In March this year, the World Obesity Association released the "World Obesity Map 2023", once again sounding the alarm for the world - it is expected that by 2035, more than 4 billion people will be overweight or obese (BMI≥25kg/m2), accounting for 51% of the world's total population! By then, overweight people will even exceed normal size, becoming one of the most serious public health problems worldwide.
In fact, the situation of overweight or obesity on the mainland is not optimistic. The report shows that the annual growth rate of obesity in mainland China from 2020 to 2035 is as high as 5.4%; In the absence of relevant measures, almost 1 in 5 Chinese will be obese by 2035.
China's obesity rate is forecast to increase
As one of the ten major chronic diseases identified by the World Health Organization, obesity will destroy human health like a "snowball", including leading to a series of complications, such as metabolic syndrome, diabetes, non-alcoholic fatty liver, cardiovascular and cerebrovascular diseases, cancer and so on.
Recently, research published in The Lancet Regional Health-Western Pacific revealed another major harm of obesity - the bigger the belly, the more the brain hurts!
This epidemiological analysis and two Mendelian randomized studies in nearly 10,000 Asian populations showed a causal relationship between elevated visceral fat and BMI and cognitive decline - specifically, for every 0.27kg increase in visceral fat, cognitive performance declined, equivalent to a decline in cognitive age by 0.7 years.
The researchers collected 8,769 participants from the Singapore Life and Health Cohort (HELIOS) and recorded their metabolic markers and cognitive data.
Among them, the body fat composition was quantified using the DEXA whole body scan, including 16 individual lipid-related indices and 14 metabolic parameters to assess the participants' obesity and metabolism.
In this study, a BMI of >27.5 kg/m^2 was defined as obesity. The statistical results showed that 23.3% of all participants were obese, and another 12% had a BMI of more than 30kg/m^2. However, the incidence of obesity and various chronic diseases varies slightly between Asian countries.
Basic information categorized by country
The assessment of cognitive function uses a computerized test, which contains four sections, namely memory, executive function, processing speed and attention, and comprehensively calculates the cognitive index "g".
Across the population, the "g" index is normally distributed; Overall, "g" was positively correlated with years of schooling (r=0.35) and negatively correlated with age (r=-0.65).
Characteristics of the distribution of the cognitive index "g"
Univariate analysis showed that four factors most strongly associated with the "g" index were metabolic syndrome (β = −0.09), visceral fat (β = −0.07), high-density lipoprotein cholesterol (β = 0.07), and BMI (β = −0.05).
In other words, higher metabolic syndrome measurements, visceral fat, and BMI were associated with poorer cognitive performance; Conversely, increased levels of HDL cholesterol, one of the markers of metabolic health, were significantly linked to good cognitive performance.
Univariate and multivariate analysis results
In a further inverse variance-weighted Mendelian randomization, the researchers found a causal link between three major factors and cognitive function: visceral fat group (VAT), BMI, and BMI-adjusted waist-hip ratio.
Among them, "the increase in visceral fat leads to cognitive decline" has the strongest causal relationship! For every 0.27kg increase in visceral fat, or 4.52kg/m^2 increase in general fat, cognitive age will age by 0.7 years.
Higher BMI-adjusted waist circumference, blood pressure, triglycerides, glycemic index, and lower HDL cholesterol were not associated with altered cognitive function.
Mendelian randomization analysis results
In summary, in Asian populations, body fat content is one of the independent predictors of cognitive function. MR analysis revealed a causal relationship between elevated visceral fat and BMI and decreased cognitive performance. It seems that weight loss has added new benefits - "brain prevention dementia"!
The researchers highlight that the global burden of dementia is shifting from the Western Hemisphere to the Asia-Pacific region, with about 4 million Asians falling ill each year, accounting for about 40% of new cases globally. In addition, the prevalence of obesity in the Asia-Pacific region is already 7% higher than the global average and is even on the rise. Therefore, the prevention and control of obesity plays an important role in maintaining cognitive function in Asian populations and preventing dementia and other chronic diseases.
In fact, a randomized controlled study published earlier on eLife conducted lifestyle interventions in obese people for 18 months, trying to prove that "weight loss can delay brain aging."
Sure enough, a 1% loss of body weight in all 102 obese participants under lifestyle adjustments resulted in a significantly younger brain age of 8.9 months! This effect is really powerful! But how exactly do you change the habits in daily life to have such a good effect?
After inclusion of exclusion criteria, a total of 102 participants were included in this study. At baseline, the mean BMI and waist circumference (WC) were 30.1±2.5kg/m2 and 107.1±6.6cm, respectively, which met the criteria for obesity. In addition, the predicted mean baseline brain age was 52.8±4 years.
After 18 months of lifestyle intervention, participants lost 2.31 (± 5.61) kg of weight; BMI and waist circumference decreased by 0.76 (± 1.86) kg/m2 and 5.39 (± 5.89) cm, respectively, which were 6.45% and 4.35% lower than the baseline.
Further analysis revealed a correlation between changes in BMI and body weight and aging brain function. Specifically, a 1% BMI, or weight loss, led to an 8.9-month reduction in the rate of brain aging!
The relationship between changes in BMI and brain age
In addition to BMI and body weight, the researchers found a direct relationship between all fat deposition measurements and changes in subcutaneous superficial, visceral and liver fat and slowing brain aging. In other words, the more fat is lost under diet-induced fat, the younger the brain will be.
Lifestyle interventions are not one-size, but tailor-made in all aspects. So, among the many dietary and exercise lifestyle interventions, which factors have contributed to such "gratifying" results?
Correlation analysis shows that high intake of processed foods and sweets/beverages is the "culprit" that induces accelerated brain aging! But more intake of polyphenol-containing foods, such as green tea and walnuts, does not reduce brain aging.
In other words, in ordinary life, quitting junk food and sweets is the "golden key" to protect the brain!
Association between brain age decay and clinical measurements
As the researchers explain, high-weight damage to neurons is mediated by fat, metabolic dysfunction, and changes in the gut microbiome; These changes induce inflammatory metabolic processes in the central nervous system, leading to reduced gray/white matter volume, altered connectivity, and increased risk of cognitive impairment and dementia.
It should be noted that the normal range of BMI for Chinese adults is 18.5≤ BMI < 24, ≥24 and ≥28, respectively, overweight and obese. For people who are overweight or obese, it's time to adopt a healthy lifestyle to lose fat, such as reducing the intake of processed foods and sugary drinks!
In fact, whether the BMI exceeds the "point" of obesity, developing good diet and exercise habits can also effectively improve brain cognitive function and reduce the incidence of dementia, and it is also responsible for your own body, why not?
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Source: Metz Medical
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