What is obesity and its causes

Causes of Obesity

Genes certainly play a role in the development of obesity. It is known from twin studies that hereditary predispositions (genetic influences) account for about half the difference in body weight between different people.Overall, a child with one parent who is overweight has a 50% chance of becoming overweight in later life two overweight parents one 80%. The mother's influence is somewhat stronger than that of the father - which also shows that genes are not everything, but that the environment also has a say.

Today there is no doubt that the vernacular, which has long known good and bad "feed converters", is right: some people stay lean even with a large amount of food, while others put on fat more quickly. In an experiment with volunteers, researchers were able to show that with forced overeating of over 6,000 calories per day, some test participants quickly gained over 10% of their body weight, while with others the weight hardly changed even after a month Feed conversion there is a bundle of possible causes:

  • Differences in the regulation of appetite. Even when receiving chemical signals in the appetite center of the brain, some of the extremely overweight people react significantly differently than those of normal weight.
  • Differences in metabolism. There are indications that obese and non-obese people have different concentrations of certain proteins (the uncoupling proteins) in the body cells. These influence which part of the food energy dissipates as heat instead of being stored as fat.
  • According to more recent studies, the intestinal flora could also play a role in the different feed conversion rates: The composition of the bacterial flora has been shown to have an influence on how much weight the individual loses on a diet
  • Different movement behavior. Even newborns show very different spontaneous movement behavior, and paediatricians report that some infants drink almost twice as much milk as others in the first month of life - and yet they do not necessarily gain weight faster. And so the cliché of the lively slim and the cozy fat ones could actually have a correspondence in the movement behavior of people.

Environment. In order for a person to become overweight, not only genetic predisposition is required, but also environmental influences. And in the case of obesity, these are unequivocally established: excessive nutrition (overeating) and lack of exercise. How strong their effect is is shown by the fact that obesity was hardly observed in times of war and famine and that 30 years ago Germans were much slimmer than they are today. However, genes cannot change significantly from one generation to the next.

Which of the two environmental influences, lack of exercise or overeating, contributes more to the overweight problem in our society? In individual cases this is often easy to answer: Everyone knows someone who is overweight who may have a healthy meal after work in the office, but then just “hangs out” in front of the television. Clear diagnosis: lack of exercise. And of course you also know someone who is overweight who always walks around with a bite in or just in front of his mouth, but also likes to ride his bike to work. Regardless of whether exercise or nutrition is ahead in the individual case: Overeating is usually not one Eating disorder! The latter are becoming increasingly common in the industrialized world and in individual cases an eating disorder such as bulimia can lead to obesity in the long term. Overall, however, eating disorders have different causes than obesity and primarily affect young women.

Obesity is an environmental phenomenon that thrives on genetic factors.

Social influences. In order to stay slim under today's conditions, you either have to have a good hand of cards from nature or you have to succeed in making exercise an important hobby and eating healthily. While there is little that can be done for the former, the latter two strategies require some insight, strength, and other resources - psychological and social. And it is precisely these that do not exist in many cases. What we eat and how much we move around depends to a large extent on the social class in which we live, what its traditions and the life plans it mediates look like. Among adults, members of the disadvantaged classes are about three times more likely to be overweight than the rest of the population. And so the pressure comes from two directions: On the one hand, people live in an increasingly obesity-promoting environment, on the other hand, many of them live in social contexts in which health-conscious behavior is not part of the intended or traditional lifestyle. The epidemic of obesity is thus at least partially one Mirror of social change.

Psychological causes. Overweight people are in fact more psychologically stressed than people of normal weight. However, the psychological problems are often not the cause, but the consequence of being overweight. Overweight people also live more often in the marginalized social classes, which alone causes psychological problems - regardless of body weight. Therefore: Psychological factors can may be involved in the development of obesity, but they by no means explain all cases: Some people tend to overeat under stressful conditions, while others tend to lose their appetite. However, the following psychological or psychosomatic factors can cause obesity in individual cases:

  • Disorder of the feeling of satiety: The person concerned does not feel that he is full.
  • Eating out of frustration: In the context of mental crises, food can be used as a “mental filler” (“bacon”).
  • Eating as a substitute act: In dysfunctional families, emotional affection may be replaced by oral affection.

It is often said that fat people are more unhappy, but it is not easy to answer. The statement for extreme forms of obesity seems clear: Here the quality of life is consistently reduced. It is even more difficult with the less extreme forms. Though fat people on average report a lower quality of life, but when other life factors are taken into account, the relationship is significantly weakened. With a high BMI, the quality of life is consistently poorer, but if it was taken into account how much the affected person moved, it was shown that movement is more decisive for quality of life than body weight

Conclusion: fat people are just as satisfied with their lives as thin people, as long as they are fit and do not belong to the extremely fat people.

Continue reading:

Overweight - a balance sheet problem

Overweight and obesity in adults

Overweight and obesity in children


Dr. med. Herbert Renz-Polster in: Gesundheit heute, edited by Dr. med. Arne Schäffler. Trias, Stuttgart, 3rd edition (2014). | last changed on at 12:55