Economical in use or expenditure; prudently saving or sparing; not wasteful: (Dictionary.com)
Entailing little expense; requiring few resources; meager; scanty: (Dictionary.com)
Careful when using money or food, or (of a meal) cheap or small in amount. (Cambridge Dictionary)
People who are frugal or who live frugal lives do not eat much or spend much money on themselves. (Collins Dictionary)
The Difference between Frugal by Circumstances and Frugal by Choice.
Twenty habits of frugal people.