Fasting is one of the latest crazes for people looking to get fit and healthy. In animals, the effects of fasting are profound. Rodents that eat at certain times of the day appear to be healthier and live longer than those allowed to eat all the time. In some cases, fasting increases their lifespan by as much as 50 percent.
Results like these have gotten researchers interested in whether these results translate to people. They wonder if by restricting food intake, people can experience the same health benefits as animals.
Human trials of prolonged fasts more than 36 hours appear to show substantial benefits. Fasting glucose and cholesterol both go down, as well as inflammatory markers associated with the aging process. Many people swear by fasting as a weight loss technique and a way to restore their metabolisms to normal.
But should you actually try fasting? And, if so, how should you do it?
There are all kinds of fasting regimens out there. Currently, the most popular is a form called “intermittent fasting.” Here you eat during an 8-hour window in the daytime and then fast the other 16 hours, including when you are asleep. So, for instance, you might stop eating at 4 pm and then fast until 8 am the next day.
Another type of fasting is called alternate day fasting. Here people eat one day, and then fast the next. This approach is substantially harder than intermittent fasting because it requires you to fast for upwards of 30 hours at a time.
There are also longer fasts. These require medical supervision. However, research suggests that the benefits may be even more profound. If you can switch your body from glucose to ketone metabolism, it changes the way that it operates, clearing up the immune system and removing old proteins from cells. People typically do these longer fasts once every six months or less.
Who Should Fast?
Ideally, you should only fast if you are healthy. If you have ever received eating disorder treatment, you should not fast. Instead, you should find other ways to improve your health, such as eating the right kinds of foods or doing plenty of regular exercise.
If you are a healthy weight, you can fast. However, you should not try to go for longer than several days. Going for more than five days without substantial food puts most people’s bodies under too much stress.
If you are overweight, you may be able to fast for weeks at a time while your body burns through your fat reserves. However, you will need to keep a close eye on your electrolyte levels. Again, going a long time without getting any sodium, calcium or potassium can alter how your nerves work, potentially causing life-threatening complications.
People with diabetes should speak with a doctor before attempting to fast. Going without food may lower blood glucose levels dangerously.
Lastly, pregnant women should not fast during pregnancy or breastfeeding. However, they may choose to fast once weaning is over.