Some researchers say that the only true method to slow the aging process is caloric restriction (CR). The CR technique was first used in animals by Clive McCay in the 1930s. Since then, numerous studies have found that CR, often involving a reduction in daily caloric intake of 30-40%, reliably extends lifespan in a number of animal species, including fish, rats, mice, worms, insects, dogs and others. The data in humans are less clear. But ongoing experiments with primate relatives of humans, such as chimps, show that those placed on CR regimes do seem to age slower than then normally eating peers. More importantly, the CR chimps seem to be spared from the degenerative diseases that are the major killers, including cardiovascular disease, cancer, diabetes, even Alzheimer's and Parkinson's diseases. While it would be difficult to design a study focusing on the human efficacy of CR, many people have placed themselves on CR regimes in an effort to maintain health and boost longevity. This, despite the fact that there is no scientific evidence that CR will actually work in humans as it does in short-lived animal species. Nonetheless, studies of human CR advocates show that they have low bodyfat levels, low blood pressure and blood lipids, and other indicators that would point to a tendency not to die young. In truth, however, the key to their inproved health is probably not from the stringent food intake, but rather the fact that they are extremely lean. Having too much bodyfat as you age places you at risk for all the known killer and degenerative diseases. What's my proof? Show me people who have lived to 100 or more who are also obese. It just doesn't happen. Most such people without exception, tend to be small and light. In addition, a recent study of animals on CR diets showed that the animals lacked essential nutrients, a consequence of the lack of food. One of the tenents of CR is to ensure that while your restrict total caloric intake, you don't restrict the ingestion of essential nutrients.
But even if you supplement various nutrients that may be in short supply on a CR regime, you won't get enough protein to support various anabolic pathways in the body. This, besides the lack of total daily calories, is the reason why humans on CR show low levels of anabolic hormones, including testosterone and growth hormone. They also show lower thyroid hormone levels, along with increased levels of cortisol, which breaks down muscle. In short, humans on CR are in a catabolic state. They may live longer by avoiding the major killer diseases, but that life will tend to be in an energy-minimized state, making exercise a difficult, if not improbab proposition. What's paradoxical about this is that one effect of CR is that muscles stop aging, an effect that may be replicated with certain nutrient supplementation and exercise. Even worse, scientists who've studied CR suggest that CR may only add about 5-7 years to the average human lifespan, hardly a good trade off for decades of self-imposed starvation.
But some emerging animal studies, which I will discuss in detail in my next two blog entries, show that ingesting certain nutrients may improve the quality of life. This means that if you opt to ingest these nutrients, you may or may not live longer, but you will almost certainly enjoy life without weakness or infirmity, or loss of intellect and thinking ability. If you're interested, stay tuned right here.
