At a glance

  • Body weight is influenced by many factors, including diet, life circumstances, certain diseases, medication and your genes.
  • Obesity typically develops over several years or decades.
  • It increases the risk of various diseases.
  • Weight loss recommendations usually involve a combination of changing your diet and getting more exercise.
  • Various programs can help you to lose weight.


Photo of two women smiling at each other

People are said to be obese (very overweight) if they have too much body fat. This is measured by calculating the body mass index (): a over 30 is considered to be obese. Obesity increases the risk of various chronic medical conditions like diabetes, osteoarthritis, and cardiovascular diseases. So it's a good idea to lose weight if you are very obese. This is easier said than done, though, and requires a lot of commitment, persistence and good support. The good news is that losing just a few kilograms can have a positive effect on your health.

Certain programs can help you lose weight. Weight loss surgery may be an option too if you are very obese. But it's important to carefully weigh the pros and cons of this kind of procedure because it can have such a major effect on your life.

Causes and risk factors

In most people, obesity is caused by taking in more calories than they use. The extra calories are stored in the body as fat.

Many different factors can contribute to weight gain, including diet, lifestyle, your genes and certain diseases, as well as psychological and social factors. Certain medications can cause weight gain, too, like some and some diabetes medications.

Larger societal changes have made it increasingly difficult to balance the calories we take in and the calories we burn in everyday life. For example, fewer people now have jobs that involve physical activity. It is becoming more common to go places by car rather than by foot or on a bicycle. A “sedentary” lifestyle is more usual in our free time, too – we spend more time sitting in front of a TV or a cellphone. As a result, we burn fewer calories in everyday life.

At the same time, a lot of sugary drinks and high-calorie foods are readily available in industrialized countries. Snacks like candy, potato chips (crisps), and nuts are often eaten between main meals. Alcohol can also make you gain weight; it contains even more calories than sugar does.

Learn more

Causes of obesity


According to data from the Robert Koch Institute, about 24% of all men and women in Germany are obese. About

  • 17% have class 1 obesity ( between 30 and 35),
  • 5% have class 2 obesity ( between 35 and 40), and
  • 2% have class 3 obesity ( over 40).

About 6% of all children and teenagers are obese, and it is more common in teenagers.


In most cases, people become obese in adulthood. This doesn’t happen overnight, but over years or decades. Most people gain weight some time between the ages of 30 and 60. Starting your career or a family can make it harder to get enough exercise or do sports in everyday life. Other risk factors, like certain medical conditions, may come along over the course of your life.

Pregnancy can trigger long-term weight gain in women. Most women return to roughly their pre-pregnancy weight some time after the birth, but some continue to weigh more than they did before. Many women gain weight during menopause, too. It is thought that various factors may play a role here, such as hormonal and metabolic changes.

Some people become overweight during childhood or in their teenage years. It is often particularly hard for them to lose weight later.


Obesity can lead to various medical conditions, including:

Obesity can also increase your blood pressure, and it can negatively affect your cholesterol levels. This increases the risk of cardiovascular disease. Generally speaking, the longer you are obese and the more severe the problem, the greater the risk to your health.

Opinions differ on whether obesity should be considered a disease in its own right. For example, the German Association for the Study of Obesity (DAG) and World Health Organization (WHO) consider it to be a disease, while the German College of General Practitioners and Family Physicians (DEGAM) doesn’t. To DEGAM, obesity is a risk factor that should always be considered when assessing a person’s health status, along with other risk factors. Especially people with class 1 obesity often don’t feel any less healthy or less well than slimmer people do. Also, some obese people are physically fit and have a healthy metabolism.


People are considered to be obese if they have a body mass index () of 30 or higher. The is calculated based on your height relative to your body weight:

Illustration: BMI calculation – as described in the article

But it doesn't tell you anything about how your body fat is distributed. Having a lot of belly fat is linked to a greater health risk than fat in other places. Because of this, your waist circumference is measured too (roughly between the bottom of your ribs and the top of your hips). A waist circumference of over 102 cm in men and over 88 cm in women suggests that there’s a lot of belly fat. But this measurement doesn’t take into account a person’s individual build or age.

Obesity can also be caused by a medical condition, like an underactive thyroid. Because of this, it’s important to rule out these kinds of causes – for example, by measuring the levels of related to thyroid function. Sometimes people are too quick to "blame" obesity on the wrong diet or too little exercise.

The risk of developing medical conditions due to obesity can be better assessed if body weight is considered together with other risk factors. That is why doctors often check things like blood pressure, blood sugar, and kidney function too.

Some people who are obese find that doctors mainly treat the obesity-related health problems, but don’t pay enough attention to the weight problem itself. It can help to write down any questions you would like to ask your doctor beforehand so that you don’t forget them during your appointment.


You don't have to reduce your to a specific number in order to improve your health. Depending on your starting weight, doctors recommend losing 5 to 10% of your weight within six to twelve months.

To lose weight successfully, it helps to make a plan that suits your own goals and life situation. Some people want to lose weight because they feel uncomfortable in their body, others mainly want to improve their physical fitness, and some are motivated by health reasons.

Weight loss recommendations usually involve a combination of getting more exercise and changing your diet. Various weight loss programs can help you lose weight; some have been scientifically tested and recommended by medical societies. But people often have to pay for these programs themselves because they're considered to be “lifestyle measures” rather than treatment. In Germany, some statutory health insurers pay for part of the costs of participating in a weight loss program.

The programs usually include elements of behavioral therapy too. For example, they teach you how to

  • make your dietary changes flexible enough for you to stick to them in everyday life,
  • integrate more physical activity into your daily routine, and
  • handle situations you can’t change yourself (for example, at work).

If a diet and exercise program isn’t enough, using a medication too can help you lose weight.

Keeping the weight off over the long term is usually harder than losing it in the first place. This has to do with your metabolism, , and central nervous system: They tend to keep the body in balance rather than helping it to lose weight. Weight loss also reduces your muscle mass. As a result, your body needs less energy, and fewer calories. That means that the more weight you lose, the harder it is to keep off the weight, or to lose even more. A lot of people also have a hard time making long-term changes to habits and behaviors that have developed over many years.

After you have lost weight, sticking to a balanced diet and continuing to get enough exercise increases your chances of keeping off the weight or gaining only a little in the long run. The most important thing is to generally avoid taking in more calories than you burn.

For people who are severely overweight (class 2 or 3), surgical treatment may be an option. The standard techniques include gastric surgery and gastric sleeve surgery (sleeve gastrectomy). It is important to carefully weigh the pros and cons of surgery before making a decision: These procedures can lead to various complications and side effects, and you have to make quite a few changes in everyday life afterwards.

Everyday life

Obesity can reduce your physical fitness and mobility. This can make it difficult to do everyday things like climbing stairs or getting exercise. Quality of life and wellbeing may be affected too, especially in severe obesity. People who are very overweight are often confronted with prejudice and disadvantages.

Very overweight people don’t match the standards of beauty portrayed on TV, on social media, or in advertising. This can lead to low self-esteem. It can also stop them from going out in public and being physically active or going swimming, for example. Some obese people say that it helps to meet other people with the same problem – to exercise together or to talk in a support group.

Obesity is also sometimes closely linked to depression, eating disorders or other mental health problems. In those cases, it makes sense to consider the two issues together.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. In our topic "Health care in Germany" you can read about how to find the right doctor – and our list of questions can help you to prepare for your appointment.

There are many sources of support for obese people in Germany, including support groups and information centers. But there are often regional differences in how these services are organized, and they aren't always easy to find. You can use our list to help you find and make use of local services in Germany.

Deutsche Adipositas-Gesellschaft (DAG). Interdisziplinäre Leitlinie der Qualität S3 zur "Prävention und Therapie der Adipositas" (in Überarbeitung). AWMF-Registernr.: 050-001. 2014.

Deutsche Gesellschaft für Allgemein- und Viszeralchirurgie (DGAV). Chirurgie der Adipositas und metabolischer Erkrankungen (S3-Leitlinie). AWMF-Registernr.: 088-001. 2018.

Mensink GB, Schienkiewitz A, Haftenberger M et al. Übergewicht und Adipositas in Deutschland: Ergebnisse der Studie zur Gesundheit Erwachsener in Deutschland (DEGS1). Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2013; 56(5-6): 786-794.

Schienkiewitz A, Brettschneider S, Damerrow A et al. Übergewicht und Adipositas im Kindes- und Jugendalter in Deutschland – Querschnittergebnisse aus KiGGS Welle 2 und Trends. Journal of Health Monitoring 2018; 3(1): 16-23.

World Health Organization (WHO). Obesity: preventing and managing the global epidemic. Report of a WHO consultation. Geneva: WHO; 2000.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

Comment on this page

What would you like to share with us?

We welcome any feedback and ideas - either via our form or by gi-kontakt@iqwig.de. We will review, but not publish, your ratings and comments. Your information will of course be treated confidentially. Fields marked with an asterisk (*) are required fields.

Please note that we do not provide individual advice on matters of health. You can read about where to find help and support in Germany in our information “How can I find self-help groups and information centers?

Print page

Über diese Seite

Created on November 22, 2022

Next planned update: 2025


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

How we keep you informed

Follow us on Twitter or subscribe to our newsletter or newsfeed. You can find all of our films online on YouTube.