...Calories stored as adipose tissue don’t go bad. Feasting wasn’t gluttony, it was a deadly serious survival skill. Those who lacked the instinct to put on as much weight as possible when food was plentiful were less likely to survive and pass on their genes to us.
In the mid-1700s, the scientific revolution associated with the Enlightenment began to change the nutritional landscape. Before then, almost 100% of most populations engaged in subsistence agriculture and hunting. By 1776, when the American nation was formally created, only 90% of the US population worked in agriculture. A hundred years later, only half were agricultural workers. Today, less than one in a hundred Americans work in agriculture, yet we produce enough surplus to export more than $150 billion in food products annually.
This profound technological transformation changes the purpose of our holidays and traditions. More importantly, it makes genetic mechanisms that used to benefit us obsolete and potentially life threatening. Today, for the first time in history, obesity kills more people than malnutrition.
In recent decades, it has become clear that our genomes deal differently with hunger and plenty. One metabolic state is activated when we are consuming just enough calories to keep us alive. The other is activated during those periods when calories are abundant.
For decades, research has been focused on the metabolic state induced by hunger. It’s called calorie restriction and, when coupled with essential nutrients, it has significant health benefits.
In animals, calorie restriction with optimal nutrition (CRON) significantly improves health and increases life spans. CRON improves human health as well, and we believe it would also extend human life spans. We don’t know for sure because almost nobody can handle the permanent nagging hunger that CRON inflicts.
I’ve written a lot about the dietary breakthrough developed by biogerontologist Valter Longo, director of the USC Longevity Institute. Briefly, Longo’s fasting mimicking diet (FMD) entails five consecutive days of artificial famine. This is not calorie restriction, which entails just enough food to survive. Longo’s diet is five consecutive days consuming about one-third of normal caloric intake.
In the long run, such low levels of nutritional intake would lead to dangerous weight loss, malnutrition, and eventual death. Five days of hunger followed by a return to the feasting state, however, provides profound health benefits.
This indicates to me that CRON is not the optimal diet for health or longevity. Instead, we need to experience both the famine and feasting metabolic states, just as our ancestors did.
Fortunately, Longo’s work seems to show that the periods of hunger needed to reap the benefits built into our genomes are mercifully short. For people who are already at optimum bodyweight, five-day FMDs once or twice a year probably suffice. If you’re not close to ideal body weight, you can benefit from more frequent FMDs.
Long-term human trials haven’t yet been done, but animals that are periodically put on FMD live longer with fewer serious diseases—including diabetes and cancers. Short-term human trials show the same improvements in biomarkers as animals.
It’s clear to me that Longo and colleagues have created a diet that makes use of our genomes’ ability not just to survive cycles of famine and feast but to utilize both.
During the FMD, our genomes activate autophagy or “self-eating.” Our bodies begin to look for the components that are unnecessary and nonfunctioning. They are selectively broken down and the nutrients they contain are utilized.
For example, Longo measured T cells—the immune system’s defense against cancers and other diseases. At any one time, about a third of your T cells are old and nonfunctioning. So, they’re broken down and utilized for their nutritional content during the FMD.
When you’ve finished the FMD and are eating in modern feast mode, your stem cell processes quickly kick in and replace those missing T cells. So, you have a supercharged fully functioning immune system, perhaps for the first time. This may explain why cancer rates in animals fall after FMD, but there is another possibility.
Our mitochondria are essentially a symbiotic species of bacteria. These aliens within come entirely from your mother’s supply and have their own short circular DNA rings called plasmids. When they are working properly, they communicate with one another and the genome, creating the intelligent energy grid that powers our bodies.
Unlike T cells and other cells, mitochondria replicate through fission, splitting into additional mitochondria in the same way that bacteria replicate. This is called mitochondrial biogenesis and it is critical to life.
Like T cells, mitochondria get old. This is a major problem because mitochondria function like batteries. On one side of an inner membrane is an area of low ion concentration. On the other side is a higher concentration. This difference in ion levels powers the production of the energy molecules our bodies require: adenosine triphosphate.
The problem is that old mitochondria leak. Ions escape and result in the formation of free radicals or reactive oxygen species. Though free radicals play necessary and important biological roles, the unintended production of these molecules is responsible for a great deal of accelerated aging and disease.
Some scientists believe the health benefits of CRON are the result of clearing out old mitochondria through autophagy. Specifically, this process of recycling malfunctioning mitochondria for their nutrient value is called mitophagy.
This view is reinforced by research showing that calorie restriction activates the creation of new mitochondria, presumably to replace those that have been cleared out by mitophagy. This may also explain why short-term FMD does not lead to a loss of muscle tissue, which is an unfortunate side effect of long-term dieting.
If you’re comfortable extrapolating menus based on data in the published journal article (which you can download here), you can replicate the FMD yourself. If, however, you would like more specific guidance, Longo has created the company Prolon, which sells pre-packaged foods that let you do a cycle of FMD without cooking or calculation.
Personally, my nutritional biologist wife and I enjoy creating our own FMD menus, which are heavy on highly spiced Indian food and bulky nitrate-rich vegetables. For many, however, this is impractical. If you’re interested in trying Longo’s FMD, the Prolon website that sells the components is here.
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