The Real Difference Between Alternate Day Fasting And Intermittent Fasting

Intermittent fasting is one of the most popular diets around right now, and its benefits and downsides are both well-documented. As The Healthy explains succinctly, intermittent fasting involves restricting when you eat and when you don't, and many plans purport they can lead to weight loss as well as protection from several different diseases. The most well-known type of intermittent fasting is the 16:8 method, which essentially involves fasting for 16 hours and eating for just eight.


However, although most people will opt for this variety, alternate day fasting is quickly gaining prominence. As Healthline advises, you're allowed to eat whatever you want, whenever you want on non-fasting days but on fasting days, you eat nothing. Most people opt for "modified" fasting, however, which allows for 500 calories on fasting days. Alternate day fasting may also promote weight loss and protect against heart disease and type 2 diabetes. At its core, though, this is another form of intermittent fasting.

Alternate day fasting is a form of intermittent fasting

As nutrition professor and author of The Every-Other-Day Diet Krista Varady, PhD, advised The Healthy, you could lose more weight doing alternate day fasting but it might also be more difficult to stick to it, particularly considering the most popular 5:2 method involves fasting for two days a week and eating for five (hardcore fasters may choose to do 4:3 instead). Alternate day fasting aims to make your body burn fat instead of glucose, which should happen any time between eight and 72 hours, and typically encourages ketosis.


As Varady explained, "Alternate day fasting produces faster weight loss, about 10 to 15 pounds in three months, compared with time-restricted feeding. But it's harder to follow because you have to count calories every other day." Healthline reports a yearlong study of those taking an every-other-day approach, with food intake restricted to 500 calories on fasting days, ultimately wasn't more effective than overall calorie restriction every day.

The health benefits are plentiful, but it's also risky

Research suggests alternate day fasting may help to reduce inflammation and diseases related to age, according to The Healthy. Studies show that alternate day fasters had lower levels of the thyroid hormone triiodothyronine, with no thyroid problems, as well as lower levels of cholesterol and belly fat. Dangerous belly fat can increase our risk of heart and liver disease, as well as diabetes. As Healthline warns, though, you're likely to feel hungry and irritable, at least while your body gets used to the new diet.


However, as Scott Kahan, MD, told The Healthy, any kind of fasting can lead to headaches, fainting, weakness, and dehydration particularly if it's not done properly. Although there are concerns about alternate day fasting causing overeating on non-fast days, Krista Varady argued, "We have shown most people only eat 10 percent more on feast days because they get control of hunger." Simply put, if you do it properly, alternate day fasting could be an optimal method of losing weight and getting healthy.