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We know that eating a low-calorie diet for the long term can slow aging in laboratory animals. We also know that in the short term, a low-calorie diet can improve a person’s blood pressure, total cholesterol, and triglyceride levels, all risks for heart disease.
But what about the long term effects of a low-calorie diet in humans? Would people’s risk factors for heart disease (artherosclerosis, or “hardening of the arteries”) be reduced for the long term?
Researchers sought to find out. (PNAS, 101:17, 6659-6663) They recruited eighteen people, fifteen men and three women, from the Caloric Restriction Optimal Nutrition Society, a group whose members seek to prolong their lives through proper diet and nutrition. These eighteen people had been practicing caloric restriction for at least three and up to fifteen years at the time of the study.
As a control group, researchers matched the calorie-restricting group (CR) with eighteen people eating “a usual American diet”. Both groups’ members had the following characteristics:
Researchers measured Body Mass Index for all individuals and tested their blood for cholesterol and glucose levels. Their blood pressure was taken and the thickness of their carotid arteries was measured by ultrasound (to check for hardening of the arteries, or plaque buildup in the artery). They also required all test subjects to fill out a detailed food survey for seven consecutive days, detailing all foods and beverages, how the foods were prepared, and portion sizes. (They even supplied the subjects with measuring cups for accuracy.)
The individuals on Caloric Restriction design their diets to consume a variety of foods that supply 100% or more of the Recommended Daily Allowance of all the essential nutrients, while minimizing the number of calories they ate (usually between about 1200 and 2000 calories per day). About 26% of their calories come from protein, 28% from fat, and about 46% from complex carbohydrates. They avoid eating processed foods containing trans-fatty acids and keep away from refined carbohydrates, desserts, snacks, and soft drinks. By comparison, the American diet group averaged 2000-3500 calories per day, with about 18% of their calories from protein, 32% from fat, and about 50% from carbohydrates.
Some of the results aren’t surprising: the CR group had a BMI almost one-third lower than the group on the “usual American diet”. Total body fat for the men in the study averaged four times higher for the American diet group than for the CR group, which had higher lean mass.
But the cholesterol levels!
The American diet group had cholesterol levels of Total cholesterol, LDL (the bad stuff) and HDL (the good stuff) well within the average range for people in their age group in the U.S.
The CR group, by contrast, had Total cholesterol and LDL levels in the lowest 10% range for those in their age group, while having triglyceride levels “similar to the 5th-percentile values for 20-year-olds”. They also had HDL levels in the 85th to 90th percentile range for middle-aged men. Their blood pressure was normal—for ten-year-olds. Further, none of the CR group had any evidence of plaque buildup in their carotid arteries.
Remember that the labels on food are based on a 2000 calorie diet. For a lot of people this can be way too much. It’s pretty clear from this study that eating a healthy diet with a reasonable number of calories helps prevent heart disease.
The guidelines that I use in the tables for choosing a diet that’s right for you are part of eatTHISdiet. The number of calories are based on height and weight and are a good guideline. Compare the calorie levels for maintenance on eatTHISdiet with the American diet group’s average intake of 2000-3500 calories per day! You can use eatTHISdiet, either the Original or Comfort Food Diet, to lose weight, but they can also help you eat healthier even if you are already eating the right number of calories.
December 12, 2005