There is another great reason to try to lose weight if you are overweight or obese - being overweight or obese lowers blood flow to the brain in older adults. Yikes! However, one bit of good news from a study of 495 adults (average age 69) was that increased physical activity (brisk walks count!) can reduce or eliminate this association.
This could help explain why obesity increases the risk for a number of conditions as a person gets older, such as heart disease, dementia, and Alzheimer's disease.
The study was part of the Irish Longitudinal Study on Ageing. The average BMI (body mass index) was 28, which is considered overweight. One finding was that each 1 cm increase in waist circumference was associated with the same reduction of brain (cerebral) blood flow as 1 year of advancing age. (Yes, brain volume and blood flow typically diminish with age in older adults. So you want to prevent it as much as possible.)
The study found that higher levels of physical activity can reduce or remove this association of overweight & obesity and reduced brain blood flow. So if it's not possible to lose weight - then get really physically active!
How much exercise is beneficial? The researchers recommend at least 1.5 to 2 hours per day of "being active", that is, doing activities that require "moderate" effort - this means breathing somewhat harder than normal (e.g. brisk walking, cycling at a regular pace, carrying light loads). Equally beneficial is to get some "vigorous activity" which results in breathing much higher than normal (e.g., digging, aerobics, fast cycling, carrying heavy loads). But any and all movement is good!
A new study from scientists at The Irish Longitudinal Study on Aging (TILDA) at Trinity College Dublin reveals important findings, indicating that being overweight or obese significantly reduces blood flow in the brain. The study also shows that increased physical activity can positively modify, or even negate, this reduction in brain blood flow.
The study contains relevant information which is of great interest to the general public; since reduced blood flow in the brain, or 'cerebral hypoperfusion," is an early mechanism in vascular dementia and Alzheimer's disease.
What are the findings of the TILDA study?
The study investigates three different measures of obesity—body mass index (BMI), waist-to-hip ratio and waist circumference, as well as physical activity, in adults over 50 years.
Brain blood flow was measured using cutting-edge MRI scanning and analysis techniques. The findings reveal that being overweight or obese is associated with reduced blood supply to the brain. Whereas brain blood flow is known to decline with age, in this study the negative influence of obesity on brain blood flow was shown to be greater than that of age. However, being physically active helps to cancel out the negative effects of obesity on brain blood flow.
Key Findings: Increased BMI, waist-to-hip ratio, and waist size are associated with less blood supply to the brain. A waist size increase of +1cm is associated with the same reduction in brain blood flow as +1 year of age. Higher levels of physical activity modify the associations between reduced brain blood flow and obesity.
Dr. Silvin Knight, Research Fellow at TILDA and lead author, said: Consistent, healthy blood supply to the brain is critical, as it ensures that the brain is provided with enough oxygen and nutrients to function correctly. If brain blood flow becomes impaired, it can lead to serious health issues as we age, such as increasing the risk of dementia and Alzheimer's disease. We know that obesity can predispose a person to age-related conditions, illness, and disease, and even reduce life expectancy by up to six years in men and seven years in women, after the age of forty.