by Dr. Sheri Colberg, Ph.D., FACSM
As my final column on brain health, here are the final reasons why your brain needs for you to be active regularly. Beyond the brain-released hormone, leptin arising from fat cells impacts brain health, as do gut bacteria.
Leptin Is Affected by Physical Activity, Too
A lot of research has focused on leptin and its relationship to fat cells in overweight and obesity, and the general conclusion has been that having higher leptin concentrations likely leads to the development of insulin resistance. A recent study conducted on European adolescents shed more light on how physical activity may offset some of the deleterious impact of having too much leptin released by your fat cells. Researchers examined the association of physical activity and fitness with leptin concentrations in youth after taking into account their total body fat, insulin resistance, and more. They found that the kids who engage in more vigorous physical activity and who are more physically fit have lower levels of leptin, regardless of how much body fat they have, leading them to conclude that schools should implement programs to increase high intensity physical activity and fitness. Similar conclusions have been reached in studies on adults! In short, leptin levels are less likely to be elevated—even when you have a bigger waistline—if you are physically fit, and having lower leptin levels is likely related to having your insulin work better in both your body and your brain.
Being Active Alters Your Brain to Help You Lose Weight
While physical activity is good for so many reasons, you may not know that it actually alters your brain and what you are likely to eat as well. Engaging in just five weeks of moderate intensity training resulted in significantly increases levels of plasma BDNF (brain-derived neurotropic factor), a chemical compound that causes you to eat less when its levels rise in the brain. Despite claims to the contrary by some, exercise is likely to cause you to eat less, not more. Doing regular physical activity also increases the number of mitochondria in the brain, which are the powerhouses of the cell—the result being that your brain’s activity is revved up, and you may actually be getting smarter and not just thinner by being more regularly active. What’s not to like about that?
Why Exercise Is Good for Gut Bacteria
A limited body of research suggests that regular physical activity also improves the balance of the helpful bacteria in your gut. By way of example, one small study investigating adults taking a tai chi class in China found that two months of regular participation changed the microflora balance for the better in these individuals. There is also some evidence that the intestinal flora a person has may affect his or her levels of physical activity as well, with more harmful bacteria sending signals to the brain via the circulation that lead to greater inactivity.
Certainly, exercise increases gastrointestinal motility—meaning that it helps food and waste products move through your digestive system more rapidly, with waste products being excreted in normal bowel movements—which lowers your risk of getting colon or rectal cancers. A large portion of fecal matter is actually made up of bacteria, too, and the more regularly those are excreted, the faster they can be replaced (via your diet) with alternate ones. The bacteria in your gut can release cytokines, which are small protein molecules that modulate your body’s immune system. When the “bad” bacteria take over in your gut, more inflammatory cytokines are released and can lead to insulin resistance, plaque formation in arteries, and compromised immune function.
Choose the Best Physical Activities
When it comes to the brain, vigorous cardiovascular exercise undertaken at least three times a week is likely the best medicine. Even engaging in more moderate activities like walking, running, swimming, rowing, cycling, or working out on any machine that raises heart rate is beneficial, although you will likely need to engage in moderate activities more often and for longer (i.e., five times a week and for at least 150 minutes weekly) to gain similar benefits. However, even everyday chores like gardening, sweeping, raking, or cleaning can help to meet your brain’s exercise requirements.
Another critical physical activity is resistance training, which stimulates your body to retain and gain muscle mass as you age instead of losing it steadily over time or even faster due to being sedentary. It has direct effects on your brain as well, maybe even more so than aerobic exercise. For example, in a group of older women with mild memory loss, engaging in six months of twice-weekly resistance training improved their attention, conflict resolution, memory, and brain plasticity more than others doing twice-weekly balance and toning exercises. In contrast, women undertaking a similar length of twice-weekly aerobic training mainly improved their physical function, but not their brain health. Doing resistance work to enhance your muscle mass will also help prevent gains of visceral fat deep within your abdomen that contributes to the development of systemic inflammation and negative effects on your insulin action and your brain.
Don’t discount the benefits of doing other types of physical activity as well. For instance, yoga may be low intensity, but it leads to the release of dopamine and serotonin. Tai chi and qi gong also lead to similar brain effects. When you’re trying to change your behaviors and substitute in positive ways of releasing these brain compounds in place of negative ones, you have to be open to creating a new, healthy “addiction” to physical movement in all of its varying forms.