When did humans start becoming obese?


Obesity has always been an important issue of close public concern. According to the World Health Organization, about 2.8 million people die from overweight or obesity every year. "The World Obesity Atlas 2023" shows that if we do not take any action, then in the next 12 years, the global obesity population will reach 51% of the population. In other words, by 2035, there may be more than 4 billion overweight or obese people in the world! This situation will cause serious burdens on both individuals and society. So, when did humans start to gain weight? How should we respond?

When did humans start becoming obese?

As for when the obesity epidemic began, most people may subconsciously think that the obesity epidemic began when social material standards have been greatly improved in recent decades. Some epidemiologists believe the origins of the obesity epidemic can be traced to the 1970s, when rates of obesity (defined as a BMI >30) began to rise dramatically in many Western countries. However, the results of a recent study published in Science Advances, a subsidiary journal of Science, challenge our common sense - the obesity epidemic may be older than we thought...

The study investigating the origins of the obesity epidemic was conducted by scientists from the School of Health and Medical Sciences at the University of Copenhagen in Denmark. One of them, epidemiologist Dr. Thorkild Sørensen, believes that this global obesity crisis may not have formed in just 50 years - because the development of obesity is a cumulative process, and the obesity epidemic reflects What's more, the proportion of individuals exceeding this BMI threshold is getting higher and higher, so he speculated that this change in BMI distribution may have been a trend as early as the 1970s. In addition, Dr. Sørensen also believes that in addition to poor eating habits and lifestyle, there may be other important factors that play a role in the obesity epidemic.

To prove their hypothesis, Dr. Sørensen and his colleagues spent several years digitizing and then analyzing more than 2 million pieces of data collected by the Danish government on more than 520,000 subjects. The data includes height and weight data for nearly all primary school children in Copenhagen from the 1930s to the 1980s, as well as for men aged 18 to 26 drafted into the Danish army between 1957 and 1984.

Preliminary analysis of the data shows that obesity rates have been increasing since 1930. For example, 0.18% of boys born in 1930 would be classified as obese by age 10, while this increased to 1.13% of boys born in 1970.

In order to determine whether this obesity epidemic trend exists in the entire population or only in a few individuals, the researchers also investigated the distribution of BMI index according to the year of birth of the study subjects. The results were surprising: the BMI distribution of the 75% of people with a lower BMI basically remained unchanged over the decades of research. In other words, whether born in 1939 or 1959, a draftee with a body mass index of 20 would rank roughly in the 25th percentile of the general population.

Changes in BMI percentiles for young men born in different years

For those people whose BMI index is in the top 25%, their maximum body mass index is obviously increasing year by year, especially those with more extreme BMI index. For example, among draftees born in 1940, those in the top 1% had a BMI hovering around 28, while among draftees born in 1950, those in the top 1% had a BMI above 30.

Regarding these results, the researchers said that the obesity epidemic may be traced back to the 1930s, and that obesity rates began to rise slowly in the early to mid-20th century, with people in the top 25% of BMI values being the main source of the obesity epidemic.

What causes humans to gain weight?

We usually think of lifestyle and diet as the main causes of obesity, but humans became less active and ate more high-calorie or highly processed foods only gradually emerged in the late 20th century, which does not explain the gradual increase in obesity rates since the 1930s.

Some scientists speculate that this may be related to genetic factors or an increased supply of carbohydrates. But other scientists pointed out that the study has certain limitations because it lacks data on middle-aged people, and obesity is generally more common in middle-aged people. Still, the study raises a question worth exploring about obesity.

Researchers say another noteworthy phenomenon about the obesity epidemic in recent years is that obesity is spreading faster in rural areas than in urban areas. This is not just happening in Denmark, but seems to be the case around the world. While food abundance is seen as an important factor in the obesity epidemic, findings from multiple studies suggest that other, currently undiscovered, environmental factors should also be looked for that may have driven early changes in BMI distribution.

In this study, changes in those in the top BMI percentiles were dominant among those driving the obesity epidemic, possibly reflecting genetic susceptibility, epigenetic induction, or early life social environment that contributes to obesity. special susceptibility. In addition, researchers have proposed many other factors that may contribute to the obesity epidemic, including microorganisms, increasing maternal age, malnutrition during pregnancy, greater fertility in those with higher obesity rates, sleep deprivation, endocrine disorders, and obesity-causing drugs. , as well as the reduction of ambient temperature changes, etc. But so far, no factor has been found that has conclusive evidence of being associated with early changes before the obesity epidemic.

What should we do in the face of obesity?

As our understanding of the biological basis of obesity continues to deepen, and as we realize that the causes of the obesity epidemic may be diverse, obesity is no longer just a personal aesthetic problem or a manifestation of a lack of personal willpower. It is becoming It is gradually recognized as a chronic metabolic disease. People with obesity should no longer be stigmatized and blamed, but should be treated with more empathy and supported by evidence-based treatments.

In recent years, the industry has successfully developed a number of new weight-loss drugs with promising effects. They are a class of drugs based on glucagon-like peptide-1 (GLP-1) analogues, which modulate the release of insulin after eating and increase feelings of satiety by mimicking the effects of the GLP-1 hormone.

The first approved GLP-1 drug was semaglutide from Novo Nordisk, which was originally developed and approved for the treatment of type 2 diabetes. Producing significant weight loss effects, it was approved in 2021 for the treatment of obese patients. In addition to Novo Nordisk, tirzepatide, a GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptor dual agonist developed by Eli Lilly for the treatment of diabetes, also showed excellent weight loss in clinical trials. It is currently on the market, but it has not yet been approved for obesity indications. This new class of weight loss drugs has benefited many obese patients so far.

Due to the increase in the global obese population, there is a huge unmet demand for the indication of weight loss, and related clinical drug development is also moving towards target diversification, oral dosage forms (which have better patient compliance than injections) and breakthrough weight loss effects Bottlenecks These three trends move forward. According to statistics from the well-known industry media STAT, there are currently nearly 70 obesity treatments in the research and development stage. In other words, the field of weight loss therapy is ushering in a period of rapid development, and new therapies are constantly emerging, which will bring more treatment options to obese patients.

But when using this type of therapy, we also need to understand that although weight-loss drugs have shown impressive weight loss results in clinical trials, they don't work for everyone. Factors that influence its effectiveness include genetics, environmental factors, gender and starting weight, as well as the presence of type 2 diabetes, among others.

In addition, it should be noted that this type of medicine also needs to be used according to the doctor's advice. It is not suitable if it is used by oneself just to keep a slim figure. Some regulatory agencies have pointed out that in addition to the efficacy of weight loss treatments such as GLP-1 receptor agonists, some of the accompanying side effects and potential risks should not be ignored. We cannot regard these drugs as a panacea and use them blindly. The best way to lose weight should be to continue to focus on a balanced diet, control calorie intake, and maintain moderate physical exercise while assisting with medication.

Hopefully, research in the field of obesity will continue to flourish and change society’s cognitive biases about obesity so that we can better understand and support those struggling with the difficult battle of losing weight. At the same time, we also look forward to more breakthroughs in the research and development of corresponding therapies, providing more treatment options for obese patients who really need drug assistance.