European Journal of Clinical Nutrition (2015), 1–5 © 2015 Macmillan Publishers Limited All rights reserved 0954-3007/15 www.nature.com/ejcn
ORIGINAL ARTICLE
Changes in weight, body composition and physical fitness after 1.5 years at university T Deliens1, B Deforche1,2, I De Bourdeaudhuij2 and P Clarys1 BACKGROUND/OBJECTIVES: This study examined changes in Belgian students’ weight, body composition and physical fitness after 1.5 years at university. Furthermore, this study investigated whether these changes differed by gender and weight status. SUBJECTS/METHODS: In this longitudinal study, 172 students’ weight, body mass index (BMI) and waist circumference (WC) were objectively measured, whereas fat%, fat mass, fat-free mass, dynamic leg strength, handgrip strength, hamstring flexibility and cardiorespiratory fitness were estimated using validated instruments. Measurements were conducted at the start of the first semester (T0), after the first semester (T1) and after 1.5 years (T2) at university. RESULTS: Female students’ weight and BMI did not change, whereas male students gained 2.7 kg of weight and showed a 0.7 kg/m2 BMI increase after 1.5 years. After the first semester, an increase in fat% was observed in the total group of students, whereas this time effect did not remain significant when comparing T0 and T2. In contrast to females, increases in 2.1 kg of fat-free mass and 1.8 cm of WC were found in males after 1.5 years. Higher baseline BMI and WC predicted greater BMI and fat% increases in males. Handgrip strength improved for both sexes, whereas no changes in other physical fitness components were found across the 1.5-year period. CONCLUSIONS: The greatest weight and BMI gains as well as unfavourable changes in body composition were found in male students with higher baseline BMI and WC. The observed changes in body composition did not cohere with changes in physical fitness. European Journal of Clinical Nutrition advance online publication, 27 May 2015; doi:10.1038/ejcn.2015.79
INTRODUCTION The transition from secondary school to college or university is a critical period for weight gain.1–3 The meta-analysis of Vella-Zarb3 revealed an average weight gain of 1.75 kg in US freshmen. European literature confirmed the latter and showed significant increases in Belgian first year students’ weight (1 kg), body mass index (BMI; 0.3 kg/m2) and fat% (0.8%) after only one semester at university.4 Similar results were found in UK freshmen.5 As it was concluded that studies including higher proportions of female participants found greater weight gain, Vella-Zarb et al.3 suggested to examine weight gain by gender. Predictor variables of student weight or fat gain, which can be established at the start of students’ academic careers (for example, gender3 and baseline BMI6,7), may be important when designing tailored interventions. Although a more recent meta-analysis of Fedewa8 stated that gender and baseline BMI were not associated with weight and fat gains, the abovementioned Belgian study did show that male university students were more likely to show an increased BMI in comparison with their female counterparts.4 The potential predictability of baseline BMI (or fat%, waist circumference (WC)) with regard to weight or fat gain in European students has not been tested yet. Gropper et al.9 reported significant US student weight gain during the first year of college. In a follow-up study, they showed that students’ weight further increased during the second (sophomore) year.10 Across 2 years of college, average weight gains up to 4.2 kg in female and 4.3 kg in male students were reported by US literature.10,11 These weight changes were 1
accompanied by increases in fat% and WC.10 Weight gain beyond the freshman year has never been objectively studied in a European student population. Weight gain and unhealthful changes in body composition may affect students’ physical fitness levels (or vice versa).12 Little is known on changes in physical fitness among university students. One US study did not find changes in the mean recovery heart rate and mean VO2 max in female college freshman students over a 5-month period,13 whereas another study conducted in US medical students revealed a significant 4% decrease in cardiorespiratory fitness over a period of 2 years.14 The latter study reported no changes in muscular strength.14 Although it was suggested to investigate weight-related variables by gender,3 no studies on changes in students’ physical fitness assessed gender differences so far. As physical fitness and healthy body composition go side by side in reducing cardiovascular disease risk,15,16 research combining both is needed, especially in an at-risk student population. Although weight gain throughout university has been well investigated in the United States, no previous European studies investigated weight gain in university students beyond the first year. As university students in Europe and the United States clearly differ with regard to socio-cultural influences and lifestyle (for example, fast food culture), the results of the abovementioned US studies cannot be generalized. Furthermore, literature on changes in physical fitness in university students is very limited. The purpose of this study was to provide follow-up results of previous research4 by examining changes in weight, BMI, body composition, WC and physical fitness in Belgian students after 1.5
Department of Human Biometry and Biomechanics, Vrije Universiteit Brussel, Brussels, Belgium and 2Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium. Correspondence: T Deliens, Department of Human Biometry and Biomechanics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Brussels 1050, Belgium. E-mail: [email protected] Received 1 December 2014; revised 13 April 2015; accepted 15 April 2015
Weight gain after 1.5 years at university T Deliens et al
2 years at university. Second, this study investigated whether changes in anthropometrics and physical fitness differed by gender. Finally, in light of designing more targeted intervention efforts, we aimed to identify baseline predictors (BMI, fat% and WC) of weight and fat gain over the 1.5-year period.
and was converted into beats per minute (heart rate per min) and used as the outcome measure. Validation studies in female college students showed excellent reliability, as well as a strong correlation between the QCST heart recovery pulse rate and VO2 max.21–23 All measurements, except for QCST, were conducted twice, and best performance results were used for analyses.
MATERIALS AND METHODS Participants
Data analyses
Using convenience sampling (via e-mail and face-to-face recruitment on the university campus), 348 Belgian (Flemish) first year university students volunteered to take part in the study. Only students who had just finished their last year of secondary school and were in their first year of university were eligible to participate (n = 340). As self-reported data of all first year university students (n = 926) were obtained during enrolment (by the university’s registration office), we were able to verify the representativeness of our sample. Our sample with mean age of 18.0 ± 0.6 years, 59.1% females and mean BMI of 21.4 ± 2.7 kg/m2 was representative in comparison with all freshmen in gender (56.6% females; χ2 = 0.6, P = 0.431) and BMI (21.4 ± 2.8 kg/m2; t = 0.2, P = 0.851). However, mean age was higher in the total group of freshmen (18.5 ± 1.1 years; t = 9.8, Po0.001).
Procedure In this longitudinal study, baseline measurements (T0) were conducted at the start (October/November) of the first semester of students’ first academic year at university.4 All participating students were re-contacted at the start of the second semester (February/March) of their first academic year (that is, after 4 months; T1), as well as at the start of the second semester (February/March) of their second academic year ( = fourth semester; that is, after 16 months from baseline; T2). The researchers made up to 10 attempts on different moments during the day to contact a student before they were considered to have dropped out. To minimize possible effects owing to sudden short-term lifestyle changes after holiday periods, measurements were conducted after 2 weeks of academic activities. Besides, participants’ timing of measurement at baseline was taken into account during both follow-up measurements. At all three time points, students received an incentive (a lunch voucher). An informed consent was signed by all participants before the start of the study. The study protocol was approved by the Medical Ethical Committee of the university hospital (Vrije Universiteit Brussel, Brussels, Belgium).
Measurements Students were measured with bare feet, wearing only shorts and a t-shirt. They were asked to void their bladder before starting the measurements, as well as to remove all jewellery. Anthropometrics. Weight (TANITA BC-418 Body Composition Analyser, Tanita Corp., Tokyo, Japan) and height (wall-fixed stadiometer) were measured to calculate BMI. Body composition (including fat%, fat mass (FM) and fat-free mass (FFM)) was estimated using TANITA BC-418 Body Composition Analyser, which is a validated17 eight-electrode device for hand-to-foot bioelectrical impedance analysis operating with a 50-kHz current. Participants were instructed to step on the electrodes with bare feet and to grab both hand grips. Finally, WC (measured with Rosscraft Anthrotape on the narrowest part of the waist18) was measured to analyze fat distribution. All measurements, except those using TANITA, were conducted twice and an additional third time when tolerance limits were exceeded. Subsequently, mean values were calculated from the two nearest values. Physical fitness. Except for the cardiorespiratory fitness test, all physical fitness tests were adapted from the Eurofit test battery for adults.19 Dynamic leg strength was estimated by means of the standing broad jump (accuracy = 1 cm), whereas a hand dynamometer was used to estimate handgrip strength (accuracy = 1 kg). Hamstring flexibility was estimated using the sit and reach test (accuracy = 1 cm). The Eurofit test battery is a reliable and a valid instrument to measure physical fitness and is a commonly used test battery in Europe.20 The Queens College Step Test (QCST) was used to estimate cardiorespiratory fitness. Participants were asked to step on and off a 41.3 cm high bench for 3 min. After completion, the carotid pulse rate was measured from 5 to 20 s of the recovery period European Journal of Clinical Nutrition (2015) 1 – 5
SPSS Statistics 22 (IBM Corp., Armonk, NY, USA) was used for data analyses. Independent samples t-tests and χ2-tests were executed to analyse representativeness and drop-out. Repeated measures mixed design analysis of variance with Bonferroni post hoc analyses were performed to assess anthropometric and physical fitness changes across 1.5 years according to gender. When gender interaction was found, anthropometric and physical fitness changes over time were investigated for females and males separately. Univariate linear regression analyses were conducted separately for gender to identify baseline predictors (BMI, fat% and WC) of change in BMI and fat%. P-values o 0.05 were considered as statistically significant.
RESULTS Drop-out analysis Of the initial sample (n = 340), 172 students (62.2% females) were measured at all three time points, indicating an overall drop-out of 49.4%. Reasons for drop-out were not reachable, quit university and no longer interested in participating. Drop-out analysis was conducted to ensure representativeness of the retention sample. At baseline, both drop-out (n = 168) and retention group (n = 172) were similar in gender (56.0% vs 62.2% females; χ2 = 1.4, P = 0.241) and in age (18.0 ± 0.6 vs 18.0 ± 0.5 years; t = 1.2, P = 0.220). In comparison with the drop-outs (21.8 ± 2.9 kg/m2), BMI was lower in the retention group (21.0 ± 2.3 kg/m2; t = 2.6, P = 0.010). Anthropometrics As anthropometric changes during the first semester at university have already been published elsewhere,4 first semester results are only described in Table 1. After 1.5 years at university, 66.9% had gained weight and 61.0% (76.9% of males and 51.4% of females) showed an increase in BMI. The prevalence of overweight and obesity doubled (from 5.8 to 12.1%) during the first semester at university, followed by a small decrease (from 12.1 to 9.9%) during the following year. Changes in weight and BMI differed according to gender (see Table 1). After 1.5 years, female students’ weight and BMI did not change significantly (both P = 1.000), whereas male students gained 2.7 kg of weight (P o 0.001) and showed a 0.7 kg/m2 BMI increase (P o 0.001). Weight changes ranged from − 8.6 to +9.5 kg in females and from − 2.4 to +11.8 kg in male students. No time × gender interaction was found for fat%. For the total group of students, a significant time effect was observed for fat% between T0 and T1, whereas this time effect did not remain significant when comparing T0 and T2. Changes in FFM and WC differed according to gender; for both FFM (P = 0.182) and WC (P = 0.780) no changes were found in females, whereas increases in 2.1 kg of FFM and 1.8 cm of WC (both P o0.001) were found in male students after 1.5 years at university. Predictability of baseline measures Male students with a higher baseline BMI and WC showed greater increases in BMI (P = 0.001, β = 0.364; P = 0.004, β = 0.328, respectively) and fat% (P = 0.005, β = 0.316; P = 0.020, β = 0.266, respectively), whereas female students with higher baseline BMI showed greater BMI decreases (P = 0.032, β = -0.201) over 1.5 years at university. For both sexes, fat% at baseline did not predict changes in BMI or fat%. © 2015 Macmillan Publishers Limited
Weight gain after 1.5 years at university T Deliens et al
3 Table 1.
Anthropometric changes after 1.5 years at university (Mean ± s.d. and F-values)
Measurements
Start 1st semester (T0)
Start 2nd semester (T1)
Start 4th semester (T2)
Height (cm) All (n = 172) Females (n = 107) Males (n = 65)
170.9 ± 9.0 166.0 ± 6.1 178.9 ± 7.3
171.1 ± 9.1 166.3 ± 6.1a 179.1 ± 7.4
171.3 ± 9.2 166.3 ± 6.2a 179.5 ± 7.4a,b
Weight (kg) All (n = 172) Females (n = 107) Males (n = 65)
61.6 ± 9.2 57.9 ± 7.9 67.7 ± 8.0
62.4 ± 9.8 58.3 ± 8.1a 69.1 ± 8.7a
62.8 ± 10.5 58.2 ± 8.0 70.4 ± 9.7a,b
BMI (kg/m2) All (n = 172) Females (n = 107) Males (n = 65)
21.0 ± 2.3 21.0 ± 2.5 21.1 ± 2.1
21.2 ± 2.5 21.1 ± 2.6 21.5 ± 2.3a
21.3 ± 2.5 21.0 ± 2.5 21.8 ± 2.5a,b
Fat% All (n = 171) Females (n = 106) Males (n = 65)
19.9 ± 7.1 23.7 ± 5.8 13.6 ± 3.5
20.6 ± 7.2a 24.4 ± 6.1 14.4 ± 3.6
20.4 ± 7.6 24.4 ± 6.1 13.8 ± 4.5
FM (kg) All (n = 171) Females (n = 106) Males (n = 65)
12.3 ± 5.1 14.1 ± 5.2 9.3 ± 3.1
13.0 ± 5.2a 14.7 ± 5.5 10.2 ± 3.2
12.8 ± 5.5a 14.6 ± 5.5 9.9 ± 4.3
FFM (kg) All (n = 171) Females (n = 106) Males (n = 65)
49.3 ± 8.6 43.8 ± 3.9 58.4 ± 6.3
49.4 ± 8.9 43.7 ± 3.9 58.8 ± 6.4
50.0 ± 9.7 43.5 ± 3.7 60.5 ± 6.9a,b
WC (cm) All (n = 172) Females (n = 107) Males (n = 65)
70.3 ± 5.8 67.8 ± 5.0 74.3 ± 4.6
70.6 ± 6.5 67.6 ± 5.3 75.5 ± 5.1a
70.8 ± 6.8 67.6 ± 5.2 76.1 ± 5.8a
Ftime ×
gender
Ftime
7.3*** 11.1*** 13.8*** 16.7*** 3.3* 34.0*** 9.7*** 1.6 23.3*** 1.3 9.5***
1.2 15.6***
38.3*** 1.8 34.5*** 18.3*** 1.4 18.6***
Abbreviations: BMI, body mass index; FM, fat mass; FFM, fat-free mass; WC, waist circumference. aSignificantly different from baseline measurements (T0). b Significantly different from T1 measurements. *Po0.05, ***P ⩽ 0.001.
Table 2.
Changes in physical fitness after 1.5 years at university (Mean ± s.d. and F-values)
Measurements
Start 1st semester (T0)
Start 2nd semester (T1)
Start 4th semester (T2)
Standing broad jump (cm) All (n = 167) Females (n = 105) Males (n = 62)
173.2 ± 34.1 154.6 ± 23.3 204.8 ± 25.0
174.4 ± 35.1 155.5 ± 24.0 206.5 ± 26.8
173.2 ± 35.1 154.3 ± 22.1 205.1 ± 29.4
Hand grip strength (kg) All (n = 172) Females (n = 107) Males (n = 65)
38.1 ± 10.8 31.9 ± 6.0 48.3 ± 8.9
39.4 ± 11.6 32.2 ± 5.8 51.3 ± 8.4a
40.4 ± 11.7 33.3 ± 6.2a,b 52.1 ± 8.7a
Flexibility (cm) All (n = 169) Females (n = 107) Males (n = 62)
29.3 ± 9.9 31.3 ± 9.4 25.9 ± 9.8
29.6 ± 9.5 31.2 ± 9.1 26.8 ± 9.6
29.4 ± 9.5 30.7 ± 8.9 27.0 ± 10.2
QCST (b.p.m.) All (n = 169) Females (n = 105) Males (n = 64)
146 ± 22 153 ± 18 133 ± 22
148 ± 23 155 ± 21 137 ± 21
148 ± 24 155 ± 24 137 ± 20
Ftime × gender
Ftime
0.1 1.0
6.1** 9.8*** 9.2*** 3.5* 1.4 2.5 0.1 2.2
Abbreviation: QCST, Queens College Step Test. aSignificantly different from baseline measurements (T0). bSignificantly different from T1 measurements. *Po0.05, **P o0.01, ***Po0.001.
© 2015 Macmillan Publishers Limited
European Journal of Clinical Nutrition (2015) 1 – 5
Weight gain after 1.5 years at university T Deliens et al
4
Physical fitness Compared with baseline measurements (T0), both female and male students showed greater handgrip strength after 1.5 years at university (T2; see Table 2). Improvements in handgrip strength were stronger in males (3.8 kg; P o0.001) than in females (1.4 kg; Po 0.001). Time × gender interaction was found for hamstring flexibility; although for both sexes no significant time effects were found, there was a decreasing trend in females and an increasing trend in males. No interaction nor time effects for dynamic leg strength and cardiorespiratory fitness were found across the 1.5-year period. DISCUSSION Previous research showed significant increases in Belgian first year students’ weight, BMI and fat% after only one semester at university with male gender as a predictor of BMI increase.4 Providing follow-up results, this study adds insight to the limited European literature on university students’ weight gain by examining whether Belgian students’ BMI, fat% and WC continued to increase after the first semester at university. Although a small first semester weight increase (0.4 kg) in female students was found, this effect did not remain significant after 1.5 years. In contrast, our results did reveal a significant increase in weight (2.7 kg) and BMI (0.7 kg/m2) in male students after 1.5 years at university. This weight gain is comparable with the 2.3 to the 4.3 kg weight increase found in US literature after 2 academic years in male students.10,11 Individual weight change in the present study ranged from − 8.6 to +11.8 kg, suggesting that during the first 1.5 years at university students may have difficulties controlling their weight. Even small student weight gains can result in higher risk of overweight or obesity in later life.2 According to the Flemish growth curves, the average weight gain between the age of 18 and 19.5 years is 0.6 kg in females and 2 kg in males, whereas the average increase in BMI for females and males is 0.2 and 0.5 kg/m2, respectively.24 In other words, gains in weight and BMI in male university students were higher than average gains for 18–19.5-year olds. Our results suggest that especially male Belgian university students are subject to various weight-related lifestyle changes.2 Although in the present study it may seem that male students’ increase in weight and BMI is similar between the first (T0–T1) and second (T1–T2) measuring period (1.4 vs 1.3 kg; 0.4 vs 0.3 kg/m2; see Table 1), we should take the difference in measuring time (4 vs 12 months, respectively) into account. Hence, a relatively higher increase in 350 g per month was found during the first semester in comparison with an increase in 108 g per month during the following year. Moreover, significant increases in fat% and FM in the total sample of students were only found during the first semester at university. These results are similar to those of previous research, reporting that both males and females gained more weight, BMI and fat% during the freshman versus sophomore year.10,11 Results of the present study suggest that interventions aiming to decrease students’ BMI and fat gains should have a special focus on male students during their first semester at university. Body composition measures also revealed that weight gain over the first semester in males was mainly owing to an unfavourable increase in FM and WC, whereas the weight gain found in the following year (T1–T2) was mainly owing to a more favourable increase in FFM. Although Gropper et al.10 observed a FFM loss in male students during the freshman year, a catch up during the sophomore year was found. As our results demonstrate, this FFM increase might be the result of both increases in height (and thus the effect of normal growth and development) and FM. An increase in FM, which implies the extra weight the body has to carry around, might have caused extra growth in muscle mass.25,26 European Journal of Clinical Nutrition (2015) 1 – 5
Our results indicate that the unfavourable changes observed during the first semester at university4 did not continue throughout the following year. This phenomenon might be explained by the fact that students experience great difficulties to adapt to the new university environment during their first semester, whereas afterwards they manage to adapt more and more to the university lifestyle.2 However, it remains unclear whether weight and body composition measures are either stabilising or slowly restoring after the first semester. To find out, additional follow-up measurements are needed. In contrast to the conclusion drawn in Fedewa’s8 meta-analysis, baseline BMI in the present study was associated with both change in BMI and fat%. Interestingly, male students with higher baseline BMIs and WCs showed higher increases in BMI and fat%, whereas female students with higher baseline BMIs showed higher decreases in BMI after 1.5 years at university. Female students seem to handle their baseline (over)weight differently in comparison with their male counterparts. Whereas males with higher baseline BMI gain even more weight during the 1.5-year period, results suggest that females adjust their lifestyle to lose weight. However, it is not clear whether females who are trying to lose weight are doing this in a healthful way. Therefore, weight control interventions targeting students with higher BMIs at baseline should approach males and females differently. Regarding physical fitness, an improvement in handgrip strength for both male and female students was found over 1.5 years at university. This is in accordance with previous research showing that handgrip strength in Belgian (young) adults continues to increase until the age of 34–44 years.27 To the best of our knowledge, no other studies assessing changes in static handgrip strength in university students exist; hence, no comparison could be made. No changes were found for dynamic leg strength, hamstring flexibility or cardiorespiratory fitness. Although this may suggest no immediate short-term health risk increment, the unhealthy changes in body composition during the first semester might cause students’ physical fitness to deteriorate in the long term. The first strength of this study is the objectively measured weight and height. Earlier research showed that self-reports tend to underestimate weight and overestimate height, resulting in an underestimation of overweight and obesity rates.28,29 Second, the increase in height in both males and females over the three semester period seemed to be in accordance to the mean growth velocity of 0.2–0.5 cm per year in 18–19-year olds.24 Hence, as some students still grow, we chose to (in contrast to many previous studies drawing conclusions based on weight only) interpret both changes in weight and BMI. Third, as BMI has limitations and is unable to discriminate between an excess in body fat and increased lean mass, nor between different types of body fat distribution,30 body composition and WC were measured to determine whether gains in weight were owing to FM or FFM and to study changes in body fat distribution. Especially, increases in abdominal fat are strongly related to a higher risk for developing cardiovascular diseases.31 A first limitation is that only about half (n = 172) of all initial participants were measured at all three time points. According to the university’s registration office, a drop-out ( = students quitting university) of 21% can be observed after the first year at university. The latter partly explains the large drop-out in our study. Because of the reduced sample size, we should be careful interpreting results. Drop-out analysis showed that baseline BMI was higher in the drop-out than in the retention group. Also, students who gained weight between baseline and follow-up measurements may have been more likely to have dropped out. Second, baseline measurements were conducted in October/November. This is well into the start of the freshman year and thus potentially misses capturing weight gain during a critical 4–6-week window. The abovementioned limitations may implicate a potential © 2015 Macmillan Publishers Limited
Weight gain after 1.5 years at university T Deliens et al
5 underestimation of the 1.5-year weight gain in Belgian university students. Third, we did not measure anthropometrics at the end of the first academic year. Hence, we were not able to verify whether anthropometric changes during the first semester continued during the second semester. Fourth, bioelectrical impedance analysis has its limitations and its accuracy can be discussed.32 Finally, the fact that no changes in physical fitness were found may be owing to the limited sensitivity of the methods used to assess physical fitness. This is the first European study showing that the greatest weight and fat gains occur during the first semester at university and mostly in male students, whereas the observed changes more or less stabilise during the following year. Male students with higher BMI and WC at baseline were at greatest risk to gain weight and fat over 1.5 years at university. These results yield some important information to tailor interventions aiming at preventing university students’ weight gain. Furthermore, the observed changes in body composition did not cohere with changes in physical fitness. Future follow-up studies are needed to investigate whether unfavourable changes in males’ body composition will recover spontaneously during the following years at university. CONFLICT OF INTEREST The authors declare no conflict of interest.
ACKNOWLEDGEMENTS We thank all students participating in this study. Special thanks to all Master thesis students for their contribution in data collection.
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12 Lohman TG, Ring K, Pfeiffer K, Camhi S, Arredondo E, Pratt C et al. Relationships among fitness, body composition, and physical activity. Med Sci Sports Exerc 2008; 40: 1163–1170. 13 Butler SM, Black DR, Blue CL, Gretebeck RJ. Change in diet, physical activity, and body weight in female college freshman. Am J Health Behav 2004; 28: 24–32. 14 Mitchell SD, Eide R, Olsen CH, Stephens MB. Body composition and physical fitness in a cohort of US military medical students. J Am Board Fam Med 2008; 21: 165–167. 15 Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM et al. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc 2011; 43: 1334–1359. 16 Roger VL, Go AS, Lloyd-Jones DM, Benjamin EJ, Berry JD, Borden WB et al. Executive summary: heart disease and stroke statistics - 2012 update a report from the American Heart Association. Circulation 2012; 125: 188–197. 17 Pietrobelli A, Rubiano F, St-Onge MP, Heymsfield SB. New bioimpedance analysis system: improved phenotyping with whole-body analysis. Eur J Clin Nutr 2004; 58: 1479–1484. 18 Ross R, Berentzen T, Bradshaw AJ, Janssen I, Kahn HS, Katzmarzyk PT et al. Diagnostic in obesity comorbidities - Does the relationship between waist circumference, morbidity and mortality depend on measurement protocol for waist circumference? Obes Rev 2008; 9: 312–325. 19 Oja P, Tuxworth B. EUROFIT for Adults: a Test Battery for the Assessment of the Health-Related Fitness of Adults. Council of Europe, Committee for the development of sport: Strasbourg, France, 1995. 20 Adam C, Klissouras V, Ravazzolo M, Renson R, Tuxworth W. Eurofit: European Test of Physical Fitness. Council of Europe, Committee for the development of sport: Rome, 1988. 21 Mcardle WD, Katch FI, Pechar GS, Jacobson L, Ruck S. Reliability and interrelationships between maximal oxygen intake, physical work capacity and steptest scores in college women. Med Sci Sports Exerc 1972; 4: 182–186. 22 Chatterjee S, Chatterjee P, Bandyopadhyay A. Validity of Queen's College Step Test for estimation of maximum oxygen uptake in female students. Indian J Med Res 2005; 121: 32–35. 23 Skubic V, Hodgkins J. Cardiovascular efficiency test for girls and women. Res Quart 1963; 34: 191–198. 24 Roelants M, Hauspie R, Hoppenbrouwers K. References for growth and pubertal development from birth to 21 years in Flanders, Belgium. Ann Hum Biol 2009; 36: 680–694. 25 Hulens M, Vansant G, Lysens R, Claessens AL, Muls E, Brumagne S. Study of differences in peripheral muscle strength of lean versus obese women: an allometric approach. Int J Obes Relat Metab Disord 2001; 25: 676–681. 26 Duvigneaud N, Matton L, Wijndaele K, Deriemaeker P, Lefevre J, Philippaerts R et al. Relationship of obesity with physical activity, aerobic fitness and muscle strength in Flemish adults. J Sports Med Phys Fitness 2008; 48: 201–210. 27 Wijndaele K, Matton L, Duvigneaud N, Thomis M, Philippaerts R, Duquet W et al. Fysieke activiteit, fitheid en gezondheid in Vlaanderen In: Steens G (ed), Moet er nog sport zijn? Sport, beweging en gezondheid in Vlaanderen 2002–2006, vol 1. F&G Partners: Antwerpen, Belgium 2006 pp 55–70. 28 Larsen JK, Ouwens M, Engels RCME, Eisinga R, van Strien T. Validity of selfreported weight and height and predictors of weight bias in female college students. Appetite 2008; 50: 386–389. 29 Shields M, Gorber SC, Tremblay MS. Estimates of obesity based on self-report versus direct measures. Health Rep 2008; 19: 61–76. 30 Muller MJ. From BMI to functional body composition. Eur J Clin Nutr 2013; 67: 1119–1121. 31 Czernichow S, Kengne AP, Stamatakis E, Hamer M, Batty GD. Body mass index, waist circumference and waist-hip ratio: which is the better discriminator of cardiovascular disease mortality risk? Evidence from an individual-participant meta-analysis of 82 864 participants from nine cohort studies. Obes Rev 2011; 12: 680–687. 32 Dehghan M, Merchant AT. Is bioelectrical impedance accurate for use in large epidemiological studies? Nutr J 2008; 7: 26.
European Journal of Clinical Nutrition (2015) 1 – 5
ORIGINAL ARTICLE
Changes in weight, body composition and physical fitness after 1.5 years at university T Deliens1, B Deforche1,2, I De Bourdeaudhuij2 and P Clarys1 BACKGROUND/OBJECTIVES: This study examined changes in Belgian students’ weight, body composition and physical fitness after 1.5 years at university. Furthermore, this study investigated whether these changes differed by gender and weight status. SUBJECTS/METHODS: In this longitudinal study, 172 students’ weight, body mass index (BMI) and waist circumference (WC) were objectively measured, whereas fat%, fat mass, fat-free mass, dynamic leg strength, handgrip strength, hamstring flexibility and cardiorespiratory fitness were estimated using validated instruments. Measurements were conducted at the start of the first semester (T0), after the first semester (T1) and after 1.5 years (T2) at university. RESULTS: Female students’ weight and BMI did not change, whereas male students gained 2.7 kg of weight and showed a 0.7 kg/m2 BMI increase after 1.5 years. After the first semester, an increase in fat% was observed in the total group of students, whereas this time effect did not remain significant when comparing T0 and T2. In contrast to females, increases in 2.1 kg of fat-free mass and 1.8 cm of WC were found in males after 1.5 years. Higher baseline BMI and WC predicted greater BMI and fat% increases in males. Handgrip strength improved for both sexes, whereas no changes in other physical fitness components were found across the 1.5-year period. CONCLUSIONS: The greatest weight and BMI gains as well as unfavourable changes in body composition were found in male students with higher baseline BMI and WC. The observed changes in body composition did not cohere with changes in physical fitness. European Journal of Clinical Nutrition advance online publication, 27 May 2015; doi:10.1038/ejcn.2015.79
INTRODUCTION The transition from secondary school to college or university is a critical period for weight gain.1–3 The meta-analysis of Vella-Zarb3 revealed an average weight gain of 1.75 kg in US freshmen. European literature confirmed the latter and showed significant increases in Belgian first year students’ weight (1 kg), body mass index (BMI; 0.3 kg/m2) and fat% (0.8%) after only one semester at university.4 Similar results were found in UK freshmen.5 As it was concluded that studies including higher proportions of female participants found greater weight gain, Vella-Zarb et al.3 suggested to examine weight gain by gender. Predictor variables of student weight or fat gain, which can be established at the start of students’ academic careers (for example, gender3 and baseline BMI6,7), may be important when designing tailored interventions. Although a more recent meta-analysis of Fedewa8 stated that gender and baseline BMI were not associated with weight and fat gains, the abovementioned Belgian study did show that male university students were more likely to show an increased BMI in comparison with their female counterparts.4 The potential predictability of baseline BMI (or fat%, waist circumference (WC)) with regard to weight or fat gain in European students has not been tested yet. Gropper et al.9 reported significant US student weight gain during the first year of college. In a follow-up study, they showed that students’ weight further increased during the second (sophomore) year.10 Across 2 years of college, average weight gains up to 4.2 kg in female and 4.3 kg in male students were reported by US literature.10,11 These weight changes were 1
accompanied by increases in fat% and WC.10 Weight gain beyond the freshman year has never been objectively studied in a European student population. Weight gain and unhealthful changes in body composition may affect students’ physical fitness levels (or vice versa).12 Little is known on changes in physical fitness among university students. One US study did not find changes in the mean recovery heart rate and mean VO2 max in female college freshman students over a 5-month period,13 whereas another study conducted in US medical students revealed a significant 4% decrease in cardiorespiratory fitness over a period of 2 years.14 The latter study reported no changes in muscular strength.14 Although it was suggested to investigate weight-related variables by gender,3 no studies on changes in students’ physical fitness assessed gender differences so far. As physical fitness and healthy body composition go side by side in reducing cardiovascular disease risk,15,16 research combining both is needed, especially in an at-risk student population. Although weight gain throughout university has been well investigated in the United States, no previous European studies investigated weight gain in university students beyond the first year. As university students in Europe and the United States clearly differ with regard to socio-cultural influences and lifestyle (for example, fast food culture), the results of the abovementioned US studies cannot be generalized. Furthermore, literature on changes in physical fitness in university students is very limited. The purpose of this study was to provide follow-up results of previous research4 by examining changes in weight, BMI, body composition, WC and physical fitness in Belgian students after 1.5
Department of Human Biometry and Biomechanics, Vrije Universiteit Brussel, Brussels, Belgium and 2Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium. Correspondence: T Deliens, Department of Human Biometry and Biomechanics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Brussels 1050, Belgium. E-mail: [email protected] Received 1 December 2014; revised 13 April 2015; accepted 15 April 2015
Weight gain after 1.5 years at university T Deliens et al
2 years at university. Second, this study investigated whether changes in anthropometrics and physical fitness differed by gender. Finally, in light of designing more targeted intervention efforts, we aimed to identify baseline predictors (BMI, fat% and WC) of weight and fat gain over the 1.5-year period.
and was converted into beats per minute (heart rate per min) and used as the outcome measure. Validation studies in female college students showed excellent reliability, as well as a strong correlation between the QCST heart recovery pulse rate and VO2 max.21–23 All measurements, except for QCST, were conducted twice, and best performance results were used for analyses.
MATERIALS AND METHODS Participants
Data analyses
Using convenience sampling (via e-mail and face-to-face recruitment on the university campus), 348 Belgian (Flemish) first year university students volunteered to take part in the study. Only students who had just finished their last year of secondary school and were in their first year of university were eligible to participate (n = 340). As self-reported data of all first year university students (n = 926) were obtained during enrolment (by the university’s registration office), we were able to verify the representativeness of our sample. Our sample with mean age of 18.0 ± 0.6 years, 59.1% females and mean BMI of 21.4 ± 2.7 kg/m2 was representative in comparison with all freshmen in gender (56.6% females; χ2 = 0.6, P = 0.431) and BMI (21.4 ± 2.8 kg/m2; t = 0.2, P = 0.851). However, mean age was higher in the total group of freshmen (18.5 ± 1.1 years; t = 9.8, Po0.001).
Procedure In this longitudinal study, baseline measurements (T0) were conducted at the start (October/November) of the first semester of students’ first academic year at university.4 All participating students were re-contacted at the start of the second semester (February/March) of their first academic year (that is, after 4 months; T1), as well as at the start of the second semester (February/March) of their second academic year ( = fourth semester; that is, after 16 months from baseline; T2). The researchers made up to 10 attempts on different moments during the day to contact a student before they were considered to have dropped out. To minimize possible effects owing to sudden short-term lifestyle changes after holiday periods, measurements were conducted after 2 weeks of academic activities. Besides, participants’ timing of measurement at baseline was taken into account during both follow-up measurements. At all three time points, students received an incentive (a lunch voucher). An informed consent was signed by all participants before the start of the study. The study protocol was approved by the Medical Ethical Committee of the university hospital (Vrije Universiteit Brussel, Brussels, Belgium).
Measurements Students were measured with bare feet, wearing only shorts and a t-shirt. They were asked to void their bladder before starting the measurements, as well as to remove all jewellery. Anthropometrics. Weight (TANITA BC-418 Body Composition Analyser, Tanita Corp., Tokyo, Japan) and height (wall-fixed stadiometer) were measured to calculate BMI. Body composition (including fat%, fat mass (FM) and fat-free mass (FFM)) was estimated using TANITA BC-418 Body Composition Analyser, which is a validated17 eight-electrode device for hand-to-foot bioelectrical impedance analysis operating with a 50-kHz current. Participants were instructed to step on the electrodes with bare feet and to grab both hand grips. Finally, WC (measured with Rosscraft Anthrotape on the narrowest part of the waist18) was measured to analyze fat distribution. All measurements, except those using TANITA, were conducted twice and an additional third time when tolerance limits were exceeded. Subsequently, mean values were calculated from the two nearest values. Physical fitness. Except for the cardiorespiratory fitness test, all physical fitness tests were adapted from the Eurofit test battery for adults.19 Dynamic leg strength was estimated by means of the standing broad jump (accuracy = 1 cm), whereas a hand dynamometer was used to estimate handgrip strength (accuracy = 1 kg). Hamstring flexibility was estimated using the sit and reach test (accuracy = 1 cm). The Eurofit test battery is a reliable and a valid instrument to measure physical fitness and is a commonly used test battery in Europe.20 The Queens College Step Test (QCST) was used to estimate cardiorespiratory fitness. Participants were asked to step on and off a 41.3 cm high bench for 3 min. After completion, the carotid pulse rate was measured from 5 to 20 s of the recovery period European Journal of Clinical Nutrition (2015) 1 – 5
SPSS Statistics 22 (IBM Corp., Armonk, NY, USA) was used for data analyses. Independent samples t-tests and χ2-tests were executed to analyse representativeness and drop-out. Repeated measures mixed design analysis of variance with Bonferroni post hoc analyses were performed to assess anthropometric and physical fitness changes across 1.5 years according to gender. When gender interaction was found, anthropometric and physical fitness changes over time were investigated for females and males separately. Univariate linear regression analyses were conducted separately for gender to identify baseline predictors (BMI, fat% and WC) of change in BMI and fat%. P-values o 0.05 were considered as statistically significant.
RESULTS Drop-out analysis Of the initial sample (n = 340), 172 students (62.2% females) were measured at all three time points, indicating an overall drop-out of 49.4%. Reasons for drop-out were not reachable, quit university and no longer interested in participating. Drop-out analysis was conducted to ensure representativeness of the retention sample. At baseline, both drop-out (n = 168) and retention group (n = 172) were similar in gender (56.0% vs 62.2% females; χ2 = 1.4, P = 0.241) and in age (18.0 ± 0.6 vs 18.0 ± 0.5 years; t = 1.2, P = 0.220). In comparison with the drop-outs (21.8 ± 2.9 kg/m2), BMI was lower in the retention group (21.0 ± 2.3 kg/m2; t = 2.6, P = 0.010). Anthropometrics As anthropometric changes during the first semester at university have already been published elsewhere,4 first semester results are only described in Table 1. After 1.5 years at university, 66.9% had gained weight and 61.0% (76.9% of males and 51.4% of females) showed an increase in BMI. The prevalence of overweight and obesity doubled (from 5.8 to 12.1%) during the first semester at university, followed by a small decrease (from 12.1 to 9.9%) during the following year. Changes in weight and BMI differed according to gender (see Table 1). After 1.5 years, female students’ weight and BMI did not change significantly (both P = 1.000), whereas male students gained 2.7 kg of weight (P o 0.001) and showed a 0.7 kg/m2 BMI increase (P o 0.001). Weight changes ranged from − 8.6 to +9.5 kg in females and from − 2.4 to +11.8 kg in male students. No time × gender interaction was found for fat%. For the total group of students, a significant time effect was observed for fat% between T0 and T1, whereas this time effect did not remain significant when comparing T0 and T2. Changes in FFM and WC differed according to gender; for both FFM (P = 0.182) and WC (P = 0.780) no changes were found in females, whereas increases in 2.1 kg of FFM and 1.8 cm of WC (both P o0.001) were found in male students after 1.5 years at university. Predictability of baseline measures Male students with a higher baseline BMI and WC showed greater increases in BMI (P = 0.001, β = 0.364; P = 0.004, β = 0.328, respectively) and fat% (P = 0.005, β = 0.316; P = 0.020, β = 0.266, respectively), whereas female students with higher baseline BMI showed greater BMI decreases (P = 0.032, β = -0.201) over 1.5 years at university. For both sexes, fat% at baseline did not predict changes in BMI or fat%. © 2015 Macmillan Publishers Limited
Weight gain after 1.5 years at university T Deliens et al
3 Table 1.
Anthropometric changes after 1.5 years at university (Mean ± s.d. and F-values)
Measurements
Start 1st semester (T0)
Start 2nd semester (T1)
Start 4th semester (T2)
Height (cm) All (n = 172) Females (n = 107) Males (n = 65)
170.9 ± 9.0 166.0 ± 6.1 178.9 ± 7.3
171.1 ± 9.1 166.3 ± 6.1a 179.1 ± 7.4
171.3 ± 9.2 166.3 ± 6.2a 179.5 ± 7.4a,b
Weight (kg) All (n = 172) Females (n = 107) Males (n = 65)
61.6 ± 9.2 57.9 ± 7.9 67.7 ± 8.0
62.4 ± 9.8 58.3 ± 8.1a 69.1 ± 8.7a
62.8 ± 10.5 58.2 ± 8.0 70.4 ± 9.7a,b
BMI (kg/m2) All (n = 172) Females (n = 107) Males (n = 65)
21.0 ± 2.3 21.0 ± 2.5 21.1 ± 2.1
21.2 ± 2.5 21.1 ± 2.6 21.5 ± 2.3a
21.3 ± 2.5 21.0 ± 2.5 21.8 ± 2.5a,b
Fat% All (n = 171) Females (n = 106) Males (n = 65)
19.9 ± 7.1 23.7 ± 5.8 13.6 ± 3.5
20.6 ± 7.2a 24.4 ± 6.1 14.4 ± 3.6
20.4 ± 7.6 24.4 ± 6.1 13.8 ± 4.5
FM (kg) All (n = 171) Females (n = 106) Males (n = 65)
12.3 ± 5.1 14.1 ± 5.2 9.3 ± 3.1
13.0 ± 5.2a 14.7 ± 5.5 10.2 ± 3.2
12.8 ± 5.5a 14.6 ± 5.5 9.9 ± 4.3
FFM (kg) All (n = 171) Females (n = 106) Males (n = 65)
49.3 ± 8.6 43.8 ± 3.9 58.4 ± 6.3
49.4 ± 8.9 43.7 ± 3.9 58.8 ± 6.4
50.0 ± 9.7 43.5 ± 3.7 60.5 ± 6.9a,b
WC (cm) All (n = 172) Females (n = 107) Males (n = 65)
70.3 ± 5.8 67.8 ± 5.0 74.3 ± 4.6
70.6 ± 6.5 67.6 ± 5.3 75.5 ± 5.1a
70.8 ± 6.8 67.6 ± 5.2 76.1 ± 5.8a
Ftime ×
gender
Ftime
7.3*** 11.1*** 13.8*** 16.7*** 3.3* 34.0*** 9.7*** 1.6 23.3*** 1.3 9.5***
1.2 15.6***
38.3*** 1.8 34.5*** 18.3*** 1.4 18.6***
Abbreviations: BMI, body mass index; FM, fat mass; FFM, fat-free mass; WC, waist circumference. aSignificantly different from baseline measurements (T0). b Significantly different from T1 measurements. *Po0.05, ***P ⩽ 0.001.
Table 2.
Changes in physical fitness after 1.5 years at university (Mean ± s.d. and F-values)
Measurements
Start 1st semester (T0)
Start 2nd semester (T1)
Start 4th semester (T2)
Standing broad jump (cm) All (n = 167) Females (n = 105) Males (n = 62)
173.2 ± 34.1 154.6 ± 23.3 204.8 ± 25.0
174.4 ± 35.1 155.5 ± 24.0 206.5 ± 26.8
173.2 ± 35.1 154.3 ± 22.1 205.1 ± 29.4
Hand grip strength (kg) All (n = 172) Females (n = 107) Males (n = 65)
38.1 ± 10.8 31.9 ± 6.0 48.3 ± 8.9
39.4 ± 11.6 32.2 ± 5.8 51.3 ± 8.4a
40.4 ± 11.7 33.3 ± 6.2a,b 52.1 ± 8.7a
Flexibility (cm) All (n = 169) Females (n = 107) Males (n = 62)
29.3 ± 9.9 31.3 ± 9.4 25.9 ± 9.8
29.6 ± 9.5 31.2 ± 9.1 26.8 ± 9.6
29.4 ± 9.5 30.7 ± 8.9 27.0 ± 10.2
QCST (b.p.m.) All (n = 169) Females (n = 105) Males (n = 64)
146 ± 22 153 ± 18 133 ± 22
148 ± 23 155 ± 21 137 ± 21
148 ± 24 155 ± 24 137 ± 20
Ftime × gender
Ftime
0.1 1.0
6.1** 9.8*** 9.2*** 3.5* 1.4 2.5 0.1 2.2
Abbreviation: QCST, Queens College Step Test. aSignificantly different from baseline measurements (T0). bSignificantly different from T1 measurements. *Po0.05, **P o0.01, ***Po0.001.
© 2015 Macmillan Publishers Limited
European Journal of Clinical Nutrition (2015) 1 – 5
Weight gain after 1.5 years at university T Deliens et al
4
Physical fitness Compared with baseline measurements (T0), both female and male students showed greater handgrip strength after 1.5 years at university (T2; see Table 2). Improvements in handgrip strength were stronger in males (3.8 kg; P o0.001) than in females (1.4 kg; Po 0.001). Time × gender interaction was found for hamstring flexibility; although for both sexes no significant time effects were found, there was a decreasing trend in females and an increasing trend in males. No interaction nor time effects for dynamic leg strength and cardiorespiratory fitness were found across the 1.5-year period. DISCUSSION Previous research showed significant increases in Belgian first year students’ weight, BMI and fat% after only one semester at university with male gender as a predictor of BMI increase.4 Providing follow-up results, this study adds insight to the limited European literature on university students’ weight gain by examining whether Belgian students’ BMI, fat% and WC continued to increase after the first semester at university. Although a small first semester weight increase (0.4 kg) in female students was found, this effect did not remain significant after 1.5 years. In contrast, our results did reveal a significant increase in weight (2.7 kg) and BMI (0.7 kg/m2) in male students after 1.5 years at university. This weight gain is comparable with the 2.3 to the 4.3 kg weight increase found in US literature after 2 academic years in male students.10,11 Individual weight change in the present study ranged from − 8.6 to +11.8 kg, suggesting that during the first 1.5 years at university students may have difficulties controlling their weight. Even small student weight gains can result in higher risk of overweight or obesity in later life.2 According to the Flemish growth curves, the average weight gain between the age of 18 and 19.5 years is 0.6 kg in females and 2 kg in males, whereas the average increase in BMI for females and males is 0.2 and 0.5 kg/m2, respectively.24 In other words, gains in weight and BMI in male university students were higher than average gains for 18–19.5-year olds. Our results suggest that especially male Belgian university students are subject to various weight-related lifestyle changes.2 Although in the present study it may seem that male students’ increase in weight and BMI is similar between the first (T0–T1) and second (T1–T2) measuring period (1.4 vs 1.3 kg; 0.4 vs 0.3 kg/m2; see Table 1), we should take the difference in measuring time (4 vs 12 months, respectively) into account. Hence, a relatively higher increase in 350 g per month was found during the first semester in comparison with an increase in 108 g per month during the following year. Moreover, significant increases in fat% and FM in the total sample of students were only found during the first semester at university. These results are similar to those of previous research, reporting that both males and females gained more weight, BMI and fat% during the freshman versus sophomore year.10,11 Results of the present study suggest that interventions aiming to decrease students’ BMI and fat gains should have a special focus on male students during their first semester at university. Body composition measures also revealed that weight gain over the first semester in males was mainly owing to an unfavourable increase in FM and WC, whereas the weight gain found in the following year (T1–T2) was mainly owing to a more favourable increase in FFM. Although Gropper et al.10 observed a FFM loss in male students during the freshman year, a catch up during the sophomore year was found. As our results demonstrate, this FFM increase might be the result of both increases in height (and thus the effect of normal growth and development) and FM. An increase in FM, which implies the extra weight the body has to carry around, might have caused extra growth in muscle mass.25,26 European Journal of Clinical Nutrition (2015) 1 – 5
Our results indicate that the unfavourable changes observed during the first semester at university4 did not continue throughout the following year. This phenomenon might be explained by the fact that students experience great difficulties to adapt to the new university environment during their first semester, whereas afterwards they manage to adapt more and more to the university lifestyle.2 However, it remains unclear whether weight and body composition measures are either stabilising or slowly restoring after the first semester. To find out, additional follow-up measurements are needed. In contrast to the conclusion drawn in Fedewa’s8 meta-analysis, baseline BMI in the present study was associated with both change in BMI and fat%. Interestingly, male students with higher baseline BMIs and WCs showed higher increases in BMI and fat%, whereas female students with higher baseline BMIs showed higher decreases in BMI after 1.5 years at university. Female students seem to handle their baseline (over)weight differently in comparison with their male counterparts. Whereas males with higher baseline BMI gain even more weight during the 1.5-year period, results suggest that females adjust their lifestyle to lose weight. However, it is not clear whether females who are trying to lose weight are doing this in a healthful way. Therefore, weight control interventions targeting students with higher BMIs at baseline should approach males and females differently. Regarding physical fitness, an improvement in handgrip strength for both male and female students was found over 1.5 years at university. This is in accordance with previous research showing that handgrip strength in Belgian (young) adults continues to increase until the age of 34–44 years.27 To the best of our knowledge, no other studies assessing changes in static handgrip strength in university students exist; hence, no comparison could be made. No changes were found for dynamic leg strength, hamstring flexibility or cardiorespiratory fitness. Although this may suggest no immediate short-term health risk increment, the unhealthy changes in body composition during the first semester might cause students’ physical fitness to deteriorate in the long term. The first strength of this study is the objectively measured weight and height. Earlier research showed that self-reports tend to underestimate weight and overestimate height, resulting in an underestimation of overweight and obesity rates.28,29 Second, the increase in height in both males and females over the three semester period seemed to be in accordance to the mean growth velocity of 0.2–0.5 cm per year in 18–19-year olds.24 Hence, as some students still grow, we chose to (in contrast to many previous studies drawing conclusions based on weight only) interpret both changes in weight and BMI. Third, as BMI has limitations and is unable to discriminate between an excess in body fat and increased lean mass, nor between different types of body fat distribution,30 body composition and WC were measured to determine whether gains in weight were owing to FM or FFM and to study changes in body fat distribution. Especially, increases in abdominal fat are strongly related to a higher risk for developing cardiovascular diseases.31 A first limitation is that only about half (n = 172) of all initial participants were measured at all three time points. According to the university’s registration office, a drop-out ( = students quitting university) of 21% can be observed after the first year at university. The latter partly explains the large drop-out in our study. Because of the reduced sample size, we should be careful interpreting results. Drop-out analysis showed that baseline BMI was higher in the drop-out than in the retention group. Also, students who gained weight between baseline and follow-up measurements may have been more likely to have dropped out. Second, baseline measurements were conducted in October/November. This is well into the start of the freshman year and thus potentially misses capturing weight gain during a critical 4–6-week window. The abovementioned limitations may implicate a potential © 2015 Macmillan Publishers Limited
Weight gain after 1.5 years at university T Deliens et al
5 underestimation of the 1.5-year weight gain in Belgian university students. Third, we did not measure anthropometrics at the end of the first academic year. Hence, we were not able to verify whether anthropometric changes during the first semester continued during the second semester. Fourth, bioelectrical impedance analysis has its limitations and its accuracy can be discussed.32 Finally, the fact that no changes in physical fitness were found may be owing to the limited sensitivity of the methods used to assess physical fitness. This is the first European study showing that the greatest weight and fat gains occur during the first semester at university and mostly in male students, whereas the observed changes more or less stabilise during the following year. Male students with higher BMI and WC at baseline were at greatest risk to gain weight and fat over 1.5 years at university. These results yield some important information to tailor interventions aiming at preventing university students’ weight gain. Furthermore, the observed changes in body composition did not cohere with changes in physical fitness. Future follow-up studies are needed to investigate whether unfavourable changes in males’ body composition will recover spontaneously during the following years at university. CONFLICT OF INTEREST The authors declare no conflict of interest.
ACKNOWLEDGEMENTS We thank all students participating in this study. Special thanks to all Master thesis students for their contribution in data collection.
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