Let’s Clarify the Real Definition of Intermittent Fasting

Intermittent fasting has taken the world by storm in recent years. Due to its colossal spike in many health and wellness communities, this dieting strategy has branched into an absurd amount of forms. Consequently, the true definition of intermittent fasting has started to get cloudy amongst its many variations.

Please know that this isn’t an opinion-based article about the efficacy of intermittent fasting, but rather a simple reminder of what it truly is. This clarification is absolutely critical as consistent language is key for proper prescription and adherence to health advice. Just imagine a dietician recommending a specific diet program, only for you to go off and do something completely different because that’s what you saw in a magazine.

If we want to continue to push the envelope for health and wellness, we must be on the same page to begin with.

Intermittent Fasting vs. Time-Restricted Feeding

Yes, these are two different things. Although they both fall under the weight loss strategies that involve energy restriction, they hold some key differences. Intermittent fasting (IF) can take on several forms, so let’s begin by clarifying what it isn’t.

Intermittent fasting is not about limiting your daily window of eating.

The proper form of this caloric-restriction strategy is performed in two main ways. Either you limit your energy intake by >60% on 2–3 days per week, or you go on a complete fast of at least 24 hours once every week, month, or every few months (all depending on the person and program). On the days when there is no intervention, one will be feeding ‘ad libitum’ (eating as desired). If this occurs consistently every other day, it is officially labeled as alternate day fasting. The fasting portion of all IF methods is usually a ‘water-only’ fast in which water and teas/minerals are allowed, but any calories or sweeteners are a no go. Just to clarify…

Intermittent fasting (IF) = alternating between periods of restricting calories or completely fasting, and eating ad libitum.

Time-restricted feeding, however, is something we’re a little more familiar with. This occurs when you limit the hours you eat each day to a feeding window. This can also take on several forms, with ratios (fasting/feeding) including 14/10, 16/8, and even 18/6. The most common definition for TRF is limiting the daily period of food intake to 8–10 hours or less on most days of the week. Again, just to clarify…

Time-restricted feeding (TRF) = limiting your daily feeding window as a means to lower your day-to-day caloric intake.

Again, I won’t get too ‘food political’ here and dive into the pros and cons. The reality is, research around health, and especially nutrition, can often fall short due to the sheer complexity of what is trying to be studied. If you’re an apparently healthy individual (with no chronic diseases), then experimentation is never a bad idea. Just know that adherence to weight loss is the greatest predictor of sustainable success.

The healthiest relationship with food is the one you can see yourself keeping for the long term. Whether that includes intermittent fasting or not isn’t a game changer.

In Closing,

Let this be heard loud and clear: intermittent fasting and time-restricted feeding are two very different things. While the general public views intermittent fasting as a strategy to shrink the daily ‘feeding window’, its true form is alternating between periods of restricting calories and eating ad libitum. This can occur several times per week or may involve longer fasting periods interspersed throughout the year.

As the health and wellness industry grows, diets and exercise regimes will only continue to become more complex. Throughout this development, we must strive to set consistent language and standards to remain on the same page. Only then will we continue to push the envelope in health education and optimize our reach to the world around us.