AJCN EB Program 2010
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hill, A. M
Right arrow Articles by Howe, P. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hill, A. M
Right arrow Articles by Howe, P. R.
Agricola
Right arrow Articles by Hill, A. M
Right arrow Articles by Howe, P. R.
American Journal of Clinical Nutrition, Vol. 85, No. 5, 1267-1274, May 2007
© 2007 American Society for Nutrition

ORIGINAL RESEARCH COMMUNICATION

Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors1,2,3

Alison M Hill, Jonathan D Buckley, Karen J Murphy and Peter RC Howe

1 From the Nutritional Physiology Research Centre and the Australian Technology Network Centre for Metabolic Fitness, University of South Australia, Adelaide, Australia (AMH, JDB, KJM, and PRCH), and the Discipline of Physiology, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, Australia (AMH and PRCH)

2 Supported by a University of Adelaide postgraduate award (to AMH). Fish oil and placebo capsules were donated by Nu-Mega Ingredients Pty Ltd.

3 Reprints not available. Address correspondence to PRC Howe, School of Health Sciences, University of South Australia, GPO Box 2471, Adelaide, SA 5001, Australia. Email: peter.howe{at}unisa.edu.au.


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Background: Regular exercise and consuming long-chain n–3 fatty acids (FAs) from fish or fish oil can independently improve cardiovascular and metabolic health, but combining these lifestyle modifications may be more effective than either treatment alone.

Objective: We examined the individual and combined effects of n–3 FA supplements and regular exercise on body composition and cardiovascular health.

Design: Overweight volunteers [body mass index (BMI; in kg/m2): >25] with high blood pressure, cholesterol, or triacylglycerols were randomly assigned to one of the following interventions: fish oil (FO), FO and exercise (FOX), sunflower oil (SO; control), or SO and exercise (SOX). Subjects consumed 6 g tuna FO/d ({approx}1.9 g n–3 FA) or 6 g SO/d. The exercise groups walked 3 d/wk for 45 min at 75% age-predicted maximal heart rate. Plasma lipids, blood pressure, and arterial function were assessed at 0, 6, and 12 wk. Body composition was assessed by dual-energy X-ray absorptiometry at 0 and 12 wk only.

Results: FO supplementation lowered triacylglycerols, increased HDL cholesterol, and improved endothelium-dependent arterial vasodilation (P < 0.05). Exercise improved arterial compliance (P < 0.05). Both fish oil and exercise independently reduced body fat (P < 0.05).

Conclusions: FO supplements and regular exercise both reduce body fat and improve cardiovascular and metabolic health. Increasing intake of n–3 FAs could be a useful adjunct to exercise programs aimed at improving body composition and decreasing cardiovascular disease risk.

Key Words: n–3 Fatty acids • body fat • flow-mediated dilatation • lipids • dual-energy X-ray absorptiometry • DXA


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Obesity is a risk factor for cardiovascular disease (CVD), and its prevalence is increasing in Western society (1, 2). Moreover, obesity clusters with several other risk factors for CVD and diabetes in what is known as the metabolic syndrome (3). Hence, interventions for obesity should target multiple cardiovascular and metabolic risk factors.

Evidence from several studies supports an inverse relation between the intake of n–3 fatty acids (FAs) from fish or fish oil and the rate of mortality from coronary artery disease (4). Furthermore, regular consumption of n–3 FAs, particularly docosahexaenoic acid (DHA), has the capacity to ameliorate several cardiovascular risk factors, including elevated blood pressure and triacylglycerols, platelet aggregation, endothelial dysfunction, and arrhythmia (5). Evidence also suggests that n–3 FAs may have a favorable effect on metabolism by modulating gene expression (6). Indeed, animal studies have found that fat mass deposition is reduced after feeding with n–3 FAs (7, 8). In human studies, however, the evidence is less clear: some (9, 10) but not all studies indicate that n–3 FAs can reduce body fat with (11) or without (12) concomitant dietary restriction.

Physical activity is often recommended for weight loss, although most studies find that physical activity alone produces relatively small changes in body weight (13-15). The extent of weight loss that can be achieved through exercise may be small, but it is clear that physical activity plays a key role in preventing weight gain; however, as much as 60–90 min/d of moderate-intensity physical activity can be required to maintain body weight (16). In addition, much evidence suggests that exercise with or without weight loss may independently improve several risk factors for CVD, including lowering blood pressure, favorably altering blood lipid profiles (17), and improving blood vessel function (18).

Although several studies have investigated the potential for regular aerobic exercise to independently improve body composition and CVD and metabolic risk factors, few properly controlled studies have investigated the effect of n–3 FA supplementation on these risk factors, particularly body composition. Only 2 studies have previously investigated these 2 interventions in combination (19, 20), and those study designs were such that it could not be determined whether this combined intervention was effective in reducing cardiovascular risk and improving body composition in overweight volunteers. In the present study, we made a placebo-controlled comparison of the effects of 3 mo of n–3 FA supplementation and regular aerobic exercise, alone and in combination, on body composition and cardiovascular risk factors in overweight subjects with characteristics of the metabolic syndrome.


   SUBJECTS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Subjects
We recruited for the study adult volunteers aged 25–65 y who had a body mass index (BMI; in kg/m2) > 25 and ≥1 of the following cardiovascular risk factors: mild hypertension (140/90–160/100 mm Hg), elevated plasma triacylglycerols (>1.6 mmol/L), or elevated total cholesterol (>5.5 mmol/L). Initial suitability for the study was determined by completion of a simple diet and lifestyle questionnaire. Volunteers were then invited to attend a screening appointment to confirm eligibility for study entry. During screening, height, weight, blood pressure, and fasting triacylglycerols and total cholesterol in venous blood were measured. Subjects also completed a medical screening, which included electrocardiogram monitoring (Nihon Kohden, Tokyo, Japan) during a graded exercise test, to confirm their suitability for exercise training.

Subjects were excluded if they exercised >1 time/wk for the purposes of improving their health; took fish-oil (FO) capsules or ate >1 fatty fish meal/wk; had diabetes, liver disease, or CVD; took blood pressure or lipid-lowering medication; were pregnant or lactating; or were following a weight-reduction diet. Twenty-eight men and 53 women were enrolled.

Written informed consent was obtained from all subjects before their participation. Ethical approval was obtained from both the University of Adelaide and the University of South Australia.

Study design and intervention
Subjects were allocated to 1 of 4 groups, and each group was balanced for sex, BMI, and triacylglycerols. The groups were then randomly assigned to 1 of 4 treatments. Two groups took 6 g tuna fish oil/d (Hi-DHA; Nu-Mega Ingredients Pty Ltd, Brisbane, Australia), which provided 260 mg DHA and 60 mg eicosapentaenoic acid (EPA) in each 1-g capsule, and 2 groups took 6 g placebo oil (sunflower oil; SO)/d for 12 wk. All capsules were identical in color, shape, and flavor and were administered in a double-blind fashion. One of the groups assigned to each oil treatment also participated in a program of regular physical activity. The 4 groups were therefore identified as SO (n = 20), FO (n = 18), SO and exercise (SOX; n = 18), and FO and exercise (FOX; n = 19) (Figure 1Go). Subjects allocated to an oil plus exercise group (FOX and SOX) were required to run or walk 3 times/wk for 45 min at a heart rate (HR) that corresponded to 75% of their age-predicted maximum [208 – (0.7 x age)] (21). Subjects were provided with individual HR monitors (Polar F1; Polar Electro, Kempele, Finland) to facilitate their exercising at the appropriate HR.


Figure 1
View larger version (12K):
[in this window]
[in a new window]

  		FIGURE 1.. Flow chart showing numbers of subjects recruited and their attrition patterns during the study. FO, fish oil; FOX, FO and exercise; SO, sunflower oil; SOX, SO and exercise. Reasons for subject withdrawal were as follows: adid not take required number of capsules; bchange in work or family circumstances; ccould not meet exercise intensity; and ddid not comply with exercise protocol.

 
Outcome measures were assessed and compared across each intervention group at 0, 6, and 12 wk, except body composition, which was assessed at 0 and 12 wk only. Subjects attended 2 clinic visits at each of these timepoints when fasting blood samples and cardiovascular and anthropometric data were collected. All subjects were instructed to maintain their normal diet during the study. If not asked to exercise as part of the intervention, subjects were instructed to maintain their normal level of physical activity. Subjects completed a 3-d physical activity diary [adapted from Bouchard et al (22)] and a weighed food record [analyzed with FOODWORKS PROFESSIONAL EDITION (version 3.02; Xyris Software, Highgate Hill, Australia)] on 2 weekdays and 1 weekend day before attending the clinic at each of the 3 timepoints. Compliance was assessed by capsule count, erythrocyte FA analysis, monitoring of regular participation in supervised exercise sessions, and completion of weighed food records and physical activity diaries.

Clinical assessments
Arterial compliance, heart rate, and endothelial function
Blood pressure, HR, and compliance of large and small arteries were measured with the use of the HDI/Pulsewave CR-2000 Cardiovascular Profiler (Hypertension Diagnostics Inc, Eagan, MN) while subjects were in a supine position after a minimum 10-min rest period. Endothelial function was assessed with the use of flow-mediated dilatation (FMD) (23). The diameter of the brachial artery was measured by a single operator with the use of 2-dimensional B-mode ultrasound (LOGIQ 5; GE Medical Systems, Waukesha, WI). Optimal imaging of the artery has been described by Raitakari and Celermajer (24). For the production of reactive hyperemia, a sphygmomanometer cuff was placed around the midpoint of the forearm (ie, distal to the scanned part of the artery) and inflated to a pressure of 200 mm Hg for 5 min. Images of the artery were taken before cuff inflation, 10 s before cuff release, 10 s after cuff release, and then every 30 s for an additional 3 min. For the assessment of endothelium-independent vasodilatation, 300 µg glyceryl trinitrate (Anginine; Sigma Pharmaceuticals Pty Ltd, South Croydon, Australia) was administered sublingually after baseline images were recorded. Images were then taken every minute for 10 min. Arterial diameter was measured as the maximum perpendicular distance between the intima with the use of digital calipers (LOGIQ software, version 5 1.1X; GE Medical Systems).

Anthropometry and body composition
Each subject's height and weight were recorded to calculate the person's BMI at each laboratory visit. Body composition was assessed in all subjects with the use of dual energy X-ray absorptiometry [(DXA) Lunar Prodigy; General Electric, Madison, WI] at 0 and 12 wk. Subjects were scanned while wearing a hospital gown and while in a supine position, in accordance with the manufacturer's instructions. The DXA scanner was calibrated according to the standard procedures recommended by the manufacturer.

Laboratory analyses
Blood sample collection and plasma lipid analysis
Fasting blood was obtained at each visit by venipuncture. Plasma concentrations of triacylglycerols (including second-day repeats) and total cholesterol were measured on an automated centrifugal analyzer (Cobas-Bio, Rotkreuz, Switzerland) with the use of reagents from Roche Diagnostica (Indianapolis, IN). HDL-cholesterol concentrations were measured by using an enzymatic colorimetric test on a Hitachi Autoanalyser system 911 (Hitachi, Tokyo, Japan) with the use of Roche Diagnostica test kits. LDL-cholesterol concentrations were calculated with the Friedewald equation (25).

Erythrocyte fatty acids
Erythrocytes were isolated, washed with isotonic saline (0.9%), frozen, thawed, and then lysed in hypotonic 0.01 mol Tris EDTA buffer/L (pH 7.4), and the membrane lipids were extracted and transmethylated according to the method of Lepage and Roy (26). FA methyl esters were measured with the use of a gas chromatograph 20A (Shimadzu Corp, Kyoto, Japan) fitted with a flame ionization detector and a 50-m BPX70 column (0.32-mm internal diameter and 0.25-µm film thickness; SGE, Ringwood, Australia). Individual FAs were identified by comparison with known standards for FA methyl ester (Nuchek Prep Inc, Elysian, MN) and expressed as a percentage of total FAs quantified from peak areas.

Statistical analysis
Statistical analysis was performed with the use of STATISTICA for WINDOWS software (version 5.1; StatSoft Inc, Tulsa, OK). On the basis of previous estimates of variance in triacylglycerol assessment, 80 subjects provided 80% power at P < 0.05 for detection of a 0.2-mmol/L (10%) change in triacylglycerols. Baseline comparisons of age, sex, and height were made with one-factor analysis of variance (ANOVA) (ie, FO compared with FOX compared with SO compared with SOX). The effects of the treatments on the dependent measures were analyzed by using a 3-factor repeated-measures ANOVA with oil treatment (FO or SO) and exercise treatment (exercise or nonexercise) as the between-group factors and time (0, 6, or 12 wk) as the within-subject repeated measurement. In the case of FMD, because the magnitude of the dilatory response is inversely related to the resting brachial artery diameter (27), and, because resting arterial diameter varied at 0, 6, and 12 wk, the resting diameter measured at 0, 6, and 12 wk was included in the model as a changing covariate. When the ANOVA indicated a significant main effect, differences between individual means were identified with the use of Tukey's procedure. To optimize the analysis of differences between treatments, when appropriate, a nested ANOVA design was used to examine changes in dependent variables from baseline with the oil and exercise treatments nested in time. Pearson's product-moment correlation coefficients were used to identify relations between variables. P ≤ 0.05 was considered significant. Results are presented as means ± SEMs.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Eighty-one subjects were initially enrolled in the study; 75 subjects were randomly assigned to an intervention group. The subject enrollment and attrition patterns in the study are shown in Figure 1Go. Six subjects withdrew during the trial; 1 subject was unable to reach the required exercise intensity; 1 did not consume the required number of daily capsules; 3 subjects had a change in work or family circumstances, and 1 subject was lost to follow-up. Data for an additional 4 subjects were excluded from analysis because they failed to comply with the exercise requirements of the study. Thus, 24 men and 41 women (ie, 87% of those who began the trial) completed the trial requirements. Their characteristics at baseline (week 0) are shown in Table 1Go. No differences were observed between groups in any of these characteristics.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Effect of treatment on selected study risk factors after 12 wk of supplementation with 6 g docosahexaenoic acid–rich fish oil/d (FO), 6 g sunflower oil/d (SO), FO and exercise (FOX), or SO and exercise (SOX)1

 
Effects on erythrocyte fatty acid concentrations
FA profiles of erythrocyte membranes were obtained from 46 subjects at 0, 6, and 12 wk. The percentage of long-chain n–3 FAs [EPA + docosapentaenoic acid (DPA) + DHA] in erythrocytes increased substantially in both groups treated with FO (from 10.7% to 13.7% in the FO group and from 10.4% to 13.5% in the FOX group), which resulted in a significant oil x time interaction (P < 0.0001; Figure 2Go). This increase was entirely attributable to the change in DHA, which increased by 85% in the FO group and by 86% in the FOX group but decreased by 6% in the SO group and by 9% in the SOX group (P < 0.0001 for oil x time interaction; Figure 2Go). No change was observed in EPA or DPA in any group as a result of supplementation.


Figure 2
View larger version (24K):
[in this window]
[in a new window]

  		FIGURE 2.. Mean (± SEM) erythrocyte fatty acid concentrations for eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) after supplementation with 6 g DHA-rich fish oil/d (n = 24) or 6 g sunflower oil/d (n = 19) for 12 wk. No differences were observed between groups for EPA, DPA, DHA, or long-chain n–3 fatty acids (EPA + DPA + DHA) at baseline (P > 0.05, ANOVA). A significant oil x time interaction was observed for DHA and total n–3 fatty acids, which increased in the fish oil–supplemented group, P < 0.0001.

 
Effects on plasma lipids
Plasma lipids were marginally high in all treatment groups at baseline (Table 1Go). The modest exercise intervention undertaken in this study did not improve lipids. However, nested analysis showed that FO reduced triacylglycerols ({approx}14%) significantly (P < 0.05) more than did SO ({approx}5% increase) (Figure 3Go). At the same time, FO increased HDL cholesterol ({approx}10%) significantly (P < 0.05 for oil x time interaction) more than did SO ({approx}3% increase) (Figure 3Go). Regression analysis showed that the changes in both total long-chain n–3 FAs and DHA content in erythrocytes from 0 to 12 wk were correlated with the changes in HDL cholesterol over this same period (n–3 FA: r2 = 0.16, P = 0.008; DHA: r2 = 0.13, P = 0.02) but not with changes in triacylglycerols (n–3 FAs: r2 = 0.06, P = 0.12; DHA: r2 = 0.05, P = 0.17). Exercise was associated with a marginal increase in total cholesterol (P < 0.05 for exercise x time interaction; Table 1Go), but post hoc analysis did not find any significant differences between means.


Figure 3
View larger version (9K):
[in this window]
[in a new window]

  		FIGURE 3.. Mean (± SEM) changes in serum lipid concentrations by oil treatment after supplementation with 6 g docosahexaenoic acid–rich fish oil/d (n = 31) or 6 g sunflower oil/d (n = 31). Analysis of oil treatment nested in time showed a significant reduction in triacylglycerols (TAG) with fish oil supplementation, P < 0.05. A significant oil x time interaction was detected for HDL cholesterol, which increased in the fish oil–supplemented group, P < 0.05.

 
Effects on cardiovascular risk factors
Measures of blood pressure, HR, and arterial function were assessed in 65 subjects, except glyceryl trinitrate–mediated dilatation, which was assessed in 62 subjects (Table 1Go). ANOVA did not find any significant oil x exercise x time interactions for any of these risk factors. However, a significant (P < 0.05) oil x time interaction was observed for FMD when resting brachial artery diameter at each measurement at 0, 6, and 12 wk was used as a changing covariate (Figure 4Go). Post hoc analysis found a significantly (P < 0.01) greater improvement in FMD with FO than with SO by 12 wk. A significant (P < 0.05) exercise x time interaction was observed for small arterial compliance (SAC) (Figure 5Go), and post hoc analysis indicated a significant increase in SAC in subjects who undertook the exercise training program (P = 0.05): SAC increased by 26 ± 8% in the exercise group and by 1 ± 4% in the nonexercise group. Large artery compliance was not affected by either exercise or oil treatments.


Figure 4
View larger version (11K):
[in this window]
[in a new window]

  		FIGURE 4.. Mean (± SEM) change in endothelium-dependent dilatation of the brachial artery by oil treatment after supplementation with 6 g docosahexaenoic acid–rich fish oil/d (n = 33) or 6 g sunflower oil/d (n = 31). Endothelium-dependent dilatation was evaluated by ANCOVA (oil x exercise x time interaction) with resting artery diameter as a changing covariate. Dilatation increased significantly in the fish oil–supplemented group (P < 0.05 for oil x time interaction).

 

Figure 5
View larger version (10K):
[in this window]
[in a new window]

  		FIGURE 5.. Mean (± SEM) changes in small artery compliance (SAC) index by exercise treatment after aerobic exercise training (n = 30) or no exercise (n = 34) for 12 wk. SAC increased significantly after aerobic exercise training (P < 0.05 for exercise x time interaction).

 
Energy intake and effects on weight and body composition
As with the cardiovascular risk factors, no significant oil x exercise x time interaction was observed for energy intake after intervention. The average energy intake across all groups was 9785 ± 383 kJ at 0 wk, 9686 ± 433 kJ at 6 wk, and 9767 ± 469 kJ at 12 wk.

No significant oil x exercise x time interactions were observed for body weight or body composition, but a significant (P < 0.05) exercise x time interaction was observed for body weight (Table 1Go). Oil and exercise interactions were also evident for fat mass (exercise x time, P < 0.05; oil x time, P < 0.05; Figure 6Go), which indicated that both FO supplementation and regular aerobic exercise reduced fat mass. No significant effects of either exercise or oil treatments were observed on lean mass.


Figure 6
View larger version (7K):
[in this window]
[in a new window]

  		FIGURE 6.. Dual-energy X-ray absorptiometry assessed changes in fat and lean mass after supplementation with 6 g docosahexaenoic acid–rich fish oil/d (n = 17), 6 g sunflower oil/d (n = 18), fish oil and exercise (n = 16), or sunflower oil and exercise (n = 14) for 12 wk. Significant oil x time and exercise x time interactions were detected for fat mass, P < 0.05. Fat mass was significantly reduced by both fish-oil supplementation (P = 0.043) and aerobic exercise (P = 0.005). The oil x exercise x time interactions were not significant.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
The results of this study confirm that regular supplementation with a moderate dose of DHA-rich FO can improve multiple cardiovascular risk factors (ie, plasma triacylglycerols, HDL cholesterol, and FMD). Regular moderate-intensity exercise, either alone or in addition to the FO supplementation, had no effect on these risk factors, although it improved the compliance of small resistance arteries. It is interesting, however, that both FO supplementation and regular exercise significantly reduced body fat, which indicates the potential benefit of a combined treatment strategy for optimizing body composition.

Evidence is limited that FO supplementation can reduce body fat in overweight or obese subjects, and, in the studies that do provide evidence, little effort was made to control for the confounding influence of physical activity. Only 2 trials have investigated the effect of n–3 FA supplementation from fish, FO, or both in combination with aerobic exercise training on body composition (19, 20). Warner et al (20) investigated the effect of 12 wk of aerobic exercise training (walk or jog 3 d/wk for 45–50 min at 75–80% maximal HR) in hyperlipidemic subjects allocated to 1 of 4 groups: FOX, FO, corn oil, or control. The percentage of body fat was reduced only in the combined FOX group. However, the design of that study did not make it possible to determine how much of this change was due to exercise, because the study did not include an exercise-only control. In their study of young, lean, healthy men, Brilla and Landerholm (19) combined fish and FO with exercise and had appropriate fish and FO–only and exercise-only control groups. They found no effect on body fat with a combination of fish and FO, but it is possible that this may be because the volunteers were relatively lean at the start of the study (ie, 15–22% body fat). The present study is the first properly controlled trial to show an improvement in body composition in overweight or obese subjects after intervention with n–3 FAs and regular aerobic exercise.

Both exercise and n–3 FAs have the potential to influence the mechanisms responsible for FA mobilization and its delivery to and oxidation in muscles. By up-regulating several nuclear receptors, n–3 FAs can effectively mediate a shift in fuel metabolism away from storage and toward oxidation (28). Evidence suggests that both exercise and n–3 FAs can increase the expression of genes that code for key enzymes involved in FA transport and ß-oxidation, such as lipoprotein lipase, acetyl-CoA carboxylase-2 (29), FA translocase, carnitine palmitoyl transferase 1 (6, 30, 31), and mitochondrial uncoupling protein 3 (7). Indeed, several animal studies have shown a reduction in fat mass after supplementation with n–3 FAs (7, 8). However, few human studies have specifically investigated the effect of FO supplementation on body composition in overweight or obese adults, along with rigorous control of diet and physical activity. Couet et al (9) replaced 6 g visible dietary fat/d with 6 g FO/d for 3 wk and observed an increase in basal lipid oxidation and a reduction in fat mass in young, healthy adults. A limitation of that study was that the order of treatment was not randomized or balanced, and the changes in fat oxidation may have been due to seasonal variation or some other order effect. In a well-designed study, Groh-Wargo et al (10) reported that preterm infants fed a DHA-enriched formula for 12 mo accumulated significantly less fat mass than did their age-matched controls. In comparison, other studies that examined the effects of weight-loss diets supplemented with n–3 FAs have not observed any effects on body weight or fat mass beyond those induced by dietary restriction alone (11, 12). However, either those latter studies did not include n–3 FA control groups (11, 12) or they used the somewhat insensitive method of skinfold-thickness measurement to predict changes in body composition (11).

Exercise training was shown to improve FMD, albeit at higher intensities of exercise than was used in the present study (32). Although exercise appeared to have no effect on FMD in the present study, several studies have shown that n–3 FAs can independently improve endothelial function (33-37). This improved endothelial function may be due to increased endothelial production of nitric oxide (38), vasodilatory eicosanoids (39), or both. Recently, it was also shown that FO can increase arterial dilatation and blood flow to skeletal muscle during exercise (40), which has implications for FA delivery to sites of metabolism (ie, skeletal muscle) during physical activity. It is therefore possible that some of the change in body composition with FO supplementation in the present study may be due to improved blood flow that increased the delivery of fats to skeletal muscle, which, in conjunction with exercise and n–3 FA–induced changes in gene expression, may have facilitated fat oxidation during exercise. This proposition is indirectly supported by our own observation of an improvement in FMD, which indicated an improvement in vasodilatory capacity, in response to n–3 FA supplementation.

It is well recognized that n–3 FAs lower triacylglycerols (41-43), and our results confirm this finding. Triacylglycerol reductions of 25–30% were seen with intakes of 3–4 g EPA and DHA (44), and the 14% reduction in triacylglycerols after daily supplementation with {approx}1.9 g n–3 FAs in the present study is consistent with this magnitude of effect per gram of n–3 FAs. The 10% increase in HDL cholesterol in response to n–3 FA supplementation did not differ significantly from that reported from other studies, despite the fact that those studies used different DHA doses and durations of supplementation (42, 45). It is thought that exercise can also have a favorable effect on triacylglycerols and HDL cholesterol, but the data from the present study and the results of several meta-analyses indicate that this may not be the case, because most studies show great variability in the effects of exercise on triacylglycerols and HDL cholesterol between populations and individual persons (46, 47).

To date, only 2 trials have investigated the effect of n–3 FAs in combination with aerobic exercise training on blood lipids (19, 20). The combination of FO and 12 wk of exercise training was shown to reduce serum concentrations of LDL cholesterol and apolipoprotein B in hyperlipidemic persons more than FO alone (20). However, in healthy subjects, 10 wk of exercise training and fish and FO supplementation had no effect on HDL, LDL, or total cholesterol or triacylglycerols (19). We suggest that the lack of effect in the present study may have been attributable to the normal range of blood lipids seen in the subjects recruited for the trial.

The present trial is the first to evaluate the metabolic and cardiovascular benefits that can be achieved by combining n–3 FA supplementation and regular aerobic exercise in overweight or obese adults. We have confirmed the independent benefits of supplementation with DHA-rich FO for triacylglycerols, HDL cholesterol, and FMD and the independent benefit of regular moderate exercise for improving SAC. We also showed that both FO supplementation and regular moderate exercise reduced body fat in overweight or obese subjects who were at risk of CVD. The high compliance rate (>85%) within the present study indicates that this intervention is well tolerated, probably because of the modest level of physical activity required and because subjects did not need to change their background diet, and thus compliance may be sustainable in the longer term. Future research should evaluate the efficacy of this combined intervention over a longer duration and investigate the mechanism underlying the improvements in body composition.


   ACKNOWLEDGMENTS
 
We thank David Saint, Daniel Ninio, and Cristina Blefari for their helpful advice and assistance with various aspects of this study. We especially thank Adrian Esterman, professor of biostatistics, for his statistical advice.

The authors’ responsibilities were as follows—PRCH: initiated and designed the study, supervised the project, secured the funding, and contributed to the drafts of the publication; AMH: recruited subjects, conducted study visits and data collection; performed dietary, laboratory, and statistical analyses; and prepared the drafts of the manuscript; JDB: initiated and designed the study, supervised the project, and contributed to the drafts of the manuscript; and KJM: initiated and designed the study; supervised part of the project; helped with recruitment, study visits, and laboratory analyses; and contributed to the drafts of the manuscript. None of the authors had a personal or financial conflict of interest.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Cameron AJ, Welborn TA, Zimmet PZ, et al. Overweight and obesity in Australia: the 1999–2000 Australian Diabetes, Obesity and Lifestyle Study (AusDiab). Med J Aust 2003;178:427–32.[Medline]
  2. Ogden CL, Carroll MD, Curtin LR, McDowell MA, Tabak CJ, Flegal KM. Prevalence of overweight and obesity in the United States, 1999–2004. JAMA 2006;295:1549–55.[Abstract/Free Full Text]
  3. Grundy SM. Metabolic syndrome: connecting and reconciling cardiovascular and diabetes worlds. J Am Coll Cardiol 2006;47:1093–100.[Abstract/Free Full Text]
  4. Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA 2006;296:1885–99.[Abstract/Free Full Text]
  5. Mori TA, Woodman RJ. The independent effects of eicosapentaenoic acid and docosahexaenoic acid on cardiovascular risk factors in humans. Curr Opin Clin Nutr Metab Care 2006;9:95–104.[Medline]
  6. Power GW, Newsholme EA. Dietary fatty acids influence the activity and metabolic control of mitochondrial carnitine palmitoyltransferase I in rat heart and skeletal muscle. J Nutr 1997;127:2142–50.[Abstract/Free Full Text]
  7. Baillie RA, Takada R, Nakamura M, Clarke SD. Coordinate induction of peroxisomal acyl-CoA oxidase and UCP-3 by dietary fish oil: a mechanism for decreased body fat deposition. Prostaglandins Leukot Essent Fatty Acids 1999;60:351–6.[Medline]
  8. Ruzickova J, Rossmeisl M, Prazak T, et al. Omega-3 PUFA of marine origin limit diet-induced obesity in mice by reducing cellularity of adipose tissue. Lipids 2004;39:1177–85.[Medline]
  9. Couet C, Delarue J, Ritz P, Antoine J-M, Lamisse F. Effect of dietary fish oil on body mass and basal oxidation in healthy adults. Int J Obes Relat Metab Disord 1997;21:637–43.[Medline]
  10. Groh-Wargo S, Jacobs J, Auestad N, O'Connor DL, Moore JJ, Lerner E. Body composition in preterm infants who are fed long-chain polyunsaturated fatty acids: a prospective, randomized, controlled trial. Pediatr Res 2005;57:712–8.[Medline]
  11. Fontani G, Corradeschi F, Felici A, et al. Blood profiles, body fat and mood state in healthy subjects on different diets supplemented with omega-3 polyunsaturated fatty acids. Eur J Clin Invest 2005;35:499–507.[Medline]
  12. Krebs JD, Browning LM, McLean NK, et al. Additive benefits of long-chain n–3 polyunsaturated fatty acids and weight-loss in the management of cardiovascular disease risk in overweight hyperinsulinaemic women. Int J Obes (Lond) 2006;30:1535–44.[Medline]
  13. Garrow JS, Summerbell CD. Meta-analysis: effect of exercise, with or without dieting, on the body composition of overweight subjects. Eur J Clin Nutr 1995;49:1–10.[Medline]
  14. Miller WC, Koceja DM, Hamilton EJ. A meta-analysis of the past 25 years of weight loss research compared with diet, exercise or diet plus exercise intervention. Int J Obes Relat Metab Disord 1997;21:941–7.[Medline]
  15. Wing RR. Physical activity in the treatment of adulthood overweight and obesity: current evidence and research issues. Med Sci Sports Exerc 1999;31(suppl):S547–52.
  16. Hill JO, Wyatt HR. Role of physical activity in preventing and treating obesity. J Appl Physiol 2005;99:765–70.[Abstract/Free Full Text]
  17. Warburton DER, Nicol CW, Bredin SSD. Health benefits of physical activity: the evidence. CMAJ 2006;174:801–9.[Abstract/Free Full Text]
  18. Hornig B, Maier V, Drexler H. Physical training improves endothelial function in patients with chronic heart failure. Circulation 1996;93:210–4.[Abstract/Free Full Text]
  19. Brilla LR, Landerholm TE. Effect of fish oil supplementation and exercise on serum lipids and aerobic fitness. J Sports Med Phys Fitness 1990;30:173–80.[Medline]
  20. Warner JG, Ullrich IH, Albrink MJ, Yeater RA. Combined effects of aerobic exercise and omega-3 fatty acids in hyperlipidemic persons. Med Sci Sports Exerc 1989;21:498–505.
  21. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37:153–6.[Abstract/Free Full Text]
  22. Bouchard C, Tremblay A, Leblanc C, Lortie G, Savard R, Theriault G. A method to assess energy expenditure in children and adults. Am J Clin Nutr 1983;37:461–7.[Abstract/Free Full Text]
  23. Corretti MC, Anderson TJ, Benjamin EJ, et al. Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery. J Am Coll Cardiol 2002;39:257–65.[Abstract/Free Full Text]
  24. Raitakari OT, Celermajer DS. Flow-mediated dilatation. Br J Clin Pharmacol 2000;50:397–404.[Medline]
  25. Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972;18:499–502.[Abstract]
  26. Lepage G, Roy C. Specific methylation of plasma nonesterified fatty acids in a one-step reaction. J Lipid Res 1988;29:227–35.[Abstract]
  27. Pyke KE, Dwyer EM, Tschakovsky ME. Impact of controlling shear rate on flow-mediated dilation responses in the brachial artery of humans. J Appl Physiol 2004;97:499–508.[Abstract/Free Full Text]
  28. Davidson MH. Mechanisms for the hypotriglyceridemic effect of marine omega-3 fatty acids. Am J Cardiol 2006;98:27–33.
  29. Schrauwen P, van Aggel-Leijssen DPC, Hul G, et al. The effect of a 3-month low-intensity endurance training program on fat oxidation and acetyl-CoA carboxylase-2 expression. Diabetes 2002;51:2220–6.[Abstract/Free Full Text]
  30. Flachs P, Horakova O, Brauner P, et al. Polyunsaturated fatty acids of marine origin upregulate mitochondrial biogenesis and induce beta-oxidation in white fat. Diabetologia 2005;48:2365–75.[Medline]
  31. Tunstall RJ, Mehan KA, Wadley GD, et al. Exercise training increases lipid metabolism gene expression in human skeletal muscle. Am J Physiol Endocrinol Metab 2002;283:E66–72.[Abstract/Free Full Text]
  32. Lavrencic A, Salobir BG, Keber I. Physical training improves flow-mediated dilation in patients with the polymetabolic syndrome. Arterioscler Thromb Vasc Biol 2000;20:551–5.[Abstract/Free Full Text]
  33. Engler MM, Engler MB, Malloy M, et al. Docosahexaenoic acid restores endothelial function in children with hyperlipidemia: results from the EARLY study. Int J Clin Pharmacol Ther 2004;42:672–9.[Medline]
  34. Goodfellow J, Bellamy MF, Ramsey MW, Jones CJ, Lewis MJ. Dietary supplementation with marine omega-3 fatty acids improve systemic large artery endothelial function in subjects with hypercholesterolemia. J Am Coll Cardiol 2000;35:265–70.[Abstract/Free Full Text]
  35. Khan F, Elherik K, Bolton-Smith C, et al. The effects of dietary fatty acid supplementation on endothelial function and vascular tone in healthy subjects. Cardiovasc Res 2003;59:955–62.[Abstract/Free Full Text]
  36. McVeigh GE, Brennan GM, Johnston GD, et al. Dietary fish oil augments nitric oxide production or release in patients with type 2 (non-insulin-dependent) diabetes mellitus. Diabetologia 1993;36:33–8.[Medline]
  37. Mori TA, Watts GF, Burke V, Hilme E, Puddey IB, Beilin LJ. Differential effects of eicosapentaenoic acid and docosahexaenoic acid on vascular reactivity of the forearm microcirculation in hyperlipidemic, overweight men. Circulation 2000;102:1264–9.[Abstract/Free Full Text]
  38. Harris WS, Rambjor GS, Windsor SL, Diederich D. n–3 Fatty acids and urinary excretion of nitric oxide metabolites in humans. Am J Clin Nutr 1997;65:459–64.[Abstract/Free Full Text]
  39. James MJ, Gibson RA, Cleland LG. Dietary polyunsaturated fatty acids and inflammatory mediator production. Am J Clin Nutr 2000;71(suppl):343S–8S.[Abstract/Free Full Text]
  40. Walser B, Giordano R, Stebbins C. Supplementation with omega-3 polyunsaturated fatty acids augments brachial artery dilation and blood flow during forearm contraction. Eur J Appl Physiol 2006;97:347–54.[Medline]
  41. Howe PR, Clifton PM, James MJ. Equal antithrombotic and triglyceride-lowering effectiveness of eicosapentaenoic acid-rich and docosahexaenoic acid-rich fish oil supplements. Lipids 1999;34(suppl):S307–8.[Medline]
  42. Lungershausen YK, Abbey M, Nestel PJ, Howe PR. Reduction of blood pressure and plasma triglycerides by omega-3 fatty acids in treated hypertensives. J Hypertens 1994;12:1041–5.[Medline]
  43. Mori TA, Burke V, Puddey IB, et al. Purified eicosapentaenoic and docosahexaenoic acids have differential effects on serum lipids and lipoproteins, LDL particle size, glucose, and insulin in mildly hyperlipidemic men. Am J Clin Nutr 2000;71:1085–94.[Abstract/Free Full Text]
  44. Harris WS. n–3 Fatty acids and serum lipoproteins: human studies. Am J Clin Nutr 1997;65(suppl):1645S–54S.[Abstract/Free Full Text]
  45. Davidson MH, Maki KC, Kalkowski J, Schaefer EJ, Torri SA, Drennan KB. Effects of docosahexaenoic acid on serum lipoproteins in patients with combined hyperlipidemia: a randomized, double-blind, placebo-controlled trial. J Am Coll Nutr 1997;16:236–43.[Abstract]
  46. Kelley GA, Kelley KS, Franklin B. Aerobic exercise and lipids and lipoproteins in patients with cardiovascular disease: a meta-analysis of randomized controlled trials. J Cardiopulm Rehabil 2006;26:131–9.[Medline]
  47. Kelley GA, Kelley KS, Vu Tran Z. Aerobic exercise, lipids and lipoproteins in overweight and obese adults: a meta-analysis of randomized controlled trials. Int J Obes (Lond) 2005;29:881–93.[Medline]
Received for publication August 24, 2006. Accepted for publication December 19, 2006.




This article has been cited by other articles:


Home page
 J. Nutr.Home page
M. Asserhoj, S. Nehammer, J. Matthiessen, K. F. Michaelsen, and L. Lauritzen
Maternal Fish Oil Supplementation during Lactation May Adversely Affect Long-Term Blood Pressure, Energy Intake, and Physical Activity of 7-Year-Old Boys
J. Nutr., February 1, 2009; 139(2): 298 - 304.
[Abstract] [Full Text] [PDF]

Home page
 Sports Health: A Multidisciplinary ApproachHome page
A. Yates, J. Norwig, J. C. Maroon, J. Bost, J. P. Bradley, M. Duca, D. A. Wecht, R. Grove, A. Iso, I. Cobb, et al.
Evaluation of Lipid Profiles and the Use of Omega-3 Essential Fatty Acid in Professional Football Players
Sports Health: A Multidisciplinary Approach, January 1, 2009; 1(1): 21 - 30.
[Abstract] [Full Text] [PDF]

Home page
 Nutr Clin PractHome page
J. O. Clarke and G. E. Mullin
A Review of Complementary and Alternative Approaches to Immunomodulation
Nutr Clin Pract, February 1, 2008; 23(1): 49 - 62.
[Abstract] [Full Text] [PDF]

Home page
 J. Am. Coll. Nutr.Home page
A. M. Hill, A. M. Coates, J. D. Buckley, R. Ross, F. Thielecke, and P. R.C. Howe
Can EGCG Reduce Abdominal Fat in Obese Subjects?
J. Am. Coll. Nutr., August 1, 2007; 26(4): 396S - 402S.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hill, A. M
Right arrow Articles by Howe, P. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hill, A. M
Right arrow Articles by Howe, P. R.
Agricola
Right arrow Articles by Hill, A. M
Right arrow Articles by Howe, P. R.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS