The most obvious sign that you are in a calorie is weight loss. If you're weighing yourself and the numbers are going down, it's the best sign you are in a calorie deficit. While it is normal to see scale fluctuations from one day to the next (i.e., weight loss vs. fat loss), a pattern of weight loss over the course of long periods of time is an indication that you are in a calorie deficit. In addition to decreases in weight, decreases in measurements (i.e., inches of hips, bust, and waist) and clothes fitting looser are also typically indications that you are in a calorie deficit, as there are situations when fat loss can occur without changes in the scale.