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Reduced Dietary Intake Can Prevent Obesity and Increase Longevity

Aging has been defined as the multifaceted process of the collection of biological damages in the molecules, cells, and organs of the body. These damages are thought to cause decrease in function and increase in susceptibility to disease and death. Despite how complex aging is, recent studies have shown that changes in diet and genes can significantly lengthen healthy life span in laboratory organisms.

New research has found that dietary restriction, “a reduction in food intake without malnutrition”, lengthens the life span of a variety of organisms that include yeast, flies, mice, fish, worms, and rhesus monkeys. By reducing the level of normal dietary consumption by 10 to 50% in these organisms, the researchers found that age-related decline in function and vulnerability to disease significantly improved.  In human studies, a reduction in risk factors for cardiovascular disease, cancer, and diabetes was found. The researchers sought to understand the influence this change in dietary consumption had on longevity in order to discover treatments for preventing a variety of age-related diseases and degeneration.

Mutations in growth hormone have been found to significantly increase life span in rodents, although the specific mechanism that causes this is poorly understood.  In studies that involved rhesus monkeys and human volunteers, some individuals were found to have naturally low levels of growth hormone receptors. In these cases, diabetes and cancer were not common, but there was also no existing advantage in increasing life span to very old ages, possibly explained by developmental defects and the higher mortality at younger ages.  In participants with growth hormone receptor deficiencies, there were no incidences of cancer. It was found that although growth hormone deficiencies increased the risk of obesity and hyperlipidemia, whereas growth hormone treatment improved the effects on both traits, replenishing growth hormone levels promotes fat accumulation in the arteries and cardiovascular disease. Further research with human volunteers are needed to confirm the beneficial effects of reduced growth hormone receptor signaling in order to consider pharmaceutical treatment options that could prevent specific diseases.

In regards to dietary restriction, a recent study that conducted a 30% dietary restriction on adult rhesus monkeys for a span of 20 years showed a decrease in age-related deaths.  These animals experienced a 50% decreased risk of neoplasia and cardiovascular disease compared to controls (those that did not undergo dietary restriction.  Moreover, none of the dietary-restricted monkeys developed prediabetes or diabetes.  Substantial reductions in body fat mass, increases in insulin sensitivity, and decreased inflammation and oxidative damage were also seen in dietary-restricted monkeys. Furthermore, immune senescence, age-related loss of muscle mass, and brain atrophy were diminished. Further studies that investigate the negative effects of dietary restriction, such as decreased resistance to infection or poorer wound healing, are needed.

In humans, researchers found that dietary restriction has long-term beneficial effects against “obesity, insulin resistance, inflammation, oxidative stress, and left ventricular diastolic dysfunction. It is important to note that there are significant differences in dietary restriction effects between mice and humans.  Extreme dietary restriction can result in various health consequences that include “amenorrhea, infertility, sarcopenia, osteoporosis, and immune dificiencies.”  It is therefore important to consider these negative effects when implementing dietary-restriction and avoid malnutrition. Further experimental research is needed to identify the optimal calorie intake and composition of macro- and micro-nutrients to promote healthy aging in humans, taking into account age, gender, genotype, and energy use.