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True and false about obesity

Professor Jan-Wilhelm Kornfeld is an expert on the molecular biology of obesity. Here are his answers to five common obesity statements

By Birgitte Svennevig, , 2/26/2024


Now that we have the weight-loss medicine Wegovy and Zepbound, the world's obesity problem is solved.


The medicine is expensive, and even in wealthy countries, there are people who cannot afford it. Obesity is no longer a problem only in developed countries. The largest increase in the number of obese individuals is now seen in developing countries, where only a few can afford the medicine. Currently, the highest percentage of obese adults is found in Pacific island nations and Middle Eastern countries such as Kuwait, Qatar, Jordan, and Saudi Arabia. The USA ranks 30th (38.16% of the adult population). Denmark ranks 136th with 17.71%. Data for all countries can be found at the Global Obesity Observatory.


If you consume fewer calories than you burn, you will lose weight.


It is basic physiology. However, reducing calories by a small amount, such as 200, is not enough because the body will compensate for the missing 200 calories. The body does not like to be in a calorie deficit, so when it senses a lack of 200 calories, it will react by burning fewer calories – it simply lowers its basal metabolic rate. Therefore, one must be prepared to cut more calories or increase metabolism through physical activity.

What is obesity?

According to WHO, one is considered obese, if your BMI is 30 or more. You are overweight if your BMI is between 25 and 30. BMI is calculated as follows: Weight in kg divided by (height x height). For example: 90 kg divided by (1.80 m x 1.80 m) = 90 divided by 3.24 = BMI 27.78. BMI does not distinguish between fat and muscles, so it may be more accurate to measure in one of these two ways:

  • Waist-hip ratio: This is the circumference around the waist divided by the circumference around the hips. It is common to consider a waist-hip ratio ≥0.90 in men and ≥0.85 in women as abdominal obesity and overweight.
  • Waist circumference: There is a slightly increased risk if the waist circumference is >94 cm and >80 cm for men and women, respectively. There is an increased risk if the waist circumference is >102 cm and >88 cm for men and women, respectively.


Obesity can be hereditary.


There are certain genes that predispose individuals to obesity. If a person has specific variants, for example in the so-called FTO gene, he or she will be, on average, several kilograms heavier. How these genes specifically increase weight gain is  not known, but studies in mice lacking FTO suggest that this might be due to the gene's influence on the brain's appetite regulation and activation of reward centers, causing satisfaction from eating fatty and carbohydrate-rich food, leading to increased eating and weight gain. These are the same reward centers triggered by smoking, alcohol consumption, or drug use. Other hereditary obesity genes also act in the brain and for instance more directly increase food intake by a heightened appetite. 


A body can have fat deposits that are almost impossible to get rid of.


But these are probably not the deposits most of us think about. We all store fat differently. Some store it around the organs, which may be visible on the belly. Others store it on hips and thighs. Factors influencing fat distribution and difficulty in getting rid of it include gender, genetics, age, and overall cardiovascular and metabolic health. However, with enough calorie deficit, even stubborn fat deposits will disappear. The very last to disappear are the fat depots in skin and bone marrow, and these we should not wish to lose. Skin fat helps with insulation, and bone marrow fat is crucial for maintaining bone health.


A person can be fat and healthy.


One cannot only rely on BMI to indicate health – even if the number is high and classifies one as overweight or obese. BMI does not indicate how much fat is on the body, where it is located, or whether it is healthy fat. Healthy fat can be found on hips and thighs, while unhealthy fat is around the organs and often seen as belly rolls. People with the latter type are called apple shaped, and the former pear-shaped. Apple shape is unhealthy, pear shape is healthy. Women are more often pear shaped, and men are more often apple shaped. Why some fat is healthy and others unhealthy is not yet known. It also has a significant impact on your health whether you have just become overweight or have been for many years.

Meet the researcher

Jan-Wilhelm Kornfeld is a professor and co-founder of the Center for Adipocyte Signaling, Department of Biochemistry and Molecular Biology. His research focus is to understand how gene activity is dysregulated in obesity. This includes studying fat cells from obese mice and humans. Together with physicians, chemists, and experts in gene therapy, he is also working to develop new treatment methods that may, in the future, correct the dysregulated gene activity in the fat cells of obese individuals. His research group is supported by the Novo Nordisk Foundation, Independent Research Fund Denmark, Sygeforsikringen Denmark, the Danish Diabetes and Endocrine Academy (DDEA), and the Danish Cardiovascular Academy (DCA).

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Editing was completed: 26.02.2024