。
She cut back on food to lose weight.
Literal
[topic-は] become-thin [in-order-to-ために] meals [object-を] restricted.
~ために ('in order to') connects the purpose やせる ('lose weight') to the action of restricting meals. 食事を制限する ('to restrict meals/food intake') uses 制限 ('restriction, limit') as a Sino-Japanese noun paired with する; the construction is the standard formal way to talk about dietary control. 食事 covers any meal — breakfast, lunch, dinner — and is more general than 食べ物 ('food').