According to a recent expert consensus1, obesity is defined as a pathology characterized by a body mass index greater than 30 kg/m² associated with an excess of fat mass responsible for clinical complications degrading the patient’s health status. From a pathophysiological point of view, this excess fat mass causes low-grade systemic inflammation through the production of pro-inflammatory cytokines by adipose tissue (i.e., adipokines). When this is associated with a diet rich in simple carbohydrates and saturated fatty acids and/or a sedentary lifestyle and physical inactivity, systemic inflammation is the origin of metabolic complications (e.g., type II diabetes) and cardiovascular complications (e.g., hypertension or even risks of myocardial infarction)2. In addition, excess fat mass and body mass increase mechanical stresses on the musculoskeletal system (i.e., muscles, skeleton, tendons, etc.), which are the origin of many disorders of the locomotor system (e.g., osteoarthritis). It is also responsible for an increase in bone mass and skeletal muscle mass. Indeed, mechanical loading is the main stimulator of protein synthesis at the muscular level and of bone tissue mineralization3,4, which explains why individuals with obesity present high muscle and bone mass.
Currently, the therapeutic management of obesity is organized around two main axes:
- medicinal management of associated clinical complications and
- lifestyle modifications through interventions in psychology, nutrition, and physical activity.
The objective is twofold: to limit or even treat comorbidities related to obesity, such as type II diabetes and/or cardiovascular pathologies, while establishing a healthy physiological and psychological environment that allows for the maintenance of healthy lifestyle habits. Indeed, nutritional modifications and the practice of physical activity are the origin of:
- an improvement in body composition by decreasing fat mass, notably visceral fat which is responsible for the comorbidities observed in obesity5,
- the regulation of cellular and systemic metabolism by improving, for example, hormonal functions and mitochondrial function within cells6,7,
- the lowering of the level of systemic inflammation considering that inflammation is strongly involved in the pathophysiology of comorbidities associated with obesity8.
The World Health Organization recommends 150 minutes of moderate physical activity, or 75 minutes of vigorous physical activity, or a mixture of the two, per week. However, in certain situations, the specific choice of an exercise modality may be crucial to induce specific beneficial adaptations. When we engage in physical activity, our body undergoes temporary stress that triggers an adaptive response. The repetition of these stresses is responsible for the beneficial adaptations associated with regular exercise. Thus, it is essential to understand which structures will be solicited and stressed depending on the type and intensity of exercise chosen, in order to induce the desired adaptations. The choice of the exercise modality must be made according to the objectives sought but also according to the acute physiological changes, so that these are aligned with the individual’s capacities. Classically, exercises are divided into two major modalities: endurance exercise and resistance exercise. Conversely, resistance exercise involves the skeletal muscles and the nervous system, and is therefore often associated with exercises such as weight training.
I. Aerobic Exercise
Aerobic exercises are long-duration, moderate-intensity exercises that strongly involve the muscle energy systems as well as the cardiovascular system during exercise. They are often performed at an intensity between 55 and 75% of the maximum heart rate, which allows the recruitment of aerobic muscular energy systems that produce energy via mitochondria from carbohydrates/lipids. In the context of obesity management, aerobic exercise promotes normal metabolic functioning, notably by increasing mitochondrial density and function9, improving cardiovascular function10, and blood glucose regulation11. Therefore, this type of exercise is particularly relevant for inducing fat mass loss while improving the physiological functioning of the body.
It can be performed during several activities (walking, running, cycling, swimming, …) which share the common feature of being of long duration and moderate intensity, that is to say, below the first ventilatory threshold. The simplest way to be at this intensity is to use a heart rate monitor and calculate the maximum heart rate using the formula: HRmax = 220 – age. However, not everyone owns a heart rate monitor, and it is possible to rely on the talk test, meaning we are able to maintain a conversation but need to catch our breath sporadically. Ideally, the patient is in the cardiac zone mentioned above while being able to maintain a conversation during physical activity.
II. Resistance Exercise
Resistance exercises include weight training exercises with external loads or body weight; consequently, they will be beneficial for the musculoskeletal system but also for the nervous system. During this type of exercise, the action of moving a load causes an increase in the tension applied to the muscle, which will stimulate muscle protein synthesis (and therefore hypertrophy). Therefore, this type of exercise must be accompanied by an adapted protein intake (i.e., greater than 1.6 g/kg body weight/day) to maximize hypertrophy12. Furthermore, performing these movements is also accompanied by significant nerve messaging exchanges between the skeletal muscles and the central nervous system, which can modify its functioning. This will notably allow an improvement in proprioception, that is, the ability to feel one’s body in space, and therefore balance, ability to move, etc.
In the context of obesity, this type of exercise allows for the maintenance or gain of skeletal muscle mass, which is particularly interesting in cases of sarcopenic obesity or functional limitations expressed by the patient. Indeed, skeletal muscle is responsible for movement, and insufficient muscle mass can cause increased fatigability that limits the patient’s ability to perform physical activity13. They are therefore interesting for a progressive return to movement while limiting unpleasant sensations for the patient. They can also be combined with aerobic exercise to benefit from the effects of both modalities, a benefit already demonstrated in other pathologies14–16. Depending on the therapeutic objectives, several modalities of resistance exercises exist and are organized in the form of blocks of repeated movements, interspersed with periods of rest. Classically, strength training exercises are divided in the following way:
- For strength gains, between 3 and 5 sets of 4–5 repetitions close to maximum (80–90%) interspersed with 1 min 30 – 2 min of rest.
- For muscle hypertrophy, between 3 and 5 sets of 10–12 repetitions at 70–80% of maximum, depending on the training level, interspersed with 1 min – 1 min 30 s of rest. It is also possible to perform this type of exercise with lighter loads or longer rest periods, in the case of individuals who have difficulty lifting heavy loads.
III. Interest of Bioelectrical Impedance in Obesity Management
By its ability to assess body composition, bioelectrical impedance is a useful and relevant tool during the management and follow-up of the effects of physical activity in patients with obesity. It allows in particular the evaluation of skeletal muscle mass and therefore, indirectly, the patients’ capacity to perform physical activity beneficial to their health without creating unpleasant sensations. Indeed, the benefits of physical activity appear and consolidate through the repetition of acute physiological stresses during exercise that, chronically, will cause physiological adaptations associated with good health. Therefore, it is necessary that the patient enjoys performing this activity so that he or she can maintain a sufficient volume of exercise throughout life to induce these adaptations. Moreover, it is also capable of assessing the percentage of fat mass, which can allow the setting of goals and thus involve the patient in their management.
Thus, if the patient’s muscle mass is sufficient and he or she does not express difficulties in carrying out activities of daily living, it is interesting to orient them towards aerobic component exercises in order to facilitate fat mass loss and the metabolic and cardiovascular adaptations associated with this type of exercise. Conversely, if it is not sufficient, it may be more relevant to direct them towards resistance exercises with the aim of increasing their muscle mass before directing them towards aerobic component activities. In both cases, it remains necessary to interact with the patient to guide them towards an activity adapted to their needs and in which he or she feels good in order to maintain adherence to it.le-ci n’est pas suffisante, il peut être plus pertinent de l’orienter vers des exercices en résistance dans le but d’augmenter sa masse musculaire avant de l’orienter vers des activités à composante aérobie. Dans les deux cas, il reste nécessaire d’échanger avec le patient pour l’orienter vers une activité adaptée à ses besoins et dans laquelle il/elle se sente bien afin de maintenir une rétention dans celle-ci.
References
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