Fasting and Longevity: What Does Science Say?

Fasting isn’t the new kid on the block – it's an age-old practice that’s been around for thousands of years. With advances in research, scientists have now been able to uncover many of the beneficial effects of fasting, including promoting longevity.

Fasting is the intentional restriction of calories and food for a period of time to induce physical, mental and/or spiritual change. Fasting’s impact on longevity – the quality of life, as well as the length of life – is one surging area of interest and research.

Types of Fasting

Fasting is defined as intentional restriction over a period of consecutive days, or may be intermittent. Fasting days may be water-only, reduced calorie (often around 25% of daily calorie needs), or a combination of both.

• Intermittent Fasting (IF). Fasting that alternates regular days of healthy eating with fasting days, such as 5:2 (5 days of eating and 2 non-consecutive days of fasting) or alternate-day (4 days of eating, 3 days of fasting per week).
• Periodic Fasting (PF). Fasting that extends for 16 hours up to 5-7 days. This may also be referred to as prolonged or long-term fasting, though both terms usually apply to regimens greater than 24 hours.
• Water-Only Fasting (WF). The type of fasting restricts all food and calories aside from water. Sparkling water, mineral water and flat water are commonly accepted. Some water-only fasting regimens also allow for unsweetened tea and coffee.
• Time-Restricted Eating (TRE). Fasting that involves a daily shortened eating window (such as 8-10 hours) and a prolonged fasting window (such as 14-16 hours).

What Does Science Say?

Longevity research is the scientific endeavor to promote a longer, healthier life. Some scientists explore the lives of centenarians and “longevity genes” such as Dr. Nir Barzilai, while others such as Dr. Valter Longo, Dr. David Sinclair, and Dr. Mark Mattson research ways for non-centenarian families and individuals to “hack” their way into longevity. Popular longevity podcasts that help educate the public on the latest research include those of Rhonda Patrick, PhD and Dr. Peter Attia.

Much of the current research explores fasting’s effects on factors that influence the rate of aging, and ultimately longevity. Factors such as cellular health, mitochondrial health, autophagy, neural networks, stress responses, cardiovascular and diabetes disease risk are highlighted below.

Fasting Improves Autophagy

Autophagy is the body’s natural “detox” process that cleans up and eliminates damaged cellular tissue, microorganisms, and debris. When autophagy is down-regulated, damaged material and debris builds up in the body and aging accelerates.

Dr. Valter Longo and Dr. Mark Mattson report that fasting encourages stem-cell regeneration, metabolic health, adaptive cellular responses, DNA repair and up-regulates or “turns on” autophagy.

Fasting Improves Inflammation and Pain

One animal study showed IF improved inflammatory pathways that helped preserve brain health. Similarly, Dr. Longo and Mattson reported IF has been shown to reduce inflammatory cytokines such as IL-6, TNFα, IL-1β.

A 2001 study in adults with Rheumatoid arthritis reported reduced pain, lasting up to two years, when they followed a periodic fasting regimen followed by a vegetarian diet.

Fasting Reduces Stroke and Brain Disease Risk and Death

Animal research from 2011 found that young and middle-aged mice on IF diets had reduced brain damage, impairments and death from stroke than those on regular diets.

Another study from 2003 reported similar benefits and positive adaptive responses in brain tissue, including improved BDNF levels in neurodegenerative-disease mice who were alternate-day fasting compared to those on control diets.

Fasting Improves Metabolic Function

Diabetes, cardiovascular disease and metabolic syndrome are leading causes of disability, rising healthcare costs and death, essentially impacting both healthspan and lifespan of individuals around the globe. Metabolic health and disease risk is influenced by blood sugar levels, blood pressure, belly fat, insulin sensitivity and other factors.

Dr. Varady, et.al., reports that study participants following an 8-week alternate-day fasting regimen (at 25% of calorie needs on fasting days) experienced reduced blood pressure, cholesterol, triglycerides, body weight and more.

2022 research in the journal Nutrients confirms similar benefits from both intermittent and periodic fasting regimens, including reductions in total body fat, belly fat, blood sugar levels and improved insulin sensitivity.

Fasting May Improve Cancer Treatment Outcomes

Cancer is the second leading cause of death worldwide. Cancer prevention and treatment is therefore a large segment of longevity research. Periodic fasting lasting 2 days or longer has shown similar effectiveness as chemotherapy in delaying the progression of a variety of cancers while protecting healthy cells. In addition to cancer prevention, reductions in tumor growth have also been reported.

Fasting Risks

Since fasting involves significant restriction, it is not recommended for those with malnutrition or eating disorders. If you are acutely ill, wait to fast until you feel better.

Intermittent fasting is recognized as generally safe for most people, with few side effects. But, be prepared to feel hunger and/or fatigue as your body adjusts to reduced calorie intake. If you feel unwell, you must stop. Dr. Jason Fung, MD, a renowned fasting proponent writes, “You can feel hungry, but you should not feel sick.”

The abundance of research makes it clear that calorie restriction through various fasting regimens positively impacts disease risk, progression, quality of life and length of life, and enables you to “hack” your way to improved health. Discuss your fasting intentions with your healthcare provider before getting started, especially if you are taking medications. It’s often wise to start with a less aggressive regimen such as intermittent fasting versus a long periodic fast unless directed and closely followed by your doctor.