Intermediate fasting plans are among today’s most popular diets. Many people embrace fasting as an effective way to shed pounds, reduce risk for various weight-related illnesses and improve overall health. 
Interest in intermediate fasting is growing, and experts offer varying opinions about the best and safest ways to make the most of this diet strategy.
Fasting comes in various forms. With the 5:2 fast, for example, individuals follow a traditional diet for five days of the week. The remaining two days are fast days. Those fast days allow only water as sustenance, but often include caloric intake that does not exceed 500 to 600 calories. 
Alternate-day fasting is another option, with one day of having normal caloric intake, followed by the next with the 500-calorie limit; rinse and repeat.
Other fasting plans involve timed eating. With the 16:8 diet, people eat whatever they like within a predetermined window of time, typically between 6 a.m. to 6 p.m. They then fast for the remaining 16. A study published in the journal Nutrition and Health Aging and led by Krista Varady, an associate professor of kinesiology and nutrition at the University of Illinois at Chicago,  found the 16:8 diet a successful way for obese individuals to lose weight. The study also found that this diet helped to lower blood pressure in participating individuals. On average, when compared with the control trial, those on the 16:8 diet consumed 350 fewer calories and lost 3 percent of their weight. In addition, their blood pressure dropped by an average of seven millimeters of mercury over the length of the study. 
In addition to weight loss and improved blood chemistry metrics, fasting may also improve longevity, suggest researchers. An ongoing study by the National Institute on Aging conducted on rhesus monkeys, which share 93 of their genetic makeup with humans, found calorie-restriction diets helped certain monkeys live anywhere from 14 to 17 years longer in captivity. Restricting calories may activate genes that direct cells to preserve resources and stall out instead of grow. In this state, the cells are resistant to stress and illness.
It can take some time for people to find a fasting plan that works for them. Before the body becomes acclimated to fasting, headaches, hunger pangs, low energy, and mood swings may occur. Eating high-fiber foods can help a person feel fuller longer. Consuming plenty of water also can help. Always consult with a doctor before beginning a new diet regimen.