Introduction: Since 1980, the prevalence of overweight and obesity has increasedand a total of 2.1 billion individuals are considered overweight or obese. Obesity is amajor public health concern because it is a key risk factor for a wide range of chronicdiseases. Both obesity and metabolic syndrome are becoming worldwide epidemicsat an alarming rate.Although both dietary and physical exercise interventions are effective fat-lossstrategies, programmes that also include physical activity are more effective in theshort and long terms. Besides, moderate levels of hypoxic training results inimprovements in body composition and other cardiometabolic risk factors. Inaddition to leading to improvements in fat mass, promising benefits for somemetabolic risk factors such as blood glucose and blood pressure have been reportedwith the use of prolonged programmes of moderate hypoxia. Related to exercisetherapies, current weight management exercise strategies based in moderateintensity are ineffective in the long term. Conversely, high-intensity has beensuggested as an exercise modality that could lead to greater adipose tissue loss andis more effective in reducing abdominal and visceral fat mass.Thus, hypoxia exposure combined with high-intensity exercise may have a synergisticeffect due to the fact that both stimuli regulate crucial pathways in the metabolismof glucose and lipids; this could be considered a new feasible and valuabletherapeutic strategy. However, more research is needed to examine the impact ofthis new therapy on physiological responses, the underlying mechanisms, and theoptimal combination of exercise and hypoxia.Aims: The aims of the present thesis were a) to update the current scientific statusregarding active hypoxia conditions in obese humans and b) to investigate effects ofdifferent HIT in normobaric hypoxic conditions on fat mass and differentcardiometabolic risk factors in overweight/obese women. These general aims werefurther divided into four specific aims.Methods: The four specific aims of this thesis were investigated through onesystematic review of randomized controlled trials; two four-group randomizedcontrolled workouts investigating the effects of simulated hypoxia combined withhigh-intensity exercise on human body composition; cardiometabolic risk markers;and, finally, the detraining effects on cardiometabolic risk markers.Three well-known databases were selected: EMBASE, MEDLINE, and Web of Science.The studies were selected using the following inclusion criteria: (a) healthyoverweight or obese human adults, (b) studies using randomized controlled trials, (c)original experimental studies, (d) English language, and (e) therapies withintermittent hypoxia and exercise.For the control trial, the participants included 82 overweight/obese women, whostarted a 12-week programme of 36 sessions, and were randomly divided into fourgroups: (1) interval training in hypoxia (IHT; FiO2 = 17.2%; n = 13), (2) interval trainingin normoxia (INT; n = 15), (3) sprint interval training in hypoxia (SITH; FiO2 = 17.2%; n= 15), and (4) sprint interval training in normoxia (SITN; n = 18). Anthropometric andbody composition measures (body mass, body mass index, percentage of total fatmass, percentage of trunk fat mass, muscle mass, waist circumference, hipcircumference, waist-hip ratio), basal metabolic rate (basal metabolic rate, respiratoryquotient, fat and carbohydrate oxidation, and fat and carbohydrate energy),biochemical and clinical measures (glucose, triglycerides, total cholesterol, systolic,diastolic and mean blood pressure, and resting heart rate) were assessed. Outcomeswere measured at baseline (T1), after 18 training sessions (T2), during the 7 days afterthe last session (T3), and 4 weeks after the last session (T4). All time points forevaluations consisted of the same measurements.Results and discussion: Effects of cyclical hypoxia combined with moderate-intensityexercise on cardiometabolic parameters in adult obese people were analysed fromfive studies. Compared with baseline, body composition parameters and systolicblood pressure improved after hypoxic conditions in some of the analysed studies.However, other cardiometabolic parameters, such as the lipid profile or the aerobiccapacity, were not reduced significantly.A training programme of 12 weeks of high-intensity training in hypoxia reducedgeneral and abdominal fat mass, increased muscle mass, and altered triglyceridesand total cholesterol differently compared with normoxia groups. The percentage oftrunk fat mass decreased in the participants who underwent hypoxic high-intensitytraining, despite the cessation of the training programme. These results are especiallyrelevant because a programme of HIT in hypoxia may mitigate disadvantages thatoverweight/obese confront; this would enable the development of high-intensitytraining programmes which take less time and help to maintain the obtained benefitseven four weeks after the cessation of the programme.Conclusions: The results were inconsistent, but suggested that combined intermittenthypoxia with exercise may help to improve cardiometabolic parameters in obesepeople. Define optimal dose of hypoxia and intensity exercise are necessary in futureinvestigations. High-intensity interval training under normobaric intermittent hypoxiaduring 12 weeks is promising for reducing body fat content with a concomitantincrease in muscle mass. Both protocols under normobaric cyclic hypoxia were moreeffective in causing a decrease in abdominal fat in overweight/obese women and,possibly, beneficial changes on triglycerides at the middle of the program. Besides,after a period of 4 weeks of the percentage of fat mass located in the trunk improvessignificantly, an effect that was not observed in the normoxia groups. Overall,biochemical parameters remained unchanged after the detraining period. It may beparticularly feasible for overweight/obese patients for whom exercise capacity islimited by orthopaedic conditions.