Imagine a world where over a quarter of the population, that’s roughly one billion people, aren’t able to reach their cognitive peak. Well, I hate to break it to ya but we’re living in that world right now. Over a quarter of the world’s population is estimated to have metabolic syndrome (MetS), which is a cluster of physical diseases characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia (Saklayen, 2018). It sounds scary enough as is, but it’s impact on our brains is even scarier. MetS is implicated in several cognitive impairments, including deficits in memory, visuospatial abilities, executive functioning, processing speed, overall intellectual functioning, overall IQ, attention and concentration in both adults and children (Yates et al., 2012). It has even been linked to cognitive decline in neurodegenerative diseases such as Alzheimer’s and Dementia (Kullman et al., 2016). And the scariest part? We might not even know it’s happening. According to the newest research, only about 12.2% of the entire U.S. population is optimally metabolically healthy (Araujo, Cai, & Stevens, 2018). Even those who are not overweight or obese, and have not been diagnosed with any of the risk factors associated with MetS may not be optimizing their metabolic health. Not only is this a concern when it comes to the physical health of our nation, but the ability of ourselves and future generations to reach their cognitive peak as well. Let’s learn a bit more about what metabolic disorders are, how they impact the brain, and what we can do to reverse or prevent them from taking over our mental performance.
What is Metabolic Syndrome?
MetS is not just one disease, but instead a cluster of risk factors that can be related to the development of Cardiovascular Disease (Haase et al., 2021). Although not synonymous with MetS, obesity is associated with increased risk of developing many of these risk factors that make up this syndrome. There is also significant overlap with Type 2 Diabetes (T2D) and MetS (Hassentab et al., 2010). In order to be diagnosed with Metabolic Syndrome, an individual must have the presence of 3 or more of the criteria (Yates et al., 2012):
Abdominal obesity with a waist circumference over 40 inches for men, and 35 inches for women
Elevated triglycerides ≥ 150mg/dL
HDL < 40mg/dL for men or < 50 mg/dL for women
Blood pressure ≥130/≥85 mm Hg (or current use of blood pressure medications)
Fasting glucose levels ≥110 mg/dL
According to the American Heart Association, underlying causes of this disorder include overweight and obesity, insulin resistance, physical inactivity, genetic factors, and age (heart.org). As far as it sounds now, MetS is largely a physical condition, so what does it have to do with cognitive performance? Let’s keep learning…
MetS and Cognition
As I mentioned before, MetS is intricately connected to cognitive performance. Studies have shown that there are significant reductions in cognitive performance with each additional MetS criterion met (Yates et al., 2012). These reductions happen not only in elderly who are experiencing cognitive decline associated with aging, but also in young adults, adolescents, and even children. In adolescents and children, individual factors for MetS such as obesity and T2D were linked to volume loss in the hippocampus and the frontal lobe. These structural changes were correlated with worse memory, attention/concentration, global functioning and IQ, and executive functioning, than their peers who were also obese but without T2D (Yates et al., 2012). In adults with MetS, there has been evidence of impaired memory, visuospatial abilities, executive functioning, processing speed, and overall intellectual functioning (Yates et al., 2012).
Potential causes for the cognitive impairment that accompany MetS include impairments in cerebrovascular reactivity, reductions of white matter microstructural integrity (Yates et al., 2012), neuroinflammation and its subsequent impact on blood brain barrier (BBB) permeability (van Dyken & Lacoste, 2018), and decreases in the sensitivity of the brain to insulin (Kullman et al., 2016). The carotid artery is the main blood source for the brain. In MetS, there is increased carotid stiffness, which leads to a decrease in the blood flow to the brain. This can lead to cell death and shrinkage in specific brain regions such as the hippocampus, frontal lobe, and white matter (Yates et al., 2012). The inflammation that is correlated with MetS can cause cognitive problems as is, but this inflammation is also shown to cause damage to the blood brain barrier (BBB). The BBB is a protective barrier that surrounds the brain to keep anything that’s not beneficial to its functioning out of there. When there is inflammation, the BBB is disrupted and becomes permeable. This leads to toxins, cytokines, and other molecules making their way into the Central Nervous System (van Dyken & Lacoste, 2018). All of this to say that there is structural damage that is done to the brain in response to the physical ailments that accompany MetS. The damage that is done impairs the brain’s ability to think, learn, remember, process information, focus, and function in general.
Dietary Modifications for Metabolic Health
If you’re one of the billion people who are suffering from MetS and want to improve your health in order to improve your cognitive function, you’re in luck. Diet is a key environmental factor that influences MetS, and therefore interventions that include dietary modifications can be beneficial to improve metabolic health. Below are a few dietary modifications that have been shown effective in treating and reversing MetS.
Carbohydrate restriction: because many factors associated with MetS can be contributed to carbohydrate intolerance, lowering overall intake of carbohydrates can be useful for reversing many of the risk factors associated with this syndrome (Hyde et al., 2019). When consuming carbs, focus on whole foods that are rich in fiber and micronutrients, such as non-starchy vegetables, berries, and low glycemic fruits.
Time restricted eating: “intermittent fasting” seems to be the craze these days. Truth is, some aspects of this style of eating may be beneficial for those suffering from MetS (and those who want to decrease their risk of developing MetS!). Sticking to a “fasting” window of about 10-14 hours has shown to lower blood pressure and atherogenic lipids, promote weight loss, reduce body fat percentage, and visceral fat; several of the risk factors associated with MetS (Wilkinson et al., 2020). Before beginning a time-restricted eating protocol for yourself, consult with a doctor, nutrition coach, or other healthcare practitioner to make sure this is the right protocol for you.
Mediterranean diet: this type of diet is characterized by those who live alongside the Mediterranean sea. It consists of high levels of Extra Virgin Olive Oil, nuts, seeds, green leafy vegetables, whole grains, legumes, fruits, and fish. This type of diet is also high in polyphenols, which we know are beneficial in decreasing inflammation, a risk factor implicated in MetS. The Med Diet is found to be helpful in preventing MetS, but it is also shown to have improved some of the individual criteria related to MetS such as weight circumference, blood pressure, and triglycerides (Castro-Barquero et al., 2020).
In a world where you can be anything, be metabolically healthy. Your body will thank you, and so will your mind! The food environment that we currently inhabit makes it difficult for us to take care of our metabolic health, which is presented by the statistic that only 12.2% of us are truly optimally metabolically healthy. Although genes do play a role, I would argue that the increasing rate of this disease points to the fact that it’s more about our diet and lifestyle choices. And, that’s good news! Just as we’ve been able to expand this disease, we can reverse it just as easily, and take back control over our cognition and mental performance, and I’m here to help. Is your metabolic health taking a toll on your brain power? Sign up for a free 30 minute consultation with me to find out how we can help you reach your peak.
References
Araújo, J., Cai, J., & Stevens, J. (2019). Prevalence of Optimal Metabolic Health in American Adults: National Health and Nutrition Examination Survey 2009–2016. Metabolic Syndrome and Related Disorders, 17(1), 46–52. https://doi.org/10.1089/met.2018.0105
Castro-Barquero, S., Ruiz-León, A. M., Sierra-Pérez, M., Estruch, R., & Casas, R. (2020). Dietary Strategies for Metabolic Syndrome: A Comprehensive Review. Nutrients, 12(10), 2983. https://doi.org/10.3390/nu12102983
Haase Alasantro, L., Hicks, T. H., Green-Krogmann, E., & Murphy, C. (2021). Metabolic syndrome and cognitive performance across the adult lifespan. PLOS ONE, 16(5), e0249348. https://doi.org/10.1371/journal.pone.0249348
Hassenstab, J. J., Sweat, V., Bruehl, H., & Convit, A. (2010). Metabolic Syndrome Is Associated with Learning and Recall Impairment in Middle Age. Dementia and Geriatric Cognitive Disorders, 29(4), 356–362. https://doi.org/10.1159/000296071
Hyde, P. N., Sapper, T. N., Crabtree, C. D., LaFountain, R. A., Bowling, M. L., Buga, A., Fell, B., McSwiney, F. T., Dickerson, R. M., Miller, V. J., Scandling, D., Simonetti, O. P., Phinney, S. D., Kraemer, W. J., King, S. A., Krauss, R. M., & Volek, J. S. (2019). Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss. JCI Insight, 4(12). https://doi.org/10.1172/jci.insight.128308
Kullmann, S., Heni, M., Hallschmid, M., Fritsche, A., Preissl, H., & Häring, H. U. (2016). Brain Insulin Resistance at the Crossroads of Metabolic and Cognitive Disorders in Humans. Physiological Reviews, 96(4), 1169–1209. https://doi.org/10.1152/physrev.00032.2015
Power, M. C., Su, D., Wu, A., Reid, R. I., Jack, C. R., Knopman, D. S., Coresh, J., Huang, J., Kantarci, K., Sharrett, A. R., Gottesman, R. G., Griswold, M. E., & Mosley, T. H. (2019). Association of white matter microstructural integrity with cognition and dementia. Neurobiology of aging, 83, 63–72. https://doi.org/10.1016/j.neurobiolaging.2019.08.021
Saklayen, M. G. (2018). The Global Epidemic of the Metabolic Syndrome. Current Hypertension Reports, 20(2). https://doi.org/10.1007/s11906-018-0812-z
Segura, B., Jurado, M. A., Freixenet, N., Falcon, C., Junque, C., & Arboix, A. (2009). Microstructural white matter changes in metabolic syndrome: A diffusion tensor imaging study. Neurology, 73(6), 438–444. https://doi.org/10.1212/wnl.0b013e3181b163cd
van Dyken, P., & Lacoste, B. (2018). Impact of Metabolic Syndrome on Neuroinflammation and the Blood–Brain Barrier. Frontiers in Neuroscience, 12. https://doi.org/10.3389/fnins.2018.00930
Wilkinson, M. J., Manoogian, E. N., Zadourian, A., Lo, H., Fakhouri, S., Shoghi, A., Wang, X., Fleischer, J. G., Navlakha, S., Panda, S., & Taub, P. R. (2020). Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome. Cell Metabolism, 31(1), 92–104.e5. https://doi.org/10.1016/j.cmet.2019.11.004
Yates, K. F., Sweat, V., Yau, P. L., Turchiano, M. M., & Convit, A. (2012). Impact of Metabolic Syndrome on Cognition and Brain. Arteriosclerosis, Thrombosis, and Vascular Biology, 32(9), 2060–2067. https://doi.org/10.1161/atvbaha.112.252759