Obesity is defined as an abnormal accumulation of fat which may affect health. What are the reasons for this accumulation of fat? On the one hand, children's diets contain too many empty calories and insufficient fibre. On the other hand, excess calories – and thus the released energy – are not properly consumed. The body saves each extra calorie in anticipation of “lean times” ahead. This saving principle begins after birth: the fat cells in small children (aged between two and six) learn early how much fat the body is able to store and how much they can stockpile. So the cells receive a default or reference value right from the start. The body will seek to achieve this value for the remainder of the child’s life. The basis of this phenomenon is over-nutrition or poor nutrition with sugary and fatty foods such as sweets, fast food, etc.
On the other hand, ingesting too many carbohydrates pushes the body's cells to their limits. Glucose enters the bloodstream with every intake of carbohydrate. At this moment, the body releases insulin to regulate blood glucose levels. The glucose is thus stored in the muscle, liver and fat cells and serves as an energy supplier. The body must constantly secrete insulin to deal with the excessive nutrition of unhealthy foods. Over time, the insulin receptors become overused and blocked; it can also lead to insulin resistance.
Countermeasures can be taken, however, with a proper diet from the start; the microbiome only fully develops in terms of diversity and complexity at the age of three. In addition to avoiding a diet with excessive sugar and fat, it is also important to consume foods with a high fibre content. Fibre is important for building up a healthy gut flora or microbiome.
Research has also shown that there are even differences in the microbiome of children classed as normal and overweight. It is therefore all the more important to focus on providing a healthy diet, even at an early age.
Interview with Prof. Dr. Holger Till, Leipzig University Hospital and Integrated Research and Treatment Center Adiposity Diseases, Leipzig University.
HOCHDORF: Obesity in children is not a new issue. What developments have there been over the past 10 years?
Prof. Dr. Holger Till: The global epidemic of obesity (adiposity) has affected not only adults but also children and adolescents for many years. In areas such as China and the Middle East, the rates of increase seem to be literally exploding and preventive measures do not currently appear to offer an adequate solution. This makes "morbid" obesity the number one problem many societies face in terms of medicine and health economics. Similar to adults, obese children and adolescents also face serious accompanying conditions such as blood sugar fluctuations, manifest type 2 diabetes, lipid metabolism disorders, fatty liver disease or high blood pressure.
Is the cause hereditary (genes) or does the environment in which the children are brought up (parents with obesity) play a role?
Prof. Dr. Holger Till: Of course, there are rare genetic disorders of lipid metabolism that lead to morbid obesity. The best known is the monogenic inherited leptin deficiency. In the vast majority of patients, however, the cause is over-nutrition and poor diet; too many calories are taken in as food and this energy is not sufficiently consumed by physical activity. The body stores each extra calorie "for lean times". The family and the social environment naturally play an important role in eating and behaviour habits.
And how does obesity develop in children?
Prof. Dr. Holger Till: This storage principle begins immediately after birth and is developed strongly in infancy (between the age of two and six), so obesity can already begin and be determined in infants. At this age, the fat tissue cells learn how much fat the body is able to store and how much they can stockpile. The body will seek to reach this target value again and again for the rest of the child's life, even if the person tries to reduce their weight.
What are the basic causes and the most important factors for this phenomenon?
Prof. Dr. Holger Till: Over-nutrition and poor diet are often signs of an affluent society with a general oversupply of food (calories) and a luxurious, high-calorie food basket (sweets, fast food etc.) We have been experiencing this situation in many European and American countries since the end of the World War II and in Asia or the MENA states (Middle East, North Africa) for around a decade. In most cases, infants are not yet affected as long as they are supplied with high-quality, healthy milk-based nutrition. But as soon as their parents spoil them with chocolate bars and jelly babies, fatty foods or sugary drinks, the imbalance between excessive energy intake and insufficient energy consumption begins. The lifestyle in such affluent societies is often characterised by little physical exercise and too much sitting, resting or "chilling". Again, parents and siblings have an important role to play here too.
As a result, diabetes is becoming increasingly common in children. One possible cause of this is insulin resistance. How does insulin resistance develop?
Prof. Dr. Holger Till: Carbohydrates from food are split into glucose in the small intestine and absorbed via the intestinal wall barrier, thus entering the bloodstream. As well as the enzymes, the gut bacteria play an important role in digestion. We will come back to this later. The more carbohydrates we eat, the more glucose enters into the bloodstream. The body reacts to this with a very finely tuned and efficient regulatory system of hormones. At this moment it releases insulin so that the glucose is stored in the muscle, liver and fat cells. If, however, too many carbohydrates are eaten or they are consumed too often, the body cells are pushed to their limits. The insulin receptors are blocked and the insulin there (peripherally) is less effective (peripheral insulin resistance). In the worst case, the blood sugar level remains above the norm (diabetes mellitus).
What should we do? What are the important elements of our diet?
Prof. Dr. Holger Till: There are countless nutrition tips and all of them have important components. It is not therefore possible to give ONE recommendation here. However, it is important to point out, especially for small children and schoolchildren, that eating foods containing sugar and fat regularly and excessively can lead to obesity and possible secondary diseases. If snacks are offered as a reward, then they should be "healthy" children's snacks (fruit, dried fruit, wheat products) instead of chocolate bars and sweets. Fibre is also important: as well as containing fewer calories, it also helps to build up a healthy gut flora.
Another important research finding is the difference between the gut microbiome of a person of normal weight and an overweight person.
What are the differences in the gut microbiome? Where do the differences come from? And how can this difference be prevented?
Prof. Dr. Holger Till: A gastrointestinal microbiome is a multitude of micro-organisms living in the intestine (bacteria, viruses, fungi, etc.) Since the human microbiome was decoded using the latest gene sequencing techniques (from 2007), we have also become more familiar with the various functions or malfunctions of the microbiome. From the first day of life, the intestinal microbiome plays an important role in the development of the immune system, the stabilisation of the intestinal wall barrier against parasites and, of course, in the breakdown of food components. It was important to recognise that when children are born it takes the gut microbiota about three years to develop the diversity and complexity of adult microbiota. Nutrition is a crucial factor in this process. Conversely, any imbalance in the child's diet could lead to a lifelong imbalance (dysbiosis) in the gut microbiota. In addition, obesity research has shown that the microbiome is not only involved in many metabolic processes such as the synthesis of vital vitamins or short-chain fatty acids (acetic acid, acetate), but also in the direct utilisation and absorption of energy from food ("energy harvesting"). In this context, science is intensively searching for mechanisms that can contribute to the normalisation of body weight by influencing the microbiome. We already know, however, that a balanced diet rich in milk proteins, fibre, vitamins and minerals – but without excess sugar or fat – is a crucial factor in developing a favourable microbiome in the intestine and general vitality, even in healthy infants.
Prof Dr. Holger Till, thank you for the interesting interview.
Facts on obesity in children
According to the WHO, more than 41 million children under the age of five worldwide are overweight and likely to remain so in adulthood. These children are already prone to diabetes and cardiovascular diseases in their younger years (1).
Being overweight or obese is caused by an imbalance between calorie intake and consumption. Above all, too many foods with a high sugar and fat content are being consumed globally. At the same time, we are generally less mobile and physically active.
To avoid obesity in children, the WHO recommendations focus primarily on promoting a healthy diet and physical exercise. Educating parents on prevention issues is also important, making sure that children do not become obese in the first place (2).
- Article "The first 1000 days determine the future"
2) WHO Report of the commission on ending childhood obesity, 2016, ISBN 978 92 4 151006