Obesity has become a significant epidemic in both developed and developing countries due to its association with increased morbidity and mortality [1]. Overweight and obesity have also reached epidemic proportions in Portugal [2,3]. The consequences of obesity include physical, psychological and social aspects, which impact one’s quality of life. Although genetics is a strong component of obesity [4], lifestyle and environmental changes typical of industrialized societies are more likely to explain the recent obesity epidemic [5]. Indeed, obesity occurs when energy intake exceeds energy expenditure over time.

Physical inactivity has been viewed as one of the most important risk factors for coronary heart disease and other chronic diseases [6,7]. For instance, physical activity (PA) levels, as well as sedentary behavior appear to play an important role in long-term weight regulation [8]. Thus, the need to increase PA is a public health priority [9]. Current public health campaigns to reduce obesity and type 2 diabetes have largely focused on increasing PA and/or exercise, but have paid little attention to the reduction of sedentary behaviors [10]. Moreover, some studies have shown that non-exercise activity thermogenesis (NEAT) plays a key role in differences of energy expenditure in special populations such as the obese [11]. In fact, altering one’s postural allocation from a seated to standing position or engaging in light ambulation has been shown to significantly increase energy expenditure [11]. Conversely, it has been shown that workers performing their job functions in their usual fashion (seated) might expend more than 200 extra calories daily using a walking workstation [12]. Therefore, sitting is strongly and inversely associated with caloric expenditure that is likely an important cause of the obesity epidemic. Indeed, in our daily contemporary life, sitting is a predominant behavior for many hours per day [13].

Several studies have shown positive associations between BMI and different measures of sedentary behavior, such as TV viewing [14–16] motorized transportation [17,18] occupational sitting time [19] or sedentary behaviors during leisure time [20,21]. However, these studies fail to address total sedentary behavior and/or adjust the analysis for total PA.

In this context, the purpose of this study was to examine cross sectional relationship between body mass index (BMI) and total sitting time (i.e., sitting across all three main domains: transportation, occupational and leisure time), adjusting the analysis for total PA time in Azorean adults.

Of the 4,091 men included in this study, 96.3% were employed full-time. Of those, 73.4% of men had a low level of education (≤9 school years) and 71% were manual workers.

Participants had an average BMI of 26.3 ± 3.7 kg/m² and spent on an average 25.5 ± 17.5 % of their waking hours sitting (about 250 min/day). Descriptive characteristics are presented in Table 1.

As depicted in Table 2, men with high sitting time and insufficient PA presented a highest mean of BMI −26.8 ± 3.8 kg/m² (p < 0.05 for all).

Linear regression analysis showed that after adjustments for potential confounders total sitting time was positively associated with BMI (B = 0.078; p < 0.001—model 2).

In conclusion, our results show that total sitting time was positively associated with BMI after adjustments for potential confounders (including total PA time). Although the cross sectional design precludes us from establishing causality our findings emphasize the importance of reducing sedentary behavior to decrease the risk of obesity.