According to a recent study by Norwegian scientists, since 1975, the proportion of adults worldwide is obese mainly due to diet changes and lazy exercise. However, genes also decide a small part to each person's physical condition and shape.
So far, the standard measure of obesity is body mass index (BMI). This index is calculated based on weight and height. If the index is 25-30, it means that the person is overweight. Over 30 corresponds to obesity and the higher the index, the higher the risk of cardiovascular disease, stroke, and diabetes.
About 4% of adults in the mid-1970s had a BMI of 30 or more. But according to WHO, by 2016, that rate has increased to 13%, in which the proportion of women who are obese is higher than that of men.
Currently there are about 2 billion people aged 18 and over, equivalent to 39% of all adults with a BMI above the overweight threshold, ie over 25 and about 700 million obese people. Overweight rate has even increased sharply in children, from 4% in 1975 to over 18% in 2016.
In order to assess the impact of the environment and genes on obesity, besides dietary factors, scientists at the Norwegian University of Science and Technology, led by scientist Maria Brandkvist have concluded Combining data of height and weight of nearly 120,000 people in Norway between 1963 and 2008.
In which data show that adults begin to be obese since the 1980s and 1990s. Especially those born after 1970 are more likely to have a significantly higher BMI than the children of the previous generation. .
Half of the people in the study were divided into five groups depending on their genetic sensitivity to obesity.
For people with "obese" genes from an early age, unhealthy lifestyles will make the weight gain even more complicated.
When comparing groups at the two extremes, the team found that 35-year-old men with latent genetic variants with the ability to gain weight possessed heavier body weight than men. The same age does not have genes that cause obesity.
About four decades later, even when obesity rates increase in all age groups, that gap continues to double. Women also showed a similar upward trend despite a smaller increase in time.
Brandkvist explains: "Genetic predisposition will make a 35-year-old man with an average height of 3.9kg heavier than those without obese genes in the 1960s. In Norway today, vulnerable genes have can make a man 6.8kg heavier than other people ".
In addition, the person may increase by 7.1kg if he lives in an environment that is easy to cause obesity. The weight of a man can even increase to 13.9 kg if the lifestyle is not healthy and his genes interact with the environment.
Although the relationship between genes and the degree of obesity in one person is very large, the study has not yet identified a causal relationship. Only clinical trials can highlight direct causal relationships. But such experiments are impossible for humans for both practical and moral reasons.
The study was published in the famous medical journal The BMJ.
Refer to AFP