What are the health consequences of obesity?

Obesity has become a global health problem (Why are more people becoming obese?) associated with diseases that affect almost all body systems [Finer, 2015] and often occur in combination. Some of these diseases are summarised below.

Type 2 diabetes

Obesity is thought to be the main cause of the global increase in type 2 diabetes. The risk of developing this form of diabetes increases with increasing body fat mass and duration of obesity [Hauner & Scherbaum, 2002]. Approximately 80-90% of people with type 2 diabetes also suffer from obesity [Mehnert & Standi, 2000]. Type 2 diabetes is a lifelong disease characterised by insulin resistance and a lack of insulin production [Bundesministerium für Gesundheit, 2023].

But what is the role of insulin? Insulin is a hormone that regulates blood glucose levels. After a meal, the blood glucose level rises. Insulin is then released into the blood by the pancreas and ensures that the sugar taken in with food is absorbed by the cells. This causes the blood sugar level to sink again [Stiftung Gesundheitswissen, 2024].

What happens if you are insulin resistant? The body's cells become less sensitive to insulin. As a result, the sugar in the blood is no longer absorbed properly. The pancreas has to produce more insulin to bring blood glucose levels back to a healthy level. However, the increased insulin production in type 2 diabetes eventually exhausts the pancreas and eventually leads to a shortage of insulin. As a result, blood glucose levels remain dangerously high and can lead to a range of health problems, including cardiovascular disease, eye disease, nerve damage and kidney problems [Stiftung Gesundheitswissen, 2024]

Cardiovascular diseases

Obesity can have a significant impact on the cardiovascular system. For example, obesity is often associated with increased blood pressure. High blood pressure is a permanent increase in pressure in the arteries that carry oxygen from the heart to the rest of the body. One study showed that around 30% of people with high blood pressure were also obese [Macmohan et al, 1987]. This can lead to circulatory problems, strokes, heart attacks and many other diseases [Deutsches Herzzentrum der Charite, 2024].

Long-term obesity is also associated with diastolic heart failure, a condition in which the left ventricle fails to fill properly with blood before it is pumped out of the heart and into the circulatory system. The risk of diastolic heart failure is significantly higher in both overweight (BMI between 25 and 29.9 kg/m²) and obese (BMI > 30 kg/m²) people compared to people with a normal weight (BMI < 25 kg/m²) [Russo et al, 2011].

In addition, obesity increases the risk of coronary heart disease [Jahangir et al., 2014], which is a narrowing or blockage of the blood vessels that can lead to symptoms such as shortness of breath, chest pain or even heart attacks [Centers for Disease Control and Prevention, 2024].

Obstructive sleep apnoea

Obesity is considered one of the main factors in the development of obstructive sleep apnoea [Gami et al., 2003], a condition in which the airway is partially or completely blocked during sleep [Hader et al., 2004]. This problem can be caused by fat deposits in the throat area, leading to a narrowing of the upper airway [Herkenrath & Randerath, 2016]. The consequences: excessive daytime sleepiness, high blood pressure, complete cessation of breathing during sleep or even strokes [Hader et al, 2004].

Cancer

In addition to the classic secondary diseases, people suffering from obesity are also more likely to develop cancer. Obesity increases the risk of developing and dying from a variety of cancers, including colorectal cancer, oesophageal cancer, kidney cancer, pancreatic cancer, gallbladder cancer, ovarian cancer, cervical cancer and liver cancer [Calle & Thun, 2004; Wolin et al., 2010]. More information on "How is obesity linked to cancer?”.

Mental illnesses

Mental illnesses such as depression or anxiety disorders can also occur as a result of obesity [Onyike et al., 2003; Simon et al., 2006]. One possible reason for the development of depression in people with obesity can be an impaired quality of life. This can be attributed to physical limitations on the one hand and other secondary diseases of obesity such as diabetes or cardiovascular diseases on the other [Fontaine & Barofsky, 2001; Sach et al., 2007]. In addition, obesity and, not least, the stigma associated with obesity can have a negative impact on people's self-esteem [Değirmenci et al., 2015] and thus significantly affect their mental health.

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