Chronicles

The idea that physical exercise is advantageous for maintaining good health and longevity is not novel. In fact, organized exercise for physical, mental and social well-being is documented in Chinese history records from over 4.000 years ago. Later on, famous ancient Greek philosophers and physicians such as Hippocrates, Plato and Galen also reflected on the importance of periodic exercise to preserve the good condition of the human being. Since then, the research done has not only confirmed these hypotheses and beliefs but has also demonstrated that many of the benefits of exercise on health are the result of its effects on metabolism. But what is metabolism?

Metabolism is a never-ending cycle of chemical reactions within our cells that respond to the environmental conditions to which we are exposed, and which allows for our survival. We are permanently interacting with the environment, and we get exposed to all kinds of substances, those in the air that gets into our lungs, those in the products that touch our skin, or those in the food or drink that we intake. All these substances are transformed by metabolic processes into elements that can be either incorporated into our body, converted into energy, or discarded as waste. For the particular case of food, the nutrients that compose it are an essential need for the human body.

One of the vital functions of food is to provide a source of energy that allows the organism to grow and reproduce, to maintain their structures and respond to the environment. We need energy for our heart to pump, our lungs to breathe and our limbs to move, but also for our cells to generate heat, to build cellular components, to replace structures, or transform toxic compounds to less harmful forms that can be easily eliminated from our system. Without access to food to provide energy, we would eventually die. To prevent that, our body has evolved to display a complex metabolic system coordinated by the brain that ensures the maintenance of energy balance over long periods of time. A healthy metabolic profile is achieved when the amount of energy intake, obtained from the food that we eat, is equal to the amount of energy that we spend, for example moving and performing other body functions. This equilibrium is called energy homeostasis and assumes that all the daily calories that a person ingests will be equivalent to those burned by the activities that the body performs during this interval. In that case, we eat what we spend and neither lose or gain weight. Sometimes, however, the physical activity of the day and the energy spent by the body on other life functions is not enough to compensate for the number of calories that we eat. This results in a positive energy balance, in response to which, there is a net metabolic conversion of excess nutrient to fat that is accumulated under the skin. A certain amount of fat accumulation is important for survival since it serves as a reservoir of energy for occasions when access to food is limited.

However, if there is a constant nutrient surplus, fat deposits keep increasing and we become overweight. Excess fat deposits around or in organs such as the heart and the liver can have devastating health consequences. Our body can respond badly to excessive fat through the overactivation of immune responses, resulting in allergies and inflammatory diseases, as well as the proliferation of cancer cells. These long-term energy imbalances are also the origin of several metabolic disorders such as obesity, which according to the World Health Organization is defined as the abnormal or excessive accumulation of fat in the body that may impair health. Other metabolic disorders that are the result of a chronic positive energy balance are hyperlipidemia, in which there is an excess of fat circulating in the blood, Non-Alcoholic Fatty Liver Disease (NAFLD), in which there is an excessive deposition of fat in the liver, or Type 2 Diabetes (T2DM), a disorder where the fat accumulates in the pancreas and impairs its function, leading to elevated levels of blood sugars and this in turn causing serious damage to the heart, the eyes, the kidneys and the nerves. These metabolic diseases are growing more common since the comforts of our modern society tilt us towards over-eating while at the same time promoting more sedentary lifestyles.

This takes us back to the importance of exercise. Besides adopting a healthier diet and reducing the amount of food that we eat, exercise is crucial in the maintenance of energy homeostasis. For one, physical activity and exercise involve body movement, a process where the muscles consume large amounts of energy. But an even more interesting effect of physical exercise is that it can significantly influence the metabolic rate, that is, the pace at which metabolic reactions take place. By speeding these processes up, exercise increases the amount of energy that the body burns even when resting. With a faster metabolic rate, the caloric expenditure is higher, which not only induces weight loss, but also reduces the risk and/or severity of metabolic diseases. In fact, researchers have proven that modest increments in energy expenditure (~1000 kcal per week) are associated with a 20% reduction in mortality.

Exercise is part of the prevention and therapeutic strategy to fight metabolic disorders, but its beneficial effects are equally important to stay healthy and preserve our well-being. Exercise is a need for everyone, regardless of whether young or old, man or woman, healthy or diseased. So, let us keep our metabolism pumping!

Authors: Inês Simões and Tawhidul Islam are early stage researchers of the FOIE GRAS project. Inês Simões is doing her research at the Instytut Biologii Doświadczalnej (NENCKI), in Warsaw (Poland), at the Center for Neuroscience and Cell Biology (CNC), at the University of Coimbra (UC), in Coimbra (Portugal), and at the Universidade do Porto. Tawhidul Islam is performing his research at the Faculdade de Farmácia, Universidade de Lisboa (Portugal), at the Institut National de la Santé et de la Recherche Médicale (INSERM), in Paris (France), and at the company Mediagnost (Germany).

The project: This chronicle results from the collaboration between the Center for Neuroscience and Cell Biology (CNC) of the University of Coimbra, the European Training Network FOIE GRAS (http://www.projectfoiegras.eu), the Erasmus+ Program and the Academic Sports Federation University (FADU) in the scope of the European University Games Coimbra 2018.

Coordination: Anabela Marisa Azul, João Ramalho-Santos, Mireia Alemany i Pagès, Paulo Oliveira and Sara Varela Amaral

Revision of the text: Mireia Alemany i Pagès, Anabela Marisa Azul, John Jones, João Ramalho-Santos, Mariuz Wieckowski, Fernanda Borges, José Magalhães, Cecília Rodrigues, Carina Prip-Buus, Andrea Normann and Paulo Jorge Oliveira

Illustration: Rui Tavares

This chronicle reflects only the authors’ views and the Commission is not responsible for any use that may be made of the information it contains.