Intermittent Fasting

Why has intermittent fasting (IF) gained such popularity in recent years?

Simplicity is one of the principal reasons. There are a million and one diets that focus on specific foods or nutrients, but IF avoids such specifics. Let's examine the various types of intermittent fasting and the weight loss and other health effects supported by the evidence.

IF variants

IF, also known as time-restricted feeding, consists of alternating periods of normal food intake with extended periods (usually 16–48 hours) of minimal to no food intake. This strategy lends itself to various variants, including:

  • Alternating Fasting Days (also known as Alternate-Day Modified Fasting). This diet can take various forms: you can eat for 12 hours and then fast for 36 hours; you can eat for 24 hours and then fast for 24 hours; or you can eat normally for 24 hours and then consume very few calories (around 500 kcal) for the next 24 hours.
  • Eat-Stop-Eat. You fast or severely restrict your caloric intake for 24 hours, either on a regular basis (two days per week on the 5:2 Diet) or occasionally.
  • Random Meal Skipping. Throughout the week, you randomly skip meals.
  • Feeding Slot. Daily eating is restricted to a specific time frame (from 10 a.m. to 6 p.m, for instance).

Select a form of intermittent fasting that you believe you can adhere to for at least a few weeks if you choose to experiment with it.

impact on weight

Yes, IF does work, though to varying degrees according to different studies. This variability could be explained by a number of factors, including the IF variant under investigation. In one study, skipping breakfast resulted in modest weight loss, whereas in another study, it had no effect. In each of these two studies, the control group was given a standard breakfast, such as oatmeal, but neither group was limited in what they could consume the rest of the day.

It's also possible that people with more weight to lose will benefit more from an IF approach, but one thing is certain: if you make up for the meals you skipped by eating more later in the day, the next day, and the day after that, you will not lose weight. The equation for losing weight is straightforward: you must consume fewer calories than you burn. IF is only one method for achieving this goal, but it is a method that some individuals find easier than the more conventional "eat smaller meals" method.

To lose weight, you must either consume fewer calories than you burn or burn more calories than you consume. Some individuals find it easier to achieve this objective through intermittent fasting than through the conventional "smaller meals" approach.

Health consequences

A number of studies have reported improvements in health markers other than weight, notably lipids, despite the fact that the body of evidence on IF in humans is still relatively limited. Whether intermittent fasting has unique metabolic benefits over chronic caloric restriction (CCR, the traditional "eat smaller meals" approach) is still a matter of debate.

Life extension is the most intriguing of these contested advantages. It has been known for a very long time that caloric restriction in general (i.e., both CCR and IF) can slow the aging process and increase lifespan in numerous animal models, in part by stimulating certain regenerative processes. Keep in mind, however, that for the majority of their lives, these animals were either fed low-calorie diets or were subjected to periods of fasting. It is still unknown if IF can reliably produce greater life extension than CCR in animal models, much less in humans, and if it can, which variant is optimal and how many weeks, months, or years are required to make a difference.

The evaluation of the potential metabolic benefits of CCR and IF is a lengthy process, and IF is a relatively new concept. It may provide unique metabolic benefits over CCR, as well as mood benefits; however, "further human research is required before fasting can be recommended as a health intervention."

Fasting may have unique metabolic benefits, such as life extension, but these must be confirmed by additional human research.

Additional considerations

Depending on the duration of your fast, you may experience anxiety, headaches, constipation, and dehydration. Keeping hydrated is especially important; it will also help alleviate headaches and constipation.

Some preliminary evidence suggests that periodic caloric restriction may produce physiological benefits comparable to those of fasting. A diet that mimics a fast consists of consuming a low-calorie diet for five consecutive days per month, as opposed to completely abstaining from food. The typical protocol involves consuming 1,090 kcal (10% protein, 56% fat, 34% carbohydrate) on the first day, followed by 725 kcal (9% protein, 44% fat, 47% carbohydrate) on each of the following four days.

Remember that IF is not suitable for everyone. People with impaired glycemic control should avoid fasting because it results in a decreased glucose response. Also, if you are pregnant, underweight, younger than 18 years old, or have a history of eating disorders, intermittent fasting is likely not for you.

Intermittent fasting is an effective method for losing weight or maintaining a healthy weight. In this regard, however, the benefits of continuous caloric restriction (the traditional "eat smaller meals" diet) are comparable to those of intermittent caloric restriction. Consistency is the most important factor. People who find consuming fewer calories easier than consuming fewer calories would benefit most from intermittent fasting. Concerning the unique metabolic health benefits of fasting, the debate continues.