Echoing numerous animal studies published in years past, new research on humans is finding that eating a diet full of low-calorie, nutrient-rich foods like fruits, vegetables, and whole grains appears to slow the aging process.
Body Temperatures, Insulin
The latest study, from Louisiana State University, compared healthy overweight people following a typically calorie-rich American diet with healthy, overweight people on a 900-calorie-a-day diet.
After six months, the low-calorie eaters not only lost a lot of weight but also had significantly lower insulin levels and body temperatures compared to the high-calorie eaters.* Both animal and human studies have shown that those with lower body temperatures tend to live longer, as do those with lower fasting insulin levels, wrote lead author Dr. Eric Ravussin and team.
What’s more, less DNA damage was occurring in the low-calorie dieters, which is very important information, pointed out the authors, because one of the many theories of aging is that there is more DNA damaging happening. Smokers, for example, have more DNA damage.
1,800 Vs. 2,700 Calories
In related new research, scientists from Washington University in St. Louis compared 28 adults who had been following a low-calorie (about 1,800 calories daily), nutritionally-packed diet for the last 3 to 15 years with 28 adults eating a typical high-calorie Western diet (about 2,700 calories daily).**
For both groups, the scientists measured several biochemical indicators linked with aging and longevity, including a thyroid hormone called T3, involved in the control of body temperature and cell metabolism. Low levels of T3, lead investigator Dr. Luigi Fontana and team explained, may slow down aging. They observed reduced concentrations of T3 only in the low-calorie dieters.
In the low-calorie group, levels of two other thyroid hormones – T4 and TSH – were normal, indicating that this 1,800-calorie-a-day group was not afflicted with a thyroid disease called hypothyroidism.
An earlier study by Dr. Fontana and colleagues also affirmed the anti-aging, disease-fighting power of low-calorie, nutrient-dense diets for humans. The scientists compared 18 people who for several years had been following diets ranging from 1,100 to 1,950 calories daily with 18 other people who ate 1,975 to 3,550 calories per day.***
The Right Carbs
One key dietary difference between the two groups: the low-calorie dieters ate mostly fiber-filled, unrefined carbohydrates like fruits, vegetables, beans, and whole grains; the higher-calorie group ate a lot of "white” carbs – refined, processed carbohydrates like white bread and potato chips as well as sugar-rich drinks.
Compared to the higher-calorie diet, the low-calorie diet had “profound and sustained beneficial effects on the major atherosclerotic risk factors that usually increase with advancing age,” including total cholesterol, LDL choelsterol, levels of inflammation, insulin resistance, and blood pressure, concluded the authors.
The average blood pressure of the low-calorie group was about 100/60, akin to the blood pressure of a healthy 10-year-old.
BIG Foods
What’s the optimal diet for people wanting to cut calories?
The late Dr. Roy Walford of UCLA, who in the 1970s and 80s spearheaded research linking low-calorie diets with longevity, recommended the Pritikin Eating Plan because its abundance of high-volume foods wouldn’t make people feel as if they were on a calorie-restricted diet. Plenty of BIG foods like fruits, vegetables, beans, and whole grains, staples of the Pritikin diet, do a great job of helping people fill up on a minimum of calories.
Plus, the high-nutrient content of these natural, fiber-packed foods would help ensure that those on very low-calorie diets were getting all their essential vitamins and minerals.
Concludes Dr. Jay Kenney, Nutrition Research Specialist at the Pritikin Longevity Center in Aventura, Florida: “If you follow a low-calorie-dense, nutrient-rich diet like Pritikin and exercise regularly, you give yourself the best chance of staying thin without having to live with chronic hunger, and the best chance for living a longer, healthier life.”
* JAMA, 2006; 295: 1539.
** Journal of Endocrinology and Metabolism published May 23, 2006, as doi:10.1210/jc.2006-0328.
*** Proceedings of the National Academy of Sciences, 2004; 101: 6659.
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