Even a modest calorie restriction can positively impact muscle quality and has been found to be beneficial for healthy aging, as it reduces inflammation and improves metabolism.
Calorie restriction (CR), defined as decreasing calorie intake without depriving the body of essential vitamins and minerals, has been shown to delay the progression of age-related diseases in animal models. Research has also linked CR to lifespan extension, preservation of function, and increased stress resistance.
The new study that appeared in Aging Cell suggests that the same biological mechanisms may also apply to humans.
Researchers analyzed data from the participants in the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE), a study supported by the National Institute on Aging (NIA).
The study included healthy young and middle-aged Americans without obesity who aimed to reduce daily calorie intake by 25% for two years. However, a 12% reduction was the highest the group was able to reach.
"A 12% reduction in calorie intake is very modest," said corresponding author and NIA Scientific Director Luigi Ferrucci, M.D., Ph.D, in a statement. "This kind of small reduction in calorie intake is doable and may make a big difference in your health."
The researchers found that calorie restriction affected the same gene pathways in humans as in animals. For example, a lower caloric intake upregulated genes responsible for energy generation and metabolism. At the same time, it downregulated inflammatory genes, leading to lower inflammation.
"Since inflammation and aging are strongly coupled, calorie restriction represents a powerful approach to preventing the pro-inflammatory state that is developed by many older people," said Ferrucci.
Among other affected genes were those related to circadian rhythm regulation, DNA repair, and the death of cells that are damaged beyond repair.
When the researchers analyzed thigh muscle biopsies from the CALERIE participants, they found that calorie restriction has induced minor muscle mass losses without changing muscle strength.
The benefits of calorie restriction
A 2020 systematic review of 29 studies examining the role of CR on health status in adults suggested the benefit of calorie restriction on body weight, body mass index (BMI), fat mass, and total cholesterol. Only a minor impact was shown for low-density lipoproteins (LDL), also called the "bad" cholesterol, fasting glucose, and insulin levels.
Meanwhile, calorie restriction did not appear to affect high-density lipoprotein (HDL) cholesterol, known as the "good" cholesterol, and blood pressure.
The review authors concluded that while CR may improve cardiometabolic status, more high-quality studies are needed to determine the impact on health status and longevity.
A phase 2 CALERIE clinical trial, the findings of which were published earlier this year in Nature Aging, found that calorie restriction slowed the pace of aging by 2% to 3% compared to following a regular diet, but whether the slowdown remained after two years of intervention is unclear. The participants, on average, lost 10% in body weight and sustained much of this weight loss after two years.
The new study adds to the growing body of evidence that calorie restriction is beneficial for maintaining overall health and extending lifespan.
- National Institutes of Health. Calorie restriction in humans builds strong muscle and stimulates healthy aging genes.
- National Institutes on Aging. Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE).
- National Library of Medicine. Calorie restriction modulates the transcription of genes related to stress response and longevity in human muscle: The CALERIE study.
- Nature Aging. Effect of long-term caloric restriction on DNA methylation measures of biological aging in healthy adults from the CALERIE trial.
- National Institute on Aging. Calorie restriction and fasting diets: What do we know?