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.
Plus, a 2013 study from the University of California, Berkeley suggests that skipping sleep makes your brain's reward zone react to fatty and sugary treats way more enthusiastically. What's more, a study published in the Journal of Clinical Nutrition found that people who didn't get enough sleep ate an average of 385 extra calories that day. In short, more sleep = less calories in your mouth and less fat on your body.
The upshot of all these chemicals floating around is big trouble for big-bellied guys. In a study at the University of Alabama at Birmingham, researchers took 137 men of all ages and sizes and used seven different measurements to determine their risks of cardiovascular disease. The single best sign of multiple heart-disease risks? No, it wasn't the guys' family histories or their cholesterol profiles. It was the amount of abdominal fat they carried.
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.