Not all of us have the time to cycle enough to burn the calories we consume. A simple way to limit obesity is cutting sugar from one's diet. I used to drink a lot of sugary drinks, mainly cola, and finally stopped drinking them. I dropped nearly 2 pounds per month. I am a fairly active person who does a lot of walking and cycling, but still managed to put on a little extra weight, cutting the sugar got rid of that weight.
Living in Japan, I am more active than a person living in most other places. Though I live in the middle of Tokyo where everything is within walking distance, even short walks are healthy. Obesity is not a problem in Japan, and people live longer here than anywhere else. It has little to do with diet or watching one's health. People in Japan eat lots of processed food, mainly because fresh foods and meats are more expensive than other places. Japanese people also smoke and drink more than in other places, and the Japanese eat more salt than any other nationality.
What keeps obesity low and longevity high in Japan is physical activity. People don't drive often, many don't drive at all. When I first came to Japan, I worked at a bank in Otemachi, and I lived in Chiba. Every morning I would leave my third-floor apartment, climb down 3 flights of stairs, walk 3km to the train station, and climb two flights of stairs to get to the train platform. I would get on a standing-room-only train for a twenty-something minute commute to Tokyo Station. From the Keio line platform I had to navigate half a dozen escalators to get to the B1 level, then walk 1km to my building. From the B1 level, I had to climb 3 flights of steps to get to my second-floor office. Going to lunch or on break meant 6 more more flights of stairs, not to mention the walk to wherever it was I decided to eat. Then I would have to repeat the process going home. Your average Japanese worker does a hell of a lot of walking, and climbs many stairs. In Japan, there is nothing like the ADA in America, many shops, stores, and restaurants are accessible by stairs only, and often many stairs.
Now I work from home, and no longer have to commute. But I walk my daughter to school, walk to the local shops and stores, try to ride my bike for an hour or so each day. I have a nice car, but I don't often drive it. Parking is hard to find around the city, and the time it takes to get my car out of the automated garage, drive it where I need to go, find a place to park, and park it, I could have done the commute more quickly by bicycle or train.