Journal of the American College of Nutrition, Vol. 25, No. 2, 123-127 (2006)
Published by the American College of Nutrition
Changes in Body Weight, Body Composition and Resting Metabolic Rate (RMR) in First-Year University Freshmen Students
Laleh Hajhosseini, MS, RD,
Tawni Holmes, PhD, RD, LD,
Parinez Mohamadi, MS, RD,
Vida Goudarzi, MS, RD,
Lucy McProud, PhD, RD and
Clarie B. Hollenbeck, PhD
Department of Nutrition and Food Science, San Jose State University, San Jose, CA (L.H., P.M., V.G., L.M., C.H.)
Human Environmental Sciences, University of Central Oklahoma, Edmond, OK (T.H.)
Address reprint requests to: Clarie B. Hollenbeck, PhD, Department of Nutrition and Food Science, San Jose State University, One Washington Square, San Jose, CA 95192-0058. E-mail: clariebh{at}casa.sjsu.edu
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ABSTRACT
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Objectives: The purpose of the present study was to document any changes that might occur in body weight, body composition, RMR, and dietary intake in newly enrolled college freshmen.
Methods: Body weight, RMR by ventilated O2 consumption, body composition by bioelectrical impedance and dietary intakes were recorded in 27 first-year college freshmen during their initial 16-week semester.
Results: Mean body weight increased significantly with time (3.0 lbs; p < 0.001); 16 subjects (59%) gained 
3.0 lbs, while 6 subjects (22%) gained 6 lbs. Percent fat mass significantly increased (p < 0.001), while lean body mass decreased (p < 0.001). Changes in RMR failed to reach statistical significance; however, there was a significant correlation between changes in weight and RMR (r = 0.45; p < 0.02). Mean reported calorie intake did not differ significantly between the beginning (1905 ± 664 kcal) and end (1960 ± 687 kcal) of the study. However, the differences (
55 kcal) are in the range necessary to support the mean 3 lb. weight gain.
Conclusions: The present study supports the notion that freshmen students, on average, gain weight during their first semester; however, this weight gain may be more modest than generally perceived. The study also provides important new data on changes in diet, body composition and RMR.
Key words: college freshmen weight gain, body composition, resting metabolic rate
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INTRODUCTION
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Approximately 60% of the adult population in the United States is currently clinically defined as overweight, or obese [1], and the number of individuals clinically defined obese (BMI > 30 kg/m2) has increased by 50% over the past decade [2]. Recent studies evaluating self-reported data to calculate BMI suggest that approximately 27% [3] to 35% [4] of college students are overweight or obese (BMI 25.0 kg/m2). Similar findings have also been reported when heights and weight were measured; more importantly Huang et al. reported that overweight students were almost 3 times more likely to experience at least one component of metabolic syndrome than normal weight students [5]. Once obesity is established it is difficult to reverse. Therefore, the development of effective strategies for the prevention of obesity is of extreme clinical importance [2]. In this regard, understanding the time when people are more likely to gain weight throughout the life cycle is important for the development of strategies towards weight control [2–7].
It is generally believed that college freshmen gain 15 pounds weight during the first year of college [8]. This belief is popularly known as the "Freshmen 15". Currently the experimental evidence in support of this belief is incomplete and there is disagreement in the extent to which this phenomenon may occur. Although there is accumulating evidence that may allow researchers to better define the norms of weight gain occurring among freshmen students, the nature of this weight gain has not been adequately addressed. For example it is not evident from existing studies of freshman students, whether the weight gain results from increased energy intake, decreased energy expenditure, or both. In addition, previous studies have not documented changes in resting metabolic rate (RMR) or body composition. Therefore, the purpose of the present study was to document any changes that might occur in body weight, body composition and RMR in newly enrolled college freshmen during their first semester of college.
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METHODS AND PROCEDURES
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Subject Population
A convenience sample of 27 male and female freshmen students attending San Jose State University (SJSU), a large culturally diverse metropolitan university, were recruited for the present study. Changes in dietary habits and body composition of freshmen students were emphasized as a purpose of the study so as not to focus on changes in body weight.
Experimental Design
The study was designed as a longitudinal study completed over the course of one 16-week semester beginning in the fall when students began academic classes. Approval for the study was obtained from the Human Subjects Committee at SJSU. After obtaining informed consent, all prospective subjects completed a general health questionnaire, were instructed on how to complete the 3-day diet record and were scheduled for an initial visit (clinic visit 1). The experimental protocol is illustrated in Fig. 1.
During the initial study visit, subjects had their height, weight, resting metabolic rate and body composition assessed. They were individually queried about their response to 3-day dietary record by one of the study investigators for purposes of clarity and to eliminate any ambiguity in their responses. Subjects were scheduled for subsequent clinic visits and were seen two additional times, once between weeks 7 & 8 (clinic visit 2) and again between weeks 14 & 16 (clinic visit 3). Measurements of body weight, body composition and 3-day diet record were repeated at clinic visit 2 and at clinic visit 3. Measurement of resting metabolic rate was repeated only during clinic visit 3.
Participants were asked not to consume any food or engage in any exercise activity for at least two hours prior to their scheduled appointment time. Subjects were instructed on the importance of proper hydration in the measurement of body composition, and hydration was estimated during body composition analysis. All subjects were sufficiently hydrated, and mean hydration percentages during the three measurement periods were 52%, 52% and 50% at the three clinic visits, respectively.
Height, Weight and BMI
Height was measured using a stadiometer at the initial visit. Body weight was measured with a dual-beam balance scale (Healthometer, Sunbeam Products, Inc. Boca Raton, FL) during each scheduled visit. Weights were obtained without shoes in light clothing. Body Mass Index (BMI) was calculated from measured height and weight as kg/m2 at each clinic visit.
Determination of Body Composition
Body composition was estimated by total body bioelectrical impedance (BIA; Physiological Event Analyzer (PEA), RJL Systems; Clinton Twp, MI) [11]. Fat mass was calculated by subtraction of lean body mass from total body weight.
Resting Metabolic Rate
Resting metabolic rate was calculated by measurements of ventilated oxygen consumption while seated and at rest using the BodyGem (HealtheTech, Inc. Golden, CO) [12]. The continuous measurement of oxygen consumption during rest serves as the basis for calculating resting energy expenditure.
Coefficient of Variation of BIA and RMR Methods
BIA measurements were repeated ten times, one minute apart in nine individuals to determine an intra-assay coefficient of variation (repeated measurement within an individual) for body composition. This same method was repeated one week later in the same nine individuals to assess inter-assay coefficient of variation for body composition (repeated measurements between different days). Inter-assay variation for BIA was 1.1 ± 0.9%, while inter-assay variation was 0.3 ± 0.2%. Measurements of RMR were performed three times during the same visit in 13 individuals to determine an intra-assay coefficient of variation in RMR. Inter-assay variability in RMR was 4.6 ± 2.5%.
3-Day Dietary Records
Three-day diet records were collected at each of the three clinic visits. The dietary records were recorded over three days including two weekdays and one weekend day, excluding Friday. Specifically, records were kept Wednesday, Thursday and Saturday, or Sunday, Monday and Tuesday. Participants were asked to record estimated portions of all food and to include brand names of items when possible, to indicate which foods were consumed in restaurants and which were prepared at home, and were queried about the relative amounts of ingredients in all combinations foods (burritos, pizza, casseroles, etc). All dietary records were checked by the investigators during each visit for completeness, clarity, and accuracy. Recorded intakes of food were analyzed, using both USDA food guide pyramid and by computer-based analysis using the Food Processor Nutrition and Fitness software (version 8.0, 2002, ESHA Research, Salem, OR).
Statistical Analysis
Descriptive statistics, t test for paired comparisons and general linear model (GLM) were performed to compare means between visits. Pearson’s correlations were used to assess associative relationships among variables. All statistical analysis was performed using SPSS software version 11.0 for windows. Data were expressed as mean ± standard error of the mean (SEM) and statistical significance was set at p < 0.05.
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RESULTS
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The clinical characteristics of the study population are presented in Table 1. The subjects were mostly female (n = 22) with five males. The mean (± SEM) age was 18.3 (± 0.2) yrs. The mean body weight was 140.4 (± 6.6) lbs and the mean BMI was 23.5 (± 0.7) kg/m2. Most of the individuals were of normal body weight, although three had a BMI below 20 kg/m2, five had a BMI between 25.0 and 29.9 kg/m2 (grade 1 obesity), and two had a BMI 30.0 kg/m2 (grade 2 obesity). There were no discernable patterns in either ethnicity or gender among those individuals who fell outside the normal range of BMI. The population was ethnically diverse, with 12 of the 27 students (44%) Asian and Pacific Islander, 10 (37%) Caucasian, 3 (11%) Hispanics, 2 (8%) African American. Although the study population was primarily Caucasian and Asian/Pacific Islanders (81%), the ethnic distribution of the subjects represented the ethnic distribution at San Jose State University.
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Table 1. Baseline Clinical/Demographic Characteristics of 27 College Freshmen During a 16-Week Period (Mean ± SEM)
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The results of changes in body weight, body composition, RMR and dietary intake are presented in Table 2. Mean body weight increased continuously with time, and reached statistical significance (GLM; p = 0.001) by the end of the study period. Upon entry into the study, mean body weight was 140.4 (± 6.6) lbs, increased to 141.4 (± 6.5) at week 7–8 and was 143.4 (± 6.6) by week 16 (Table 2). The average weight gain over the 16-week period was 3.0 ± 0.7 (p = 0.001). Individual changes in body weight are presented in Fig. 2. It is clear from the data presented in this figure that the majority of individuals (n = 18) experienced weight gain 2 lbs. It is also clear that there was considerable variation among subjects, and in many of them the changes in weight were not trivial in magnitude; 16 subjects (59%) gained 3.0 lbs, while 6 subjects (22%) gained 6 lbs. Seven individuals remained within 1 lb or less of their initial weight and only two of the subjects lost weight. The two individuals who lost substantial weight were both engaged in intercollegiate athletics (cross country) at the time of the study. Changes in BMI were also noted; mean BMI increased from 23.5 ± 0.7 to 24.1 ± 0.8 kg/m2 (p = 0.002) over the 16-week period. Most of the individuals remained within their weight classification, although two of the subjects increased from normal body weight to overweight classification by the 16th week.
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Table 2. Changes in Body Weight, Fat Mass, Lean Mass, Resting Metabolic Rate (RMR) and Dietary Intake of 27 College Freshmen During a 16-Week Period (Mean ± SEM)
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There was also a small but significant change in body composition. Percent fat mass increased from a mean of 30.1 ± 1.1 at the beginning on the study to 32.2 ± 1.3 (p = 0.001), while lean body mass decreased proportionally from 69.9 ± 1.2 to 67.8 ± 1.3 (p = 0.001) by the end of the study period. There were no significant changes in RMR (1659.5 ± 75.8 vs. 1596.3 ± 84.3 kcal (p = 0.31) over the study period. Mean calorie intake did not differ significantly between the beginning (1905 ± 664 kcal) and end (1960 ± 687 kcal) of the study. However, the difference (55 kcal/day) is in the range necessary to support approximately 3 lb weight gain. There were no significant changes in fat and protein intake. However, carbohydrate intake increased significantly from 226 ± 89 to 267 ± 97 g (p = 0.045). Correlations between changes in body weight, fat mass, lean mass, RMR and dietary intake are presented in Table 3. The results indicated a significant association (r = 0.45; p = 0.02) between changes in body weight and RMR. No other correlations reached statistical significance.
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Table 3. Correlation Coefficients Between Changes in Body Weight, Body Composition and RMR (Resting Metabolic Rate) Of College Freshmen Subjects During a 16 Week Study Period
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DISCUSSION
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In our sample of college freshmen students, approximately 26% had BMIs at baseline that would classify them as being overweight or obese (25.0 kg/m2). These findings are in good agreement with the estimates by Huang and colleagues [3,5], however, they are somewhat less than that estimated by reported heights and weights [4]. The results from the present study clearly support the notion that freshmen students experience significant weight gain upon entering a college or university setting. Specifically, 18 of the 27 students gained two pounds of weight or more, with 16 subjects gaining in excess of three pounds over the 16-week period. The increase in mean body weight in the present study was 3.0 lbs over the 16-week period. This number is in relative agreement with Megel et al [10] who reported a weight gain of 2.5 lbs over a similar period of time. However, it differs from Hodges et al [9] who reported no significant weight gain overall; but for those students who did gain weight there was an average weight gain of approximately 7 lbs over the school year (9 months). Assuming constant weight gain over the course of the school year, the expected weight gain over an entire academic year in the present study would have been approximately 6.8 lbs. Thus, there is some quantitative similarity even with Hodges’ study.
The present study also indicates that there were significant changes in body composition that occur during this period. These results are consistent with the results of a semi-quantitative study by Graham et al [8], who observed an increase in fat mass of 2.9% during a nine month period using a single site skin fold measurement. Body composition has not generally been reported and the present study provides additional important information in terms of physiological changes that freshman students may undergo in body composition.
Although the mean change in RMR (27 kcal/day) was not statistically significant, there was a significant association between the changes in resting metabolic rate and changes in body weight (r = 0.45; p < 0.02), which suggest that approximately 20% of the increase in RMR was associated with the increase in weight (r2 = 0.20). The inability to demonstrate statistically significant changes in RMR may be due to the fact that quantitative changes in lean body mass was relatively small. Indeed, neither RMR nor total caloric intake varied significantly over the course of the study. Therefore, they cannot fully explain the changes in weight and suggest that at least a portion of the observed weight gain may be due to differences in physical activity level in these individuals. The present study did not address changes in physical activity. Therefore, we cannot comment directly on that important aspect of the energy equation. Clearly additional studies designed to address changes in weight, body composition and RMR should include quantitative and qualitative assessments of physical activity. Finally, although no statistically significant changes were noted in total energy intake, there were significant changes in total carbohydrate intake, which suggest that changes occurred in dietary intake. It is important to note that the difference in energy intake necessary to support a three pound increase in body weight over a 16 week period (approximately 94 kcal/day) is relatively small and may be difficult to detect given the semi-quantitative nature of 3-day dietary records.
In conclusion, San Jose State University is an institution with a relatively large ethnically diverse population. In this sense, it differs from previous studies of this nature. The majority of subjects in the present study were Asian/Pacific Islanders, followed by Caucasians, Hispanics and African American. The fact that the changes observed in body weight were in agreement with other studies using largely Caucasian populations suggests that this phenomenon may be universal among young adults experiencing similar social and environmental changes. Although the results of the present study suggests that weight gain may be much more modest (5 to 7 lbs) during the first year of college, there was a significant change in body composition that may predispose these individuals to future complications of weight gain and consequent health problems associated with being overweight (type 2 diabetes, hypertension, and cardiovascular disease). Additional studies focusing on the relative roles of energy intake and expenditure are indicated. Understanding the nature of changes in weight, body composition, and RMR may help future researchers to develop evidence-based solutions to control the diet and weight at a particularly susceptible time in a young adults life.
Limitations
As with all research, there are limitations in data collection, interpretation, and application of this research. First, the relatively few subjects in the present study may have limited our ability to define significant changes in RMR as well as dietary energy and macronutrient intakes. The study was largely female, and this could have influenced weight gain and body composition results; future studies should be extended to include a greater number of males. Finally, although the study population was more ethnically diverse than all previous studies assessing weight gain among freshmen students, it was predominately Caucasians and Asian/Pacific Islanders, Hispanics were under represented in relationship to the ethnic distribution in California, and this could have influenced the results of the study.
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ACKNOWLEDGMENTS
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This research was supported by a Small Research Grant Award from the College of Applied Sciences and Arts at San Jose State University, a Research Assistance Award through the Circle of Friends in the Department of Nutrition and Food Science at San Jose State University, and by a Zellmer Scholarship Grant from the California Dietetic Association. We would like to acknowledge and thank all the study participants who offered their time and support for this research project. Special thanks are extended to Dr. Kathryn Sucher for her valuable assistance and editorial comments in the preparation of the manuscript, and Danielle Greiner, MS for her valuable assistance in the physiological and metabolic measurements.
Received September 27, 2004.
Accepted November 23, 2005.
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ABSTRACT
INTRODUCTION
