Problem 5 - Biology of Aging

Question

Using examples from both nonhuman primates and humans, describe why calorie restriction may not be as effective in humans as in other species.

Step-by-Step Solution

Answer

Calorie restriction has been found to be beneficial in nonhuman primates, shown through improved longevity and reduced disease incidence. In humans, while some health benefits are observed, the long-term effects are uncertain and there could be potential adversity such as decreased bone density and cognitive function. Differences could be due to variations in metabolism, reactions to hunger and socio-environmental influences.

Step 1: Understanding Calorie Restriction

Calorie restriction refers to reducing average daily caloric intake below what is typical or habitual, without deprivation of essential nutrients. It has been studied largely using animal models.

Step 2: Calorie Restriction in Nonhuman Primates

Studies have demonstrated that calorie restriction can extend lifespan and delay age-related diseases among nonhuman primates. The effects are found to be more pronounced when the restriction begins at a young age. For instance, studies on rhesus monkeys show significant improvements in longevity and reductions in cancer incidence, cardiovascular disease, and insulin resistance.

Step 3: Calorie Restriction in Humans

In humans, the effectiveness of calorie restriction as a means for extending lifespan and combatting disease is still under investigation. Preliminary data indicate some health benefits, such as improved markers for cardiovascular disease and reduced fat mass. However, long-term effects are still unclear and other studies suggest potential adverse effects including reduced bone mineral density, loss of muscle mass and decreased cognitive function.

Step 4: Understanding the Differences

There could be multiple reasons why calorie restriction might produce different results in humans compared to other species, including differences in metabolism and body composition, variation in responses to hunger, and the influence of social and environmental factors.