The influence of genes on the human body has been the subject of intense scientific research for many years. Although great progress has already been made in decoding the human genome, there are still some controversial points: What part do genes as well as environmental influences play in the expression of certain physical and psychological characteristics? How strongly is an individual shaped by the inherited genes of the parents and how strongly by upbringing as well as other external influences (e.g. nutrition)? These questions will be explained on the basis of the two physical characteristics of height and body weight. In addition, it is explained why certain ideal values should not determine the relationship to one’s own body.
Factors influencing body size
The genetic material of every human being is stored in the DNA or DNA (deoxyribonucleic acid, English: deoxyribonucleic acid, DNA) in the cell nuclei. DNA consists of looped strands connected by chemical building blocks. A gene is a unit in DNA that controls the functions of the respective body cell and thus contains information about the development of an individual. Thus, genes determine the later physical characteristics of a person, and some genes even determine psychological characteristics. There are genes that control the expression of a body characteristic all by themselves; this is the case, for example, with eye color. The development of body height is an example of a physical trait that several genes control together. So far, according to SPIEGEL ONLINE, about 180 hereditary regions are known to play a role. In addition, there are even more complex areas in the human body in which a large number of genes act in concert. These include intelligence and basic character traits such as empathy. Genetics plays a major role in the development of body size. About ninety percent of a person’s height is determined by his or her genes. The genetic makeup sets the upper limit here, with environmental influences deciding the final percentages. This is not only the case with height; according to this source, mental development is also determined to a certain extent by external influences. Encouragements and motivations, as well as the opportunities that are or are not offered to a person in the course of life, are very likely to have an influence on mental development. Pre-existing conditions and emerging diseases, as well as diet, can also affect height development.
The influence of external living conditions on body size
Pre-existing conditions and diseases that occur
For a long time, the prevailing opinion in science was that genes are the decisive factor in human development. However, recent scientific findings in the field of epigenetics have revealed that the various expressions of genes can be influenced and sometimes even specifically controlled by external circumstances. A French video documentary from 2015 explains these findings in more detail. According to this, a finding now accepted in science is that both inherited genes and the environment together shape an individual. On the one hand, each person is given certain variants of genes that enable the individual to probably express certain traits; on the other hand, the environment can influence the switching on and off of the respective genes. Numerous diseases are closely linked to DNA; however, according to a comprehensive study, in most cases it is still unclear which gene variants or gene mutations actually cause a disease in the end.
Hygienic conditions
In medical and epidemiological research, there are studies that show a causal relationship between hygiene and the average body size of populations. Chronic diseases caused or exacerbated by poor sanitation, for example, can affect growth and physical development. Poor sanitation, particularly prevalent in some developing countries, is a major cause of the spread of bacteria that can affect children’s growth. In research, growth disorders are also frequently studied in connection with the aspect of malnutrition.
Available nutrients and nutrition
Nutrition exerts a significant influence on the physical development of a human being. Humans have enzymes through which the environment influences genes and thus the genetic makeup. However, the exact effects are difficult to measure because they often take decades to take effect. In addition, it is almost impossible to determine the exact influence of the interaction of certain genes. Proteins or proteins are among the most important nutrients for the human body. Protein is one of the main nutrients; the human body needs proteins for cell and muscle development as well as for maintaining a functioning metabolism and for defense against pathogens. Humans need an increased protein intake to maintain and build body substance, this is especially true for children and adolescents in the growth phase. During this time, the body must be supplied with sufficient high-quality protein on a daily basis. This can be found in animal products (meat, eggs, fish, cheese and other dairy products) as well as in plant products (nuts, whole grains, beans and peas). The explanations may lead to the assumption that an increased protein intake can have a positive effect on body growth. However, this is not scientifically proven on the one hand, and on the other hand, increased protein intake can be harmful for young children and adolescents. If the protein supply exceeds the daily requirement for children (about 5 grams per kilogram of body weight), this can lead to excessive stress on the kidneys. On the other hand, it is important to ensure a balanced diet (carbohydrates, proteins, fats) in order to provide the body with all the nutrients and vitamins it needs. Better education about a healthy and balanced diet, as well as the advancement of medicine, are considered the main causes of the increase in average height and physical development.
Things to know about the science of auxology
The average height of Germans – development and inventory.
Since the middle of the 19th century until the end of the 1970s, a significant increase in height and pace of physical development has been observed in most European countries, according to information from the German Medical Journal. According to this, the increase in adult height was 1-2 centimeters (cm) per decade. Since the beginning of the 1980s, the increase in height of an adult European has been lower. For Germany, the corresponding value is less than 1 cm per decade.
Reasons for this development
Scientific research suggests that even with a balanced and healthy diet and the best medical care, a person’s growth potential is not infinite. Numerous scientific studies, including the Study of Adult Health in Germany (2013), demonstrate a positive relationship between social status, health status, and health maintenance behaviors, such as dietary habits. There is widespread consensus in the scientific community that there is a positive relationship between the development of body size and socioeconomic status. Socioeconomic status is a social science term that encompasses a number of characteristics of human circumstances. Among them are the following aspects:
- Education and school-leaving qualifications and training or study.
- Occupation and income
- Place of residence and economic situation (ownership)
- Ownership of cultural property
- Opportunities to participate in cultural life (attending theater performances and exhibitions in museums, etc.).
Despite the adequately documented relationship between physical development and socioeconomic status, nutrition, and psychosocial influences (psychological and emotional stress), it is not clear how these factors affect the biological mechanisms relevant to body growth.
Body positivity – healthy relationship with one’s own body.
A healthy body weight cannot be expressed by numbers alone. There should additionally be a positive attitude towards one’s own body. This is a prerequisite for a healthy body image to develop and for measures to take effect. Beauty ideals are defined by the respective society, they change constantly.From the individual point of view, the beauty of the body is not always the actual goal of measures. It is a means to an end to express highly regarded modern social values such as individuality, performance, flexibility and freedom. Media, advertising and the fashion as well as consumer goods industry take an important role in the creation and spread of beauty ideals. Social networks reinforce this effect, offering a platform where people can present themselves as the ideal. In this way, children and young people in particular come into closer contact with the various ideals of beauty, for example in terms of body size and weight, than was the case just a few years ago. In addition to this confrontation from the outside, young people are also influenced to some extent by their parents: keeping up a “permanent diet,” so to speak, in order to come closer to a certain performance level and health image in professional life as well as everyday life, has become an important aspect of individual (Western) lifestyles in recent years. Through these attitudes and behaviors, parents influence their children in addition to external pressures and help to solidify certain ideals. If more and more young people orient themselves to these usually unattainable ideals of beauty, this can lead to them perceiving their bodies “wrongly,” so to speak, as psychoanalyst Susie Orbach explains in this interview. This can have a negative impact on their self-esteem. In this context, a distinction must be made between positive, neutral as well as negative body image:
Positive body image:
The person feels comfortable in their body, they are satisfied with it and take care of their own physical needs. Often, this is accompanied by beneficial behaviors, including, above all, a balanced and healthy diet and sufficient exercise. Neutral body image:
Here, the person is not completely satisfied with their body, but this does not have an overly disruptive effect on the overall positive self-image. Negative body image:
A negative body image is an expression of dissatisfaction with one’s own body. Here, individual body parts or the entire body can be rejected. This does not only apply to overweight or underweight people, a negative body image can also solidify in normal-weight people. The term “body image” bridges the gap between subjective feelings towards one’s own body and the influence from interaction with other individuals. Thus, the reference to society is established. In order to address body diversity in a positive way, unrealistic ideals of beauty must be broken down. In this context, it is important to sensitize the public to this topic. A critical approach to the ideal images conveyed by the respective society promotes subjective awareness with regard to both general body diversity and one’s own body.
Positive body diversity in women
People of small and large stature tend to attract stares. The feeling of being constantly watched can become a permanent psychological and physical burden. In addition, people with extreme growth forms are confronted with a variety of challenges and problems in everyday life and at work, e.g. when choosing suitable clothing, furnishing the home or the conditions at the workplace. In addition, there are health restrictions such as relatively frequent back and joint problems or impairments as a result of incorrect posture. In people with body sizes outside the norm, the metabolism and organs have to perform more than in people with a “normal” body size. However, health problems due to a physical peculiarity do not occur exclusively in short and tall people; overweight people also have an increased risk of many chronic diseases. The so-called body mass index is a well-known benchmark for determining whether a person is underweight, normal weight or overweight.
Body mass index (BMI) – guideline value about the ratio of body weight to height.
Information about body weight is basically subjective. People can feel overweight, although their weight is perfectly fine from a medical point of view. The so-called body mass index (MBI) is a guideline value that determines the ratio of body weight to height.The BMI is calculated from the body weight (kg) divided by the square of the body height (m²). The corresponding formula is:
BMI = body weight : (height in m)².
The recommended BMI value depends on the age of the person. The following table represents the BMI values for different age groups:
| Age | Body mass index |
| 19-24 years |
19-24 |
| 25-34 years | 20-25 |
| 35-44 years |
21-26 |
| 45-54 years | 22-27 |
| 55-64 years |
23-28 |
| >64 years | 24-29 |
Source : www.uni-hohenheim.de
Limitations and criticisms of BMI
The doctor measures the abdominal circumference and the body fat percentage, as well as the body mass index of the patient, in order to be able to initiate an accurate diet and further therapy. The body mass index is only to be understood as a rough guide value. In science, according to this article, the BMI is increasingly criticized as a measuring instrument. Reason: Serious investigations over the human health must consider numerous factors, the complex topic health prognosis cannot be expressed accordingly by a simple mathematical calculation. The BMI only evaluates a person’s body weight in relation to his or her height. Other important factors such as gender or body stature are not included. However, the above formula cannot be used to make reliable statements about body fat and muscle percentage and distribution in the body.
An alternative concept – The ABSI (“A Body Shape Index”).
The two American scientists Nir and Jesse Krakauer have developed an alternative measurement method for health prognosis. The so-called “A Body Shape Index” (ABSI) takes into account not only height and body weight, but also abdominal circumference. It is a more complex calculation method than the relatively simple calculation of the body mass index. Advantages over the BMI
By taking the abdominal circumference into account, the “A Body Shape Index” (ABSI) is more informative about the individual physique than the body mass index. Excess fat deposits are not always detrimental to health, but an increased amount of fat in the abdomen is said to promote the development of various diseases such as diabetes, high blood pressure or lipometabolic disorders, according to current scientific studies. By determining the ABSI value, it is possible to estimate more precisely whether there is an increased health risk due to a certain body fat distribution. The disadvantage of the ABSI is that it is based on a complicated formula and excludes important factors such as possible pre-existing conditions.
Conclusion
A complex interplay of different genes is responsible for the expression of body size. To date, researchers have been able to explain only a small part of the differences in height genetically, and DNA decoding remains the subject of scientific research. The individual expression of physical characteristics such as height or body weight is also influenced by environmental factors. Ultimately, however, it is not genes that determine one’s relationship to one’s own body. Acquiring a positive body image is not an easy undertaking, but it is an important step toward not only accepting one’s own body, but also loving it.
