenon biologically (Illingworth et al., 1987) during the early months of lactation than the parameters investigated in the current study. Thus, further clinical research is essential to unravel the lack of an observed relationship between lifestyle variables and weight gain in breastfeeding women.

Nursing Implications The complexity of daily living for new mothers cited at the beginning of this article suggests that traditional approaches to weight management may be insufficient for this population. This study indicates that counseling of postpartal women struggling with weight gain must emphasize changes in dietary fat habits and physical activity. Another constituent of a successful weight management program would include ways to enhance body image. For

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mothers who stopped smoking during pregnancy, support prevent smoking relapse also would be crucial. The development of alternative programs with these components designed specifically for new mothers is a fertile area for expanding nursing practice. to

T o counsel women effectively about postpartum weight management, nurses must recognize and promote lifestyle behaviors that positively influence nutrition and health.

Nurses must be cognizant of the interplay of a healthy diet, energy balance, lifestyle modification, and exercise (IOM, 1995) if they expect to be effective in counseling women about weight management. Collaborative approaches that include nutritionists and exercise specialists can aid nurses in providing flexible programs for new mothers to promote healthy weight loss within the context of daily living. Finally, it is essential that nurses evaluate programs for effectiveness in achieving weight loss and enhancing healthy behaviors (IOM, 1995).

Acknowledgment This research was supported in part by the Luci B. Johnson Centennial Professorship in Nursing, The University of Texas at Austin School of Nursing.

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Lorraine 0. Walker is Luci B. Johnson Centennial Professor in the School of Nursing, the University of Texas at Austin. Jeanne Freeland-Graves is Bess Heflin Centennial Professor in the Nutrition Division of the Department of Human Ecology, the University of Texas at Austin. Address for correspondence: Lorraine Walker, RN, EdD, University of Texas a t Austin, School of Nursing, 1 700 Red River St., Austin, TX 78701-1499.

Volume 27, Number 2