Ah I love January, it's always so busy at the gym But getting in shape is not one-dimensional (cardio alone or weight lifting alone). Building muscle at the same time as cutting excess simple carbs will give the most results in terms of body transformation.
But I'd never recommend dieting. It's a lifestyle adjustment, something that will stick forever, that will give the best long-term success. Examples of things I love to eat are steamed salmon, peanut butter on whole wheat, hard-boiled eggs, oatmeal, turkey chili, muscle milk (mmmmm).