Humans were never subject to constant and abundant food supply in the history preceding the agricultural revolution around 80 years ago. Before this, there were intermittent forces of nature causing food to become scarce for periods of time. The people who survived these eras passed on their advantageous genes. During periods of fasting, the brain actually releases more human growth hormone (HGH) which helps preserve lean muscle mass in men and women (8). A study done in 1992 on 9 men showed that HGH production rate increases 5-fold after a 2 day fast (9). So fasting can essentially cause increased fat loss while preserving your muscle mass. It’s for this reason that many athletes are now adopting fasting into their training routines (10).
Many of today’s trending craft beers have as much as 200–250 calories per pint, and that’s just for one. Wine has around 120 calories per 5-ounce pour, if you can limit it to just a glass. Cocktails mixed with sodas, simple syrups and tonic waters add up quickly, too — and come in much smaller portions that “vanish” rapidly. Limiting alcoholic beverages is one of the first steps you can take for successful weight loss.
Suprisingly, though, fasting may be a good idea. A recent review by Stephen Anton and colleagues, in the journal Obesity, found that intermittent fasting may come with a variety of health benefits, including reducing inflammation, improving the ratio of lean tissue to fat, improving cognitive function, preventing type 2 diabetes, and possibly even prolonging life span.
It’s important to know certain situations where fasting of any kind is not advisable. Pregnant and breastfeeding women should not fast, due to the nutrient demands of the developing child. Underweight people should not fast, as it could cause dangerous levels of further weight loss. People with a history of eating disorders should take precaution with fasting, as it may lead to overall emotional and restrictive eating. Lastly, it’s not advised to do a complete fast without drinking liquids and taking electrolytes. Some may choose to do a complete fast for religious reasons, but from a health standpoint, it is not advisable, especially when doing more extended periods of fasting.
How does fasting produce these benefits? Professor Valter Longo of USC, one of the leading researchers on fasting and longevity, hypothesizes that fasting forces your body to recycle many of its immune cells, particularly white blood cells. Then your body works hard to replenish its white blood cells, essentially re-setting parts of your immune system. Longo is also the inventor of the fast-mimicking diet, where you eat a special diet for 5 days every month, one that makes your body think you're fasting even though you're getting adequate calories and nutrients. (See Alice Walton's story in Forbes for more about that.)
There are some downsides, however. As she explains, "By day two you may as well have all your calls forwarded to the toilet because you will be spending a lot of time in the bathroom. The first time I did the cleanse, I was out with my kids at the mall when all of a sudden I needed a bathroom, stat! It was a nightmare, trying to pack everyone up and find the restroom. I learned the mall is not the place you want to be when your body starts trying to eliminate toxins."