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Studies on energy metabolism and body composition of healthy women before, during and after pregnancy
Linköping University, Department of Biomedicine and Surgery, Nutrition. Linköping University, Faculty of Health Sciences.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Current recommendations propose that an entire pregnancy requires an additional amount of energy from the diet equivalent to 335 000 kJ. This figure is mainly based on increases in the basal metabolic rate (BMR) and retention of total body fat (TBF). The BMR response to pregnancy varies considerably among women, but the factors responsible for this variability are unknown. TBF can be calculated from total body water (TBW) and the hydration factor (HF), using the so-called two-component model. However, the validity of this model during pregnancy has been questioned. Furthermore, current recommendations propose that energy needs during pregnancy may be partly offset by reductions in physical activity, but this statement is supported by little experimental evidence. The aims of this thesis were: to evaluate if the physical activity level (PAL) can be estimated by means of heart rate recording, accelerometry, and a questionnaire in women planning pregnancy; to assess the effect of pregnancy on energy expenditure due to physical activity, on activity pattern and on the biological variability of HF; to evaluate the use of bioimpedance spectroscopy (BIS) for assessing TBW during pregnancy; and to identifY factors explaining the variability of the BMR response to pregnancy.

Healthy women were studied before pregnancy (n=38), and in gestational weeks 8, 14, 20, 32, 35 and 2 weeks post partum (n=23). Total energy expenditure (TEE), BMR, TEE/BMR, activity pattern, body composition, circulatory variables and serum levels of thyroid hormones and insulin growth factor-I (IGF-1) were measured. Foetal weight in gestational week 31 and infant birth weight were assessed.

All estimates of PAL were imprecise and too low in women planning pregnancy. There was little change in TEE/BMR in gestational week 14, but it was significantly reduced in gestational week 32. However, activity pattern was largely unaffected by pregnancy. The biological variability of HF was 2%, 3% and 1.7% or less of average HF before pregnancy and in gestational weeks 14 and 32, respectively. BIS underestimated TBW during pregnancy. In gestational week 14, the increase in BMR correlated significantly with the increase in body weight and with TBF (%)before pregnancy. Together these variables explained about 40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with changes in body weight, TBF, fat-free mass, IGF-I, cardiac output and free triiodothyronine. At this stage of gestation the increase in body weight in combination with foetal weight or with the increased levels of IGF-I in serum explained about 60% of the variability of the increased BMR.

In conclusion: I) Heart rate recording, accelerometry and the questionnaire produced inappropriate PAL estimates. 2) In women maintaining their pre-pregnant activity pattern the increase in BMR represents the major component of the increased energy expenditure during pregnancy. 3) The two-component model for assessing TBF is appropriate in late gestation, while its precision may be impaired in early pregnancy. 4) BIS in its present form is not appropriate for assessing TBW during pregnancy. 5) Nutritional factors are important regarding the variability in the BMR response to pregnancy.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2004. , 58 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 853
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-23970Local ID: 3520ISBN: 91-7373-825-5 (print)OAI: oai:DiVA.org:liu-23970DiVA: diva2:244286
Public defence
2004-05-28, Aulan, Hälsans Hus, Hälsouniversitetet, Linköping, 13:00 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-10-31Bibliographically approved
List of papers
1. Comparison of commonly used procedures, including the doubly-labelled water technique, in the estimation of total energy expenditure of women with special reference to the significance of body fatness
Open this publication in new window or tab >>Comparison of commonly used procedures, including the doubly-labelled water technique, in the estimation of total energy expenditure of women with special reference to the significance of body fatness
2003 (English)In: British Journal of Nutrition, ISSN 0007-1145, E-ISSN 1475-2662, Vol. 90, no 5, 961-968 p.Article in journal (Refereed) Published
Abstract [en]

According to the report of the World Health Organization (1985), total energy expenditure (TEE) in human subjects can be calculated as BMR × physical activity level (PAL). However, other reports have pointed out limitations in the suggested procedure related to the % body fat of the subjects. The purpose of the present study was to evaluate the World Health Organization (1985) procedure in thirty-four healthy women with BMI 18-39 kg/m2. BMR and TEE were measured using indirect calorimetry (BMRmeas) and the doubly-labelled water method (TEEref) respectively. When assessed using the doubly-labelled water and skinfold-thickness methods, the women had 34 (SD 8) and 33 (SD 6) % body fat respectively. On the basis of guidelines provided by the World Health Organization (1985), 1.64 was selected to represent the average PAL of the women. Furthermore, PAL was also assessed by means of an accelerometer (PALacc), heart-rate recordings (PALHR) and a questionnaire (PALq). These estimates were: PALacc 1.71 (SD 0.17), PALHR 1.76 (SD 0.24), PALq 1.86 (SD 0.27). These values were lower than TEEref/BMRref, which was 1.98 (SD 0.21). BMR assessed using equations recommended by the World Health Organization (1985) (BMRpredicted) overestimated BMR by 594 (SD 431) kj/24 h. However, when TEE was calculated as BMRpredicted × PALacc, BMRpredicted × PALHR and BMRpredicted × PALq respectively, average results were in agreement with TEEref. Furthermore, TEE values based on BMRpredicted and PALacc, PALHR, PALq as well as on PAL = 1.64, minus TEEref, were significantly correlated with body fatness. When the same PAL value (1.64) was used for all subjects, this correlation was particularly strong. Thus, the World Health Organization (1985) procedure may give TEE results that are biased with respect to the body fatness of subjects.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25016 (URN)10.1079/BJN2003975 (DOI)9437 (Local ID)9437 (Archive number)9437 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
2. Activity pattern and energy expenditure due to physical activity before and during pregnancy in healthy Swedish women
Open this publication in new window or tab >>Activity pattern and energy expenditure due to physical activity before and during pregnancy in healthy Swedish women
2006 (English)In: British Journal of Nutrition, ISSN 0007-1145, E-ISSN 1475-2662, Vol. 95, no 2, 296-302 p.Article in journal (Refereed) Published
Abstract [en]

Human pregnancy is associated with increased requirements for dietary energy and this increase may be partly offset by reductions in physical activity during gestation. Studies in well-nourished women have shown that the physical activity level (PAL), obtained as the total energy expenditure (TEE) divided by the BMR, decreases in late pregnancy. However, it is not known if this decrease is really caused by reductions in physical activity or if it is the result of decreases in energy expenditure/BMR (the so-called metabolic equivalent, MET) for many activities in late pregnancy. In the present study activity pattern, TEE and BMR were assessed in twenty-three healthy Swedish women before pregnancy as well as in gestational weeks 14 and 32. Activity pattern was assessed using a questionnaire and heart rate recording. TEE was assessed using the doubly labelled water method and BMR was measured by means of indirect calorimetry. When compared to the pre-pregnant value, there was little change in the PAL in gestational week 14 but it was significantly reduced in gestational week 32. Results obtained by means of the questionnaire and by heart rate recording showed that the activity pattern was largely unaffected by pregnancy. The findings support the following conclusion: in a population of well-nourished women where the activity pattern is maintained during pregnancy, the increase in BMR represents approximately the main part of the pregnancy-induced increase in TEE, at least until gestational week 32.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-35738 (URN)10.1079/BJN20051497 (DOI)28349 (Local ID)28349 (Archive number)28349 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
3. Hydration of fat-free mass in healthy women with special reference to the effect of pregnancy
Open this publication in new window or tab >>Hydration of fat-free mass in healthy women with special reference to the effect of pregnancy
2004 (English)In: American Journal of Clinical Nutrition, ISSN 0002-9165, E-ISSN 1938-3207, Vol. 80, no 4, 960-965 p.Article in journal (Refereed) Published
Abstract [en]

Background: Knowledge of the biological variability of the hydration factor (HF), ie, the ratio between total body water and fat-free mass, is important when calculating total body fat by means of the commonly used two-component model, which is based on estimates of body weight and total body water. The effect of pregnancy on the biological variability of HF, and consequently on the precision of the two-component model, is unknown.

Objective: Our goal was to assess the effect of pregnancy on HF and its biological variability.

Design: HF was assessed in 33 women planning pregnancy and in 17 of these women during gestational weeks 14 and 32 and 2 wk postpartum. HF was calculated by using estimates of body weight, total body water obtained by means of deuterium dilution, and body volume measured by using underwater weighing.

Results: In the 17 women who became pregnant, HF was 0.718 ± 0.023, 0.723 ± 0.031, 0.747 ± 0.017, and 0.734 ± 0.020 before pregnancy, in gestational week 14, in gestational week 32, and 2 wk postpartum, respectively. The biological variability represented ≈2% of average HF in the nonpregnant state. The corresponding figure was >3% in gestational week 14 but ≤1.7% in gestational week 32.

Conclusion: The two-component model for assessing body fat is as appropriate during late gestation as it is in the nonpregnant state, although its precision may be impaired when applied during the first part of pregnancy.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-23923 (URN)15447906 (PubMedID)3471 (Local ID)3471 (Archive number)3471 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
4. Evaluation of bioimpedance spectroscopy for measurements of body water distribution in healthy women before, during, and after pregnancy
Open this publication in new window or tab >>Evaluation of bioimpedance spectroscopy for measurements of body water distribution in healthy women before, during, and after pregnancy
2004 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 96, no 3, 967-973 p.Article in journal (Refereed) Published
Abstract [en]

Bioimpedance spectroscopy (BIS) is a technique of interest in the study of human pregnancy because it can assess extracellular (ECW), intracellular (ICW), and total body water (TBW) as ECW plus ICW. The technique requires appropriate resistivity coefficients and has not been sufficiently evaluated during the reproductive cycle. Therefore, in a methodological study, we estimated ECW, ICW, and TBW, by means of BIS, and compared the results with the corresponding estimates obtained by using reference methods. Furthermore, results obtained by means of population-specific resistivity coefficients were compared with results obtained by means of general resistivity coefficients. These comparisons were made before pregnancy, in gestational weeks 14 and 32, as well as 2 wk postpartum in 21 healthy women. The reference methods were isotope and bromide dilution. Average ICW, ECW, and TBW, estimated by means of BIS, were in agreement with reference data before pregnancy, in gestational week 14, and postpartum. The corresponding comparison in gestational week 32 showed good agreement for ICW, whereas estimates by means of BIS were significantly (P < 0.001) lower than the corresponding reference values for ECW and TBW. Thus the BIS technique, which was based on a model developed for the nonpregnant body, estimated increases in ICW accurately, whereas increases in ECW and TBW tended to be underestimated. Estimates obtained by using population-specific and general resistivity coefficients were very similar. In conclusion, the results indicated that BIS is potentially useful for studies during pregnancy but that further work is needed before it can be generally applied in such studies.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-23933 (URN)10.1152/japplphysiol.00900.2003 (DOI)3481 (Local ID)3481 (Archive number)3481 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
5. Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth
Open this publication in new window or tab >>Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth
Show others...
2005 (English)In: American Journal of Clinical Nutrition, ISSN 0002-9165, E-ISSN 1938-3207, Vol. 81, no 3, 678-685 p.Article in journal (Refereed) Published
Abstract [en]

Background: The total energy cost of pregnancy is largely due to an elevated basal metabolic rate (BMR). Large variations in the BMR response to pregnancy have been reported, but the factors associated with this variability are incompletely known.

Objective: The objective was to identify factors associated with variability in the BMR response to pregnancy.

Design: In 22 healthy women, BMR, body weight (BW), total body fat (TBF), fat-free mass (FFM), circulatory variables, serum concentrations of insulin-like growth factor I (IGF-I), and thyroid hormones were measured before pregnancy and in gestational weeks 14 and 32. BMR and BW were also measured in gestational weeks 8, 20, and 35. Fetal weight was estimated in gestational week 31.

Results: In gestational week 14, the increase in BMR correlated significantly with the corresponding increase in BW and with the prepregnancy percentage of TBF. Together these variables explained ≈40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with the corresponding changes in BW, TBF, FFM, IGF-I, cardiac output, and free triiodothyronine. The increase in BW in combination with fetal weight or with the elevated concentration of IGF-I in serum explained ≈60% of the variability in the increase in BMR.

Conclusions: Weight gain and the prepregnancy percentage of TBF—ie, factors related to the maternal nutritional situation—are important factors with regard to the variability in the BMR response to pregnancy. Thus, it is important to consider the nutritional situation before and during gestation when assessing pregnancy energy requirements.

Keyword
Basal metabolic rate, cardiac output, body composition, free triiodothyronine, insulin-like growth factor I, pregnancy
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24769 (URN)7030 (Local ID)7030 (Archive number)7030 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13

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