People who restrict their caloric intake drastically reduce their risk of developing diabetes or atherosclerosis.
In fact, according to researchers at Washington University School of Medicine in St Louis, some risk factors were so low they were comparable with those of people decades younger.
"It’s very clear from these findings that calorie restriction has a powerful, protective effect against diseases associated with aging," said lead investigator John O. Holloszy, MD. "We don’t know how long each individual actually will end up living, but they certainly have a much longer life expectancy than average because they’re most likely not going to die from a heart attack, stroke or diabetes."
Research on mice and rats has shown that stringent and consistent calorie restriction increases the animals’ maximum lifespan by about 30% and protects them against cancer. This study is the first to examine people who have been on calorie-restricted diets for a long period.
The researchers recruited participants through a national organization called the Caloric Restriction Optimal Nutrition Society.
By eating small amounts of nutrient-dense foods, members of this group try to consume between 10 and 25 percent fewer calories than the average American while still attempting to maintain proper nutrition. The 18 individuals who participated in the study had voluntarily been following this very low-calorie diet for three to 15 years. This group was compared with 18 age- and gender-matched individuals who ate a typical Western diet.
Holloszy’s team found the two groups not only differed in the number of calories consumed, but also in the composition of their diets. Individuals in the calorie-restriction group ate between about 1,100 and 1,950 calories per day depending on height, weight and gender, and these calories consisted of about 26% protein, 28% fat and 46% complex carbohydrates.
In contrast, the comparison group consumed between about 1,975 and 3,550 calories per day, with only 18% of their calories from protein, 32% from fat and 50% from carbohydrates, including refined, processed starches.
Atherosclerosis is already the leading cause of death in the Western world, and the problem is continuing to grow. So Holloszy’s team specifically focused on the risk factors for this condition. The team measured multiple indications of early or impending atherosclerosis, including blood pressure and levels of several biological markers in the blood, including cholesterol and triglycerides. They also measured the levels of glucose and insulin in the blood to gauge diabetes risk.
People in the calorie-restriction group had total and low-density lipoproteins comparable to the lowest 10% of the population in their respective age groups. Their high-density lipoprotein (HDL) levels were in the 85 to 90 percentile for middle-aged men.
That finding was a surprise because HDL levels typically decrease when individuals follow low-fat diets to lose weight.
Triglyceride levels were even more impressive in the calorie-restriction group: They were lower than more than 95% of Americans in their twenties, despite the fact that the study participants’ ages ranged from 35 to 82.
In contrast, cholesterol and triglyceride levels in the comparison group were in the 50th percentile for average middle-aged Americans. Moreover, 12 of the individuals in the calorie-restriction group provided medical records from before and during the diet. Their cholesterol and triglyceride scores also were close to the 50th percentile for middle-aged Americans before the diet, and levels fell the most dramatically during their first year of calorie restriction.
Blood pressure scores in the restricted group also were equivalent to those of much younger individuals. The average blood pressure in the normal diet group was about 130/80, which is standard for the typical American.
In comparison, the calorie-restriction group’s average was about 100/60, akin to the blood pressure of an average 10-year-old. Fasting glucose and insulin - both markers of the risk of developing diabetes - also were significantly lower in the calorie-restriction group, with insulin concentrations as much as 65% lower. The team is conducting a controlled, prospective study comparing calorie restriction with the average American diet. They ultimately hope to follow these individuals for a longer period to assess the long-term effects of calorie restriction on biological markers of aging.
Tuesday, August 10, 2004