For trans people it depends.

If you’re just starting estrogen-oriented HRT and you’re at a weight considered ideal for your pre-HRT body, then it is helpful to actually gain a few kg of fat, together with weekly bursts of activity. Then fat redistribution will be more effectively towards a )( body shape, with breast growth improved.

For testosterone-oriented HRT, I assume the same applies, though with the accent more on weight loss and exercise.