Measurement and control of body fat percent during pregnancy

Abstract

The present invention provides a method for measuring the body fat percent and fat accretion during pregnancy, which preferably utilizes a Fourier transform near infrared spectroscopy (FT-NIR) fat determination method. The FT-NIR results can be used to measure and monitor body fat percent, and used to measure the mother's fat accretion rate. A method to monitor weight gain in a pregnant subject is provided wherein the body fat percentage of the subject is maintained at a constant level during gestation, and the subject's fat accretion rate is monitored so as to follow the fat accretion rate provided by using pre-defined fat accretion determination formulae. By measurement of the body fat percent and fat accretion rates, the weight gain of a subject can be monitored and/or controlled during pregnancy.

Claims

1. A method for the measurement and control of body fat percent and body fat accretion during pregnancy comprising: measuring the body fat percentage of a mammal at the beginning of said pregnancy using an FT-NIR technique, and monitoring the body fat percentage of said mammal using said FT-NIR technique during the course of said pregnancy; measuring the body fat mass of a mammal at the beginning of said pregnancy using weight scales and said measured body fat percentage value, and monitoring the body fat mass of said mammal using said scales and monitored body fat percentage value during the course of said pregnancy; pre-establishing guidelines, in a calculation device, for the body fat mass gain for a plurality of periods for said pregnancy; and controlling the weight gain of said mammal during said pregnancy to: (i) ensure that the body fat percentage of said mammal remains essentially constant during the course of said pregnancy; and (ii) ensure that the body fat mass gain of said mammal is within the pre-established guidelines for body fat mass gain, for each period of said pregnancy, wherein said mammal is a female human and said pregnancy is broken down into three 13 week trimesters, and the body fat mass gain during each of said trimester is pre-established by guidelines related to each trimester, and wherein said guidelines provide that: the body fat mass gained during a first trimester is calculated in the calculation device by Formula I,
Y=X(I) wherein Y is the fat gain in kg, X is the number of weeks since inception, and is between 0.08 to 0.16; the body fat mass gained during a second trimester is calculated in the calculation device by Formula II,
Y=(X13)(II) wherein Y and X are as previously defined, and is between 0.25 and 0.42; and the body fat mass gained during a third trimester is calculated in the calculation device by Formula III,
Y=(X26)(III) wherein Y and X are as previously defined, and is between 0.1 and 0.2.

2. A method as claimed in claim 1 wherein said FT-NIR technique has been calibrated using a calibration model adapted for these applications.

3. A method as claimed in claim 1 wherein the body fat percentage is controlled so that it varies by less than 10% during the course of said pregnancy.

4. A method as claimed in claim 1 wherein said human female is one having a pre-pregnancy weight of between 45 and 100 kg, and having a body fat percent of between 12 to 45%.

5. A method as claimed in claim 4 wherein said human female is one having a pre-pregnancy weight of the woman is between 55 and 75 kg, and the pre-pregnancy body fat percent is between 20 and 35%.

6. A method as claimed in claim 1 wherein is between 0.12 and 0.14; is between 0.317 and 0.36; and is between 0.08 and 0.16.

7. An apparatus for measurement and control of body fat percentage and body fat accretion of a human female mammal during pregnancy comprising: an FT-NIR device which is suitably calibrated using a suitable matrix for measurement of the body fat percentage of said mammal at the beginning of said pregnancy, and throughout said pregnancy; weight scales for use with said FT-NIR device, for measurement of the body fat mass of said mammal at the beginning of said pregnancy, and throughout said pregnancy; a database to record the body fat percentage and body fat mass data collected for said mammal during the course of said pregnancy; a calculation device for determining pre-established guidelines for the body fat percentage and body fat mass during each of three 13 week trimesters of said pregnancy; and notification means to alert said mammal that their diet requires modification, if their body fat percentage is not essentially constant, or if their body fat mass is outside of the pre-established guidelines calculated by the calculation device using Formulae I, II and III: wherein the body fat mass gained during a first trimester is calculated by Formula I,
Y=X(I) wherein Y is the fat gain in kg, X is the number of weeks since inception, and is between 0.08 to 0.16; the body fat mass gained during a second trimester is calculated by Formula II,
Y=(X13)(II) wherein Y and X are as previously defined, and is between 0.25 and 0.42; and the body fat mass gained during a third trimester is calculated by Formula III,
Y=(X26)(III) wherein Y and X are as previously defined, and is between 0.1 and 0.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of this invention will now be described by way of example only in association with the accompanying drawings in which:

(2) FIG. 1 is the FT-NIR absorption spectra for two subjects with 29% (subject 1) and 44% (subject 2) body fat percent in FIG. 1A. The first derivative of the expanded region from 5500 to 6100 cm.sup.1 of the absorption spectra for the two subjects, is shown in FIG. 1B;

(3) FIG. 2 is a graph of body fat percent during pregnancy for various subjects, as determined by FT-NIR;

(4) FIG. 3 is a graph of the fat mass accretion for two subjects, during gestation as determined by FT-NIR spectroscopy; and

(5) FIG. 4 is a graph of the weight gain during pregnancy for two subjects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The novel features which are believed to be characteristic of the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following discussion, and by use of examples describing experimental results. It is expressly understood, however, that the results are presented for the purpose of illustration and description only and are not necessarily intended as a definition of the limits of the invention.

(7) Also, unless otherwise specifically noted, all of the features described herein may be combined with any of the above aspects, in any combination.

(8) Materials and Methods

(9) All spectra were obtained using a Bruker Optics (Billerica, Mass., USA) FT-NIR spectrometer, model Matrix F, equipped with a diffuse reflection fiber optic probe, and using a proprietary software from instrument supplier (OPUS). The FT-NIR spectrometer was equipped with a thermoelectrically cooled InGaAs detector. Data were collected at 8 cm.sup.1 resolution using the Blackman-Harris 3-term apodization function at room temperature.

(10) During the FT-NIR measurement, the fiber optic probe was placed on the back of the ear, upper part, and absorption spectra were collected. Five replicate absorption spectra were measured each time. This was repeated 2 or 3 times following a visual inspection of the absorption spectra for any light scattering due to imperfections of the ear cartilage.

(11) Previous experience had shown that ear piercing caused irregularities in the cartilage that resulted in greater light scattering and lower reflection of the light beam. This affected the results, since the model is based on the assumption that the scattering coefficient for both the reference and the subject spectra is the same. These spectra were subsequently used to generate an average spectrum. Average spectra collected were processed and analyzed using a pre-developed Partial Least Squares (PLS) calibration model (NIR Technologies, Oakville, Ontario, Canada) for the determination of subcutaneous body fat, in minutes. The OPUS program uses PLS1.

(12) Weight gained was measured by a standard set of weight scales, and the fat gained, was calculated from the collected data.

(13) Results and Discussion

(14) In this experiment, the body fat percent of women during pregnancy was measured using FT-NIR. These measurements are not generally available with reliable MRI or DXA body fat percent measurement techniques due to the health concerns of using these techniques.

(15) As background, FIGS. 1A and 1B show the FT-NIR absorption and the first derivative spectra of the pregnant subjects with a body fat percent of 29% (subject 1at 29 weeks) and 44% (subject 2at 32 weeks), respectively. There are significant differences in the absorption spectrum in the region of first overtone for CH and CH2 vibrations between 5500 and 6100 cm.sup.1. The first derivative spectrum of this expanded region shows substantial spectral difference for the first subject with 29% and second subject with 44% body fat percent (FIG. 1B).

(16) Table 1 shows data measurements for fat and fat free mass from before pregnancy to 52 wks post partum, for the three test subjects, and the results from a prior art Swedish study showing only the beginning and end fat and fat free mass values (A. Sohlstrm, E. Forsum E. Changes in Total Body Fat During the Human Reproductive Cycle as Assessed by Magnetic Resonance Imaging, Body Water Dilution, and Skinfold Thickness: a Comparison of Methods. Am. J. Clin. Nutr. 1997. 66(6): 1315-1322.). The average fat mass with the standard deviation for repeat measurements for the three subjects obtained at twenty different occasions throughout the pregnancy was 28.10.5 kg body fat.

(17) In Table 2, results related to the amount of fat gained during pregnancy for the same three subjects is shown, together with prior art values from a study conducted by the WHO (ibid). This data shows the WHO level of weight gain was 12.9 kg. It can be noted that while subject 1 of the present study gained a total of 21.9 kg, which is clearly above the WHO recommendation, subject 2 gained less weight for a more moderate increase of only 13.2 kg. Subject 3 gained a total of 18.9 kg, which was again, clearly above the WHO desired value.

(18) As stated above each actual measurement shown in the table, represents an average of five individual spectra taken.

(19) Only two FT-NIR measurements were taken of the first subject during pregnancy, even though many more could have been taken, since the technique poses no health hazards to the mother or fetus. To further investigate the apparent difference in the rate of fat accretion before and after the 29 wk measurement in subject 1, several additional measurements of subject 2 and 3 were taken throughout their pregnancys.

(20) The body fat percent results for the three subjects of the present study, are shown in FIG. 2 and these results show that the body fat percent remains essentially constant (5%) during the entire pregnancy.

(21) Values from several other test subjects (Nos. 4 to 8) are also included in the graph, showing that body fat percentage for virtually all subjects remained essentially constant.

(22) From the more detailed information from subjects 2 and 3, the fat gained during gestation is shown in FIG. 3, and it can be seen that fat mass gained, or fat mass accretion, for the mother, follows an S curve. In particular, it can be seen that the fat mass accretion was moderate in the first trimester, increased significantly in the second trimester, and levelled off during the third trimester. Suggested body fat mass gain lines for each trimester, are also shown as dashed lines, to indicate a selected range of body fat mass gain. Maintaining body fat mass gain between these lines would be beneficial, although keeping the body fat mass gain towards the lower line, would be preferred.

(23) In FIG. 3, the lower dashed line has , and values of 0.11, 0.29 and 0.07 respectively. The upper dashed line has , and values of 0.15, 0.36 and 0.12 respectively.

(24) It can be noted that in trimester 3, subject 2's fat mass increased to a level above the suggested upper level. As such, she would have likely has been advised to better control this fat gain, and adjust her diet accordingly.

(25) The benefit of the present invention is that using the FT-NIR technique, these measurements could be made directly in minutes to provide accurate and individualized support throughout the pregnancy.

(26) In FIG. 4, the weight gain for two subjects, as taken from Table 1, is shown. The total weight gain during pregnancy can vary from the mother's fat mass gain depending on other factors, including for example, the rate of non-fat mass gain, the accumulation of water or amniotic fluid, and the fact that the body fat content of the baby may vary from that of the mother.

(27) From this data, it can be noted that the percent body fat of the subjects in this study remained relatively constant throughout pregnancy at about 29% for subject 1, about 44% for subject 2, and about 29% for subject 3, while the fat and fat free masses both increased for all three subjects (Table 1).

(28) Two weeks after giving birth (baby's birth weight for subject 1, was 3.38 kg, for subject 2, was 3.64 kg, and for subject 3, was 3.53 kg.) there were significant differences in fat mass and changes in percent fat between the three subjects (Table 1). Subjects 1 and 3, but not subject 2, retained much of the fat accumulated during pregnancy, which was also reflected in their respective percent body fat percentages (Table 1). Subjects 1 and 2 lost most of the accumulated weight and all of the accumulated fat in the year following the pregnancy (Table 1). The corresponding data for subject 3 is not available.

(29) The fat gain and weight gain of all of the subjects in this study, up to 38 wks, were generally higher than those reported by the WHO even after extrapolating the 36 wk data to 38 wks (Table 2); subjects 1 and 3, but not 2, were outside the range of 10 to 14 kg, while subject 2 was at the upper edge of this suggested value.

(30) However, the results observed for the three subjects do not appear to show a consistent relationship between the mother's fat gain and the mother's weight gain, as evidenced by the fat gain/weight gain ratio. It might also be noted that subject 2 with a lower weight gain had a slightly higher fat gain (Table 2), which would be opposite to that predicted by a body mass index (BMI) assessment, if that approach to body fat percentage measurement, had been used.

(31) TABLE-US-00002 TABLE 1 Pregnancy.sup.1 Postpartum.sup.2 Pre- 9 15 19 23 29 32 38 2 52 Subjects Pregnancy wks wks wks wks wks wks wks wks wks Swedish study [5] Fat mass (kg) 17.5 21.1 19.1 Fat free mass (kg) 47.1 50.1 48.2 Fat (%) 26.6 29.4 27.8 This study subject 1 Fat mass (kg) 22.5 26.9 29.3 28.2 21.7 Fat free mass (kg) 52.9 66.3 68.1 57.9 59.2 Fat (%) 29.9 28.8 30.1 32.7 26.8 This study subject 2 Fat mass (kg) 30.2 31.1 32.1 33.0 35.2 37.4 38.1 30.7 27.8 Fat free mass (kg) 42.5 42.6 42.9 44.0 43.8 46.5 47.8 46.1 41.1 Fat (%) 41.5 42.2 42.8 42.9 44.6 44.6 44.4 40.0 40.3 This study subject 3 Fat mass (kg) 20.9 22 23.1 24.7 25.4 26.6 27.5 27.5 25.2 Fat free mass (kg) 54.1 54.1 58.5 59.0 62.1 62.7 64 66.4 59.8 Fat (%) 27.9 28.9 28.3 29.5 29 29.8 30.4 29.3 29.6 .sup.1No MRI measurements were possible during pregnancy .sup.2Postpartum 52 weeks measurement for subject 3 is not available

(32) TABLE-US-00003 TABLE 2 Subjects 19 wks 15 wks 19 wks 23 wks 29 wks 32 wks 36 wks 38 wks .sup.1 WHO study [1] Mean fat gain (kg) 3.7 4.0 Mean weight gain (kg) 11.9 12.9 Fat gained/weight 0.31 0.3 gained This study subject 1 Fat gain (kg) 4.4 6.8 Weight gain (kg) 17.8 21.9 Fat gained/weight 0.25 0.31 gained This study subject 2 Fat gain (kg) 0.5 1.6 2.8 5.0 7.2 7.9 Weight gain (kg) 0.9 2.3 4.3 6.3 11.2 13.2 Fat gained/weight 0.56 0.70 0.65 0.79 0.64 0.60 gained This study subject3 Fat gain (kg) 1.1 2.2 3.8 4.5 6.5 7.1 6.8 6.6 Weight gain (kg) 1.2 6.6 8.7 12.5 14.3 17 18.3 18.9 Fat gained/weight 0.96 0.33 0.44 0.36 0.45 0.42 0.37 0.35 gained .sup.1 Extrapolated data from the WHO report from 36 to 38 wks

(33) From this assessment, it can also be noted that subjects 1 and 3 could have been encouraged during their pregnancy to reduce their caloric intake, in order to reduce weight gain during gestation, while maintaining healthy fat mass gain.

(34) Additionally, it can be noted that the current FT-NIR measurements before and after pregnancy can be compared to the Swedish study (Table 1) in which pre and post pregnancy body fat changes were determined using MRI. Even though the fat measurements of the subjects in the current study were slightly higher than the mean values reported in the Swedish study, they were within the observed variation.

(35) As such, it is submitted that the present invention is the first report of a direct and accurate determination of the body fat percent of women during pregnancy. The determination of these results was facilitated by the use of FT-NIR spectroscopy. The FT-NIR method also permitted repeated measurements throughout pregnancy to monitor the subject and provide individualized nutritional guidance in the future to maintain a healthy weight gain. The results indicate that the changes in body fat percent and the rate of fat accretion were easily detected during pregnancy, and the suggested actions resulting from this technique, could be based on direct measurements rather than estimates and unreliable methods.

(36) As such, the present invention provides a method to monitor weight gain in a pregnant subject wherein the body fat percentage of the subject is preferably maintained at a constant level during gestation, and the subject's fat accretion rate is monitored so as to preferably follow the fat accretion rate provided by using one or more pre-defined fat accretion determination formulae. By measurement of the body fat percent and fat accretion rates, the weight gain of a subject can be monitored and/or controlled during pregnancy, and thus promote a more healthy weight gain, during pregnancy.

(37) As a result, the present invention provides a major advance in tracking the potential for excessive gestational fat mass accretion, preferably using FT-NIR spectroscopy.

(38) Thus, it is apparent that there has been provided, in accordance with the present invention, a method for measuring and monitoring the fat gain and body fat percent of a subject during pregnancy, which fully satisfies the goals, objects, and advantages set forth hereinbefore. Therefore, having described specific embodiments of the present invention, it will be understood that alternatives, modifications and variations thereof may be suggested to those skilled in the art, and that it is intended that the present specification embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.

(39) Additionally, for clarity and unless otherwise stated, the word comprise and variations of the word such as comprising and comprises, when used in the description and claims of the present specification, is not intended to exclude other additives, components, integers or steps. Further, the invention illustratively disclosed herein suitably may be practised in the absence of any element which is not specifically disclosed herein.

(40) Moreover, words such as substantially or essentially, when used with an adjective or adverb is intended to enhance the scope of the particular characteristic; e.g., substantially planar is intended to mean planar, nearly planar and/or exhibiting characteristics associated with a planar element.

(41) Also, while this discussion has addressed prior art known to the inventor, it is not an admission that all art discussed is citable against the present application.