Our study explored the association between daily step count, step intensity and overweightness/obesity indicators in older women in the community. To the best of our knowledge, this is the first study to report on the joint effect of step count and step intensity on overweightness/obesity and the recommended amount of step intensity in older Chinese community women. Overall, this cross-sectional study showed that in a fully adjusted model, total daily steps, peak 1 cadence and peak 30 cadence were all significantly and negatively associated with indicators of overweightness/obesity and the effect was most pronounced in the HSHI. Notably, daily step count is not associated with BMI. Older community women were more likely to be overweight/obese when daily step count, peak 1 cadence, peak 30 cadence was less than 9 135, 126.9steps/min, 89.0steps/min respectively. This suggests that increasing the count or intensity of steps in walking activities is an effective method for weight reduction.
One of the significant findings emerging from this study is that daily steps were an independent factor in reducing the risk of overweightness/obesity. Each 1 000 step increase in daily steps was associated with a 0.2%, 0.05kg, 0.16kg and 0.12kg reduction in BFR, VFM, SFM and TFM respectively. There has been numerous evidence that daily step counts reduce the risk of overweightness/obesity. Bruce Wayne Bailey et al.[39] who found that daily step counts in young adult women were associated with BFR, but this relationship diminished with increasing steps. An intervention study found a reduction in weight in subjects by increasing participants' steps by 1 000 steps per week (up to 10 000 steps)[40]. Other studies have found that people with high step counts have lower BMI[41] and that increasing step count reduces BMI [13, 14]. Nevertheless, these studies did not take into account the effect of step intensity. We found that the linear association between total daily steps and BMI disappeared after additional control for peak 1 cadence. It’s consistent with the findings of Gerson Ferrari et al. [15] who found that daily step count was not associated with BMI in women. However, in addition to BMI, we included more disaggregated indicators of overweightness/obesity. Such as BFR, and their negative linear association with daily step count persisted after adjusting for peak 1 cadence and other confounders. It seems possible that these results are due to BMI can be influenced by muscle mass, organs, bone structure and fat mass, but cannot be used to measure body tissue composition. It cannot be used as an absolute measure of being overweight/obese. What’s more, the ageing process can lead to nutritional, morphological and physiological changes, such as a decrease in height, weight, muscle mass and fat mass (especially in women). And most older people will lose more muscle tissue than fat [42, 43]. So BMI can underestimate the level of obesity in older women to some extent. Overall, although we did not find an independent association between daily steps and BMI, in the fully adjusted model, daily steps were significantly negatively associated with other indicators of overweightness/obesity. These outcomes still suggests that daily step counts have an effect on indicators of overweightness/obesity and are an independent risk factor for reducing it. In order to provide further walking advice to older community women to improve their overweightness/obesity, ROC analysis was conducted. As BMI is not an appropriate measure of obesity levels in older women [42, 43], predictions were made based on BFR classification criteria only in this study. Our results concluded that higher steps was associated with a reduction in overweightness/obesity. The optimal cut-offs for predicting overweightness/obesity of steps per day were 9 135 (AUC = 0.59). Ferrero-Hernández, P et al. conducted a ROC analysis according to waist-to-height ratio (WHtR) and waist-to-hip ratio (WHR) classifications in women aged 51–65 years. They came up with optimal cut-off values of 9 127 steps (AUC = 0.586) and 10 465 steps (AUC = 0.546) per day to distinguish overweightness/obesity[44]. It’s close to our results and supports our study.
After controlling for confounding factors such as total daily steps, we found that peak 1 cadence and peak 30 cadence were significantly negatively associated with each of the overweightness/obesity indicators. Each 1 step/minute increase in peak 1 cadence was significantly associated with a 0.05kg/m2, 0.09%, 0.04kg, 0.09kg, and 0.08kg decrease in BMI, VFM, SFM, and TFM, respectively. Each 1 step/minute increase in peak 30 cadence was associated with a 0.05kg/m2, 0.07%, 0.03kg, 0.08kg and 0.06kg decrease in BMI, BFR, VFM, SFM and TFM, respectively. This suggests that step intensity is an independent factor in reducing the risk of overweightness/obesity. Peak cadence, as the best natural effort in a free-living environment, have often been applied in recent years to explore the association with risk of various diseases [36]. For example, a cross-sectional study concluded that daily step count and peak cadence appear to offset the risk of sedentary time and cardiometabolic health in older adults [45]. In addition, studies have also found the association between peak 30 cadence and overweightness/obesity indicators[29]. Their results suggest that peak 30 cadence is inversely related to body weight, waist circumference, and BMI, consistent with our results. However, John M Schuna Jr et al.[28] found that the association between BMI and peak 30 cadence was reduced and the difference was not statistically significant after controlling for daily steps. This may be due to the heterogeneity of analytical method used. The former used Spearman's correlation analysis, which performed a biased correlation analysis by controlling for individual variables. Whereas we used a multivariate linear regression model for data analysis by controlling for multiple confounding factors, controlling for more covariates. No studies have yet explored the association between peak 1 cadence and indicators of overweightness/obesity. Our results shed new light on this. In short, step intensity was associated with reduced risk of overweightness/obesity. Based on these results and the ROC analysis, we found that the peak 1 cadence and peak 30 cadence cut-off values for differentiating overweightness/obesity were 126.9steps/min (AUC = 0.61), 89.0steps/min (AUC = 0.59) respectively. These recommendations reported in this study should be considered as a simple first attempt. Our results provide a new reference for public recommendations and health programs to improve overweightness/obesity in older community women.
Walking activity indicators include both the step counts and intensity. In daily walking activities, there are cases where people walk a lot but slowly or walk less but fast, so we further investigated the joint effect of step count and step intensity on overweightness/obesity in older women.Our results show that the association with overweightness/obesity is stronger in the HSHI compared to the LSLI. It indicating that the HSHI was more effective than the LSHI in reducing overweightness/obesity than the HSLI. To our knowledge, no studies have reported the combined effect of step count and walking intensity on indicators of overweightness/obesity in older community women. But previous cohort studies have found a joint associations between step counts and intensity with the risk of hospitalization and all-cause mortality. The group having high step counts and intensity are significantly associated with lower risk of hospitalisation and all-cause mortality in older adults [46]. And there is also evidence for the joint association between daily steps, step intensity and diabetes risk[47]. It suggests that at a certain accumulation of daily step count, the greater the proportion of high-intensity steps, the lower the risk of diabetes. We report for the first time the joint effect of different combinations of step count and intensity on overweightness/obesity. Our results can be further translated into three specific messages that can be easily conveyed to the public: i. Under the condition of a certain intensity, the more walking, the better. ii. The higher the walking intensity, the better, given a certain steps counts and the ability to do so. iii. To improve overweightness/obesity, the most effective way is to increase the daily step count and walking intensity at the same time.
There are several limitations to this study. Firstly, it is a cross-sectional study and the findings do not reflect a causal association between overweightness/obesity and daily step counts and intensity, and future in-depth studies on vertical design are needed. Secondly, the study population was from one city in China, therefore it is not fully representative of older Chinese people. Thirdly, the participants were from a coastal city and may have overlooked the measure of water-related activities such as swimming on overweightness/obesity. What's more, it is difficult to obtain an area under the ROC curve of 0.9 or more as the results are often confounded by various factors in studies on physical fitness and health promotion. Hence, in condition of this study, our daily step count and cadence cut points should only be used as recommended thresholds rather than assessment criteria in a clinical setting. Finally, participants were based on a voluntary basis and those who were willing to participate in this study may have been healthier.