Health Matters: Fasting and longevity
More than ever before, the importance of ‘good health’, and overall well-being, is obvious. We remain uncertain why some people infected with COVID-19 suffer such debilitating and/or mortal consequences, while others recover uneventfully. Different eating patterns have been evaluated as a way of achieving or maintaining good health and, so very important, our resistance to disease. It would seem according to many experts, it also happens to mean living longer.
We are not talking about temporary weight-loss plans. Decades of research on calorie-restricted feeding, with a great variety of animals (from worms to rodents, crabs to snails), have demonstrated an obvious delay in the onset of many age-related disorders with restricted dietary intake. In many of these studies, extended lifespan was also noted. But most of the relevant studies have been conducted in the laboratory or on animals, yeast cells to primates. How much do these findings correlate to humans?
Clinical trials involving humans have typically been of insufficient duration, weeks or months, and conducted on overweight subjects. These studies are almost always examining weight loss specifically, and not any consequences to the aging processes. The longest trial to date lasted 2 years, not enough to learn about the long-term effects. Despite significant research on fasting and calorie restriction, we are able to make few definitive conclusions about the benefits to health in homo sapiens.
There are a variety of diets requiring some fasting, generally referred to as “intermittent fasting.” In contrast is “calorie restriction,” the reduction of average daily calories consumed below what is usual, but without malnutrition occurring. Calorie restriction is a regular pattern of reduced daily caloric intake, although calorie-restriction does not mean starvation. The weight loss achieved with calorie restriction regimens should not result in body weights outside the normal range. Fasting focuses primarily on the frequency of dining. When someone is on a fasting diet, they don’t eat at all (or severely limit intake) during some designated, recurring length of time.
Another dietary plan is “time-restricted feeding” in which all foods consumed are done so over a limited time, often over 6 to 8 hours, and nothing is eaten the remainder of the day. Recent articles have focused on “alternate-day fasting”, in which there are no restrictions on diet every other day, and no calories consumed on the alternate days. Another pattern proposed is the 5:2 system, in which there is unrestricted intake for 5 straight days each week, followed by 2 days of restricted caloric intake. When calories are restricted for multiple consecutive days every month, then unrestricted all others, it is referred to as periodic fasting.
Many health benefits are associated with prolonged calorie restriction. Long term calorie restriction is theorized to decrease one’s susceptibility to many chronic diseases and also aiding in longevity. Those who routinely fast are less likely to have clogged arteries or coronary artery disease. Those who practice calorie-restriction have reduced risk factors for hypertension and high cholesterol levels.
Age-related diseases such as diabetes, heart disease, and stroke are less common in those who practice fasting regularly. Also beneficial, calorie-restricted diets appear to reduce systemic levels of various inflammatory markers. There appear to be few side effects for those practicing a calorie-restricted diet, many favorable ones, including quality of life, mood, sexual function, and sleep. And by combining physical activity with calorie restriction, you can protect against bone loss, improve muscle mass, and aid aerobic capacity.
During fasting, the body uses up the available glucose, the primary form of sugar in the body, and then turns to the energy reserves stored in fat. This stored energy is released as chemicals known as ketones (the star of the “keto-genic” diet!). Ketones provide a very efficient energy source for cells, allowing them to continue to function, brain cells included. Fasting of sufficient duration seems to initiate a change from glucose-derived energy to ketone-based. This entails greater stress resistance, increased longevity, and a decreased incidence of many diseases. If further research can prove these claims, dietary patterns incorporating fasting offer new approaches to better health, without drugs, with multiple public health benefits.
After decades of research, scientists still don’t know why calorie restriction extends lifespan and delays age-related diseases in laboratory animals. Calorie restriction, practiced regularly appears to improve health and increase longevity, regardless of whether or not we know how. Virtually all organisms age more slowly and live longer when forced to undereat. This has been demonstrated repeatedly, in various animal studies. On the basis of these strong findings, many experts contend we all need to institute these principles, perhaps a necessity with the global population sky-rocketing.
All of the human studies performed to date have been concerned with weight loss in the obese. Consequently, we don’t understand how calorie restriction and fasting affect people who are not. Are these eating patterns safe over the long run? How can these findings be applied to humanity? If practiced by a sufficient number of people, the global supply of foodstuffs could be extended tremendously. But how many individuals are going to willingly practice such a dietary plan? Eating can be one of the great joys in life, the sharing of a good meal with family, filling an empty stomach.
According to a multitude of animal studies, regular fasting, practiced appropriately, aids in improving longevity. Are we so different these results don’t apply to us? The studies on chimps were definitive and we share approximately 97% of our DNA with them. Unfortunately, humans are too difficult to study when it comes to diet. We are all individuals and we all make food choices. And you can choose what you put on your plate.
EDITOR’S NOTE: Dr. Conway McLean is a physician practicing foot and ankle medicine in the Upper Peninsula, with a move of his Marquette office to the downtown area. McLean has lectured internationally on wound care and surgery, being double board certified in surgery, and also in wound care. He has a sub-specialty in foot-ankle orthotics. Dr. McLean welcomes questions or comments at firstname.lastname@example.org.