Is the root cause of obesity due to "brain" abnormalities? After 5 years of weight loss, an average of 80% of the weight is regained! Why is it harder to lose weight after regaining weight?
The average weight gain is 80% in 5 years! Is the root cause of obesity in the brain?
Obesity is one of the most serious non-communicable diseases in the world. It also increases the risk of diabetes, metabolic syndrome, cardiovascular disease, degenerative arthritis, sleep apnea, depression, non-alcoholic fatty liver disease, infertility, and cancer. Risk factors for comorbidities such as gastroesophageal reflux. According to statistics from the World Health Organization, the global obesity rate tripled between 1975 and 2014, and the cost of treating related complications is as high as US$1 trillion per year.
The “obesogenic environment” is considered to be the main cause of adult obesity. Modern people consume fast food and processed foods that are large in portion, cheap, calorie dense (high in sugar and fat) but lacking in nutrients, which can easily lead to weight gain. In addition, genetic inheritance also plays an important role. Currently, 11 single genes and 227 multiple genes have been found to be related to biological mechanisms such as regulating appetite and lipogenesis. For example, young children with severe obesity often have MC4R gene receptor mutations, which affects leptin signaling. In fact, 75% of BMI variation may be directly affected by genetic inheritance.
However, even if they adjust their lifestyle or exercise hard, “weight loss” is still a very difficult task for some people. Statistics show that people who successfully lose weight will regain 50% of their weight within two years and 80% of their weight within five years. The reason why obesity is regarded as a “stubborn” disease is likely to be restricted by the “brain”. Some scholars call obesity a “disease of the brain.” For those with morbid obesity or some people who have difficulty losing weight, obesity should not be labeled as a lack of “willpower.” They need appropriate intervention strategies, including reset. Correct connections for brain signal transmission.
Abnormal appetite and pleasure secretion! Does the brain area become immobile after obese people eat?
Stimulated by the intestines, hormones, and the environment, the brain sends signals telling the body that it does or does not need to eat. Most people may think that they can control their eating, but they have to control their eating impulses through their own consciousness. In fact, it has little impact on overall eating. The brain’s appetite secretion is regulated by various neurotransmitters, including dopamine and leptin.
A study published in “The Physician” pointed out that obese people lack dopamine receptors and must overeat in order to feel satisfied. However, another recent preprint study pointed out that obese people may have too much dopamine, which results in the pleasure stimulated by eating not being strong enough. Whether there is too much or too little dopamine, it means that appetite is related to the sense of satisfaction secreted by the brain after eating. Insufficient sense of satisfaction is the main cause of overeating.
What is even more noteworthy is that in obese people, the neural communication circuit of the “brain-gut axis” may have “malfunctioned”, preventing the brain from correctly judging when to stop eating. A Yale University research team assembled two groups of lean and obese people and used functional magnetic resonance imaging (fMRI) to observe the brains. They found that after eating 500 calories in the brains of the thin people, the striatum in the brain, which is related to appetite secretion, gradually quieted down. On the contrary, after eating 500 calories in the brains of obese people, the operation of various brain regions remained “motionless”. Abnormalities in nerve conduction circuits may be one of the fundamental causes of obesity and bulimia.
The brain tends to maintain a variety of homeostasis, including stable blood sugar and body weight, to ensure that body load does not exceed limits. Therefore, when the body feels that there is insufficient fat storage, it will trigger the brain to secrete feelings of hunger and fatigue. On the contrary, when the “leptin” level in the body increases, it will send a signal to the brain, letting the brain know that there is too much fat in the body, reducing the appetite signal produced by the hypothalamus, and reducing the body’s desire to eat.
Under the same conditions, food type does affect weight changes. A 2019 study found that people who consumed ultra-processed foods ate 500 more calories per day. In contrast, the group that consumed unprocessed foods experienced weight loss. Dana Small, a neuroscientist at Yale University, wrote in a commentary that the nutrients in processed foods do not appear to be delivered to the brain and promote normal appetite rise and fall. In animal experiments, these processed foods also rewire brain circuits to dislike the healthy prototype foods.
The inability to maintain a stable weight is the key! The future of obesity
Up to now, adjusting lifestyle and engaging in appropriate exercise training are still the primary treatments for obesity. However, for patients who have failed to lose weight or have gained weight again after undergoing interventional drugs or weight loss surgery, how to prevent abnormal secretion of appetite for a long time is still a problem. In recent years, it has been discovered that enterocin analogs (GLP-1) can inhibit gastric emptying and reduce the secretion of appetite signals from the hypothalamus, which is regarded as a therapeutic hope for weight management. In addition, whether transcranial magnetic stimulation and deep brain stimulation (DBS), which are mostly used for neurodegenerative diseases, can regulate the animal brain to reduce abnormal appetite promotion, is also being studied.
Some voices are worried that the progress of weight loss drugs may become a kind of dependence, making obese people or ordinary people have to use medical technology to maintain a normal posture? David Ludwig, professor of nutrition at the Harvard School of Public Health, pointed out that treating obesity as a brain disease may be an oversimplified view. There are many metabolic factors in the human body related to obesity, including an evolutionary tendency to store fat. For patients with severe obesity, a multi-pronged approach of surgery, medication, and lifestyle adjustment is still indispensable.
For most weight loss cases, the biggest problem is the inability to maintain long-term and stable weight control. Most people will experience repeated weight loss and regaining weight. There is currently no consistent definition of “weight cycling”. Most studies define it as regaining weight after losing 4.5 kilograms. Gaining weight again after losing weight will cause fat to be redistributed from the periphery to accumulate in the internal organs, reducing basal metabolism and making it more difficult to lose weight in the future. Therefore, only by understanding the reasons for failure, adjusting weight loss methods, and consulting medical personnel to intervene in appropriate treatment, can we have a chance of stabilizing weight and maintaining health.
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