Why it is important to get enough protein in your diet? When your body doesn’t have enough glucose (its primary source of energy) it can convert either fat or muscle into energy. It’s easier for your body to convert muscle mass into energy, and if you don’t eat enough protein you will lose muscle instead of fat on a 1200 calorie diet. The American College of Sports Medicine reports that to lose fat, rather than muscle, at least 18 to 20 percent of your calories should come from protein. For a 1200 calorie diet, 75-100 grams of protein daily is optimal.