I find the idea of calorie restriction as a means of extending life and delaying aging rather surprising. I'm with the majority of scientists in being skeptical that calorie restriction is beneficial and can extend human life. Just because it works for animals doesn't mean it will work for humans.

Over-nourishment as is commonly seen in the U.S. is definitely detrimental and contributes to diseases that can shorten the human lifespan. As a culture we've focused on the negative health effects of being over-weight and practically ignored the negative health impacts of being underweight.

Our text mentions that consuming fewer calories results in less frequent cell duplication. Makes sense as the body doesn't have enough macro-nutrients (measured in calories) to function properly so it has to allocate resources and make do with what it has. Michael Rae, one of the leaders of the Calorie Restriction Society, pictured in our textbook, looks rather thin and undernourished to me. My guess is he wouldn't have much endurance in a race, resistance to pathogenic organisms, or reserves to fall back on if injured or ill. Undernourishment shortens the lifespan of thousands of people in poorer countries, this is due in part to lower disease resistance.

When you don't get enough nutrition non-essential things such as bones suffer. With a slower metabolism, all of the body's processes slow down, including mineral and bone metabolism, which are essential for skeletal health. People who are underweight are at greater risk of bone fractures and osteoporosis.

Adequate nutrition, not too much and not too little is best for sustaining and supporting the health and longevity of the human body.

References

Alam, I., Larbi, A., & Pawelec, G. (2012). Nutritional status influences peripheral immune cell phenotypes in healthy men in rural Pakistan. Immunity & Aging, 916-25. doi:10.1186/1742-4933-9-16

Bialo, S. R., & Gordon, C. M. (2014). Underweight, overweight, and pediatric bone fragility: Impact and management. Current Osteoporosis Reports, (3), 319.

Rytter, M. H., Kolte, L., Briend, A., Friis, H., & Christensen, V. B. (2014). The immune system in children with malnutrition—A systematic review. Plos ONE, 9(8), 1-19. doi:10.1371/journal.pone.0105017