The CR Diet Truth: Will Calorie Restriction Prolong your Life?

“We’ve known for a long time that if you reduce the calorie intake of rats or mice, they live much longer,” says Mark Mattson, chief of the laboratory of neurosciences at the National Institute on Aging (NIA) in Baltimore.

What happens in species closer to humans is more complicated. Rhesus monkeys fed 30 percent fewer calories lived longer in a study at the University of Wisconsin, but not in a study at the NIA.

Why the different results? One possibil­ity: The Wisconsin monkeys were fed few­er calories than monkeys fed as much high-sugar, high-fat food as they want­ed. In contrast, the NIA monkeys were fed fewer calories than monkeys fed as much (low-sugar, low-fat) food as they needed to maintain their weight.


“One take-home message is that if you are an overweight monkey like those in Wisconsin, cutting back on calories will extend your lifespan,” says Mattson. “Whereas if you are eating a healthy diet and not overweight like the NIA monkeys, cutting back on calo­ries may not extend your life, although you may experience some health benefits.”

What if you’re human? In the first good study in normal-weight or slightly over­weight (but not obese) people, researchers asked roughly 150 men and women to consume 25 percent fewer calories at each meal than they needed to maintain their weight, and 75 similar people to follow their normal diet, for two years.

The calorie cutters managed to eat 12 percent fewer calories, and they lost 10 percent of their body weight. That may explain why their blood pressure was lower and their insulin worked better than those who ate their normal diets.

“They lowered their risk factors for heart attack, stroke, and diabetes,” says Eric Ravussin, director of the Nutrition Obesity Research Center at the Pennington Biomed­ical Research Center in Baton Rouge, Loui­siana. The study hasn’t yet been published.

Why didn’t the calorie cutters cut more? “Eating less than you would like to every day is a struggle,” says Ravussin. “Some people can do it, but many cannot.”

Cutting calories only on some days may be easier

Calorie restriction doesn’t have to happen every day.

“There’s the alternate-day modified fast,” says Ravussin. “Every other day you eat only one meal with maybe 30 percent of your normal daily calorie intake.”

And there’s the 5:2 diet, in which you eat a normal diet five days of the week, and only 30 percent of what you would normally eat on the other two days.

“Whichever it is, you have to make sure you don’t overeat on the normal days,” cautions Ravussin.

So far, intermittent fasting shows prom­ise in both animals and people. “Laboratory animals that get no food at all on alternate days live about 30 percent longer than animals that eat their regular diets every day,” says Mattson.

In humans, the 5:2 plan seems to hold an edge over fasting every day.

In two of the best studies, Mattson and colleagues divided 166 overweight middle-aged women into two groups. Both were told to cut calories by 25 percent—one by trimming the calories in each meal, the other by following a 5:2 plan.
In both studies, the women were told to eat a high-protein “Mediterranean-type” diet with fruits, vegetables, whole grains, nuts, seafood, and olive oil, and only moderate amounts of dairy, poultry, eggs, and lean red meat.

On the two fasting days of the 5:2 diet, one study prescribed just four cups of low-fat milk, four servings of vegetables, and one serving of fruit. The other study prescribed about 9 oz. of lean protein, 3 servings of low-fat dairy, 4 servings of low-carb vegetables, and a low-carb fruit. Both also recommended low-calorie drinks and a multivitamin-and-mineral.

In each study, both calorie-cutting groups lost about the same weight. “But insulin resistance declined more in the 5:2 groups than in those who cut calories daily,” says Mattson. And in the three-month trial (the other trial lasted six months) the women on the 5:2 regimen lost more body fat.

Why did the 5:2 dieters do better? They were more likely to stick to their plan. “And on the two days that they ate only 500 to 600 calories, their metabolism shifted to burning fat,” says Mattson.

Brain Diet?

Middle-aged rats, after being deprived of all food every other day for three months, lost 23 percent of their body weight and had better motor coordina­tion and cognitive skills than similar rats who could eat all they wanted.
One possible reason: “Intermittent fasting increases brain levels of a protein that stimulates the growth of new brain cells and the connections between them,” says Mattson.

“We think what’s happening is that when you’re hungry, your brain cells are more active so you can figure out how to find food,” he explains. “During evolu­tion, those who were able to figure out how to get food were the ones who survived.”

Today, our brain cells may respond in a similar way when we’re hungry. Intermittent fasting also seems to postpone dementia, at least in animals. In mice bred to show signs of Alzheimer’s disease by middle age, eating only every other day delays the onset of dementia by the human equivalent of about 10 years.

“That’s a big effect,” says Mattson. “But we’re nowhere near being able to say the same about humans.”

The bottom line: Cutting calories may not prolong your life, but it may lower your blood pressure and make your insu­lin work better.

Sources: Science 325: 201, 2009; 2 Nature 489: 318, 2012; Mech. Ageing Dev. 55: 69, 1990; 4 Int. J. Obes. 35: 714, 2011; Br. J. Nutr. 110: 1534, 2013; Age 34: 917, 2012; Endocrinology 144: 2446, 2003; Neurobiol. Dis. 26: 212, 2007.

4 Replies to “The CR Diet Truth: Will Calorie Restriction Prolong your Life?”

  1. In order to reduce fat contamination in my site center I had to reduce my intake of saturated fat. That is if I wanted to see to be able to drive home from the restaurant. After a 6 year journey I found myself in the organic vegetarian isle of my super market. My LDL is 50 was 135. You can imagine how difficult this journey had been. This is the isle where I could find low saturated food. Since then the whole Giant food market has changed. I can even find organic chicken hot dogs without nitrates in the same rack as the crappy hot dogs. Why am I bothering you. Because in order to maintain my weight in a narrow range between 173 and 175 I have to follow the 5:2 diet. But it is easy on this diet because I only eat fruits and vegetables and a small amount of organic chicken each day for added protein. You can call this diet by some name if it makes you feel better. Since our food supply has been poisoned, it’s the only safe way to eat. The food, especially the organic meat, is like it was when I was a boy, back before supermarkets. We bought our meat from a local store where the sides of beef where hanging up in a meat locker. There was no processed food for sale in the market. It didn’t exist. All this crappy food has been engineered in my lifetime. And it is slowly killing us. Add to it alcohol and prescription drugs to overcome the damage and it is a recipe for disaster. The majority of illness in this country is not related to virus and bacteria. It is related to the food we eat and the cigarettes, alcohol, and crappy food we stuff in or mouths continually all day long. No small wonder we have insulin resistance and fat children. There is one area that needs more research. The pleasure centers in our branes are being overloaded with simulation from the binge eating. When we stop, part of our brain function crashes and we go into a terrible state. Reaching for candy bars fixes that until we damage the branes response systems. There was a drug used in Wall Street about 20 years ago which did the same thing. After about three years on the drugs, the users brain stopped responding and they could hardly move let alone think. The same kind of thing happens when a person who has been eating like a pig tries to go on a diet. Please research what happened on Wall Street. WE HAVE A VERY BIG PROBLEM IN THIS COUNTRY. AND IT IT VERY SERIOUS.

    Thanks for all your help. It is saving my life.

    1. Howard, This is great! I have yet to get to my maintenance weight but am halfway there, I am guessing, and like you, I find myself typically in a co-op which I am fortunate enough to have within three miles of home or at least OUT of aisles of processed, poisonous food, if I am at any supermarkets. My son, too, is making better choices slowly but surely. I mention that because I think that young men (he is 29) are especially targeted for processed as well as high LDL cholesterol containing foods. I have learned that I can’t get anywhere with an over-enthusiastic buying of all sorts of veggies I had rarely ever heard of much less eaten, which is what I used to do when I had well-meaning start-ups in attempts at reprogramming my eating ways, not just the temporary plan we seem to call going on a diet. More helpful for me is getting to know or adapt to one new veggie that has an important nutritional need in it at a time. This next few weeks it is the, I think, infamous kale, since my naturopath (N.D.) has told me I need a lot more magnesium, for one thing. Putting it in an omelet occasionally or, more frequently, in a mix of favorite salad veggies helps this effort to gradually include more newcomer veggies and build my body’s feelings of reward through the healthful rather than the insidious pleasure binges that you’ve mentioned. Well, I am carrying on in a reply a bit, but I really read your post on journeying to a whole different aisle or area of stores as something so familiar and well put. I am also going to check out the Wall Street drug experience findings, since I never heard of that. To our collective health!

  2. I’ve followed the “Fast Diet”‘ , 5:2 plan to successfully lose weight and maintain it. Highly recommend it. It helps keep me focused on eating healthy amounts but don’t feel deprived because I can eat normally the other five days.

  3. I follow a low salt, low fat, low sugar menu as much as possible because I believe those 3 ingredient causes high blood pressure, heart problems and diabetes. Organic food causes so much more, I do feel guilty when most food my family eats is not in that category. We do minimize meat portions and eat more vegies and fruits most of the time. My teen is allowed more “space” with junk food but is gradually realizing how some spicy junk food affects her complexion. Her dad is in compliance and had lost the extra pounds and feels better. I maintain my weight with reasonable limits. I don’t know what diet you call this. So far we are fine.

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