Can Eating Too Few Calories Stall Your Metabolism?

Learn why cutting out too many calories can keep you from losing weight.

By Krisha McCoy, MS
Medically reviewed by Christine Wilmsen Craig, MD


If you're like most people who want to lose weight, you want to lose it fast. So you may be tempted to make drastic changes in your diet to dramatically reduce the number of calories you consume. But what you may not know is that eating too few calories can actually backfire and sabotage your weight-loss efforts.

"It would make sense to stop eating [when you are trying to lose weight], but it actually works in the opposite way," says Kimberly Lummus, MS, RD, Texas Dietetic Association media representative and public relations coordinator at the Austin Dietetic Association in Austin, Texas.

Calories and Your Health

The most effective way to lose weight is to consume fewer calories than you expend, creating a calorie deficit. But if your calorie intake dips too low, says Lummus, your body could go into starvation mode. "Your body will start to store fat because it thinks it is not going to get anything," says Lummus. "You will be at a point where your body is kind of at a standstill."

Lummus says that when your body goes into starvation mode, your metabolism slows to a crawl, burning calories as slowly as possible to conserve its energy stores. This is why people who cut their calories too much may reach a plateau and stop losing weight.

Eating too few calories can be the start of a vicious cycle that causes diet distress. When you cut your calories so low that your metabolism slows and you stop losing weight, you probably will become frustrated that your efforts are not paying off. This can lead you to overeat and ultimately gain weight.

"It is so hard to sustain cutting calories and eating too little. What typically happens is that the person will go in the opposite direction; they will just become too hungry and go into a binging mode," says Lummus. "Because you are getting frustrated by not seeing any weight loss, you just sort of throw in the towel."

In addition to sabotaging your weight-loss efforts, eating too few calories can also harm your health. When your body goes into starvation mode, you are at increased risk for the following:

• Abnormally low blood pressure and slow heart rate
• Heart rhythm abnormalities
• Electrolyte imbalances, especially potassium deficiency
• Gallstones
• Hair loss
• Brittle fingernails
• Loss of menstrual periods in women
• Soft hair growth over entire body
• Dizziness
• Trouble concentrating
• Anemia
• Swelling in your joints
• Brittle bones
• Depression

Coming to Terms With Calories

Remember that calories are not your enemy. They are a vital part of a healthy and energetic life. "Your body needs a certain amount of calories just to sustain proper function," says Lummus. This is why fad diets that force you to cut out too many calories leave you feeling lethargic, shaky, and ready to give up.

Instead of opting for a fad diet, find a reasonable eating and exercise plan that allows you to lose one-half to two pounds per week. There is evidence that people who lose weight at this rate — by making better nutrition choices, eating smaller portion sizes, and exercising — also have the best chance of keeping it off. Make a plan to adopt new healthful habits that you will be able to stick to indefinitely, and always allow yourself a little wiggle room for special occasions.

http://www.everydayhealth.com/weight/fewer-calories-stalls-metabolism.aspx?xid=nl_EverydayHealthDietandNutrition_20090916