Since Kathmandu lies at a higher altitude than Biratnagar, the value of acceleration due to gravity is less in Kathmandu than in Biratnagar.

The value of acceleration due to gravity (g) is maximum at the surface of the Earth and decreases as we move to higher altitudes.

Since, weight is dependent upon g, i.e., the object has more weight in Biratnagar than in Kathmandu.