Self-reported dietary intake following endurance, resistance and concurrent endurance and resistance training.

Abstract

With regards to obesity-related disease the impact of exercise training on health depends on the ability of exercise to promote a negative energy balance. Exercise's effect on promoting a negative energy balance is more likely to occur if exercise can induce a favourable dietary intake such as a reduced relative fat content in the diet. As such, the aim of this study was to evaluate and compare the effectiveness of aerobic training, weight training and concurrent aerobic and weight training on self-reported dietary intake. The effects of 16 weeks of aerobic (n = 12), weight (n = 13) and concurrent aerobic and weight training (n = 13) on self-reported dietary intakes were compared in previously sedentary males using the computer-based Dietary Manager[R] software programme. Only the concurrent aerobic and weight training group showed significant (p [less than or equal to] 0.05) reductions in total kilocalories, carbohydrates, proteins and fats consumed while the aerobic training group showed significant reductions in fat intake at the completion of the experimental period (before: 91.0 [+ or -] 42.1g versus after: 77.1 [+ or -] 62.1g). However, no changes were observed in self-reported dietary intake in the weight training or non-exercising control groups. It is concluded that concurrent aerobic and weight training is the most effective mode of exercise at promoting a favourable improvement in self-reported dietary intake in the short term. This finding provides support for efforts to promote increases in overall physical activity in an attempt to modify the patterns of dietary intake.

Key words: Kilocalories, carbohydrate, diet, exercise, fat, protein.

Introduction

Exercise has frequently been a method used to promote good health. One expected favourable effect of exercise training is a positive change in dietary habits and nutritional status (Ambler et al., 1998; Tremblay and Almeras, 1995). Epidemiological studies have also focused on the interaction between exercise and diet (Sallis, 1993; Sclicker et al., 1994). This is due to the ever-increasing incidences of diseases such as hypertension, dyslipidemia, diabetes mellitus, obesity and cardiovascular disease resulting from sedentary lifestyles (Sallis, 1993; Sclicker et al., 1994) and an increased over-consumption of energy-dense food (whether fat, protein or carbohydrate) (Olivares et al., 2004). Since exercise is known to affect carbohydrate, protein and fat metabolism and/or stores, it is hypothesized that exercise also affects their dietary intake via its metabolic effects (Tremblay and Almeras, 1995). This hypothesis is supported by Saris (1989) who stated that there is a strong association between daily energy expenditure and dietary intake.

With regards to exercise, Verger et al. (1992) found that energy intake increased from carbohydrate (but not fat or protein) following a two-hour vigorous exercise bout using college-aged males and females. However, a later study of Verger et al. (1994) found that protein (but not carbohydrate or fat) intake increased above rest in a male-only sample following two hours of various athletic activities. These contradictory findings might be explained by Ambler et al. (1998) when they found that fitness is associated with increased energy intakes in males but not females while females consumed greater quantities of fat and lesser quantities of carbohydrate. Additionally, a study by Titchenal (1988) found that while athletes increase energy intake in response to an increased exercise volume, obese subjects did not alter their energy intake. Further confounding the effect of exercise on dietary intake, Costill et al. (1988) found that an increase in swimming training volume over a 10-day period resulted in their sample of athletes failing to increase their dietary carbohydrate intake leading to decreases in muscle glycogen levels and concomitant fatigue. This may be explained by a study by Janssen et al. (1989) who found that carbohydrate intakes increased by 3% to 4% in novice marathon runners but not in champion marathon runners. In this regard, champion athletes may increase energy intake through other dietary sources other than carbohydrates (de Wijn et al., 1979). This is confirmed more recently by Burke et al. (2003) when these researchers found that the dietary behaviour of 167 male and female Australian Olympic athletes following training was sub-optimal with regards to their dietary intake of carbohydrates, fats and proteins. Despite an increasing number of epidemiologic studies being conducted on the effect of aerobic exercise modalities and/or aerobic fitness, relatively few studies have been forthcoming on whether resistance training or a combination of aerobic and resistance training may affect energy intake through dietary sources. As such, the aim of the study was to evaluate and compare the effectiveness of aerobic training, weight training and concurrent aerobic and weight training on self-reported dietary intake.

Methods

Subjects were recruited from the Gauteng region in Johannesburg South Africa. A total of 50 subjects took part in the 16-week study (Table 1). The study was approved by the Rand Afrikaans University, Department of Human Movement Studies' Research Committee and informed consent was obtained from each subject. The subjects included were all males (mean age: 25 years and six months). The subjects were screened and only those who were previously sedentary, free of preexisting disease and not on any prescribed diet or supplement which could have altered their dietary intake or energy expenditure were allowed to enter the study. To account for the effect of exercise training on dietary intake, the subjects had to complete a self-reported dietary intake form specifying the type and quantity of food and fluids consumed over seven days before and after the experimental period. Portion sizes were illustrated with the aid of measuring cups, glasses, bowls and food items. The records were reviewed in detail with each subject upon completion to ensure completeness. The dietary records were analyzed for total kilocalories consumed, carbohydrates, proteins and fats. The Dietary Manager[R] computer-based software programme (Dietary Manager, Program Management, South Africa) was used to analyze the data. The body mass of the subjects was measured to the nearest 0.1 kilogramme on a calibrated medical scale (Mettler DT Digitol, Mettler-Toledo AG, Ch-8606 GreiFensee, Switzerland) wearing only running shorts. Percentage body fat was assessed using the seven-skinfold method of Jackson and Pollock (1978) which has a correlation of 0.915 when compared to hydrostatic weighing to estimate body density. The standard error of estimate was 0.008 expressed in body density and a standard error of estimate of 3.5 when expressed in % BF using the equation of Siri (1961) and standard errors of their formulae ranged from 3.6% to 3.8%.

After the initial completion of the dietary intake, no dietary advice was given to the subjects and the subjects were randomly assigned to either an aerobic training group (AER) (n = 12), weight training group (WEI) (n = 13), concurrent aerobic and weight training group (WEI+AER) (n = 13) or control group (CONT) (n = 12) which remained sedentary throughout the study. All the subjects performed a five minute warm-up before starting each training session and concluded with stretching and a five minute cool-down. The subjects in the AER group trained for a total of 60 minutes; 45 minutes at 60% heart rate maximum (target heart rate was increased by 5% every four weeks and was monitored via a telemetry strap (Polar Fitwatch, Polar Electro Oy, Finland) and confirmed manually at the radial artery via palpation). Each workout of the WEI group was designed according to National Strength and Conditioning Association (NSCA) guidelines (Baechle et al., 2000; Earle and Baechle, 2000) and consisted of three sets of seated machine shoulder press, latissimus dorsi pull-downs, vertical chest press, seated rows, unilateral leg press, unilateral knee extensions and unilateral hamstring curls at 60% of the individual's one-repetition maximum for 15 repetitions each. Each WEI group subject had to perform bent-knee sit-ups for three sets of 15 repetitions at 60% of the maximum performed during the initial evaluation. The WEI+AER group had to perform similar exercises to the WEI group but instead had to perform two sets of 15 repetitions each and 22 minutes of aerobic training at the same target heart rate as AER. The weight training intensity was reevaluated through 10-repetition maximum (RM) testing and the training programmes adjusted by increasing the resistance accordingly to maintain 60% of the estimated 1-RM every four weeks.

The Kruskal-Wallis test was utilized to determine whether the four groups within the study were significantly different (i.e. heterogeneous) or statistically the same (i.e. homogenous) at pre-test. The dietary intake records that were obtained before and after the 16-week period were analyzed using a mixed factorial analysis of variance. P [less than or equal to] 0.05 was selected as being indicative of statistical significance. Values are expressed as means [+ or -] standard deviation (SD). The control group's self-reported dietary intake was utilized to calculate test-retest reliability by quantifying test-retest reliability using the intraclass correlation coefficient. Spearman's correlation coefficient was also utilized to measure the strength of the linear relationship between the measured dietary intake variables and body mass and percentage body fat.

Results

The three exercising groups and the non-exercising control group were found to be homogeneous at the start of the study regarding their mean self-reported dietary intakes for total kilocalories (p = 0.686), carbohydrates (p = 0.627), proteins (p = 0.729) and fats (p = 0.517). At the end of the 16-week experimental period, the mean kilocalorie, carbohydrate and protein intakes for the AER remained unchanged despite the finding of a significant decrease the dietary intake of fat (91.0 [+ or -] 42.1 grammes (g) at baseline versus 77.1 [+ or -] 62.1g at post-test). In the WEI, no significant alterations were found in the measured dietary variables. However, following 16 weeks of concurrent aerobic and weight training, the WEI+AER was found to have had significant (p = 0.05) decreases in total kilocalories (2228 [+ or -] 598 kilocalories versus 1711 [+ or -] 675 kilocalories), carbohydrates (236.4 [+ or -] 107.2g versus 185.5 [+ or -] 86.0g), proteins (103.5 [+ or -] 38.2g versus 80.2 [+ or -] 33.0g) and fats (91.9 [+ or -] 27.6g versus 67.9 [+ or -] 26.2g). As expected, the CONT were found to have had no significant (p [less than or equal to] 0.05) decreases in their total kilocalories, carbohydrates, proteins and fats consumed.

Despite the four groups being found to be heterogeneous (p = 0.008) at the start of the study, the subjects assigned to the AER weighed significantly (p = 0.05) less than at the start of the experimental period (74.7 [+ or -] 8.2 kilogrammes (kg) versus 72.3 [+ or -] 7.4kg) whereas the WEI weighed significantly more at the completion of the study (69.1 [+ or -] 8.5kg versus 70.7 [+ or -] 9.5kg). In contrast, the mean body mass values of the WEI+AER and CONT were unchanged (85.0 [+ or -] 12.8kg versus 85.1 [+ or -] 11.0kg and 80.3 [+ or -] 12.8kg versus 79.6 [+ or -] 10.9kg, respectively). No significant relationship was found between body mass and total kilocalories (r = 0.078; p = 0.591), carbohydrates (r = - 0.118; p = 0.413) and fats (r = 0.201; p = 0.162), indicating that these dietary intake variables had no impact on body mass. However, a significant relationship was found between the dietary intake of protein and body mass (r = 0.308; p = 0.029) indicating that a significant decrease in protein intake could have assisted in a concomitant significant decrease in body mass. However, only the WEI+AER significantly decreased their intake of protein, but this was in the absence of a significant change in body mass.

Percentage body fat (%BF) decreased significantly (p [less than or equal to] 0.05) following all of the exercise interventions. The AER displayed a significantly decreased %BF (15.6 [+ or -] 6.7% versus 11.9 [+ or -] 4.6%; p = 0.002) as did the WEI and WEI+AER (9.3 [+ or -] 7.3% versus 6.9 [+ or -] 5.2%; p = 0.009 and 22.0 [+ or -] 11.9% versus 17.0 [+ or -] 9.0%; p = 0.002, respectively). However, the CONT's %BF remained unchanged from pre- to post-test (17.9 [+ or -] 7.9% versus 17.8 [+ or -] 8.0%; p = 1.000). Further, no significant relationship was detected between %BF and total kilocalories (r = 0.204; p = 0.156), carbohydrates (r = 0.124; p = 0.399), proteins (r = 0.172; p = 0.232) and fats (r = 0.234; p = 0.103), indicating that dietary intake had no impact on %BF.

Discussion

According to the findings of the present study, engaging in concurrent aerobic and weight training appears to result in a decreased consumption of the usual self-reported dietary intakes regarding total kilocalories consumed and from carbohydrates, proteins and fats in the short term. Aerobic training resulted in a decreased self-reported dietary intake of fats only, and weight training alone did not result in any change in self-reported dietary macronutrient intake in the short term. This finding is of interest because frequently the reduction in body mass associated with exercise is less than is expected due to compensation for the increased energy expenditure during exercise by either eating more food or having less spontaneous physical activity throughout the day (Donnelly and Smith, 2005). When combining this study's finding of a decreased self-reported dietary consumption following concurrent aerobic and weight training with the findings of a decreased %BF, the present data therefore suggests that the most favourable technique for stimulating a negative energy balance that might lead to reduced body mass is a combination of aerobic and resistance exercise.

The accuracy of self-reported dietary intake is questionable, as people tend to report nutrient intakes that may more closely approximate perceived norms than actual intake and people tend to underreport their dietary energy intake (Hoidrup et al., 2002; Schoeller, 1990). In the present investigation, the participants were given detailed instructions on how to measure and report their dietary intake, and the dietary records were individually reviewed prior to analysis. The lack of change in self-reported dietary macronutrient intake and body composition in the control group suggests that the subjects were consistent in their dietary recording, regardless of the tendency for people to underreport energy intake. Additionally, using the control group's self-reported dietary intake, test-retest reliability using the intraclass correlation coefficient yielded a value of 0.444 for kilocalories, carbohydrate, protein and fat, indicating an overall reliability. When considering the individual self-reported dietary intake variables, the intraclass correlation coefficient yielded values of 0.361 for kilocalories, 0.792 for carbohydrates, 0.613 for protein and 0.800 for fats, again indicating test-retest reliability. It has been suggested that males (as used in this study) maintain or decrease their energy intake in response to exercise more so than do females (Donnelly and Smith, 2005; Janssen et al., 1989). Furthermore, females are more likely to compensate for the increased energy expenditure through exercise by increasing their energy intake (Donnelly and Smith, 2005). There are several reasons why the concurrent resistance and aerobic exercise may have produced a favourable change in dietary composition. Firstly, the WEI+AER group subjects weighed significantly more and consumed slightly more kilocalories than the other two training groups. As such, the subjects in this group had a greater opportunity to decrease their macronutrient intake. The favourable change in the self-reported dietary macronutrient intake caused by concurrent aerobic and weight training in the present study may physiologically have been due to this mode of exercise inhibiting short-term eating via increased levels of fat being broken down and released into the blood stream (Lipostatic theory), improvements in blood sugar levels (Glucostatic theory) and/or alterations in amino acid levels in the blood (Aminostatic theory) all leading to an increased satiety. Further, this intervention may also have increased satiety by elevating postpranial levels of the satiety hormones; polypeptide YY, glucagon-like peptide-1 and pancreatic polypeptide (Martins et al., 2008). Also, the findings of Rivest and Richard (1990) demonstrated that exercise may have a direct effect on a specific neurosystem influencing feeding behaviour leading to an increased carbohydrate preference due to the composition of the fuel mix oxidized during this mode of exercise.

Exercise is of paramount importance in improving overall health and most, if not all, adults should engage in regular exercise to prevent numerous untoward health complications (Haskell et al., 2007). Furthermore, in order to treat obesity and its numerous comorbidities including type 2 diabetes and heart disease, exercise should induce a negative caloric balance (Braun and Brooks, 2008). The present data suggest that weight training alone and aerobic training alone do not induce changes in self-reported dietary energy intake in the short term, such that the negative caloric balance would be due solely to the energy expenditure during exercise. In contrast, concurrent aerobic and resistance training induces a negative caloric balance through both the energy expenditure during exercise and reduced self-reported dietary energy intake, which is a key common factor observed in those with long weight loss success (Hill et al., 2005).

The results of the study supports previous research findings that an increase in energy expenditure through exercise was not compensated for by an increase in self-reported dietary intake as compared to the male subject's usual diets and this can be viewed as a favourable short-term adaptation to concurrent aerobic and weight training.

Conclusion

Concurrent aerobic and weight training is the most effective mode of exercise at promoting a favourable improvement in self-reported dietary intake in the short term. As such, efforts should be increased to promote increases in overall physical activity in an attempt to modify the patterns of dietary intake.

Key points

* Concurrent aerobic and weight training can significantly reduce the amount of total kilocalories, carbohydrates, proteins and fats consumed.

* Aerobic training can significantly reduce fat intake.

* Weight training resulted in no changes in dietary intake.

* Concurrent aerobic and weight training is the most effective mode of exercise at promoting a favourable improvement in self-reported dietary intake.

Acknowledgements

The authors are grateful to the Rand Afrikaans University, Johannesburg, South Africa for the use of the Centre for Sport Science and Biokinetics and the Vaal University of Technology for its statistical support.

Received: 08 February 2008 / Accepted: 09 April 2008 / Published (online): 01 June 2008

AUTHORS BIOGRAPHY

Brandon S. SHAW

Employment

Lecturer--Tshwane University of Technology

Degree

PhD

Research interests

Sports nutrition, Food preference and macronutrient intake in the obese and non-obese, metabolic diseases.

E-mail: [e-mail]

Ina SHAW

Employment

Lecturer--Vaal University of Technology

Degree

PhD

Research interests

Diet and the aetiology of non-communicable diseases, Exercise and weight co ntrol, obesity.

E-mail: [e-mail]

Gregory A. BROWN

Employment

Associate Professor - University of Nebraska at Kearney 

Degree

PhD Health and Human Performance

Research interests

Obesity, endocrinology of obesity and hunger, exercise and

appetite regulation.

E-mail: [e-mail]

References

Ambler, C., Eliakim, A., Brasel, J.A., Lee, W.N., Burke, G. and Cooper, D.M. (1998) Fitness and the effect of exercise training on the dietary intake of healthy adolescents. International Journal of Obesity and Related Disorders 22(4), 354-362.

Baechle, T.R., Earle, R.W. and Wathen, D. (2000) Resistance training. In: Essentials of strength training and conditioning. Eds:

Baechle, T.R. and Earle, R.W. 2nd Edition. Champaign, IL: Human Kinetics. 393-426.

Braun, B. and Brooks, G.A. (2008) Critical importance of controlling energy status to understand the effects of "exercise" on metabolism. Exercise and Sport Science Reviews 36(1), 2-4.

Burke, L.M., Slater, G., Broad, E.M., Haukka, J., Modulon, S. and Hopkins, W.G. (2003) Eating patterns and meal frequency of elite Australian athletes. International Journal of Sport Nutrition and Exercise Metabolism 13(4), 521-538.

Costill, D.L., Flynn, M.G., Kirwan, J.P., Houmard, J.A., Mitchell, J.B., Thomas, R. and Park, S.H. (1988) Effects of repeated days of intensified training on muscle glycogen and swimming performance. Medicine and Science in Sports and Exercise 20(3), 249-254.

de Wijn, J.F., Leusinkb, J. and Post, G.B. (1979) Diet, body composition and physical condition of champion rowers during periods during periods of training and out of training. Bibliotheca Nutritio et Dieta 27, 143-148.

Donnelly, J.E. and Smith, B.K. Is exercise effective for weight loss with ad libitum diet? (2005) Energy balance, compensation, and gender differences. Exercise and Sport Science Reviews 33(4), 169-174.

Earle, R.W. and Baechle, T.R. (2000) Resistance training and spotting techniques. In: Essentials of strength training and conditioning. Eds: Baechle, T.R. and Earle, R.W. 2nd Edition. Champaign, IL: Human Kinetics. 343-392.

Haskell, W.L., Lee, I.M., Pate, R.R., Powell, K.E., Blair, S.N., Franklin, B.A., Macera, C.A., Heath, G.W., Thompson, P.D. and Bauman, A. (2007) Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & Exercise 39(8), 1423-1434.

Hill, J.O., Wyatt, H., Phelan, S. and Wing, R. (2005) The National Weight Control Registry: is it useful in helping deal with our obesity epidemic? The Journal of Nutrition Education and Behaviour 37(4), 206-210.

Hoidrup, S., Andreasen, A.H., Osler, M., Pedersen, A.N., Jorgensen, L.M., Jorgensen, T., Jorgensen, M., Schroll, M. and Heitmann, B.L. (2002) Assessment of habitual energy and macronutrient intake in adults: comparison of a seven day food record with a dietary history interview. European Journal of Clinical Nutrition 56(2), 105-113.

Jackson, A.S. and Pollock, M.L. (1978) Generalized equations for predicting body density of men. British Journal of Nutrition 40(3), 497-504.

Janssen, G.M.E, Graef, C.J.J. and Saris, W.H.M. (1989) Food intake and body composition and diet in novice athletes to run a marathon. International Journal of Sports Medicine 10(Suppl), S17-S21.

Martins, C., Robertson, M.D. and Morgan, L.M. (2008) Effects of exercise and restrained eating behaviour on appetite control. Proceedings of the Nutrition Society 67(1), 28-41.

Olivares, S., Kain, J., Lera, L., Pizarro, F., Vio, F. and Moron, C. (2004) Nutritional status, food consumption and physical activity among Chilean school children: a descriptive study. European Journal of Clinical Nutrition 58(9), 1278-1285.

Rivest, S. and Richard, D. (1990) Involvement of corticotropin-releasing factor in the anorexia induced by exercise. Brain Research Bulletin 25(1), 169-172

Sallis, J.F. (1993) Epidemiology of physical activity and fitness in children and adolescents. Critical Reviews in Food Science and Nutrition 33(4-5), 403-408.

Saris, W.H.M. (1989) Physiological aspects of exercise in weight cycling. American Journal of Clinical Nutrition 49(5 Suppl), 1099-1104.

Sclicker, S.A., Borra, S.T. and Regan, C. (1994) The weight and fitness Status of United States children. Nutritional Reviews 52(1), 11-17.

Schoeller, D.A. (1990) How accurate is self-reported dietary energy intake? Nutritional Reviews 48(10), 373-379.

Siri, W.E. (1961) Body composition from fluid spaces and density. In: Techniques for Measuring Body Composition. Eds. Brozek, J.R. and Henschel, A. Washington, DC: National Academy of Sciences.

Titchenal, C.A. (1988) Exercise and food intake. What is the relationship? Sports Medicine 6(3), 135-145.

Tremblay, A. and Almeras, N. (1995) Exercise, macronutrient preferences and food intake. International Journal of Obesity and Related Disorders 19(Suppl 4), S97-S101.

Verger, P., Lanteau, M.T. and Louis-Sylvestre, J. (1992) Human intake and choice of foods at intervals after exercise. Appetite 18(2), 93-99.

Verger, P., Lanteau, M.T. and Louis-Sylvestre, J. (1994) Free food choice after acute exercise in men. Appetite 22(2), 159-164.

Brandon S. Shaw ([mail]) (1), Ina Shaw (2) and Gregory A. Brown (3)

(1) Tshwane University of Technology and (2) Vaal University of Technology, Republic of South Africa (3) University of Nebraska at Kearney, Nebraska, USA ([mail]) Brandon S. Shaw Tshwane University of Technology, Department of Sport, Rehabilitation & Dental Sciences, Faculty of Science, Pvt. Bag X680 Pretoria 0001, Republic of South Africa. [e-mail]

Table 1. Subject descriptive data. Values are means ([+ or -] SD).

                    AER          WEI         WEI+AER        CONT

Age (yrs)        25.0 (5.6)   25.0 (3.5)   26.0 (3.1)    25.0 (2.4)
Height (m)       1.77 (.04)   1.76 (.06)   1.79 (.07)    1.79 (.12)
Body Mass (kg)   74.7 (8.2)   69.1 (8.5)   85.0 (12.8)   80.3 (12.8)

AER: aerobic training; WEI: weight training: AER+WEI:
concurrent aerobic and weight training; CONT: control group