Intermittent fasting (IF) is a term for cycling between a period of fasting and non-fasting. Many common fasts are 16:8 (sixteen hour fast with an eight-hour eating window) and 18:6 (eighteen hour fast with a six-hour eating window). While these are common ways of fasting, you can fast using pretty much any time window of feeding you would like.
Intermittent fasting (or meal frequency) in itself does not promote weight loss, but caloric balance does. However, many proponents of IF find the strategy helps to manage their hunger with low calories while dieting and helps them reduce caloric intake overall.
There are many important aspects to understand about intermittent fasting but the basis of it hinges on a few key ideas:
- Optimizing fat loss periods throughout the day.
- Reducing insulin levels in the body.
- Helping you live longer.
While it is true that going long periods without eating increases your body’s usage of fat for fuel, it doesn’t appear that this by itself enhances fat loss. However, there is some evidence that there may be a very small effect for intermittent fasting leading to lower levels of fat mass when calories are matched, but the effect is quite small.
The reduction of insulin is an interesting one, as it appears that this may be true. However, we don’t really know if that is of any actual benefit as no real data in humans shows this to be a major benefit in most scenarios.
Intermittent fasting doesn’t really appear to make you live longer. At least not in humans. It may be true that fasting might make you live longer, but no data really supports that. However, there may be some improvement to cellular health by increasing a process known as autophagy, which is essentially a “cleaning” system for the cells of the body .
- (Bellisle et al. 1997) Meal frequency and energy balance.
- (Moro et al., 2016) Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males.
- (Yang et al. 2016) Long-Term Calorie Restriction Enhances Cellular Quality-Control Processes in Human Skeletal Muscle.