Conscious Choice: Lower Calorie Diets

November 2000

Lower Calorie Diets

by Jami Dawn Kessler R.N., B.S.N.

What would it be like to live to be 120 years old? Could it really become possible in the twenty-first century? If it were possible, how many people would actually want to live that long?

In 1900, before the age of antibiotics and modern medical technology, the average life span was only forty-seven years. Today the average human life span has already increased to about seventy-five years for those in the U.S., and more for many Europeans. But seventy-five years may not be the upper limit.

Since 1935, scientists have found repeatedly that feeding a nutrient-rich diet to rats and mice with a 30 to 50 percent caloric restriction has resulted in them living 30 percent longer than control groups that were fed a regular diet. As long as proper nutrients were provided, the animals not only lived longer, but also lived robust and healthy lives. Similar studies have been done with guppies, water fleas, and spiders. The theory is that as the rate of metabolism decreases with the reduction in caloric consumption, there is also a reduction in free radical production. (Free radicals, oxidants and other harmful metabolic byproducts can accelerate the aging process by causing cellular damage.)

A 1999 study by Thomas Prolla and Richard Weindruch, of University of Wisconsin, Madison, supported these findings. Gene samples were taken from mice at various ages comparing those who ate a regular diet to those on a lower calorie diet. The findings revealed that in the mice who were fed the restricted diet, approximately 84 percent of the genetic alterations related to aging were partially or completely suppressed.

A ten-year study of rhesus monkeys (reported in Journals of Gerontology, January 1999) revealed that caloric restriction produced a stable long term body weight, preventing obesity and diabetes. In addition, energy expenditure was reduced, indicating a reduction in metabolism. Some day, studies like these may lead to the development of drugs that can slow aging in humans. In the meantime, human studies are underway to examine the effect of lower calorie diets on health and longevity.

Physician and researcher Roy Walford has published three books, Maximum Lifespan, The 120-Year Diet, and The Anti-Aging Plan, all based on the theory that life may be extended by caloric restriction. He believes that up to a 30 percent caloric restriction in people of normal bodyweight can significantly increase their lifespan. Under his "Anti-Aging Plan" guidelines, healthy men of normal weight are encouraged to lose up to 18 percent of their body weight and healthy thin women up to 10 percent of their body weight in the first six months. Dr. Walford has a devoted following of people who have committed to stringent dietary guidelines with the hope of being able to lengthen their lives and maintain optimum health. Only time will tell whether or not these practices will show similar results to the studies that have been done in animals.

There are several problems with long- term caloric restriction in the human population. If 30 to 50 percent of normal caloric intake were withheld from the average person, it would be difficult for them to get adequate nutrition unless the proper vitamin and mineral supplements were given to replace what would be lost from lack of sufficient food intake. Intentional steps would need to be taken in order to avoid malnutrition, osteoporosis, and various types of anemias. Another issue is that of compliance. Tasting and eating are two of the most enjoyable activities in life. In addition to the sensory satisfactions of eating, humans are social beings who often enjoy sharing meals with others. The potential feeling of deprivation and hunger caused by a severely restricted diet for life could make it very difficult to sustain. This is one of the reasons why the majority of people who start a weight loss diet will fall off the wagon, so to speak.

Edye Wagner, a dietician at Lake Forest Hospital on Chicago’s North Shore, was asked about her experience with dietary compliance in people placed on lower calorie diets. She stated that "people start out motivated, but they usually comply only for the short term because of feeling unsatisfied; thus the risk of falling off is very high." In her experience, dietary reinforcement by a professional or a peer group can often help. She does not, however, condone diets with severe calorie restrictions, noting that people who undertake such severe measures most likely would be "slowing their metabolic rate and losing weight slower."

Another concern is that people often cut back on fruits and vegetables that contain anti-oxidants, as well as dairy products, which are rich in calcium and grains high in B-complex vitamins. For those who want to lose weight, Wagner will typically cut 300-500 calories from the daily diet. Her recommendation for weight loss is to consume 1,000-1,200 calories per day for women, and 1,500-1,800 calories per day for men. Of course, if a person started out by consuming 4,000 calories per day, they may still be able to lose weight if they cut down to 3,000. Wagner’s suggestions for maintaining a healthy eating program in the long run include consuming at least five servings per day of fruits and vegetables with an emphasis on high fiber, complex carbohydrates, and a low fat intake of less than 30 percent of the total.

A third reason for caution lies with the all-to-human tendency to overdo, even when it comes to deprivation. In order for a person to lose weight, their energy expenditure (calories burned) must be greater than the energy taken in (calories ingested). But most people who succeed at losing weight by drastically limiting their food intake gain it all back, and then some. That’s because the body goes into "starvation mode," not knowing when it will be fed next, and thus slows down, in an attempt to conserve energy. After being on a lower calorie diet, the body will continue to have a decreased metabolic rate for a long time after intake returns to normal levels. In some cases, the decrease in metabolic rate can continue permanently. The result is that the dieter must eat fewer calories than ever before, just to maintain their newly achieved weight.

Unfortunately, it is very common for people to initiate low calorie diets and deprive themselves for the short run in hopes of obtaining quick weight loss. Disappointment often sets in when the numbers on the scale aren’t going down fast enough. (By losing a pound per week, weight loss can be maintained without the drastic metabolic shifts.)

No doubt some weight loss could improve the overall health in the U.S.; obesity (defined as having a body fat percentage greater than 20 percent for men, 30 percent for women and a body weight over 20 percent above the ideal for height and age) is one of the most prevalent health problems in America today. Despite the explosive market for fat-free this and sugar-free that, Americans continue to pack on the pounds. Between 1991 and 1998, the percentage of obese Americans who are at least thirty pounds overweight skyrocketed from 12 percent to 18 percent. In addition, it is startling to note that one-quarter to one-third of all Americans report being physically inactive.

This can be a deadly combination. Research has shown that being significantly overweight can increase a person’s risk for heart disease, hyperlipidemia (high levels of cholesterol and blood triglycerides), high blood pressure, certain types of cancer, degenerative arthritis, diabetes, hernias, gallbladder disease, hemorrhoids, and varicose veins, just to name a few.

Research has shown that diet has played a role in an estimated one-third of all cancer deaths in the western world. A study done by Dr. Sandra Dunn and colleagues at the National Institutes of Health in 1997 demonstrated that calorie-restricted diets in mice slowed the progression of bladder cancer by reducing blood levels of a hormone called insulin-like growth factor-1, or IGF-1. In this study, bladder cancer in the mice was chemically-induced to resemble those bladder cancers which are found in humans. Subsequently, the mice’s dietary caloric intake was reduced by 20 percent. As a result, the IGF-1 declined by 24 percent, retarding the growth and spread of the cancer. When the IGF-1 levels were restored to normal, the scientists saw the bladder cancer proliferation increase.

A 1999 study by Steven Clinton and colleagues at Ohio State University Comprehensive Cancer Center showed that caloric intake influenced the growth of prostate tumors in both rats and mice. Malignant prostate cancer cells were transplanted into cancer-free rats and mice. In the different experimental groups, calories were cut by either 20, 30, or 40 percent. The type of caloric restriction was also studied by limiting carbohydrate intake in some groups and fat intake in others. The results showed that tumor size and growth rate were reduced in the caloric restricted animals. As long as there was a caloric restriction, tumor size was reduced, but the type of restriction from fat or carbohydrate had no significant influence. Clinton states "Our findings provide further evidence that prostate cancer development might be influenced by lifestyle...maintaining an appropriate weight for height may inhibit the progression of prostate cancer."

The average person never will (nor should) look like a Barbie or Ken doll. But in the light of current research such considerations are becoming passé. More to the point is the fact that a reasonably healthy diet and plenty of exercise can increase the quality and length of a person’s life. The American Dietetic Association, the American Cancer Society, the National Cancer Institute, and the American Heart Association all essentially agree on dietary recommendations for disease prevention and risk factor reduction. These include limiting fat intake to 30 percent or less of total calories, increasing carbohydrates to 55-60 percent of total calories and keeping cholesterol intake below 300 mg per day, as well as keeping sodium intake below 2,400 mg per day. In addition, at least thirty minutes of moderately intense physical exercise (prolonged or cumulative) on all or most days are recommended by the American Heart Association, the Centers for Disease Control, and the American College of Sports Medicine.

Those guidelines may not make a person live to be as old as Rip Van Winkle, but they certainly can help to prevent many lifestyle-related illnesses as well as improving energy levels and quality of life. The question whether or not severe caloric restriction can lengthen the human lifespan may not be answered for many years. In the meantime, the reward is in preventing diet-related diseases. That, in itself, can be enough reason to exercise and eat wisely, rather than too well.

Jami Dawn Kessler R.N., B.S.N., is the founder of the Reflective Movement process for goal setting, exercise, and life balance. Consultations available. First session free. 847-347-0975.

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