Want to dodge diabetes? Walk. Want to strengthen your heart? Walk. Want to lower your risk of breast or colorectal cancer? Walk.

Growing evidence suggests that taking a brisk walk every day—or at least on most days—can also shore up your brain, elevate your mood, and increase your mobility.

It may even lengthen your life.

1 Build a bigger, sharper brain.

“Walking definitely affects the brains of adults in their 60s, 70s, and 80s,” says University of Illinois psychologist Arthur Kramer.

Studies that track people’s behavior for years see healthier brains in more-active people.

“Older folks who walk more, like a mile to two miles a day versus less than a quarter of a mile, tend to have about a 35 percent lower rate of developing Alzheimer’s disease and other dementias,” Kramer points out.1,2

Studies that randomly assign sedentary older people either to an aerobic activity (like walking) or to a control group (that does stretching or toning) have yielded mixed results on memory, attention, and decision-making.3,4

But Kramer notes that some studies actually see changes in the brains of the walkers. “We find larger volumes of the areas of the brain controlling reasoning and memory, which are signs of increased brain health.”5

And you don’t have to speed-walk.

“These are very deconditioned older adults when they start off,” Kramer explains. “I would call them professional couch potatoes.”

The goal is to get them moving. “Nobody’s winning any races here,” says Kramer. Most people average about three miles an hour.

Kramer’s bottom line: “Exercising by walking tends to buy you a few extra years of avoiding Alzheimer’s and other dementias. If we had a drug that would do that, we’d pay anything for it.”

2 Live longer.

“Americans typically spend two-thirds of their day sitting,” says epidemiologist Charles Matthews of the National Cancer Institute. That’s equivalent to almost two full-time jobs every week.

“It’s a lot of sitting. And it has a really negative effect on our health,” Matthews notes. (See Dec. 2009, p. 9.)

What if you replaced just one hour of sitting each day with walking or with routine chores that require standing and moving round?

Matthews and his colleagues took a stab at answering that question by tracking 150,000 people in the NIH-AARP Diet and Health Study who had filled out questionnaires about how active they were.6

“Nearly half were inactive,” says Matthews. “They were physically active less than two hours a day. They probably weren’t getting out much and were watching a lot of television and reading.”

Compared to those inactive participants, study participants who walked or exercised for just one more hour a day were about 40percent less likely to die over the next seven years. Those who did household chores, gardening, or other tasks for one more hour were about 20 percent less likely to die.

That’s consistent with the findings of a new European study of 334,000 men and women. Those who exercised for the equivalent of just 20 minutes of brisk walking a day were about 20 percent less likely to die during the next 12 years than people who didn’t do brisk walking or other moderate exercise.7

In the NIH-AARP Study, increased activity also helped people who started out active, but not as much.

“Compared to people who were active for at least two hours a day, those who did one more hour of exercise, usually walking, cut their risk of dying by about 10 percent,” notes Matthews.

“But doing an extra hour of household chores or gardening wasn’t enough exertion to cut their risk.”

3 Ease your aching knees.

“Mobility is really key as we age,” says Stephen Messier. “When you lose your mobility, you lose your independence and things can go downhill pretty quickly.”

Messier directs the J.B. Snow Bio-mechanics Laboratory at Wake Forest University.

“Our objective is to help people restore some of their mobility lost because of osteoarthritis and improve their quality of life,” Messier explains.

You can do that, he says, with an exercise like walking.

“Walking for 40 to 60 minutes three to five times a week can reduce the pain of arthritic knees by about 30 percent,” notes Messier. “And if you combine walking with weight loss, the reduction in pain can be up to 50percent. That’s greater than what you’d get from taking NSAID medications like ibuprofen.”

Messier and his colleagues have conducted two large, long-term studies in overweight or obese sedentary men and women aged 55 and older with osteoarthritis of the knees.

■ In the Fitness Arthritis and Seniors Trial (FAST), 293 people were randomly assigned to walk for 40 minutes three times a week or to participate in an exercise-free program with information about controlling arthritis.8

After 18 months, the walkers reported less pain and less difficulty with the activities of daily living than the non-exercisers. They also walked 53 yards farther during a six-minute test, could get out of a car much faster, and had stronger knees.

■ The Intensive Diet and Exercise for Arthritis (IDEA) study tested whether diet plus exercise was better than either one alone. Roughly 400 participants were randomly assigned to do 30 minutes of walking and 20 minutes of strength training three times a week for 18 months, to cut 800 to 1,000 calories a day, or to do both.9

At the end of the study, the exercise-plus- diet group had lost an average of 23 pounds. Nearly 40 percent of them—but just 20 percent of the diet-only group and 20 percent of the exercise-only group—reported little or no pain in their knees.

And the people in the exercise-plus-diet group, who averaged around 70 years of age, were walking as fast as healthy 40-to-60-year-olds, says Messier.

“Increasing your walking speed when you’re older is a big deal,” he notes, “because it helps maintain your mobility.”

4 Improve your mood.

“Walking for exercise can help people who have been diagnosed with mild or moderate depression as much as drugs or psychotherapy sessions,” says exercise psychologist Panteleimon Ekkekakis of Iowa State University.

In one study, researchers randomly assigned 80 overweight, sedentary people with mild to moderate depression to do aerobic exercise on a treadmill or stationary bicycle or to do stretching exercises.10

After 12 weeks, those who did the equivalent of brisk walking for roughly 180 minutes a week reported a greater reduction in symptoms than those who exercised for around 80 minutes a week or did stretching. And nearly half of those who spent the most time each week doing aerobic exercise were no longer depressed.

Exercise appears to work in a way similar to antidepressant medications, notes Ekkekakis.

The drugs correct an imbalance in levels of serotonin, a chemical messenger that helps keep mood balanced. “In animals where we can observe what’s happening in their brains,” says Ekkekakis, “we see significant increases in serotonin levels with exercise.”

And exercise is the surest way to produce brain-derived neurotropic factor, or BDNF, “which we presume to be therapeutic for depression,” says Ekkekakis.

Like psychotherapy, exercise also helps patients feel that they have regained some control over their lives. “Individuals who suffer depression and who exercise report feeling greater self-efficacy and empowerment,” says Ekkekakis.

Since 2010, American Psychiatric Association guidelines have recognized that exercise may be valuable for treating mild depression, notes Ekkekakis. “But exercise is largely ignored by psychiatrists and primary care physicians in the United States.”

5 Lower your risk of cancer.

“People who are more physically active, including those who walk for exercise, are less likely to develop one of the major cancers,” says researcher Christine Frieden reich of the University of Calgary in Canada.

“There is consistent evidence that physical activity can reduce the risk of breast, colorectal, and endometrial cancers.” (Exercise may only help prevent endometrial cancer if it helps keep women lean, though.)

Take the Women’s Health Initiative Observational Study, which tracked some 74,000 U.S. women aged 50 to 79. Those who exercised the equivalent of 75 to 150 minutes a week of brisk walking had an 18 percent lower risk of being diagnosed with breast cancer over five years than those who were inactive.11

“Even if someone hasn’t been physically active before in their lives, they can still reduce their risk of those cancers by doing moderate-intensity activity like brisk walking,” notes Friedenreich.

Walking may also help cancer patients. “Physical activity can be of benefit to people who have breast or colorectal cancer,” says Friedenreich. “It can help them recover more quickly after their treatments and it improves their quality of life.”

In fact, says Friedenreich, “we’re seeing 30 to 40 percent improved survival among patients treated for these cancers if they are also physically active.”

During the five-year Women’s Health Initiative study, for example, women with breast cancer who walked briskly for at least three hours a week were 40 percent less likely to die of the disease than those who were inactive.12

And in a meta-analysis of five studies that tracked more than 5,500 colorectal cancer patients for five to 12 years, those who exercised the equivalent of walking briskly for at least 2½ hours a week were 35 percent less likely to die of their cancer than those who did similar exercise for less than one hour a week.13

Brisk walking may also lower the risk of recurrence or progression of tumors in men with prostate cancer.14

How might exercise affect cancer? For starters, it can help people stay lean. Excess weight increases the risk of cancers of the colon, esophagus, kidney, uterus, pancreas, and, in postmenopausal women, of the breast.

Exercise may also curb high insulin levels and inflammation.

“It’s likely that physical activity is going to have an impact on many pathways,” notes Friedenreich.

Exercise also empowers people, she adds. “They can take control over their lives a bit more. And it doesn’t have to be something complicated—just walking as much as you can.”

6 Strengthen your heart.

“A large number of epidemiological studies have consistently demonstrated that regular physical activity reduces the risk of heart attack, stroke, sudden cardiac death, atrial fibrillation, and congestive heart failure,” says Howard Sesso, an epidemiologist at the Harvard School of Public Health.15 (Atrial fibrillation is an irregular heart rhythm.)

One of the longest: the Nurses’ Health Study, which tracked more than 72,000 women aged 40 to 65 for eight years. 16 Those who walked briskly for three or more hours a week were 35 percent less likely to suffer a heart attack or die from coronary heart disease than those who walked infrequently.

“Ideally, the greater the intensity of physical activity the better,” notes Sesso. “So the more you sweat the better.”

But no sweat doesn’t mean no benefit. Walking around the block or hitting a shopping mall is better for your heart than sitting around the house.

And don’t worry if you can’t do too much at one time. “It’s the total amount that matters,” says Sesso.

“If you have time for only a half-hour brisk walk during lunch and then another half-hour walk at the end of the day, you’ll essentially get the same benefit as taking an hour-long walk.”17

Exercise like walking helps the heart pump more efficiently, explains Sesso. It also improves the strength of the heart and the way blood vessels respond to increased demands on the heart.

Worried that exercising more might trigger a heart attack?

“The rate at which that happens is quite low, and should not preclude exercising in the first place,” notes Sesso.

“And if you’ve had a heart attack or some sort of cardiovascular procedure, cardiac rehabilitation programs do a great job monitoring and ensuring that the types of exercises that are being done are safe.”

While walking is the most natural way to begin to exercise, says Sesso, you can do whatever you enjoy. “It can be sports, going to the gym, social activities like dancing, or joining a walking group and doing a daily route.”

7 Dodge diabetes.

“If people don’t stay physically active as they get older, their muscles become insulin resistant,” says Loretta DiPietro. That means their insulin does a poor job of moving blood sugar into their muscle cells.

“And when people reach their 70s, the pancreas doesn’t work as well as it used to, so insulin secretion becomes sluggish,” adds DiPietro, who heads the exercise and nutrition sciences department at George Washington University.

With less or less-effective insulin, blood sugar levels stay elevated for a longer time after a meal, and even fasting blood sugar creeps up over the years.

“Exercise is very effective at improving insulin sensitivity in the muscles,” DiPietro explains. (What’s more, when you exercise your muscles contract, which lets them take in blood sugar even without insulin.)

“So we thought, Why not exercise when it’s needed the most, about a half hour after people finish eating?” says DiPietro. That’s when digested food gets absorbed into the bloodstream. “It’s the perfect time to use muscle contractions to help clear glucose from the blood.”

DiPietro and her colleagues recruited 10 sedentary older adults who had pre-diabetes to go for a short (15-minute) walk after breakfast, lunch, and dinner or a long (45-minute) walk either at 10:30 a.m. or at 4:30 p.m.

“It was all barely moderate-intensity walking, about three miles per hour on a treadmill,” says DiPietro.

Both the three short walks after meals and the one long morning walk helped control blood sugar levels throughout the day, lowering the average to 117 instead of about 128 on the days they didn’t walk. In contrast, the late afternoon 45-minute walk had a smaller impact (which wasn’t statistically significant in this small study).18

“The only catch is that on the days you don’t do the three 15-minute walks, you don’t get the benefit,” cautions Di Pietro, who notes that “you can use a 15-minute bout to walk a dog or run an errand.”

One advantage of the longer walk: as long as you’re walking briskly, you may not have to do it every day.

“If you can consistently walk briskly for 45 minutes to an hour, it would train your muscles to clear glucose more efficiently, so that you might be able to skip a day or two every week.”

But no matter how you choose to walk, “doing it consistently may delay the onset of type 2 diabetes.”

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18 Diabetes Care 36: 3262, 2013.