Reduced caloric intake without malnutrition is the oldest known life span–extending intervention. Laboratory studies throughout the 20th century established and confirmed the benefits of caloric restriction (CR) in multiple model systems. CR not only increased life span across evolutionarily distant organisms but also reduced age-associated disease burden and functional decline in these studies.
Epidemiological data from human populations is also generally consistent with the idea that lower caloric intake is associated with increased life expectancy. In recent years, numerous diet modalities that are purported to be “antiaging” have sprung from these observations.
These diets restrict particular macronutrients (carbohydrates or protein) or feeding intervals and can be divided into those that impose reduced caloric intake versus those that are isocaloric to control diets.
A group of researchers from the University of Washington in Seattle and Pennington Biomedical Research Center in Baton Rouge, CA, conducted a review of popular anti-aging diets. These include not just caloric restriction but also diets that strictly limit a person’s intake of carbohydrates, proteins, or particular amino acids.
Remarkably, most of these diets appear to exert favorable effects on health and aging through their influence on a single metabolic pathway that yeast, worms, rodents, and humans have in common.
While the authors of the new review offer an optimistic forecast for the future of anti-aging diets, they caution that they may not work equally well for everyone. The reviewers emphasize that there are no clinically proven anti-aging diets and conclude that more research is needed before doctors can recommend such diets for otherwise healthy people. Some examples of the diets included in the study are:
When researchers restrict the calorie intake of mice and rats while providing all the essential nutrients they need, the animals are healthier and their average lifespan increases compared with animals fed an ordinary lab diet. In addition, these rodents have a. In addition, these rodents have a reduced incidence of age-related diseases, including cancer, neurodegenerative disorders, cardiovascular disease, and type 2 diabetes.
Whereas the results of research into calorie restriction in lab animals are clear cut, say the authors of the review, whether they apply to humans is less obvious.
The authors point out that researchers typically house mice and rats in ideal, pathogen-free conditions and keep a close eye on their health.
By contrast, the enormous variations in human environments and lifestyles are likely to have a large impact on the health effects of potential life-extending diets. Genetic variation between individuals is also likely to play a role in the diets’ outcomes.
Extreme calorie restriction suggests that is likely to yield the greatest life extension, but it also comes at a cost. Potential side effects include poor cold tolerance, loss of libido, psychological problems, chronic fatigue, poor sleep, muscle weakness, increased risk of infection, impaired wound healing.
While no clinical trial has tested whether there is an increase in overall lifespan with calorie restriction, a series of shorter trials lasting from a few months to 2 years have found clinical benefits that are likely to extend a healthy lifespan.
The studies have found that a 25% reduction in calorie intake is associated not only with decreased weight but also enhanced insulin sensitivity and glucose tolerance and improvements in risk factors for cardiometabolic disease.
Diets that strictly limit intake of carbohydrates but allow unrestricted consumption of healthy fats force the body to use molecules called ketones — a byproduct of fat metabolism in the liver — as fuel.
This kind of diet, known as a ketogenic diet, may reduce the frequency of seizures in people with epilepsy and promote weight loss in overweight and obesity.
In 2017, two studies reported that a low carbohydrate, low protein ketogenic diet increased the average lifespan of mice and improved the animals’ health in old age.
One of the studies found that the diet reduced mortality in midlife and improved memory in aging mice. The other study found that it increased longevity and a healthy lifespan. The review authors note that the long-term effects of such diets in humans remain to be determined.
There are different variations of fasting diets, the main 3 are:
- Intermittent fasting, which typically involves consuming few or no calories for 1-4 days each week.
- Fasting-mimicking diets include the same metabolic changes by following a low-calorie, low protein diet for around 5 days each month.
- Time-restricted fasting, which restricts eating to a certain number of hours each day.
The authors of the review say most preclinical animal studies of these diets are effectively investigating different forms of calorie restriction. This is because the animals in the experimental group usually end up consuming fewer calories than animals in the control group. So it’s difficult to distinguish the potential benefits of fasting from the well-established benefits of calorie restriction.
The researchers evaluated a study that compared mice allowed to eat only on alternate days with mice that consumed the same calories but without fasting and found improvements in metabolism and reduced inflammation in the intermittent fasting group.
However, an equivalent study in people found that individuals who fasted every other day saw fewer benefits for their health than individuals who simply ate a calorie-restricted diet with the same overall energy intake.
Protein and amino acid
The review authors note that numerous studies have found that restricting protein intake increases the lifespan of rodents and reduces age-related disease.
They report that while protein restriction in itself increases lifespan, the benefits are considerably weaker than those from calorie restriction. In addition, say the authors, there is evidence that restricting dietary intake of particular essential amino acids, which the body is unable to synthesize for itself, can extend lifespan.
James Kingsland (2021, Nov 22). Do “anti-aging” diets work? Medical News Today. Retrieved December 24th, 2021 from:
Mitchell B. Lee, et al. Antiaging diets: Separating fact from fiction. Science. Nov 2021. Vol. 374, Issue 6570. DOI: 10.1126/science.abe7365.