Are you a man? Or a Mouse? I know, I know!- I should bite my tongue at such cliches, but we all know that many of the animals found in laboratory testing are in fact rodents, or mice. The thing that must then be asked is, Will it work in humans, just because it worked in mice? This can be approached with demographics, but even then, it isn’t always an effective gauge.
In this case-, don’t we already know the answer? Now I want you to understand I am sympathetic to being big boned. I am 6″4′ and weigh in at 240lbs. However, this is nothing compared to my dad who was also a rather large fellow at 6″2′ weighing in at 360lbs. So, growing up, I experienced some of the issues that one experiences being overweight. Likewise, I have witnessed how these problems dramatically increase as the weight goes above and beyond what is considered normal.
So, these aren’t just studies to me. We should ask if what is known about obesity, and calorie restriction in rodents and mammals in laboratory studies also applies to humans. I think we have a decent idea. Sure, we don’t hear a lot about mice with a problem with high cholesterol, even though mice do dig cheese.
Caloric Intake And Lifespan
However, we do see that when you lower the caloric intake, you increase the lifespan of both rodents and mammals alike. We see that less calories means lower body weight, and lower body temperature. Which in humans would translate to less pressure on the joints, the heart, internal organs, and you can be sure this would translate to overall feelings of health and well-being. Also, in calorie restricted animals, we see a lower number of tumors than those found in animals of a similar age range (Barzilaj and Bartke). Sounds good to me.-
This research goes further to try and attempt to pinpoint the amounts of various hormones found at higher or lower levels within the body of the animals in question. The reasoning no doubt, is trying to determine which hormones are healthier, or necessary to a longer life. In our calorie restricted animals, we see that the animal maintains a slightly higher level of testosterone throughout their life. We also see moderate levels of thyroid stimulating hormone, thyroxine, triiodothyronine; all used by the body to regulate the body’s metabolic rate, heart and digestive functions, control of the muscles, as well brain function, and maintaining the bones. (Snyder, Wostmann, Pollard).
In another study, we see lower levels of stress related hormones like adrenocorticotropic hormone in the anterior pituitary. It also shows that the proopiomelanocortin mRNA primary transcript went up in rodent’s plasma, but not in the anterior pituitary. This study goes even further, to look at how the hormones are regulated at various times of day, and by divergent means than otherwise extrapolated (Han, Levin, etc.)
The most recent of these studies is the Barzilaj and Bartke one, which looks at the effects of reduced levels of growth hormone. It would even go so far as to suggest that it is a trade-off of diminished capacity for reproduction for slower aging. Which, if you look at the previous study proopiomelanocortin, is a precursor for Melanotropin (Melanocyte-Stimulating Hormone, or-MSH), It can also be a precursor for the forementioned ACTH, or -endorphin and [Met]encephalin. All depending on where it is secreted. So seeing the lower levels of ACTH, you see what was meant by the divergent functions (since it obviously isn’t making that particular peptide). However, if Barzilaj and Bartke are right, this would figure in with higher levels of -MSH as a regulator regulates the sex drive (neurons in the arcuate nucleus) and the appetite. Only time will tell.
This research has been going on for decades, and time and again it is repeated that animals that eat less – live longer. Likewise, it can be extrapolated from our own lives that it is harder on the organs of the body as well as the joints to live with a higher body mass index. Yet knowing this and accepting it into our lives can be two separate things entirely, and then comes the question of what is the best path for achieving this goal in your own life?
David L. Snyder, Bernard S. Wostmann and Morris Pollard, “Serum Hormones in Diet-Restricted Gnotobiotic and Conventional Lobund-Wistar Rats,” Journal of Gerontology, 43 (1988)(6): B168-B173
Nir Barzilai and Andrzej Bartke, Biological Approaches to Mechanistically Understand the Healthy Life Span Extension Achieved by Calorie Restriction and Modulation of Hormones, The Journals of Gerontology: Series A , 64 (2009)(2): p. 187-191.
Eun-Soo Han1, Nancy Levin2, Nomsa Bengani2, James L. Roberts2, Yongman Sun1, Katarzyna Karelus1 and James F. Nelson, Hyperadrenocorticism and Food Restriction-Induced Life Extension in the Rat: Evidence for Divergent Regulation of Pituitary Proopiomelanocortin RNA and Adrenocorticotropic Hormone Biosynthesis,! The Journals of Gerontology: Series A, 50A, (1995) (5): B288-B294