Exercise does deplete stores of glucose, glycogen and fats from the body’s tissues, but these fuels are restored when a person eats, said Michael Jonesco, a sports medicine and orthopedics specialist at Ohio State University’s Wexner Medical Center.
Rather than thinking of energy stores as a battery, “a better analogy would be like the fire that you continue to fuel with more coal or wood,” Jonesco said. “You need to continue to add fuel, or your flame will die. This is true whether you exercise or not. . . . Simply by existing, we are burning energy.”
What’s more, although exercise puts a temporary stress on the body, the body adapts to that stress so that the heart and muscles become stronger and more efficient. “If we can create a battery that, every time it’s used, actually becomes more powerful and efficient, then sure, our body is like that battery,” Jonesco said.
Some studies have even found that exercise makes people feel more energized. In one study, conducted in 2008, researchers tested the effects of exercise on 36 people who reported feeling chronically tired but didn’t have a medical condition to explain their fatigue. They found that those who engaged in 20 minutes of low-to-moderate-intensity exercise three times a week reported a 20 percent increase in their feelings of energy, compared with a control group of people who didn’t work out at all.
According to the American Council on Exercise, starting an exercise program can improve the delivery of oxygen and nutrients to muscle tissue, allowing muscles to produce more energy. Overall, exercise improves muscle and heart health, which boosts people's endurance, giving them more energy, according to the Mayo Clinic.
According to the Department of Health and Human Services, adults should do at least 150 minutes of moderate-intensity physical activity such as brisk walking per week.
Numerous studies have found links between physical activity and improved mood as well as reduced symptoms of depression and anxiety, according to a 2005 review paper on the topic. One study published last year found that people who got up for short bouts of activity during the day reported better mood, more energy and lower levels of fatigue than when they sat all day.
Regular exercise is also linked with a number of physical health benefits, including a reduced risk of cardiovascular disease, diabetes, cancer and osteoporosis, according to the Centers for Disease Control and Prevention.
Exercise may even help you live longer.
In a 2015 study, researchers analyzed information from more than 660,000 adults in the United States and Sweden who answered questions about how much time they spent doing physical activity. The study found that people who engaged in the recommended level of physical activity were 31 percent less likely to die during the 14-year study period, compared with those who did not engage in any physical activity.
Jonesco noted that if you ever become stranded on a desert island with limited food sources, it would be a good idea to skip working out, because you wouldn’t be able to replenish your body’s fuels.
But “any other time, your body will thank you” for exercising, he said.