Coffee can go with your breakfast, but drinking only coffee for breakfast will not start your day off right. While research has demonstrated that coffee has positive effects on mood, brain function and athletic performance, if you are only drinking coffee for breakfast, you are depriving your body of nutrients it needs to be. While you may be temporarily energetic, you will inevitably crash within a couple of hours of drinking coffee for breakfast.

Fatigue

Yes, coffee can wake you up, but this only lasts temporarily. With depleted levels of caffeine and no nutrient stores, you will become fatigued by mid morning or afternoon. Because coffee does not contain calories, protein or fiber, you will not feel satiated and your body won't be able to perform adequately. The best way to combat this is to eat a combination of low-fat protein and carbohydrates for breakfast with your coffee.

Mood

If you only drink coffee for breakfast, you probably notice that you are more irritable in the middle of the afternoon. This is because your body doesn't have the nutrients it requires to keep your blood sugar stable. When you go long periods of time without eating, your blood sugar drops and you will be less able to deal with stress. You will also have less mental focus. Even if you don't feel hungry when you wake up, try to eat within the first couple hours of being awake. This will keep you from experiencing a drastic drop in blood sugar.

Weight Gain

If you are someone who uses coffee because of its appetite suppressing effects, you should know that you would be better off eating a "real" breakfast to lose weight. If you are just drinking coffee, your insulin levels could become unbalanced. This leads your brain to crave high fat and high sugar foods, subsequently causing you to binge mid afternoon. Eating a small breakfast that contains both fiber and protein will help keep your energy going until lunch. Try scrambling two eggs with your favorite vegetables with your coffee for breakfast.

This doesn't mean that you can't have coffee with your breakfast; just don't have coffee as your breakfast. You should also limit yourself to two cups of coffee a day, or less. It should be noted that one cup of coffee is equivalent to eight ounces, not a large 24 ounce cup that you might get at a coffee shop. Coffee consumption also depends on individual differences. If you are taking certain medications, or if you are pregnant or have heart disease, you might not be able to tolerate any amount of coffee with your breakfast. It is advisable to consult your doctor to see if you need to reduce or eliminate your coffee consumption for better health.