The objectives of this study were to describe the prevalence of physical inactivity in Mexican adults, to examine changes in the prevalence of physical inactivity between 2006 and 2012, and to examine the association between physical inactivity with several sociodemographic and biological characteristics. The adjusted physical activity estimate indicates that 19.4% of the adult Mexican population was physically inactive in 2012. This represented an absolute increase of 6.0%, or a relative increase of 44%, since 2006. At the same time, 28.8% of the adult population was sufficiently active in 2012 (e.g., met minimal physical activity recommendations), and 51.8% were considered to be very active. Finally, MVPA levels varied considerably according to gender, age, BMI, region of the country, SES, and education level.
Based on unadjusted IPAQ data from the ENSANUT 2006, Gomez et al. previously reported that 11% of the adult population in Mexico did not meet physical activity recommendations . Outside of Mexico, adherence to physical activity recommendations has been reported for 121 other countries, as recently summarized by Hallal et al. . These authors estimated that the global prevalence of physical inactivity in adults is 31%, with a range of 5% (Bangladesh) to 72% (Malta). For the Mexican population, they reported a physical inactivity prevalence of 37.7%, which is 18.3 points higher than the value we reported in our article (19.4%). Potential reasons for this discrepancy includes the use of different physical activity questionnaires and difference in the physical activity and inactivity were classified.
Although the number of minutes of MVPA was significantly different between men and women, the probability of being physically inactive was not significantly lower in women after adjusting for sociodemographic variables. This result is in line with what has been found in other Latin American countries .
We observed that 60–69 year olds were approximately 1.58 times more likely to be physically inactive than 20–29 year olds. This finding is consistent with age differences in MVPA that have been described globally [1, 5]. Conversely, while SES is negatively associated with physical inactivity in developed countries , the opposite pattern has been observed in Mexican adults in our study and previous Mexican research [20, 23]. Thus, Mexican adults within the highest SES group were significantly less likely to engage in recommended levels of MVPA. A potential explanation for the SES gradient observed in Mexico is that people with a lower SES have the most physically demanding jobs, and due to a lack of resources do not have access to motorized transportation.
As noted previously in ENSANUT 2006  and in our study for ENSANUT 2012, obese adults are less active than adults with a BMI in the healthy range. In fact, in our study obese individuals were 1.30 times more likely to be physically inactive. Obesity is an independent risk factor for several chronic diseases such as type 2 diabetes, cardiovascular disease, stroke, and several cancers [19, 24]. Thus, part of the pathway through which physical inactivity influence non-communicable disease risk is by contributing to obesity. However, it is important to note that physical inactivity has an effect on non-communicable chronic disease risk that is independent of its effects on obesity . Regardless of the pathways by which physical inactivity influences health, it is clearly an important risk factor for non-communicable disease within the Mexican population. Recently, Lee et al.  estimated that 6% of coronary heart disease cases and 8% of type 2 diabetes cases in the Mexican population are directly attributable to physical inactivity . Additionally, they estimated that life expectancy in Mexican adults would increase by 0.76 years if physical inactivity was eliminated . Taken together, these findings highlight the importance of having policies and programs in place within Mexico to increase the physical activity levels of the population .
The differences between the unadjusted and adjusted MVPA data were quite striking. For instance, the mean MVPA in ENSANUT 2012 was 897 min/week before being adjusted and 310 min/week after being adjusted. We felt that it was important to provide adjusted estimates because several previous studies have reported that self-reported measures of MVPA are greatly overestimated [13, 14]. This was confirmed by our validity study in Mexican population . We believe that the adjusted physical activity estimates are a closer approximation of the true physical activity levels of the population and recommend that the adjusted data be used in future papers and reports that present data on the physical inactivity levels of Mexicans obtained using the IPAQ short.
An important limitation of this study is that the physical activity data were self-reported. We attempted to correct for the over-reporting by adjusting the self-reported IPAQ with the developed equation . However, such an adjustment is far from perfect as self-reported and accelerometer measures of MVPA are only modestly correlated [10, 11, 26–28]. This adjustment has the disadvantage to enclose moderate and vigorous activity into a single measure. Although moderate and vigorous activities are not separable with this measure, it was appropriate for estimating prevalence of physical inactivity at the given cut-points. In addition, the validity study was conducted on a reasonably small (n = 262) sample of employed adults from Mexico City and the generalizability of the findings from that sample to the more diverse ENSANUT sample is unknown.
Another important limitation is the use of the short form IPAQ to estimate physical activity levels. Although it is the most commonly used instrument within large-scale surveys, this instrument overestimates physical activity when compared to other questionnaires  and underestimates physical activity levels when compared to long form IPAQ . This underestimation could be related to the fact that the short form IPAQ does not measure the different physical activity domains (e.g., recreational physical activity, inside home activities, transportation) .