Seventy years of scientific research shows that restricting calories to 30% below normal intake can extend life span by up to 50% in laboratory animals. New research shows that calorie restriction may extend the life span of human beings as well.

Paul McGlothin and Meredith Averill, experts on calorie restriction and authors of The CR Way: Using the Secrets of Calorie Restriction for a Longer, Healthier Life, spoke about some of their important findings…

Newest Research

Reporting in Science, researchers from the University of Wisconsin revealed the results of a study on calorie restriction in rhesus monkeys, our closest "relatives." The researchers studied 76 adult rhesus monkeys (which live an average of 27 years and a maximum of 40), dividing them into two groups. One group ate a calorie-restricted diet, and one didn't. After 20 years, 37% of the monkeys in the non-restricted group had died, compared with only 13% in the calorie-restricted group. The calorie-restricted monkeys also had fewer incidences of heart disease, diabetes, cancer and brain disease.

In other research, scientists at Washington University School of Medicine in St. Louis studied the biomarkers of aging of 33 people, average age 51, who ate a calorie-restricted diet for an average of six years. Compared with another group of people who ate a typical American diet, the calorie-restricted practitioners had lab results that are typical of people much younger than themselves. They had lower cholesterol, lower blood pressure, less body fat and lower glucose (blood sugar) levels.

The study participants also had lower levels of insulin (the hormone that regulates blood sugar)...C-reactive protein (a biomarker for disease-causing inflammation)...tumor necrosis factor la biomarker for an overactive immune system)... and thyroid hormone T3 (lower levels indicate a slower, cell-preserving metabolic rate).

Why It Works

There are several theories as to why calorie restriction improves health and may increase life span. It may…

  • Reduce DNA damage.
  • Reduce daily energy expenditure, the most basic of metabolic processes, thereby reducing oxidative stress, the internal "rust" that damages cells.
  • Decrease core body temperature. The higher your normal body temperature, the faster you age.
  • Improve how the cells handle insulin, which controls glucose. Poor glucose regulation damages cells.
  • Improve the neuroendocrine system, the link between the brain and the hormones that regulate many of the body's functions.
  • Activate a type of gene called sirtuins, which protect mitochondria, tiny energy factories in the cells. Mitochondrial failure speeds aging,

Easy Way To Cut Back

The level of calorie restriction probably required to extend life in humans-about 20% to 30% of typical intake-is more than most people are willing to do on a regular basis, but reducing calories by even 5% can produce significant health benefits.

Estimated calorie requirements for a moderately active person age 51 or older are 2,200 to 2,400 calories a day for a man and 1,800 for a woman. Reducing calories by 5% would mean cutting between 110 and 120 daily calories for a man and 90 for a woman.

With just a few changes in your dietary routine, you easily can reduce calories by 5% or more and improve your health…

  • Favor nutrient-dense foods. A nutrient-dense food has a high amount of nutrients per calorie. They're the healthiest foods to eat. They include...

Animal protein: Salmon (Alaskan wild, canned, fresh or frozen), sardines, tuna.

Good fats: Nuts...avocados...grapeseed oil, extra-virgin olive oil.

Beans: Adzuki, limas, black-eyed peas, black turtle beans, garbanzos (chickpeas), lentils (red or green), mung, pinto, soy.

Veggies: Arugula, beets, bok choy, broccoli, cabbage, carrots, chard, collard greens, garlic, kale, kohlrabi, leeks, mushrooms (maitake, portobello, shiitake), mustard greens, onions, romaine lettuce, spinach, squash (butternut, summer), sweet potatoes, tomatoes.

Grains: Barley, quinoa, wild rice, sprouted-grain breads.

Fruit: Apricots, blackberries, blueberries, cantaloupe, cranberries, kiwi, lemons, limes, oranges, peaches, raspberries, strawberries, tangerines.

Spices and herbs: Season foods with herbs and spices rather than salt, butter or sugar. Examples include basil, chives, ginger, parsley and turmeric.

  • Focus on foods with low-to-moderate Glycemic Index rankings. High levels of glucose and insulin are linked to faster aging and disease. It's just as important to limit glucose as it is to limit calories.

The best way to regulate glucose and insulin is to choose carbohydrates that have a low-tomoderate score on the Glycemic Index (GIcarbohydrates that digest slowly so that glucose and insulin levels don't suddenly skyrocket.

The beans, veggies, grains and fruits that are nutrient-dense (listed above) have a low-to-moderate GI score.

Other ways to keep glucose low…

  • Start your meal with one cup of water with one tablespoon of lemon juice.
  • Finish your last meal of the day as early as possible, eating complex carbohydrates and a fat source.
  • After your evening meal, take a 45-minute or longer walk.
  • Keep protein intake moderate. Excess protein can increase blood levels of the hormone Insulin-Like Growth Factor-1 (IGF-1), which deactivates a sirtuin gene and accelerates aging.

Each day, eat 0.36 grams (g) of protein per pound of body weight-at your healthiest, ideal body weight. That's 43 g of protein a day for a woman whose ideal weight is 120 pounds and 55 g of protein a day for a man whose ideal weight is 154 pounds. For comparison, typical intake for US adults is 65 g to 90 g. One ounce of meat or fish contains about 7 g of protein.

  • Stop eating before you're full. Always leave the table slightly hungry. This helps you cut calories and prompts the hypothalamus—the emotion-generating part of the brain-to produce the hormone orexin, which boosts feelings of happiness. The Japanese have a concept for this healthful practice—bara bachi bu—which means eat until you're 80% full.

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