Whatever style of diet you're on, it's a wise idea to cut caffeine out of your diet. Caffeine is a stimulant that is found mostly in coffee, tea and soda. Two separate studies have shown that caffeine intake leads to insulin resistance. It also raises blood pressure.
The main aim of the low carb diet is to keep your systems running at a smooth, regular rate. You want to keep everything on an even track, without the highs and lows of a rollercoaster carb-rich, sugar-rich diet. Caffeine gives jolts to your system that can wreak havoc with your health.
Some studies link caffeine consumption with headaches, as the brain has a sensitivity reaction to the caffeine impact. Some doctors go as far as saying that those with heart murmurs and other rhythm problems should stay away from any caffeine products.
Caffeine is a diuretic, meaning you need to urinate more often. This flushes fluids out of your system. With water being a critical part of your diet, and 8 glasses of water a day being recommended as a healthy intake, taking a diuretic with that liquid is counterproductive.
Pregnant women are advised to stay away from all caffeinated products. Caffeine can cross over to the fetus, where the fetus' metabolism is not prepared to handle this impact. Also, research on animals found that caffeine causes birth defects. This has not been correlated with humans yet. Studies with humans have found that caffeine cuts down on fertility rates and increases the risk of miscarriage or premature delivery.
The safest course is to adjust to a non-caffeine life, with an even flow of energy, without trying to jolt yourself into action with caffeine!
Note that caffeine does not have carbs - caffeine is an innate part of another food substance. So it would be the food that the caffeine is in that has carbs or does not have carbs. You would want to check the carb count for the actual full thing you are eating in order to determine the carbs in it.
Drink 8 Glasses of Water a Day