Clock image for alternate day fasting

Healthy Aging & Lifestyle

It’s no secret that a healthy metabolism is a key part of living a healthy and long life. As we all try to live better and longer, the more we look to science-backed lifestyle strategies such as calorie restriction, which can promote optimal metabolic health and may benefit longevity.

The problem with calorie restriction

The effects of calorie restriction have been studied in different species, but it is difficult to study them in humans because restricting calories on a daily basis is hard for most people and ultimately not an easy diet to manage.

Luckily, there are alternatives, like intermittent fasting (IF) and alternate-day fasting (ADF). With the latter, you eat one day, fast the next, and then repeat. Sounds simple, and it is.

Alternate-day fasting 101

ADF involves “fast” days — where no calories are consumed — and “feast” days — where “unlimited” calories are consumed. This may be an easier lifestyle change for more people to implement, and it still provides similar health benefits to calorie restriction. Many studies have shown that ADF may improve weight, metabolism, and cardiovascular health in overweight people or those with type 2 diabetes.

ADF and aging

One recent study involved 90 participants between the ages of 48 and 52 years old. Thirty were “regular fasters” already practicing some form of ADF. The other 60 participants were randomized into either an ADF group or a non-ADF control group for four weeks. None of these additional 60 participants had any previous fasting experience.

Those assigned to the ADF group were told to eat every other day. On the fasting days, no calorie-containing foods or beverages were consumed. They were allowed only water, flavored carbonated water, unsweetened black and green tea, and black coffee. On non-fasting days, the participants were allowed to feast like royalty if they so desired.

Alternate-day fasting

Health-enhancing effects of ADF

Participants in the ADF group reduced their weekly caloric consumption by about 37%, even without deliberately restricting calories on the feast days. The results are surprising because in some human calorie restriction studies participants haven’t even managed to reduce energy intake by the target goal of 25%, suggesting ADF may be even more effective for those wanting to eat less.

ADF caused a significant reduction in body mass index (BMI) and fat mass. After just four weeks on the “diet,” blood pressure was lower. ADF also reduced a hormone called triiodothyronine or T3. Lower levels of T3 are linked to increased disease-free lifespans in humans.

Benefits of regular fasting

Overall, the long-term ADF group reported a lower caloric intake than the control group: eating about 8,700 calories per week compared to 12,300  —  a 28% difference.

Compared to the non-fasting group, those who had practiced ADF consistently had lower levels of total cholesterol and had a lower resting heart rate  — which has also been linked to longevity.

Live fast, live young

Fasting for as little as four weeks has some pretty powerful effects. Even better, ADF seems to be a more practical way to reduce total food consumption and is a routine many people might actually be able to stick to.

Many people enjoy fasting and find that it is an effective way to manage weight and promote metabolic health. It is also a way to enter into ketosis intermittently, which on its own may have considerable metabolic benefits and optimize aging.

While ADF is not for everyone, it may be worth giving it a try, since some of the benefits seem to be realized soon after you start and, potentially, last a lifetime.