Strategies designed to reduce adiposity and cardiovascular-accompanying manifestations have been based on nutritional interventions conjointly with physical activity programs. The aim of this 13-week study was to investigate the putative benefits associated to hypoxia plus exercise on weight loss and relevant metabolic and cardiorespiratory variables, when prescribed to obese subjects with sleep apnea syndrome following dietary advice. The participants were randomly distributed in the following three groups: control, normoxia, and hypoxia. All the subjects received dietary advice while, additionally, normoxia group was trained under normal oxygen concentration and Hypoxia group under hypoxic conditions. There was a statistically significant decrease in fat-free mass (Kg) and water (%) on the control compared to normoxia group (p < 0.05 and p < 0.01, respectively). Body weight, body mass index, and waist circumference decreased in all the groups after the study. Moreover, leukocyte count was increased after the intervention in hypoxia compared to control group (p < 0.05). There were no statistically significant variations within groups in other variables, although changes in appetite were found after the 13-week period. In addition, associations between the variations in the leukocyte count and fat mass have been found. The hypoxia group showed some specific benefits concerning appetite and cardiometabolic-related measurements as exertion time and diastolic blood pressure, with a therapeutical potential.

We have read with great interest the article by Kong et al [1] about a new strategy to combat obesity and accompanying adverse features, in which normobaric hypoxia training induced more weight loss than normoxia training after 4 weeks on overweight young adults. Such findings complete the view that a modest intermittent hypoxia influence circulating measures of inflammation in healthy humans as reported in a previous issue of Sleep and Breath [2] Indeed, obesity is a growing public health burden affecting affluent societies as well as transition countries [2] with prevalence rates higher than 30% in many regions. An energy intake higher than the energy expended for basal metabolic rate, physical activity or thermogenic functions is claimed as the explanation for an excessive fat accumulation, where genetics, obesogenic environmental conditions and other factors such as inflammation and oxidative stress could also be involved [3].Current therapies for obesity treatment and different approaches for body weight management involve dietary interventions based on energy restriction and/or shifts on macronutrient distribution, physical activity programs, pharmacological prescription or surgical procedures. Unfortunately, none of these therapies, either alone or combined, have been able to be fully satisfactory. Therefore, the search for alternative therapies such as the administration of thermogenic agents, satiating compounds, homeorhetic molecules, etc., are under investigation, including the possibility to use oxygen-based strategies [3].In this context, abnormal adiposity has been associated not only with self-esteem and image-related psychological problems, but also with insulin resistance, hypertension, osteoarticular problems, cancer, fatty liver disease, etc., where the link between some of these diseases appears to be the mild and chronic inflammation occurring in obesogenic conditions. Thus, one of the mechanisms triggering inflammation has been associated with adipose tissue hypoxia [4] or increased oxygen tension [5], which affect a number of genes such as HIF-1a, MCP-1, IL-6, GLUT-1, ANGPTL-4 and PPAR-γ [6] that could be involved as a cause or as a consequence reaction to pathologically low or high oxygen conditions. Interestingly, as we hypothesized previously [3] and Kong et al have nicely demonstrated in their article [1], hypoxia is not only an ethological factor or a manifestation of disease, but also a therapeutic tool following different patterns (hypoxic exposure, hypoxic training, intermittent hypoxia under hyperbaric and normobaric conditions), which has been used for pre-acclimation in climbers, or to improve athletes performance as well as for heart, respiratory and nervous system diseases or to regulate body weight [7]. Thus, putative compensatory mechanisms and responses to hypoxia has been described for the respiratory