According to its fervent proponents, humans were not made to be eating constantly; rather, we were designed to eat for short periods of time followed by hours (and sometimes days) of fasting. Much like vegetarianism, intermittent fasting is practiced for two main reasons: health and religion/spirituality. There are no food or caloric restrictions, but rather a restriction on WHEN to eat. The most popular methods include the 16/8 (8 hours of eating followed by 16 hours of fasting), the “Eat-Stop-Eat” method (two 24-hour fasts per week on non-consecutive days); and the 5/2 method (only 500 calories for 2 non-consecutive days, and 5 days of normal eating per week). While it's generally considered a healthy approach to eating when done moderately, some studies suggest extreme fasting may lead to hair loss and anxiety.
If you’ve been eating fast food for years, get real about your approach: You’re probably not going to stick to an organic, gluten-free, paleo overhaul for very long. "You want to change as little as possible to create calorie deficit," says Dr. Seltzer, who insists the best way to support sustainable weight loss is to incorporate small changes into existing habits. So instead of giving up your daily BLT bagels in favor of an egg-white wrap, try ordering your sandwich on a lighter English muffin. Or say you eat a snack bar every afternoon: Swap your 300-calorie bar for a 150-calorie alternative. "Your brain will feel the same way about it, so you won’t feel deprived," he says.