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Having A Poor Body Composition May Expedite Cognitive Decline

Author:

Jillian Kubala, M.S., R.D.

Expert reviewer:

Molly Knudsen, M.S., RDN

July 08, 2023

Registered Dietitian

By Jillian Kubala, M.S., R.D.

Registered Dietitian

Jillian Kubala, MS, RD is a Registered Dietitian based in Westhampton, NY. She holds a master's degree in nutrition from Stony Brook University School of Medicine as well as an undergraduate degree in nutrition science.

Expert review by

Molly Knudsen, M.S., RDN

Registered Dietitian Nutritionist

Molly Knudsen, M.S., RDN is a Registered Dietician Nutritionist with a bachelor’s degree in nutrition from Texas Christian University and a master’s in nutrition interventions, communication, and behavior change from Tufts University. She lives in Newport Beach, California, and enjoys connecting people to the food they eat and how it influences health and wellbeing.

Image by Bakhrom Tursunov / Unsplash

July 08, 2023

Oftentimes, the conversation around body fat focuses on dieting and weight loss, with little nuance given to different kinds of weight. Is it from lean mass like your muscles? Or from fat mass? This is where body composition comes into play. Because research shows that low levels of lean mean mass—even in the absence of high fat levels—pose health risks and may influence cognitive decline.

Here's what to know about body composition and cognitive decline.

What exactly is body composition?

Body composition refers to your levels of body fat and lean body mass,1 which includes muscle, bone, and water. There are many different ways to evaluate your body composition 2. Simple tools include taking skinfold measurements (which uses a device to pinch the skin in a few places) or measuring waist circumference (a proxy for belly fat). More complex devices involve sending a weak electrical current through your body (bioelectrical impedance analysis) or using an MRI machine.

Body mass index or BMI is not a measure of body composition since it only accounts for a person's height and weight. While it is the metric that defines overweight and obesity (and is sometimes used by researchers as a rough estimate for body composition in large studies) at the individual level, BMI misses the mark when it comes to estimating body composition and evaluating overall health.

The link between body composition and cognitive decline

Having a poor body composition (aka high levels of fat mass, low levels of muscle mass, or both) is associated with cognitive decline in older age.

High levels of body fat impact brain health in a variety of ways

A generally healthy range for body fat levels 3 falls between 20 and 30% in women and between 12 and 20% in men. However, individual studies may define high levels of body fat differently.

Research shows that having very low and high body fat levels is linked with lower total brain gray matter volume 4, which is a hallmark of aging. Gray matter is a type of tissue found in your brain that plays an important role in memory, mental function, and emotions. A loss of gray matter volume is associated with age-related cognitive decline and conditions like Alzheimer's disease.
High levels of body fat increase chronic low-grade inflammation 5, which can contribute to cognitive impairment and increase the risk of dementia and Alzheimer's disease later in life.
Hormones produced by body fat 6, including leptin and adiponectin, can cross into the brain and are correlated with cognitive dysfunction.
Excess body fat may alter your gut microbiome and negatively impact blood flow to the brain 7, which could contribute to the risk of neurodegenerative diseases, like Alzheimer's.
Studies show that midlife obesity—characterized as excess fat accumulation—is a significant risk factor for dementia. A 2021 study found that adults with obesity in their 40s were three times more likely to develop dementia 8 than those with a healthy weight.

Low levels of lean body mass impair cognition

The loss of muscle mass—known as sarcopenia—is also linked to a loss of gray matter volume and an increased risk of cognitive impairment 9.

A 2022 study published in JAMA Network Open was one of the first to pinpoint a link between low muscle mass and faster executive function decline 10(think things like recall and reasoning) in older adults. This link still held true regardless of a person's body fat percentage and strength.

This is an important finding because previous research suggests that muscle strength 11 is a more relevant marker for sarcopenia-related cognitive impairments than lean mass.

Tips to improve your body composition and brain health

It's clear that your body composition throughout your adult life can have a powerful impact on brain health in your later years.

Fortunately, there are many ways to maintain healthy body fat levels, improve strength and muscle mass, and reduce your risk of cognitive decline:

Stay active: People tend to become less active with age. Staying active by getting plenty of exercise is critical for physical and mental health. Walking is one of the easiest and most underrated ways to keep your body strong and ward off mental decline. Studies show that participating in light-intensity physical activity 12 during midlife—like walking—is associated with a lower risk of cognitive decline and improved body composition 13. If you're not physically active, try going on a few short walks per week, then increasing the length of your walks as you get stronger.
Follow a nutritious, whole-foods-based diet: Sticking to an eating pattern primarily composed of whole, minimally processed foods could help reduce your risk of cognitive decline and help you maintain healthy body fat levels. A 2018 study found that making healthy dietary changes in your 50s—like eating higher quality fats, increasing vegetable intake, and decreasing sugar and salt—was associated with a 59% reduced risk of dementia 14.
Take brain-supportive supplements: Having low or deficient levels of certain nutrients may harm your brain. For example, deficiencies in vitamin B12 15 and vitamin D 16 have been linked to a greater risk of cognitive impairment. Citicoline is a compound that has neuroprotective and memory-preserving effects. It's naturally produced by the brain, but it's also available as a dietary supplement. Supplementing with citicoline and other brain-enhancing compounds—nootropics—could help preserve cognitive function. Here are some of our favorite nootropic supplements.
Take sleep hygiene seriously: Your sleeping patterns have a major impact on the health of your brain, body composition, mood, and more. Not giving your body the sleep it needs can wreak havoc on your entire system, including your brain. Poor sleep quality 17 and short sleep duration may increase your risk for cognitive decline and dementia, including Alzheimer's disease. Sleeping too much can also harm your brain. Plus, poor sleep quality is linked with an increased risk of obesity 18. For optimal health, aim for the sleep "sweet spot" of seven to nine hours of sleep per night.

Other ways to keep your brain healthy and sharp and support a healthy body composition include avoiding smoking 19 and excessive drinking, adding weight training 20 to your exercise routine, and spending time in the great outdoors 21.

The takeaway

Maintaining a healthy body composition in your 40s and 50s can help reduce your risk of cognitive decline as you grow older.

Making small changes to your diet and lifestyle today, like working toward a healthier body composition, taking a walk, eating some veggies, or personalizing your supplement regimen, could make a major difference in your cognitive health down the road.