Bodies at rest, stay at rest; bodies in motion, stay in motion
The easiest way to keep moving, is to stay moving.
Picture your body, mind, and spirit like one of those exercise bikes they have at science museums, where you have to keep pedaling to keep a light bulb lit.
Or better yet, picture yourself as a shark. Some sharks have to swim almost constantly in order to breathe. Same thing with you. You got to keep moving to “breathe” — to maintain the vitality of both your body and mind. If you don’t keep moving, you’ll die. Not right away, but slowly. And quicker than you otherwise would.
While you wouldn’t believe it in your 20s, it does get harder to want to move as you get older. Who knows why. Less motivating dopamine in the brain? Less novelty and more boredom with routine? The cumulative effects of earth’s gravity? Whatever it is, know you’re going to have to intentionally maintain the will to move.
Remember that daily physical activity doesn’t have to be a full workout (though dedicated exercise is excellent, of course).
Do actually take the stairs. Carry a suitcase rather than wheeling one around. Take short breaks from work to walk.
People often use age as an excuse for gradual (and sometimes not-so-gradual) weight gain over the years. But while metabolism does decrease about 10% each decade, that slowdown is largely not a function of age, but a result of the loss of muscle mass. People get fatter not because they get older, but because as they get older, they stop moving. They get more and more inert. They slow down, their lifestyle becomes more sedentary, their muscles deteriorate, their metabolism declines, and fat accumulates.
At the same time, physical activity wards off depression and anxiety, so that a lack of movement sickens the mind as it weakens the body.
A sedentary life thus easily turns into a cycle of greater and greater passivity. Once you stop moving, you gain weight/get frailer, and feel more depressed, which makes you less motivated to move, and when you do move, it feels harder, more uncomfortable, and less pleasurable. This only makes you less likely to move, which makes you gain more weight, become more decrepit, and get more depressed, which drives you deeper into the chair and the couch.
On the flip side, movement (especially that which involves some resistance) preserves your mood, your muscle mass, and thus your metabolism. The more you move, the easier it is to stay moving — a positive cycle is created: your body stays leaner and your joints stay limber; your mind stays more positive and motivated; you want to move more, and it feels good when you do.
Keep swimming. Keep breathing, Keep moving. Keep living.