The Differences Between Caloric Restriction and Intermittent Fasting - 2 Experts Weigh In

I originally published this article on my blog.

When I lastt wrote on the differences between caloric restriction and intermittent fasting, I kind of wondered how important it was, given that so many writers and experts asserted that caloric restriction and intermittent fasting were, in effect, identical in their effects on the body.

However, recently I ran across two experts who explain that they are different, and the difference is critical.

Meet Dr. Jason Fung

The first one is Dr. Jason Fung. He's a nephrologist -- kidney specialist -- practicing in Toronto Canada. I just discovered him recently, but he's quite impressive. He's obviously well informed and experienced, yet manages to explain complicated concepts clearly.

Because he works with people with bad kidneys, he's seen a lot of people with advanced diabetes. The kidneys are organs that disease tends to damage eventually. It can put people on renal dialysis. That's where their kidneys don't function, so they must have a machine filter toxins from their blood in place of the kidneys, or they die.

This video of Dr. Fung explains a lot about weight loss and why ordinary dieting or caloric restriction don't work in the long term.

Because of what he saw in his work, he began recommending people eat a low carbohydrate diet, and he wrote about this in his book The Obsesity Code.

He then began prescribing fasting for his diabetes 2 patients. He just recently published a book on that with Jimmy Moore, who's a ketogenic blogger and author. Dr. Fung's book on fasting.

Full disclosure: I haven't read either book. However, based on the quality of Dr. Fung's videos and blog posts, I can't see how it could fail. I do plan on buying and reading it soon.

And he does maintain that fasting has cured many of his patients with type 2 diabetes. (Type 1 diabetes is quite different.)

Caloric Restriction is Most Like Ordinary Dieting

What caloric restriction really most resembles is ordinary dieting. The only real difference, assuming the dieter really does drastically reduce how much they eat, is that people on CR for anti-aging intend to do it all their (long, long) lives. Ordinary dieters usually intend to go back to their regular eating habits after they've lost the weight.

The never-ending aspect of caloric restriction is important, though, and I'll come back to it when I get to the second expert.

Anyway, Dr. Fung has many important things to say about how type 2 diabetes develops. That video also explains why people who eat lots of carbohydrates, and who eat often, have a hard time losing weight.

Why Ordinary Dieting Doesn't Work

When your body has glucose (sugar) available, it uses that first as fuel. It doesn't burn stored fat until it runs out of glucose.

And when you eats lots of carbohydrates, and eat often, you're constantly giving your body glucose to burn. So your fat remains in storage.

People who are dieting as most people do still eat, but they reduce their calories. They eat carrot sticks instead of candy bars, but they eat.

And the same is pretty much true of people restricting their calories for anti-aging. They eat three meals, and perhaps some snacks. That's called portion control, and it's the most recommended strategy by nutritional experts. It keeps the average calorie consumption low.

They spread the reduction of calories out through the day, perhaps in the belief spreading the hunger out makes it less miserable.

As I pointed out, in my experience, it just makes the entire day miserable. Eating a few carrot sticks never satisfied me, just made me more ravenously hunger.

The number of calories they consume in a day is below the number of calories they are burning, so the "calories in, calories out" principle means they'll lose weight.

But Timing Counts More Than the Average

In this blog post Dr. Fung points out that meal timing is more important than the average calories consumed.

He goes into a lot of depth about how caloric restriction and ordinary dieting adversely affect your metabolic rate.

Over six months, the Basal Resting Rate of the contestants in the Biggest Loser television show dropped an average of 789 calories.

By reducing the number of calories they consumed, they forced their bodies to slow down to match their calorie consumption.

You can only start losing again by cutting calories even more. It's a vicious cycle.

Actually, what usually happens is your body slows down so much that, even though you stay on your diet, you burn less than you're eating, so you start gaining weight again. Even while eating fewer calories.

Not good.

Of course, this is nothing new. The lower basal metabolism rate is "starvation mode," and it's what people threaten fasters (though not ordinary dieters) with.

Why Fasting Instead Works

It doesn't put your metabolism into starvation mode. Well, it would if you went without food long enough to actually reach starvation, but clearly that's not what anybody recommends.

And intermittent fasting is even easier. Just skip a meal or two a day. Or every other day. Or for a full day one to three days a week. Or some combination of the above that suits your personal schedule and habits.

Your basal metabolism rate doesn't slow down in just a few hours, days or even weeks (if you really want to fast that long).

Actually, studies show that four days of fasting not only doesn't reduce your resting basal rate, it increases it 12%.

And that makes sense. When Paleolithic people went without eating for four days, that meant they needed to get up off their butts and hunt and gather food. If, instead, they sat around the cave with low energy, they would have starved to death.

Without the ability to fast, the human species would have died out several Ice Ages ago.

Fasting Forces Your Body to Burn Stored Fat

When you simply reduce calories, but continue to eat regular meals, you keep on burning only glucose.

But when you actually give your body time to consume all the glucose from your last meal, it has to burn fat to continue to function.

That gives you energy to hunt with.

And it reduces your stored fat.

Intermittent Fasting is Different from Caloric Restriction Because It's Intermittent

One major difference is in ghrelin restriction. Ordinary dieting or caloric restriction increases ghrelin, which makes you feel hungry.

When ghrelin goes up, it takes all your willpower to keep from eating several packages of cookies or a large pizza, and willpower often loses.

Fasting doesn't raise ghrelin. It's counter-intuitive, but you feel less hungry while fasting.

Meet Our Second Expert on the Difference Between Caloric Restriction and Intermittent Fasting, Valter Longo

Valter Longo is the biggest name when it comes to fasting research. He's a professor of Gerontology and Biological Science at the Longevity Institute at the University of Southern California.

He and his team discovered that cancer patients who fasted for several days before chemotherapy had better results.

The fasting made the ordinary, healthy cells of the cancer patients turn to burning stored fat for fuel, and made them tougher and more resilient when exposed to the toxicity of the chemotherapy drug.

However, fasting weakened the cancer cells because they can't burn stored fat. They depend on glucose.

Another study he ran got a lot of news coverage. When people fasted for four days, they transformed or reset their immune systems.

Interesting Interview by Dr. Rhonda Patrick

Dr. Patrick has a lot of interesting videos on YouTube. In this one she interviews Longo. It's interesting for a behind-the-scenes look at his famous studies.

But he makes one comment that struck me. It's not about the importance of fasting.

It's the importance of refeeding.

That is, of eating a healthy diet after you've completed the fast.

He said that in his study on the immune system, his team found that the immune systems of the people fasting destroyed 40% of their own white blood cells. Why? They were defective, old, damaged or just plain ineffective.

The immune system "reset" came, not from fasting, but when those people began eating again.

When they began taking in new proteins and other nutrients, they replaced the 40% of white blood cells they destroyed with new ones that were young and healthy. That's what "reset" their immune systems.

As he mentions, you don't get that with caloric restriction as his old mentor Roy Walford, a pioneer of CR, advocated.

If they're following the program, CR people never "refeed." They just keep under-eating until they die.

Feast and Famine

Clearly, Vongo has found both fasting and refeeding essential to the process.

Somewhere in his videos, Dr. Fung speaks of feasting and famine. He says you don't want to be "that guy" at a party who refuses to join in. There's a time to fast and a time to enjoy the feast of life.

That advice goes back to 450-180 BCE, when someone wrote about it in Ecclesiastes.

Personally, I find it much easier to go without something if I know there's both a purpose and a time limit.

Traditional caloric restriction, with never-ending, nagging hunger . . . is too depressing.

But going without a meal or two on many (not all) days? I can handle that. I can handle going without a meal for 24 hours. I've done 4 days before, and would again if I think it'd be good for me.

Unlike exercising, intermittent fasting requires no time or effort.

And it costs no money. It even saves you money.

If Big Pharma could put the benefits of intermittent fasting into a pill or a shot, they'd charge you a million dollars and, if you could, you'd pay that.

Richard Stooker is a copywriter and content marketing strategist specializing in the health, wellness, fitness and anti-aging markets.