Is it the resistance training itself or the combined associated weight loss that improves the metabolic syndrome-related phenotypes in postmenopausal women?

Abstract

Dear editor We read the article entitled “Resistance training improves isokinetic strength and metabolic syndrome-related phenotypes in postmenopausal women” by Oliveira et al1 with great interest. In the study, the authors examined the effects of 12 weeks of resistance training (RT) on metabolic syndrome-related phenotypes in postmenopausal women. They reported that total cholesterol, low-density lipoprotein cholesterol levels, total cholesterol/high-density lipoprotein cholesterol ratio, blood glucose, basal insulin, and homeostatic model assessment of insulin resistance were all significantly reduced with RT (P<0.01). Accordingly, they concluded that a 12-week progressive RT program induces beneficial alterations on metabolic syndrome-related phenotypes in postmenopausal women. While we appreciate this detailed study,1 we have some comments on the results and subsequent conclusions. In their study, Oliveira et al reported that, in addition to the aforementioned parameters (indices), body mass (68.9±13.3 kg before RT vs 68.1±13.2 kg after 12 weeks’ RT), body mass index (BMI) (28.4±5.0 kg/m2 before RT vs 27.9±4.8 kg/m2 after 12 weeks’ RT), and waist circumference (WC) (98.3±13.2 cm before RT vs 94.6±12.6 cm after 12 weeks’ RT) were also significantly decreased after the RT period.1 Increased body weight is a very well-known major risk factor for the metabolic syndrome documented both in cross-sectional and longitudinal studies.2,3 Obesity, particularly abdominal obesity, is associated with insulin resistance. Furthermore, the importance of weight management in preventing progression of metabolic syndrome components has also already been illustrated.4 Hence, we suggest that the reported association of RT with beneficial alterations on metabolic syndrome-related phenotypes may be due to the combined weight, BMI, and WC reduction, rather than the effect of RT itself. In line with our comment, in the study aimed at addressing whether RT alone improves cardiometabolic health in overweight and obese adults, Bateman et al5 concluded that RT was not effective at improving the metabolic syndrome score; however, aerobic training (AT) was effective. Combined AT and RT was similarly effective but not different from AT alone. Importantly, in this study, body mass was significantly decreased with AT and combined AT–RT, but was not changed with RT alone.5 In a similar study aiming to clarify effects of exercise modality on insulin resistance, Davidson et al6 also reported that insulin resistance improved compared with controls with aerobic exercise alone and in the combined exercise groups, but not in the resistance exercise group. Again, in this later study, body weight was not significantly reduced in the resistance exercise group.6 On the other hand, Dunstan et al7 reported that high-intensity progressive RT was effective in improving glycemic control in older patients with type 2 diabetes when combined with moderate weight loss. The results of these studies5–7 suggest that RT seems not to affect the metabolic syndrome parameters if not accompanied with weight, BMI, or WC reduction. Therefore, we suggest that in the Oliveira et al1 study, RT and weight loss should be analyzed with regression analysis for their relation to metabolic syndrome parameters in order to clarify whether RT itself is independently associated with metabolic syndrome.