A low-calorie diet may cause anemia or electrolyte imbalances leading to fainting.
Calories from food are your body's energy currency. They provide the power for your organs to function, your blood to pump and your food to be digested; they also enable you to work, exercise and take care of your other daily tasks of living. When you eat too few calories, you'll be low on energy, which could cause you to faint. Not getting enough calories can also put you at risk of nutritional deficiencies that may result in fainting.
Effects of Too Few Calories
Your body and brain rely on glucose to function optimally. Your body converts the foods you eat into glucose. Naturally, if you're not eating enough, your body and brain may be running low on energy, which can cause dizziness, lightheadedness and fainting.
Too few calories can also make you feel fatigued a lot of the time, and you may find it difficult to concentrate. If you've been eating a low-calorie diet for a while, you may have noticed some other effects, including decreased immune function, which can make you more prone to colds, flus and other illnesses. If you're a woman, you may have noticed a change in your menstruation or a lack of menstrual periods altogether. You may also experience dental health problems and gum infections.
When you follow a low-calorie diet for a while, you may become deficient in one or more essential nutrients. The major nutrient deficiency that causes dizziness and fainting is iron deficiency anemia. Iron is important for the red blood cells that carry oxygen to the brain. Without it, your blood cells can't transport oxygen around the body, which is why you might feel fatigued as well as dizzy.
Iron is found in fruits, vegetables, meat, fish and beans. If you're not eating enough of these foods, you can easily become deficient. There are many other reasons for deficiency, including inflammatory bowel disease and intestinal infections.
How Many Calories You Need
Unless you're following a medically supervised very-low-calorie diet, or VLCD, due to obesity or another health condition, you need to eat at least 1,200 calories per day if you're a woman and at least 1,500 calories per day if you're a man. However, depending on your age and activity level, you may need much more than that. If you're a very active woman in your mid 30s, you might need as many as 2,400 calories a day, and if you're a mid-30s male, you might need as many as 3,000 calories per day.
When to See Your Doctor
Fainting is a temporary loss of consciousness caused by a loss of blood supply to the brain. It's not something that should be taken lightly. If it's your first fainting episode, you need to be evaluated by your doctor to rule out any underlying illness. You should also discuss your calorie intake with your doctor to determine whether you're eating enough and what to do if you have nutritional deficiencies. If you're struggling with an eating disorder, your doctor can help you find treatment.