When you’re cutting calories, it can be tough to make sure you’re still getting enough of all the good stuff your body runs on. “Nutrient deficiencies can stall or halt weight loss,” says Crandall. She sees lots of patients with low levels of vitamin D, for example, a nutrient that is critical to parathyroid hormone function—it helps with weight regulation. If you’re not eating a well-balanced diet, a multivitamin can be a good way to bridge those nutritional gaps and make sure you’re not missing anything that could impede weight loss or muscle building, such as calcium or iron.
The prevailing formula for a long time on how much fat you’re going to burn was calories in minus calories out, based on your basal metabolic rate (BMR) and exercise efforts, explains strength and performance specialist Joel Seedman, Ph.D., owner of Advanced Human Performance in Atlanta. But with all the different biochemical reactions in the body, hormonal response, and endocrine function, there are an infinite number of factors that can affect how your body is storing and breaking down calories.