As a note, the scientific community tends to restrict the term “intermittent fasting” to diets that drastically restrict calories for 2-4 days of the week (such as eating around 500 calories every other day, or eating no calories for a day or two out of the week). For daily fasting of set durations, the term “time-restricted eating” is preferred. For the sake of this page, the terms will be used interchangeably.
Although 16:8 is a fairly mild protocol when it comes to time-restricted eating/intermittent fasting, it could have differing effects based on age and sex, so working with a dietitian and/or physician to see how it could affect you may be prudent.
Time-restricted eating is often described as the ratio of hours spent abstaining from food and the hours where eating is permitted.
16:8 is a particular time-restricted eating protocol in which individuals abstain from any caloric intake for 16 hours, and then eat freely for 8 hours. Other popular schedules include 18:6, 20:4, and one-meal-a-day (OMAD).
Previously, these types of eating schedules fell under the category of “intermittent fasting”, but now that term generally refers to eating schedules that involve abstaining from or drastically lowering energy intake for more than 24 hours. Time-restricted eating can involve a caloric deficit to lose weight, but doesn’t have to.
16:8 is a type of time-restricted eating where you abstain from eating for sixteen hours, and then eat freely for the remaining eight. It can be combined with a caloric deficit for weight loss, but doesn’t have to be.
Following a 16:8 time-restricted eating protocol seems to be a viable tool for reducing body weight and body fat, with and without caloric restriction. Some studies have found that 16:8 can preferentially reduce fat mass while sparing muscle, but further research is still required to confirm this. At worst, this limited evidence suggests this protocol can be about as effective as standard dieting, and potentially psychologically easier for some people.
16:8 time-restricted eating can be psychologically easier than other types of dietary restriction. It may have some unique metabolic benefits, but those findings aren’t as clear.
Extended periods without food can be challenging for some, which may make adherence difficult, and some studies have reported some degree of nausea, dizziness, and hunger. There aren’t many safety studies, but in one small trial, the authors didn’t find 16:8 to cause negative impacts on body image, uncontrolled eating, or symptoms of eating disorders.
That being said, fasting can be contraindicated in some diseases such as type 1 diabetes, pregnancy, and preexisting eating disorders. For individuals with these or similar conditions, speaking with a well-informed physician is warranted.
Although no significant side effects have been reported in these studies, some individuals with medical conditions may want to exercise more caution.