There is a lot of interest in fasting to lose weight, often called “intermittent fasting.” There are a few ways people might fast to try and lose weight: they may cut calories every day (many folks don’t define this as fasting), they may consume their calories in a shorter time frame (6-8 or 12 hours) during the day, or they take in few or no calories for one or more days during the week.
Although people may reduce calories by fasting as a way to lose weight, health professionals are interested in whether fasting might improve other measures of health such as blood glucose control or high blood pressure. The improvements in health measures appeared promising in animal models (mainly rodents) but there is limited, short-term evidence in humans, and no long-term evidence. So far, it seems that weight loss in those overweight/obese is most important in improving health outcomes-not how that weight loss is achieved.
For those wishing to lose weight, the success of the different types of fasting seems individuaized-what is easiest for people to achieve and fits with their lifestyle. In summer, I cycle outside in the evening; either a total day fast or consuming all my calories at breakfast and dinner wouldn’t let me do that physical activity. Other folks may wish to be able to eat meals with their families.
Individuals considering fasting should talk to their health care provider (especially to discuss any medication use) and watch for side effects such as dizziness or lack of concentration. Also important to remember-fasting doesn’t appear to be easy for people to maintain over the long time, so to maintain weight loss, people may need to transition to another diet. We’ll cover that in another post.