Alternate-Day Fasting: Is It the Best Fasting Diet?

by Matt Weik, BS, CSCS, CPT, CSN

Alternate-day fasting is a form of intermittent fasting that can help with weight loss and possibly offers several health benefits. However, it might not be everyone’s cup of tea, especially for women and those with health issues.

The idea behind fasting’s benefits dates back to our ancestors. In ancient times, our hunter-gatherer forebears often went longer between meals, possibly letting their bodies cleanse themselves and dispose of harmful cells (also known as autophagy). Fasting also shifts your body from using food for energy to burning stored fat, creating substances called ketones. This process can lead to improved weight loss.

Intermittent fasting comes in various methods, like the 5:2 diet or the 16:8 diet.

In this article, we’ll dive deeper and look into what alternate-day fasting is, along with the potential benefits.

Disclaimer: This article is for informational purposes only and is not meant to treat or diagnose any condition. It is recommended that you speak with your doctor before making any changes to your nutrition or weight loss program.

What Is Alternate-Day Fasting?

As the name suggests, alternate-day fasting means fasting on one day and eating normally on the next. The core concept of alternate-day fasting is quite straightforward. Instead of daily calorie restriction, as many diets require, you only cut back on calories every other day.

During fasting days, your body shifts into a mode where it burns stored fat for energy, a process known as lipolysis. With time, it enters a metabolic state called ketosis, relying on fat rather than sugar for energy.

When done correctly, alternate-day fasting extends its benefits beyond just shedding pounds. Recent research suggests it can enhance metabolic indicators, support heart health, reduce chronic inflammation, and encourage cellular repair.

Benefits of Alternate-Day Fasting

Alternate-day fasting is a type of intermittent fasting where individuals alternate between days of regular eating and fasting. It shares some benefits with other intermittent fasting approaches, such as time-restricted eating, but also offers its own unique advantages.

Below are some notable benefits of alternate-day fasting:

  1. Helps with weight loss

Research has shown that intermittent fasting, including alternate-day fasting, can positively affect body fat reduction, body composition improvement, and support overall weight loss.

The findings from a review suggest that intermittent fasting can be a successful approach to reducing body weight, and it appears to be effective for individuals of varying body sizes. The majority of studies in this review emphasized the benefits of alternate-day fasting or whole-day fasting regimens.

  1. It may enable cellular repair

In a 2019 review, it was observed that alternate-day fasting has the potential to stimulate autophagy. Autophagy is an essential internal process your body uses to repair or eliminate damaged cells and molecules. For example, it plays a role in repairing or recycling damaged proteins or DNA molecules.

By increasing autophagy, fasting effectively assists in the cleansing and rejuvenation of your cells. Chris Palmer, M.D., a psychiatrist at Harvard Medical School, has previously described how fasting can help facilitate this process, leading to cellular maintenance and renewal.

  1. Improves body composition

Alternate-day fasting essentially prompts your body to engage in a recycling process. During this fasting regimen, old cell membranes are recycled and replaced with new ones. Old fat cells are utilized as a source of energy, and human growth hormone refreshes aging muscle cells. These micro-level changes collectively lead to macro-level outcomes: a revitalized, healthier, and leaner you.

Furthermore, various studies involving rodents, worms, flies, and isolated human cells have consistently demonstrated that fasting can boost autophagy.

  1. Supports blood sugar regulation

Alternate-day fasting helps train your body to achieve metabolic flexibility. This adaptability in how your body utilizes and processes energy sources comes with several advantages, primarily an enhanced ability to regulate blood sugar levels.

It’s crucial to highlight the significance of this benefit because over a third of Americans are affected by prediabetes, a condition characterized by elevated blood sugar levels that haven’t reached the clinical threshold for diabetes diagnosis. Without lifestyle changes, many individuals with prediabetes are at risk of progressing to type 2 diabetes, which currently accounts for up to 95% of all diabetes cases in the United States.

  1. Improves testosterone levels

Testosterone indeed plays a crucial role in various aspects of health, including muscle growth, intrinsic motivation, and stress regulation, and this applies to both men and women. Fortunately, alternate-day fasting has shown the potential to positively impact testosterone levels.

A study revealed that short-term fasting increased the corresponding testosterone response by 180%. These findings suggest that food deprivation, as seen in alternate-day fasting, can influence the pituitary-testicular axis differently in obese and non-obese men, potentially leading to notable increases in testosterone levels.