There's been one time in my life when a strange man's thigh was pressed against mine, and I didn't mind. He was a weight-lifter from New Zealand, as was his buddy, and the two of them and I were all assigned seats in the same row in a plane from LA to Auckland.
We were all big people, a bigness of muscle and bone, not fat. Our shoulders were pressed against each other, our thighs touched, and we had no choice. The stewardess who was checking on us promised to move me once we'd taken off. A fifteen hour flight is no place for a trio of big people to be jammed together in small seats.
Our culture expects and values thin builds: the plane seats, for example, relied on thin builds. Our bodies, however, range from the naturally thin to the naturally big.
We can't shape our bodies very much. Our basic shape is genetic - we are born to be a certain build. But we can modify which variant of that build we will become. A person born with a narrow bone structure can choose to develop a wiry strength, a dancer's grace, or a marathon runner's speed. They can also choose to aim for the thin beauty of a modern model, or of the older models of earlier eras. Another alternative is to do nothing with the body shape, and let it fall where it may. Or even to try to eat their way to curves the body is designed not to have.
Builds of the other extreme - the large builds like me or those weightlifters - have similar choices. Our strength will never be wiry, but we can develop our native strength. We can be just as graceful as the thinner dancers, but we won't be chosen for the ballet. (Arabic and Indian dance both value the larger bodied grace, however.) We're unlikely to be as fast as our thinner relatives, but we can develop what speed we have.
Larger builds can never attain the thin beauty of the modern model, the best we can hope for is a starving ugliness. Instead, we should hope to attain the beauty of Venus, as painted by Rubens or Boticelli. (Men of this build can seek sportsmen, actors or models of similar build to emulate.) Unfortunately, many of us give up on our bodies, having accurately determined that we can never resemble Kate Moss. Some of us are so naturally large we will never even resemble Marilyn Monroe or Jayne Mansfield.
There is, however, no need for the very large, the very small, or the in between to despair. Within the limitations of build, our bodies are very malleable. They'll do whatever they're asked to do, if they're asked long enough to develop the resources.
In other words: if you want the body of a dancer, dance. If you want the body of a runner, run. Your body will shape itself according to what you do with it, and to its basic build. If you have a sedentary job and sedentary hobbies, your body won't look like an athlete's. With active hobbies (or work), it will.
Choose an active hobby or sport (or several) that interests you. Study the bone structures of the professional, and active amateurs in the sport. Look at the ratio of shoulder width to height, and hip width to height, and compare theirs to yours. Look for the variation (or variations) of the sport that has several people with similar bone structures to yours: that's the form of the sport that your body is designed for, and you can realistically aspire to have your body look like theirs.
You can do sports that aren't populated by those of your build: there are heavy-set marathon runners, and lightly-built power-lifters. Just be aware that your body is (most likely) not designed for that sort of sport, and you will have more difficulty than those whose bodies are suited to it. Do it for fun, and for health, not to be spectacularly good at it nor to look like those who are, and you'll be fine.