In a previous post, I promised to talk more about anti-aging methods. I would like to focus on one that I don't read about often: lack of energy intake.
The first thing to note is that dieting leads to not just a loss of muscle mass, but to a loss of organ mass as well. Here we are talking about a reduced mass of the heart, kidneys, liver, etc. It's also important to note that older people generally have less organ mass than younger people. Here's a table showing the contribution of various tissues to metabolic rate:
TABLE 1Organ contribution to resting EE in rats and humans
Contribution to EE
Here's a hypothetical path that can put an aging person on a downward spiral: a person gains fat. Then they diet and in the process lose organ mass and muscle mass, reducing their metabolic rate. Over the years, a person repeats this cycle a few more times, leaving the person with low mass and a low metabolic rate.
I've written before about energy flux - both taking in and burning off a lot of calories. This is how our hunter-gatherer ancestors lived. It seems like those advocating restriction diets forget the fact that you need to consume substantial energy if you want to expend substantial energy. Not on a daily basis necessarily, but you can't run a continual deficit without an ensuing slowdown in the metabolic rate. Either that or a person will indirectly reduce energy expenditure (more sitting, less fidgeting, etc.).
I would think an appropriate goal for aging is to maintain a high metabolic rate - and this can not be achieved by eating less and less food.
It's pretty clear that excess body fat is not necessarily an overeating issue. If a person has a healthy metabolism and overeats healthy food, then they will burn it off through an increased metabolic rate or activity. For example, this study compared the effects of overeating candy versus overeating peanuts. The candy led to fat gain while the peanuts led to an increased metabolic rate and no fat gain.
90% of diets all have the same indirect goal - cut calories. Each diet has its own spin, but the underlying mechanics are the same. This is in spite of the fact that gaining fat is not really due to overeating as it is due to a metabolic disruption. Think of it this way: if a person has excess body fat, then they should be bursting with energy, because they have all this surplus energy to use, right? Of course not. Something is blocking the body from properly using this fuel, and that is low-quality food. This low-quality food may also have addictive properties that makes a person want to consume even more of this toxic food.
Instead of cutting calories, an aging person should be cutting the low-quality food. After that, an older person may want to try eating more quality food, not less. This can provide more energy on a daily basis, increase metabolic rate, and increase organ mass (which by itself has survival benefits).
In sum, I don't think cutting calories is the right method to counteract aging. The documented benefits of calorie restriction can probably be gained through intermittent fasting anyways. I say it's better to live like a young animal - and that means a high energy intake and a high energy output.