You probably wouldn't have observed it but your weight varies when you go from one place to another. Yes, it happens. And no, it's not the air or the food that affects your body weight.
Turns out gravity is responsible for it. If you are standing at a place that has less gravitational pull, then you will weigh less than your original weight at that particular location.
We know it sounds all sorts of crazy. Depending on the region, there are many factors that affect gravity and depending on gravity, your weight varies. Simple!
Gravity is minimum near the equator.
It means the nearer you are to the equator, the less you weigh. Similarly, presence of ocean trenches decreases the gravity, thus making a slight difference in your weight in that particular region.
Gravity is maximum at the poles.
Apart from the north and south poles, places with mineral deposits and mountain ranges are also responsible for more body weight as gravitational pull is more in those areas.
Also, the effect of gravity is not some weight loss program. Everything changes back to its original form once you are back in your latitude.
To get a clearer picture, if you apply the same phenomenon on the moon, 60 kg on Earth would weigh around 10 kg on the moon. Whoa! Imagine how high you can jump with that body weight in that low gravity zone? Maybe, let's not even imagine that!