Story at a glance…
Intermittent fasting and time-restricted eating create stress in the body which fortifies it against future stressors.
This fortifying is known as hormesis and is created through many activities like eating plants, and exercise.
Scientists studying different forms of fasting suggest unlimited access to high-calorie food is driving rates of disease in the general human population.
Over the last ten years, moving from academia to public knowledge, has been an interest in the means of restricting calories to extend health and lifespan. Commonly known as intermittent fasting, or time-restricted eating, they have shown to have a wide variety of therapeutic effects for brain, heart, and metabolic health.
However as each individual’s day-to-day schedule is highly varied, some patterns of this reduction in food intake can simply be intolerable.
Various researchers in the field of caloric restriction in all its forms have worked with different patterns of eating. Dr. Satchin Panda has published many studies on the protective effects of compressing the period in which a person eats to 8 hours of the day, say from 10:00 in the morning to 6:00 in the evening. Others, like Dr. Mark Mattson and Dr. Valter Longo, have worked with a pattern known as 5:2 intermittent fasting.
5:2 intermittent fasting is characterized, as one might imagine, by five days of normal calorie consumption, and two days of about 25% percent of one’s normal calorie intake. This has been found to be totally safe, and effective for weight loss.
Recent research has narrowed down the mechanisms of why these eating patterns protect us. It’s largely-responsible, perhaps counterintuitively, to the fact that they act as biological stressors that damage our cells.
However unlike other forms of inflammatory stress, “hormetic stress,” described as an overcompensation for mild environmental stressors, like caloric restriction, exercise, and sauna-use, and cold-water immersion, strengthens the body rather than damages it.
A stressful companion
In a broad-reaching review of the effects of over-consumption of food on human health and cognition, the aforereferenced Dr. Mattson Ph.D. from the Department of Neuroscience at Johns Hopkins University School of Medicine, details how the pursuit of higher-calorie food sources through social cooperation, tool use, and other strategies, led directly to the development of human brain mass and intelligence.
Contrastingly, animals placed in an environment where food is available 24-hours a day, experience a shrinkage of the brain compared to their non-domesticated cousins (wild fowl compared to chickens, wolves compared to poodles, etc.)
“Remarkably, measurements of cranial volumes suggest that there has been a ~10% reduction in brain volume in humans during the past 10,000 years which corresponds to the time period after the agricultural revolution and the development of effort-sparing technologies,” Mattson writes, who goes on to note progression of autism, reductions in BDNF-levels, and more in children, and other health trends that map onto the progression of increased access to food.
One of the principal predictors of survival in our early ancestors was “metabolic switching,” chiefly, the ability to switch from metabolizing glucose as a primary fuel to metabolizing fatty acids.
“When we have food available all the time and we don’t have the need to exercise to get through life, our cells become complacent. They do not maintain their ability to cope with the kinds of stressors that cause disease,” Dr. Mattson told Found my Fitness.
Hormetic stress and fasting
The reduction in energy as associated with 5:2 intermittent fasting or time-restricted eating is a hormetic stressor, meaning that it causes a very mild sort of damage to the body which elicits a much greater therapeutic effect in response.
Sauna-use, with its high temperatures, creates a hormetic effect through the release of heat shock proteins that repair muscle tissue. Plants, filled with vitamins and antioxidants, also contain a variety of stress-inducing phytochemicals that cause the body to over-prepare for potential damage.
Fasting works to create hormesis both alone, and synergistically with other hormetic stressors like exercise. Fasted cardiovascular exercise like endurance running recently gained a lot of attention as a potential appetite suppressant or for increasing the expenditure of stored energy. It’s been shown with mass-spectrometry that there is clear switching between glycolytic and ketolytic metabolism, meaning the use of ketones from fat as a principal source of energy —Mattson’s “metabolic switching,” in young men running after a period of fasting.
Intermittent fasting and caloric restriction also have neurological effects. A reduction in calories leads to the production of proteins in the brain called neurotrophic factors that support nerve cell growth. The most studied of these is called BDNF, or brain-derived neurotrophic factor, as it promotes synaptic plasticity, the hallmark of intelligence, as well as stress resistance in brain cells while providing protection against the neuronal dysfunction and degeneration of diseases like Alzheimer’s and Parkinson’s.
It’s said that whatever doesn’t kill you makes you stronger. Mattson’s work shows us a different way of imagining intermittent-fasting or time-restricted eating, not as aspects which balance the scales of blood glucose or body fat composition, but rather as instruments within the greater orchestra of synergistic biological fortification that comes from presenting your body with a challenge it must overcome.