Alternate-Day Fasting: Highlights and Health Benefits

Intermittent fasting is a diet technique that can be applied and modified according to your personal needs, dietary restrictions, and lifestyle commitments. This article details the fine points about alternate-day fasting (ADF), a practice that can help you lose weight, lower your risk for chronic diseases, and even unlock certain genetically encoded metabolisms that keep you fit and young.

What Is Intermittent Fasting?

The beauty of intermittent fasting regimens is that they’re adaptable. For example, someone on the keto diet may find that a cyclical intermittent fasting style helps them stay in ketosis by making room for “cheat” days on the weekend when they’re more likely to be out with friends or family in locations that may not have low-carb options. Some find that fasting throughout the mornings makes it easier to get through busy working weekdays without having to worry about what to meal prep and eat each day. The idea is to spend certain days or hours consuming a negligible caloric intake, which trains your body first to use the calories you do consume efficiently, and then to burn up stored body fat to meet your energy needs.

By carefully restricting your food intake on a safe, sustainable schedule, you can better control your weight, cholesterol levels, insulin sensitivity, and more. And fasting every other day is one way to make it happen.

The Top 5 Highlights of Alternate-Day Fasting

An alternate-day fasting diet alternates fast days with non-fast days, one after another. Some prefer this diet plan because it allows them to eat just about whatever they want on non-fasting days, and a minimal amount (under 500 calories) on fast days, while still losing weight safely. Here are some of the upsides of this method, with supportive scientific data.

1. Diet Only on Every Other Day

Diet for one day and eat freely the next day, but still lose weight: it may sound too good to be true, but that’s the principle behind alternate-day fasting.

On fasting days you can consume as many calorie-free beverages as you want (water, tea, black or keto coffee), and under 500 calories from food sources to meet your basic energy requirements. Those calories can be eaten throughout the day or in one meal at breakfast, lunch, or dinner—it makes no difference to the effects of the diet, and so is up to personal preference.

On the next day you’ll have entered a feeding window that allows you to eat freely and still reap weight-loss benefits. It’s a process observed and studied by Dr. Krista Varady in her book The Every-Other-Day Diet, who lost 41 pounds using this method. 

2. Sustainable Weight Loss

One of the most important aspects of dieting is sustainability, leading researchers to investigate the dropout rate of certain weight-loss regimens. While studies have found that alternate-day fasting and traditional daily calorie restriction diets both lead to equally effective weight loss and dangerous belly fat reduction, they’ve also found that alternate-day fasting is more effective when it comes to follow-through by obese adult participants, ultimately leading to better muscle mass retention and higher amounts of fat loss.

A diet that is unsustainable in practice is a diet that ultimately fails. Whether participants eat high-fat or low-fat diets does not make a significant difference, but the ability to stick with an alternate-day schedule does, allowing the fasting group to outperform the control group.

3. Body Weight and Muscle Mass Balance

Alternate-day fasting shows superior results in the area of body composition, specifically the ratio between body fat loss and the preservation of muscle mass when it comes to body weight measurements.

Comparing alternate-day fasting diets to more standard calorie-restriction diets shows that both can help decrease fat mass, but it’s the alternate-day fasting approach that makes for a better body composition ratio during dieting and during weight-maintenance timeframes. Researchers have concluded that intermittent fasting practices may be “more effective for the retention of lean mass” than daily calorie restriction diets. 

This has been found true on multiple occasions, including in a 24-week study of unsupervised participants. Results showed that alternate-day fasting helped those participants preserve more muscle mass while simultaneously dropping more fat mass than the group on a calorie-restricted diet.

4. Health Benefits

Weight-loss benefits are often the first thing people look for in a diet, hoping to slim down and look fit. While losing weight and avoiding obesity are definitely good for your health and your risk factors for metabolic syndrome, not all weight-loss diets take that into consideration. “Yo-yo” diets and short-term “crash” diets for weight loss can have detrimental long-term effects on your blood sugar levels and body composition, but where does alternate-day fasting fall on the health spectrum?

• Reduction of risk for type 2 diabetes: Many people in the U.S. are living in a pre-diabetic state, some without knowing just how at risk they are of developing a life-long disease. Restricting calories and eliminating refined sugar can help manage risk factors and symptoms of diabetes, but alternate-day intermittent fasting has also been shown to lower insulin levels and reduce insulin resistance, two factors that are also linked with heart disease and cancer.
• Prevention of heart disease: The leading cause of death worldwide among men and women, heart disease has multiple risk factors, including obesity and cholesterol. Alternate-day fasting leads to weight loss, but also lower blood pressure, triglyceride, and LDL cholesterol levels. Moreover, alternate-day fasting is linked with increasing LDL particle size, which makes LDL particles less likely to implant in our artery walls and start building up deadly plaque.

5. A Key to Autophagic Metabolism

Fasting diets and alternate metabolisms such as a state of ketosis can trigger autophagy, another quiet metabolism in our bodies that helps to consume and recycle otherwise useless cell parts. Autophagy is occurring in our bodies somewhere all the time, but, as with many normal bodily functions, it begins to slow once we age past 25. One of the side effects of sluggish autophagy is a buildup of cellular garbage all over the body, including in our brains. 

By stimulating autophagy, you can help prevent conditions as serious as cancer and neurodegenerative diseases. Not only can both short-term and long-term fasting help increase autophagy, but fasting has also been linked with tumor reduction and anti-aging. Animal studies link autophagic fasting with longer lifespans, while human trials have linked alternate-day fasting diets to reduced levels of oxidative damage, another dangerous contributor to premature aging and death.

Day-to-Day Health Benefits

Alternate-day fasting can be an easier diet style for many people to maintain and return to, and studies have shown that it helps participants lose more fat mass without the loss of muscle mass. While we’ve covered that alternate-day fasting is beneficial for weight loss for obese adults who are at risk of certain metabolic disorders, the other facets of intermittent fasting that help improve heart health and autophagic activities are also useful for those who currently maintain a normal weight. 

The health aspects that targeted fasting has on insulin levels and body composition go far beyond a weight-loss diet. Fasting is a method of dietary intake more in line with how we are evolved to eat and thrive, back and forth between feast and fasting. Even if you have no need to lose a significant amount of weight, alternate-day fasting may still improve your health or even your workout efforts by triggering latent metabolisms in your body that keep you in fighting form.