Marie-Laure Frelut
	Marie-Laure Frelut is a Paediatrician. She became involved in the field of childhood obesity in the 1990s when she had to run an inpatient unit for severely obese adolescents.
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Preface

Obesity has always existed, although it used to be very rare in children. Trouble arose when its prevalence started rising dramatically first in wealthier countries then all around the world. This led to the understanding that obesity reflects a loss of adaptation of individuals to their environment. This came as a surprise because of the belief that the environment was supposed to have reached a peak in its quality since humankind has been acting on it.

A few years were sufficient to observe that 80% of obese children around 10 years old would likely become obese adults. Despite such an alarming situation, great confusion about the way to tackle obesity still persists for two main reasons: this condition is much more complex than we had initially thought, and our understanding of it is still limited. Complexity applies to the underlying pathways, which, like in cancers, vary among individuals, although the general mechanism is always that energy intake exceeding energy expenditure leads to its storage in the form of fat tissue. Obesity-related science permitted a number of fascinating discoveries, not least that adipose tissue is an endocrine organ, that the gut flora is also an organ, and that both of these interact continuously with the brain. Gene expression is modified from conception onward via epigenetic mechanisms, i.e. through, for instance, the nutritional environment, pollutants and microbiota. This process starts in utero, indicating that good health is also dependent on the mother’s lifestyle before birth. Complexity also applies in the clinical diagnosis, management and prevention of obesity.

Diagnosis of obesity is no longer limited to a higher than desirable body mass index. Many competences are required in order to properly examine the individual biological, physical and psychological background in order to detect complications and offer an appropriate treatment.

Programs now clearly demonstrate that childhood obesity can be prevented. Cardiovascular fitness, physical function and quality of life can also be markedly improved. There are several ways to reach these goals. It is high time to stop multiplying basic experimental programs, except for original unexplored aspects, and act at the highest possible level. Funding should be invested in implementing widespread prevention and treatment strategies.

The European Childhood Obesity Group (ECOG) was founded in 1990 at the very beginning of the childhood obesity epidemic when experienced pediatricians understood that mild smokes were covering a volcano. The group, represented in most European countries, is designed to allow clinicians and researchers from a wide range of fields to meet, discuss and act in order to improve diagnosis, management and prevention of child and adolescent obesity.

This eBook, in its already updated version, is split into 9 chapters and 56 subchapters. These have been written, and contributed for free, by authors belonging to 34 European universities, research centers and international organizations, including the World Health Organization. Being attached to organizations that are committed to tackling this difficult topic, we consider it our duty to spread this knowledge, in the spirit of the Hippocratic Oath and services to medicine and science.

Special attention has been given to fields which are not usually developed in obesity courses but are, in our opinion, integral to “the science of obesity”. We are very grateful to the many colleagues who accepted with enthusiasm to disseminate their knowledge and expertise.

Most chapters encompass a few slides in order to enable the reader to him- or herself become a teacher. We hope that starting from Europe, this eBook will spread all around the world and encourage an increase in links and exchanges for the benefit of children’s health.

On behalf of the ECOG,

The Editor
Marie-Laure Frelut, MD
Past-President of the ECOG