Asking on behalf.
So my sister is skinny and she wants to workout without losing weight, she wants to tone her body up. Please help. Thanks.
She should do more weight lifting or body weight calisthenics, cardio is still good for health so at least 15 mins x3 per week... And just eat when she is hungry.
A lot of protein... No junk, a lot of veggies, some whole grains. Lots of snacks, veggies, nuts, fruits.
If she exercises and eats healthy to satisfy her hunger, she'll do great. If she is really worried, she can use a calorie counter app, and pay attention to the scale (once every other week, in the morning) to fine tune her needs, cuz those apps aren't perfect