Indica is what increases appetite the most although sativa can also increase appetite some.
Indica strains of cannabis are often known to stimulate your appetite more than sativa strains of cannabis.
Indica strains of cannabis are also often associated with sedative and relaxing effects, which can result in increased hunger that is also known as the munchies.
Sativa strains of cannabis are more energizing and uplifting than Indica strains of cannabis and often doesn't have as strong as an effect on your appetite.
The cannabinoid tetrahydrocannabivarin (THCV) is a known appetite suppressant and is sometimes dubbed "diet weed."
THCV is present in higher concentrations in sativa strains than indica strains, making indicas the better choice if you want to feel hungrier and possibly even gain weight.