Fasting

Fasting Diets

Just about every religion has periods of fasting as a show of faith or penitence. Fasting has also historically been a means to express political views and a form of protest.

Though it may not be the most practical -- or safest -- diet, some people use fasting as a way to lose weight or to cleanse the body of toxins, although experts say our bodies are perfectly equipped with organs that remove toxins. How fasting is used for weight loss varies by diet. Some fasting diets involve drinking nothing but water or eating only raw foods for a period of one or more days, while others restrict food on alternate days. Certain fasting diets allow liquids like water, juice, or tea, while others dramatically cut calories but don't eliminate food altogether.

Does Fasting Really Help You Lose Weight?

When you fast, your body is forced to dip into energy stores to get the fuel it needs to keep going, so you will lose weight. The big question is how long you'll keep that weight off. Because food was often scarce for our ancestors, our bodies have been genetically programmed to combat the effects of fasting. When you eat less food, your metabolism slows down to conserve energy. Than when you go back on your old diet, your lowered metabolism may cause you to store more energy, meaning that you'll probably gain back the weight you lost and possibly even put on more weight when eating the same calories you did before the fast.

As you fast, your body will adjust by reducing your appetite, so you'll initially feel less hungry. But once you've stopped fasting, your appetite hormones will kick back into gear and you may actually feel hungrier and be more likely to binge.

Research has shown that fasting on alternate days can help people lose weight, but not for long. In one study, people who followed an alternate-day fasting diet shed pounds, even when they ate all they wanted on the non-fasting days. However, they couldn't maintain the weight loss over time.

Can Fasting Detoxify the Body?

Some fasting diets claim that they can cleanse the body of impurities. However, there's no evidence that fasting detoxifies your body, or that your body even needs to be detoxified. It is naturally designed to remove toxins through the skin (sweating), liver, colon, and kidneys.

Could Fasting Help You Live Longer?

Studies of fasting in both rodents and humans appear to indicate a connection between calorie restriction and longevity. In one study of overweight men and women, a calorie-restricted diet improved markers of aging, such as insulin level and body temperature.

Fasting might also improve longevity by delaying the onset of age-related diseases, including Alzheimer's heart disease, and diabetes. One study showed that skipping meals once a month as the Mormons do reduces the risk of clogged arteries (the buildup of plaque that can lead to heart attacks and strokes). However, it's not clear from this research whether fasting alone or the Mormons' generally healthier lifestyle (they also abstain from coffee, alcohol, and smoking) is responsible for the improved heart health.  

Researchers don't yet know whether the effects of fasting translate into an actual increase in lifespan, because they haven't followed people for long enough periods of time.