A review study published in this year’s first issue of Neural Plasticity (2016) points out that a sedentary lifestyle, poor diet, and fast pace of life have made obesity increasingly common. Obesity refers to the excessive accumulation of body fat. Currently, the weight class of adults is mainly judged according to the BMI index (Table 1 shows the threshold values of weight class recommended by the World Health Organization). According to the World Health Organization, in 2013, more than 1.9 billion adults worldwide were overweight , accounting for 39% of the total adult population; more than 60 million of these adults were obese, accounting for 13% of the total adult population; and 42 million children were overweight or obese. Around the world, obesity has become a worrying health and social problem that seriously threatens people’s physical and mental health and daily life.
We know that obesity is associated with many health problems, such as diabetes, heart disease, high blood pressure and cancer. Obese people have a shorter life expectancy compared to people of normal weight. And our review points out that in addition to health-related problems, obesity also causes decreases in cognition, motor function and affects brain plasticity.
What? It seems understandable that fat people are less mobile and less athletic, but obesity is also associated with cognitive, brain and academic fitness?
Obesity and cognitive function (brain fitness, academic fitness)
Studies have shown that obese children and adolescents exhibit poorer executive function, attention, mental rotation, math, and reading performance; animal experiments have shown that a high-fat diet causes the same morphological and metabolic changes in young and adult mice, but that mice exposed to a high-fat diet at a young age have impaired memory flexibility and reduced neurogenesis.
Middle-aged obese individuals have lower overall cognitive levels, faster brain volume loss, and faster cognitive aging than those of normal weight. If a person is overweight or obese in midlife, he/she will have lower than normal cognitive function in old age. Obesity in midlife, when accompanied by metabolic abnormalities, can greatly increase the risk of Alzheimer’s disease.
The frontal lobe, anterior cingulate gyrus, hippocampus and thalamus appear to be atrophied in older obese individuals. As BMI increases, metabolic activity in the prefrontal cortex and cingulate gyrus is reduced, gray matter volume is reduced in many brain regions (especially in the prefrontal lobe), and white matter integrity of the hook bundle (the structure connecting the frontal and temporal lobes) is reduced.
Obesity and motor function
Studies have found that overweight or obese individuals have poorer control of gross and fine motor movements and exhibit delayed motor development. Obese children are less likely to participate in sports in their daily lives, and they do not seem to enjoy the process of exercise. Obese children have lower rates of mastery of basic movements, especially running, sliding, jumping, kicking and dribbling; they also have poorer fine motor precision, balance, running speed and agility; they have difficulty coordinating their posture and are highly dependent with vision when moving, whereas non-obese children show more automation.
Obesity causes changes in muscle mass, which in turn is related to motor nerve conduction velocity and finger tapping speed. middle-aged and older adults with high BMI or large waist circumference have slower motor speed and poorer finger dexterity. In addition, obese individuals consume more attentional resources to compensate for their motor deficits, for example, obese individuals need to use more attentional resources to maintain balance when standing on one foot.
Mechanisms of influence
Obesity does not appear to be directly related to cognitive and motor function, so how does obesity affect cognitive and motor function? Let’s see how our new review article explains it.
On the one hand, the excessive accumulation of adipose tissue in obese individuals causes the body to develop insulin or leptin resistance, enhanced oxidative stress, the appearance of inflammation, disruption of the integrity of the blood-brain barrier, changes in the cerebral vasculature, and a decrease in neurotrophic factors, which are likely to alter the structure and function of the hippocampus, cerebral cortex, cerebellum, etc., which are very important neural bases for cognitive functions such as sensation, attention, memory, and thinking The cognitive function will be impaired as a result.
On the other hand, obesity affects motor function by affecting the musculoskeletal system (e.g. muscle mass), and since motor function is partly dependent on cognitive function, obesity can also indirectly lead to a decrease in motor function by affecting cognition.
Obesity and physical activity
Physical activity is an effective way to improve obesity and related problems caused by obesity, as it improves brain structure and function at different weight levels through a variety of mechanisms, with benefits for both cognition and motor behavior.
Studies have found that exercise 5 days per week for 15 weeks improves executive function in overweight children; 4 months of intense physical activity (including aerobic and endurance training) improves cognitive and oxygen extraction function in obese individuals.
The intensity and duration of physical activity, as well as the stage of growth and development of the participant, all influence the effect of exercise.
Exercise intensity is associated with changes in brain structure and levels of neurotrophic factor (BDNF), and studies have shown that moderate intensity exercise is optimal; a single bout of exercise of appropriate intensity has very little or no effect, and exercise of longer duration is beneficial for brain changes; in addition, it was found that 4 weeks of exercise improved recognition memory in both young and adult rats, but after stopping training for 2 In addition, it was found that 4 weeks of exercise improved recognition memory in both young and adult rats, but the improvement disappeared in adult rats after 2 weeks of cessation of training, whereas the improvement in recognition memory was maintained in young rats, which means that exercise interventions in youth or earlier may be more effective.
Physical exercise should also follow several principles: the principle of individualization (according to the physical condition of the exerciser); the principle of effectiveness (rationalize the exercise content, choose the best exercise intensity, duration, etc.); the principle of safety (ensure that the exercise intensity and amount of exercise is in a safe range, gradually, choose the right time and place to avoid danger); the principle of comprehensiveness (physical exercise should not only (can enhance physical fitness, strengthen resistance, reduce disease, but also can stretch the body and mind, eliminate stress, exercise willpower, maintain human physiological and psychological balance, to achieve the purpose of “overall physical and mental health”).
From the past research results, it seems that obesity brings “brain fitness”, “academic fitness” and motor function damage may be throughout life. Obesity is becoming more common in children today and, without intervention, is likely to continue into adulthood and even old age, increasing the risk of neurodegenerative diseases (such as Alzheimer’s disease) and seriously threatening people’s health and reducing their quality of life. Therefore, parents should pay attention to their children’s diet, avoid consuming too much high-fat food, encourage them to participate in more sports, and obesity in middle age should not be ignored. In fact, not only children and adolescents, and not only obese people, physical exercise is very important to improve everyone’s physical fitness, brain fitness and academic fitness.