We have previously demonstrated that a single, moderate-intensity 30-min bout of aerobic or resistance exercise improves risk factors associated with cardiovascular disease in overweight and obese adults
], however, fasting levels of TG, cholesterol, glucose and insulin were not affected in the short-term. It is possible that some physiological changes are only seen after a longer period of training. Thus, we conducted a 12-week chronic study to explore the impact of aerobic, resistance, or combined exercise at a moderate-intensity for 30 min, five days/week. Significant decreases in body weight, BMI and total body fat were seen in the Combination group compared to Control and Resistance groups. Similarly, significant improvements were demonstrated in fat percentage, abdominal fat percentage and cardio-respiratory fitness in the Combination group compared to Control. Therefore, moderate-intensity training over 12-weeks using a variety of training modalities has beneficial effects in CVD risk factors in overweight and obese individuals compared to no exercise.
Body weight and BMI in the Combination group were significantly lower than Control and Resistance groups at 12 weeks but not Aerobic group. The absence of significant decreases in Aerobic and Resistance groups may have been due to the 30-min moderate-intensity exercise being insufficient stimuli compared to training loads reported in other studies
]. However, Park et al.
] also found that combination exercise was more effective for body composition improvements than aerobic exercise alone.
The Combination intervention produced the greatest improvements in body composition, significant decreases in total body fat, fat percentage, android fat percentage and gynoid fat percentage. Park et al.
] also observed that combination exercise was more effective in decreasing visceral fat than aerobic exercise. High levels of fat, especially in the abdomen, increase the risk of developing Type 2 diabetes and CVD
], thus combination exercise training can be beneficial in reducing this risk.
Interestingly, a similar study by Church et al.
] observed a significant decrease in body mass in the Combination group compared to Control and Resistance groups after 9 months of training, comparable to our findings. This indicates that the effects of aerobic and resistance exercise interact to have a greater effect than either type alone. However, the mechanisms involved are unclear and further investigations are warranted.
We did not observe any significant reduction in lipids, glucose or insulin after 12 weeks of training, which is inconsistent with previous studies. Generally, those studies involved higher levels of exercise
]. ApoB48 was significantly lower after training in the Resistance group compared to Control but not compared to aerobic and combination exercise. Changes to apoB48 were not reported in other studies investigating the effects of exercise training. As apoB48 is a marker for chylomicron particles, a decrease indicates a lower number of particles circulating in the blood, which is associated with decreased risk of atherosclerosis
We observed a small but significant decrease in the RQ in the Resistance group. Other studies have demonstrated a decrease in resting non-protein RQ in older women after 16 weeks resistance training
] indicating a shift in substrate utilization to increased lipid oxidation for energy. A hypocaloric diet also decreases the RQ and increases fat oxidation
]. This matches our observation of a significant decrease in energy intake in the Aerobic and Resistance groups at week 12. This change in substrate utilization may have a beneficial impact on body fat and obesity in the long-term.
We observed a significant increase in estimated maximum oxygen uptake (VO2max
) in the Combination group. Greater cardio-respiratory fitness has long been associated with decreased risk of disease and death
]. Obese individuals with higher fitness levels generally have lower mortality rates compared to sedentary normal-weight counterparts
]. Previous studies have shown increases in VO2max
from baseline levels after resistance exercise training
] and combined aerobic and resistance exercise training
]. In our study, a moderate-intensity of 60% of estimated HRR was used for aerobic exercise to target greater fat oxidation rather than cardio-respiratory fitness improvements per se
]. Combination training was more effective at increasing cardio-respiratory fitness compared to Control but not aerobic and resistance training. The lack of improvement in the Aerobic group was possibly due to variability in participants. Whilst most participants displayed an increase in cardio-respiratory fitness level, some showed a reduction in cardio-respiratory fitness level (mean −5.3 mL/kg/min, n
3) despite the training. Participant factors such as stress, anxiety and time since the last exercise session may have affected the test results. Cardio-respiratory fitness levels in the Aerobic group may eventually have increased significantly given a longer training period, such as that by Church et al.,
] which employed a six month intervention. However, our Combination intervention demonstrates that improvements in cardio-respiratory fitness in the overweight and obese can be achieved following the Australian physical activity recommendations.
The present study had a number of limitations. Participants were mainly female despite a higher prevalence of overweight and obesity in males in Australia
]. Due to limited sample size, our study may have been underpowered to detect significant changes in some variables. As several groups of participants were staggered over a 15–month period, seasonal changes may have been a factor
]. Reported energy intake in all groups decreased over the course of the intervention and this may have contributed to changes in body weight and composition. Monitoring the intensity and frequency of exercise was another challenge. Despite the completion of exercise diaries and regular contact with the researcher, we were reliant on participant honesty and accuracy in their self-reported information. If participants in the aerobic group did not complete the prescribed exercise this may explain the lack of improvements in the current study.