Losing pounds won’t gain you longevity

A low-calorie diet can improve your overall health, immunity and metabolism. It may even help you squeeze into an outfit you’ve wanted to wear for years.

But, according to a recent study, reducing your caloric intake will not increase your life expectancy.

Nature recently published the results of a 23-year-long study conducted at the National Institute of Aging in Maryland. Researchers at the NIA theorized that specific, calorie-restricted diets might prolong life in rhesus monkeys. However, to researchers’ surprise, dieting rhesus monkeys did not live any longer than non-dieting subjects.

WHAT’S A ‘CR’ DIET?

The NIA study, according to the report in Nature, analyzed two primary groups of monkeys: the first control group followed a normal, yet nutritionally balanced, diet. The second followed a calorie-restricted diet, commonly known as a CR diet, in which caloric intake dropped by 10 to 40 percent.

“I think what’s really important to recognize with full calorie restriction is we’re studying aging and the processes of aging,” NIA researcher Julie Mattison said in a phone interview.

“We’re studying why everything goes bad over time, and it’s possible that CR affects a lot of these organs.”

For years, it has been believed that CR diets prolong life and improve overall health and immunity, according to the CR Society website. CR diets were also thought to stall the onset of age and weight-related diseases, such as cardiovascular disease, diabetes, arthritis and cancer.

Since the 1930s researchers have studied the benefits of CR diets in organisms such as lab rats, yeast, fruit flies and round worms. CR organisms in these studies, which often lived up to 30 to 50 percent longer than organisms with normal diets, prompted scientists to analyze the effects of CR diets in primates, including humans.

THE RESULTS

The NIA study analyzed monkeys of all different ages in both the control group and the CR group. In the CR group, researchers imposed CR diets at different stages in subjects’ lives to determine the overall effects of diet in different points of their lives.

When monkeys died of unknown causes, autopsies were performed to determine the cause of death and its relation, if any, to diet, according to the study in Nature. After years of compiling evidence, researchers were able to formulate several working theories about CR diets:

Monkeys in the CR group had lower incidences of diabetes, cardiovascular disease and cancer than monkeys of normal diets. Some monkeys on CR diets showed signs of elevated immune system, especially in young onset adolescent males. These young-onset CR monkeys also had a lower incidence of cancer.

However, the study showed how death caused by cardiovascular disease, neoplasia, amyloidosis and old-age deterioration still occurred equally in both groups. While illnesses occurred at earlier ages in the control group monkeys, these diseases still caused the majority of deaths in CR monkeys.

CONFLICTING STUDIES

With all of the accumulated evidence, researchers at the NIA are fairly certain of one thing: eating a healthy, calorie-restricted diet will aid in health, but will not add additional years onto life in humans and in non-human primates.

However, researchers at the Wisconsin National Primate Research Centre (WNPRC) are conducting a study that suggests rhesus monkeys on CR diets do, in fact, live longer than those on normal diets.

“There is a 0.1-percent chance that our results would change and show that CR is beneficial,” Mattison said, “but we do have plans to move forward to understand why our studies are different from each other.”

Mattison said both teams intend to let their studies run their courses. For the NIA study, this could take anywhere from three to 13 or more years.

In the meantime, Mattison said, both the NIA and WNPRC will compare existing knowledge, information and test results from their studies to try and determine why each study reached a separate conclusion.

NIA vs. WNPRC

The different conclusions between the NIA and WNPRC studies may have arisen as a result of the differences between the two studies, according to the report in Nature.

One difference is that the WNPRC control monkeys who did not have a calorie-restricted diet were allowed to access food freely, a factor that, Mattison said, more properly reflects the self-controlled diet of Westernized individuals.

“It’s higher in sugar and not as nutritious and well balanced as our diet,” Mattison said. “So theirs might be more representative of what the average American is eating.”

This also means that the WNPRC may reflect the benefits of CR diets in humans.

The NIA control group monkeys, on the other hand, were given limited and controlled amounts of food, Mattison said. Furthermore, the food and protein sources used in each study were different in basis.

Another difference between the two studies is the use of vitamin and mineral supplements.

All monkeys in the NIA study were given more vitamin and mineral supplements while the WNPRC study only gave more nutrients to CR monkeys.

This raises questions as to whether vitamin and minerals supplements really benefit human longevity or even health, Mattison said. No monkeys in the NIA study showed any visible benefits from nutritional supplements.

Babi Bose, a junior in the College of Arts and Sciences, said she is not surprised upon hearing about Mattison’s words.

“I’ve always wondered if vitamins truly work,” Bose said. “I guess it makes me feel like maybe they’re not worth the money, especially if there’s not experimental evidence for it.”

Conflicting results may also be a result of genetic differences, a factor that researchers did not seriously consider prior to the study. Monkeys used in the NIA study were from Southeast Asia while the WNPRC monkeys originated in an Indian colony, according to the Nature report.

Kateri Donahoe, a CAS sophomore, said that genetic makeup could be responsible for the differences between the two studies’ results.

“I think that in our society we focus too much energy on food and diet when there are so many other factors that contribute to developing illness,” Donahoe said. “I think studies fail to emphasize how important other factors, like heredity for example, are to overall health.”

CR IN HUMANS

It is nearly impossible to conduct a lifetime CR study in humans, making it difficult to determine how long-term CR diets may aid human health, said Mattison. This is because human life spans are too long and finding subjects and researchers to participate in a study is difficult.

However, in a short-term and randomized human CR study, biomarkers of aging and an improvement in cardiovascular health occurred within six months of using a CR diet, according to the results in Nature.

“Calorie restriction alters so many things,” Mattison said.

Mattison said her team will continue to search for ways in which CR diets do this.

“We just don’t really know what ultimately the long term effect of it is going to be,” she said.

IS DIETING WORTH IT?

Despite the results of the study, students said that dieting can still be beneficial.

“It’s not about life expectancy,” said Allie Kolb, a junior in the College of Communication. “It’s about feeling good, looking good and living up to a certain standard.”

Joe Kennedy, a COM junior, said he will continue to eat healthy despite the study results.

“I do it because it helps eliminate stress, increases my mobility, improves my self-esteem and adds a level of discipline to my life,” Kennedy said. “Dieting should be about improving the quality of life, not the quantity of it.”