Creatine monohydratea -- a combination of three amino acids -- allows you to train harder during intense resistance exercise. The Atkins diet allows you to reduce body fat by controlling your caloric intake and drastically restricting carbohydrate intake. Creatine monohydrate does not require carbohydrates for effective use, so it works just as well on the Atkins diet as it does with any other type of diet. Consult a health care practitioner before beginning any diet or using any supplement.
Creatine monohydrate -- a combination of the amino acids L-arginine, glycine and L-methionine -- occurs naturally in your liver and kidneys, where you produce about 2 g per day. Creatine also occurs in your diet, most predominantly in red meat. Your muscles use creatine to help the energy cycle that powers intense muscular contractions. As your creatine levels deplete, your body must produce more, which gets shuttled to your working muscles. Supplementation gives you more creatine to work with.
Normally, your body burns carbohydrates as its primary source of energy. When you burn primarily ketones, or free-floating fatty acids for fuel, you are in ketosis. For this to occur, you must have reduce levels of available carbohydrates, both in your blood and in your muscles. Reducing your dietary intake of carbohydrates and increasing your activity levels allows you to achieve ketosis, but you must work to maintain it. Achieving and maintaining ketosis remains the basic premise of the Atkins diet. This allows you to primarily burn fat for fuel.
Creatine supplementation allows you to train longer and harder in the gym -- within reason. Achieving an extra repetition or two on heavy working sets further exhausts your muscle fibers, stimulating the growth response. Creatine can also increase your peak power output, driving intense contractions of muscle fibers and improving your performance. These are the reasons why creatine has been shown to increase lean muscle mass, according to a 1999 study in "Medicine and Science in Sports and Exercise."
Creatine supplementation might work better with a few carbohydrates. The problem lies in knowing when to consume carbohydrates and not sabotage your dietary efforts. Consuming carbohydrates immediately after a workout might allow you to not only increase the uptake of supplemental creatine, but also improve your recovery from training. Following an intense workout, your blood sugar and muscle glycogen levels remain low, and your insulin levels climb. Consuming simple sugars at this time, such as dextrose, with a simple protein such as whey while supplementing with creatine can help recovery. The addition of both whey protein and simple carbohydrates post-workout increases your ability to build muscle, according to a 2007 study published in "Applied Physiology, Nutrition, and Metabolism."