Aerobic exercise, lipids and lipoproteins in overweight and obese adults: a meta-analysis of randomized controlled trials

Abstract

Objective: Use the meta-analytic approach to examine the effects of aerobic exercise on lipids and lipoproteins in overweight and obese adults.

Data sources: (1) Computerized literature searches, (2) cross-referencing from review and original articles, (3) hand searching, and (4) expert review of reference list.

Study selection: (1) randomized controlled trials, (2) aerobic exercise > or =8 weeks, (3) adult humans > or =18 y of age, (4) all subjects overweight or obese (BMI > or =25 kg/m(2)), (5) studies published in journal, dissertation, or master's thesis format, (6) studies published in the English-language, (7) studies published between 1 January 1955 and 1 January 2003, (8) assessment of one or more of the following lipid and/or lipoprotein variables: total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and triglycerides (TG).

Data abstraction: Dual-coding by the first two authors (inter-rater agreement=0.96).

Results: In total, 13 studies representing 31 groups (17 exercise, 14 control), 613 subjects (348 exercise, 265 control), and up to 17 outcomes were available for pooling. Across all categories, random-effects modeling resulted in statistically significant improvements for TC (X +/- s.e.m., - 3.4+/-1.7 mg/dl, 95% CI, - 6.7 to - 0.2 mg/dl) and TG (X +/-s.e.m., - 16.1+/-7.3 mg/dl, 95% CI, - 30.2 to - 2.1 mg/dl) but not HDL (X +/- s.e.m., 1.6+/-0.8 mg/dl, 95% CI, - 0.02 to 3.2 mg/dl) or LDL (X +/-s.e.m., - 0.5+/-1.3 mg/dl, 95% CI, - 3.0 to 2.0 mg/dl). Changes were equivalent to improvements of 2% (TC), 11% (TG), 3% (HDL), and 0.3% (LDL). After conducting sensitivity analyses (each study deleted from the model once), only decreases in TG remained statistically significant. Increases in HDL were associated with increases in maximum oxygen consumption (VO(2 max) in ml/kg/min, r=0.75, P=0.002) and decreases in body weight (r=0.77, P<0.001), while decreases in LDL were associated with decreases in body weight (r=0.75, P=0.009).

Conclusions: Aerobic exercise decreases TG in overweight and obese adults. However, a need exists for additional randomized controlled trials in various overweight and/or obese populations above and beyond those included in our analysis.

Figure 1

Forest plot for changes in TC and 95% CI for each outcome as well as the overall weighted mean difference and 95% CI. The size of the black boxes for each outcome represents the weight given to that outcome. The overall mean difference is shown by the middle of the diamond while the left and right extremes of the diamond represent the corresponding 95% CI. The vertical dashed line represents the overall mean.

Figure 2

Cumulative meta-analysis, ranked by year, for changes in TC. Each horizontal line and black square represent the summary of results as studies from the previous years are combined with the listed study. The black squares represent the point estimates while the lines represent the lower (left) and upper (right) 95% CI. Estimates are based on 17 outcomes from 13 studies.

Figure 3

Forest plot for changes in HDL and 95% CI for each outcome as well as the overall weighted mean difference and 95% CI. The size of the black boxes for each outcome represents the weight given to that outcome. The overall mean difference is shown by the middle of the diamond while the left and right extremes of the diamond represent the corresponding 95% CI. The vertical dashed line represents the overall mean.

Figure 4

Cumulative meta-analysis, ranked by year, for changes in HDL. Each horizontal line and black square represent the summary of results as studies from the previous years are combined with the listed study. The black squares represent the point estimates while the lines represent the lower (left) and upper (right) 95% CI. Estimates are based on 15 outcomes from 11 studies.

Figure 5

Forest plot for changes in LDL and 95% CI for each outcome as well as the overall weighted mean difference and 95% CI. The size of the black boxes for each outcome represents the weight given to that outcome. The overall mean difference is shown by the middle of the diamond while the left and right extremes of the diamond represent the corresponding 95% CI. The vertical dashed line represents the overall mean.

Figure 6

Cumulative meta-analysis, ranked by year, for changes in LDL. Each horizontal line and black square represent the summary of results as studies from the previous years are combined with the listed study. The black squares represent the point estimates while the lines represent the lower (left) and upper (right) 95% CI. Estimates are based on 14 outcomes from 10 studies.

Figure 7

Forest plot for changes in TG and 95% CI for each outcome as well as the overall weighted mean difference and 95% CI. The size of the black boxes for each outcome represents the weight given to that outcome. The overall mean difference is shown by the middle of the diamond while the left and right extremes of the diamond represent the corresponding 95% CI. The vertical dashed line represents the overall mean.

Figure 8

Cumulative meta-analysis, ranked by year, for changes in TG. Each horizontal line and black square represent the summary of results as studies from the previous years are combined with the listed study. The black squares represent the point estimates while the lines represent the lower (left) and upper (right) 95% CI. Estimates are based on 14 outcomes from 10 studies.