By Gabe Mirkin, MD
Many studies show that having excess fat in your belly is associated with increased risk for dementia, but a new study shows that as a person ages, lack of muscle size and strength appears to be an even stronger predictor of dementia than having excess belly fat (Clinical Interventions in Aging, July 5, 2018;13).
The authors followed 353 men and women, average age 69, and found that those who had both excess body fat and small, weak muscles had the worst memory, speed in answering questions and executive function such as making intelligent decisions. Those who had the weakest and smallest muscles had even worse mental function than those who were just obese and did not have excessive muscle weakness. Another well-performed study of more than 5000 people, with an average age over 70, also found that low muscle size is associated with increased risk for dementia (Age and Ageing, March 2017;469(2):250–257).
Significance of “Skinny Fat”
This new study found that many people who do not have conventional measures of obesity such as excess weight or a high BMI (Body Mass Index) can still be at high risk for obesity-related diseases such as dementia, heart attacks, strokes, diabetes, certain cancers and premature death. The authors call this “skinny fat,” a combination of low muscle size and strength and high fat mass that significantly increases risk for dementia. Sarcopenia (loss of muscle size and strength) and obesity are part of the aging process for many people, and can both be used to predict potential mental decline, dementia, and diseases associated with aging. These conditions can be caused by sedentary behavior, weight gain and an unhealthful diet.
Testing and Treating People with “Skinny Fat”
Strength testing can be as simple as measuring a person’s grip strength with a simple inexpensive hand-held dynamometer. Excess fat can be measured with belly circumference or thickness of the fat layer underneath the skin near the belly button. An MRI of the body will be more accurate but is far more expensive and time consuming. People with weak grip strength or high belly fat are at increased risk for dementia with aging, even if they appear otherwise to be thin and healthy. An earlier study showed that a program of strength training and aerobic exercise and a healthful diet can help slow the frightening loss of muscle size and strength and increase in body fat in people as they age (Clinical Interventions in Aging, August 6, 2015;1267—1282). See my recent report on How Exercise Reduces Dementia Risk
A recent review of many studies showed that the typical Western diet (high in sugar, red meat, processed meat and fried foods) is associated with a marked increase in the incidence of mental decline and dementia throughout the world (presented at the 2018 Alzheimer’s Association International Conference, July 22, 2018 in Chicago, Illinois). Another study of 2200 people, presented at this same conference, shows that people who consume the equivalent of two-and-a-half teaspoons or more of added sugar a day have a 54 per cent increased risk for developing Alzheimer’s disease. A high rise in blood sugar can damage every cell in your body, particularly your brain.
To prevent blood sugar levels from rising too high, your pancreas releases insulin which lowers blood sugar by driving sugar from the bloodstream into the liver. However, if you have a lot of belly fat, you are also likely to have a liver full of fat, and a fat-filled liver cannot accept sugar from the bloodstream. Contracting muscles can lower blood sugar just by pulling sugar from the bloodstream without even needing insulin. A single bout of exercise will allow your muscles to pull sugar out of your bloodstream without needing insulin for up to 17 hours after you finish exercising. Lack of exercise and low muscle size are associated with high blood sugar levels and increased risk for both diabetes and dementia.
A high rise in blood sugar after meals is a major risk factor for dementia. You will help to prevent dementia by preventing high rises in blood sugar if you:
• grow larger and stronger muscles
• avoid foods that cause high rises in blood sugar
• avoid having excess belly fat that specifically causes high rises in blood sugar
To help you keep your muscles strong as you age, see my report on Sarcopenia (Muscle Loss with Aging) Linked to Inflammation