EVERY GENERATION has its fashionable eating programs. Think of fad diets like Atkins, Master Cleanse—even cabbage soup. Extreme diets have believers, but they are mostly dismissed by the medical establishment, which generally prefers sensible eating and exercise.
But a trio of contemporary diets is garnering interest from doctors and researchers: ketogenic, which focuses on fats and cuts back carbs; protein cycling, in which you go through periods of high- and low-protein intake; and intermittent fasting, or limiting your eating to certain windows. In his new book, The Switch, James Clement draws on 20 years of medical research and literature encompassing more than 18,000 studies to understand the biological mechanisms behind these diets. His thesis? That the body functions best when it toggles between an “on” and an “off” state. He proposes that these approaches to eating, in their own ways, do just that. We recently spoke to Clement about why these diets make the difference.
Men’s Journal: Before we get into the diets, let’s talk about the switch—which refers to the body being on or off. What does that mean?
James Clement: The cells in your body operate in two states: anabolic, which is a growth phase, and catabolic, or housecleaning mode. mTOR is a protein complex inside cells that switches them between anabolic and catabolic states. The switch is like a dimmer for lights—turning it one direction increases light and the other decreases it. The switch should move back and forth continuously, but our modern lifestyle tends to keep it turned on most of the time.
Why is turning the switch off important?
When the body is in a catabolic state, it activates autophagy, a process in which the body does cleanup on a cellular level. It’s also a quality control for proteins the body creates. Think of proteins as origami paper cranes. Your body makes millions of these paper cranes a day. They are three-dimensional and have to be folded perfectly. But some of them aren’t. Autophagy is when the body picks out the defective cranes and recycles the paper. When you’re young, there are fewer folding errors and cleanup goes quickly. As you get older, the body is slower to deal with it. That buildup of misformed proteins leads to signs of aging, like muscle weakening and joint deterioration.
Where do keto, intermittent fasting, and protein cycling fit in this picture?
These three diets affect the sensors that switch the body into catabolic state where autophagy can take place. For instance, the keto diet depletes glucose reserves in the muscles. When this happens, insulin drops and autophagy begins.
The concept of a keto diet—a strict high-fat, moderate-protein, low-carb protocol—is counter to what nutritionists say we need for optimal physical performance. How does a marathoner, for example, follow a plan like this?
When it comes to endurance, consider that the glycogen stores for a 150-pound man is about 880 calories. But that same man carries 135,000 calories of fat on his body. So someone who burns fat for fuel will run a lot longer than a body running on glucose. That’s why you’re finding a lot more endurance athletes training their bodies to turn from glucose-burning to fat-burning by fasting before a long training session.
So intermittent fasting and keto are basically sending your body the same message to burn fat?
Exactly. If you eat at 7 p.m. and not again until morning, you will have burned up those 880-calorie reserves and put yourself in a catabolic state just the way a keto diet does.
Cells operate in two states: growth and housecleaning. The switch should move back and forth continuously.
But weightlifting requires protein for muscular strength, right?
Building muscle is entirely different. When nutritionists recommend high levels of protein, they are basically putting the accelerator pedal down on cell production in an anabolic state, which is necessary for building muscle. But if you keep the pedal down all the time, the body never gets a chance to clean out and repair itself. This is the reason for protein cycling: Several days of the week or weeks of the month, you eat very low levels of protein, followed by normal protein intake. You want cell proliferation at some points. But you need to switch back and forth.
When it comes to longevity, public health experts like to point to Blue Zones—pockets of the world, like Okinawa, Japan, where people tend to live long, healthy lives. Yet they don’t fast, protein-cycle, or follow a keto plan.
Yes, but they practice calorie restriction, which keeps glycogen and protein levels low. They live longer because they are essentially living their entire lives with the switch off. If we tried it, we might not like how we felt. I tip my hat to people who can reduce calories to 70 percent of normal and not be angry or obsessively thinking about food all the time. I don’t think it’s something you should do nonstop. You still need to turn the switch on by going through an anabolic state every few months to build up stem cells and your immune system.
One criticism of these diets is that they use the habits of our hunter-gatherer ancestors to inform how we eat today. But their lives were incredibly different, and life spans were shorter then. So why is it helpful to emulate their eating patterns?
By hunter-gatherers, I mean pre-Westernized, preindustrial people, who likely had fewer diseases than we do. Plenty of research shows that when we first came in contact with less-advanced cultures around the world, they had none of the cardiovascular diseases of the West. Some of the first things we started trading with them were flour and sugar. Shortly after, their health was devastated. I mean, you don’t even find evidence of cancer, heart disease, or Alzheimer’s in the West before the industrialization of our food supply.
You suggest trying up to a five-day fast once a month. Is it safe?
Anything over three days should be done under doctor supervision, just to be safe. Assuming you’re a healthy guy without a low BMI, I don’t see it being a problem.
So the big question: Which plan is best?
None of these plans is perfect, but each can promote longevity so long as you toggle between the diet and a regular eating plan to keep moving the switch on and off. It’s more about: Which one are you going to stick with? For some, intermittent fasting is easy. Others find protein cycling easier to follow. There is no “best.” You need to choose what works for you.